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LNF: (2022-2024) Estudio experimental de flujos, turbulencia y modos MHD, y su impacto en confinamiento en los stellarators TJ-II y W7-X

2026-02-26T16:57:34Z

Teresa.estrada:

== LNF - Nationally funded project ==

'''Title''': '''Estudio experimental de flujos, turbulencia y modos MHD, y su impacto en confinamiento en los stellarators TJ-II y W7-X'''

'''Reference''': PID2021-125607NB-I00

'''Programme and date''': Proyectos de Generación de Conocimiento Año 2021

'''Programme type (Modalidad de proyecto)''': Proyectos de investigación no orientada

'''Area/subarea (Área temática / subárea)''': Ciencias Físicas / Física y sus aplicaciones

'''Principal Investigators''': [https://orcid.org/0000-0001-6205-2656 Teresa Estrada] and [https://orcid.org/0000-0002-7824-3307 Daniel Carralero]

'''Project type''': Proyecto individual

'''Start-end dates''': 01/01/2022 - 31/12/2025

'''Financing granted (direct costs)''': 160.000,00 €

== Description of the project ==

The main objective of the present proposal is to study a family of instabilities present in the strongly magnetized plasmas required for the development of a practical nuclear fusion reactor, which range from the electrostatic drift turbulence typically dominating transport among thermal populations of confined species, to magneto-hydrodynamic modes destabilized by fast ion populations, such as the Alfvèn Eigenmodes, as well as the potential interactions between them. Finding mechanisms by which these instabilities can be suppressed or controlled in reactor-relevant conditions is critical for the achievement of the high plasma confinement required for an economical exploitation of nuclear fusion. With this aim, we propose the experimental characterization of these instabilities and the plasma conditions driving them, followed by its interpretation under the best available theoretical frameworks. This project can be seen as a continuation and expansion of the previous FIS2017-88892-P grant, in which related research was carried out in the TJ-II and Wendelstein 7-X (W7-X) stellarators, including the commissioning and operation of several relevant diagnostics. From there, our work plan assesses the current state of the research and defines several lines of work such as turbulence stabilization during post-pellet phases, fluctuation and potential asymmetries, flow departure from neoclassical theory, NBI destabilization of AE modes, detection and characterization of zonal flows, etc.

TJ-II is the flagship of the National Laboratory for Fusion (LNF) and part of the Spanish ICTS catalogue. As members of the LNF, the proponents have full access to TJ-II, where the several diagnostics relevant for the study are available. In particular, a steerable Doppler reflectometry (DR) system provides the simultaneous measurement of fluctuations and flows, allowing for very detailed studies of turbulence, critical for the characterization of drift modes. As well, a helical array of Mirnov coils has been recently added to TJ-II, allowing for a detailed study of AEs, including their complex 3D structure in non-axisymmetric devices. W7-X is sited in the Max-Planck-Institut für Plasmaphysik (IPP) in Greifswald. W7X is the largest stellarator in the world and was built to reproduce a number of reactor-relevant features such as optimized magnetic field, high beta operation or actively cooled island divertor. Since 2015, the LNF has collaborated with IPP in the development of a DR system, which has already been successfully operated in previous experimental campaigns. Presently, this system is being refurbished including a number of improvements which will greatly expand the scope of the experimental measurements which can be carried out. As well, a new diagnostic has been included in the proposal: A Charge eXchange Recombination Spectroscopy (CXRS) system, which will complement the investigation of plasma flows carried out by the DR. These diagnostics will ensure access to experimental data in reactor-relevant conditions during the forthcoming OP2.1-OP2.3 campaigns, scheduled for the 2022-2024 period. On top of these purely experimental activities, we outline the data analysis and comparison of physical results to numerical simulations of turbulence (gyrokinetic codes), AE stability (gyrofluid codes), plasma profiles (neoclassical codes) or synthetic DR response to plasma conditions (2D full wave code).

== Main Results ==

This project advanced the experimental and theoretical understanding of plasma turbulence, flows, and magnetohydrodynamic (MHD) activity in the stellarators W7-X and TJ-II through coordinated diagnostic upgrades, systematic experimentation, and integrated modeling.
At W7-X, upgraded Doppler Reflectometer (DR) systems were installed, commissioned, and successfully operated during the OP2 experimental campaigns. Two systems delivered optimal performance, providing high-resolution measurements of turbulence amplitude, perpendicular flows, and long-range correlations, while a third enabled correlation studies despite alignment limitations. A wide range of magnetic configurations—including reduced mirror, low rotational transform, low magnetic shear, and island-chain scenarios—was explored using standardized density and heating power scans. Turbulence levels were found to increase with plasma density and ECH power, while edge turbulence decreased with increasing rotational transform. A clear correlation emerged between reduced edge turbulence, enhanced radial electric field shear, and improved global energy confinement time. Post-pellet enhanced confinement regimes were successfully reproduced, showing turbulence stabilization and increased plasma flow. Dedicated correlation experiments enabled the first direct measurement of zonal flows in a large stellarator, confirming their dependence on density and heating power and validating gyrokinetic predictions. CXRS flow measurements, refined through improved self-calibration, showed significantly better agreement with neoclassical calculations.
In TJ-II, three experimental campaigns ensured full operation of the DR and the helical Mirnov coil array. Dedicated calibration experiments and advanced numerical tools supported reliable magnetic fluctuation analysis. A comprehensive database of NBI-driven Alfvén Eigenmodes was obtained under varying heating and rotational transform conditions. Synthetic magnetic diagnostics and linear MHD simulations improved mode interpretation. While no direct impact of Alfvén activity on turbulence was confirmed, indirect effects linked to injection direction and fast-ion losses were identified. Pellet experiments reproduced enhanced confinement regimes similar to W7-X, though modeling suggests different underlying mechanisms. Overall, the project achieved near-complete fulfillment of its objectives and delivered substantial advances in stellarator turbulence and flow physics.

== Collaborations with other research groups directly related to the project ==

A Collaboration Agreement between the Max-Planck Institute and CIEMAT for the development of Doppler reflectometry in the W7-X stellarator (Germany) was signed in 2013, renewed in 2021 and in force until 2025.

A collaboration with the X-ray Imaging Chrystal Spectroscopy (XICS) team at W7-X (IPP, PPPL) was formalized to include the plasma flow model and assess the influence of fast parallel rotation in the XICS inversions.

Under a more global framework within EUROfusion, the collaboration with the IPP group of the Max-Planck Institute of Greifswald has allowed us to participate in the experiments carried out in the W7-X stellarator. W7-X is the largest stellarator in the world whose objective is to demonstrate the viability of this type of magnetic configuration for a future fusion reactor. Our group has participated in all experimental campaigns since the beginning of the operation of this stellarator back in 2016, with our engagement being reflected in the co-authorship of many scientific publications of the W7-X group over the last decade. During the campaigns the direct part of this participation has included the manning of the Doppler reflectometer and CXRS systems. Besides, our group has adopted a very active stance in the design and supervision of the experimental program, directly participating in its design through the submission of experimental proposals, taking charge of some experimental sessions and generally taking part in the public discussion about the objectives and conduction of the campaigns. This last part was substantially enhanced by the appointment of D. Carralero and A. Alonso as Task Force Leaders of the experimental campaigns, which allowed them a much more direct access to the decision-making process. As well, D. Carralero was part of the team in charge of the supervision of the experimental program realization, its reorganizations as a response to different operational issues and the periodic communication of the campaign status to the W7-X team through a series of regular physics meetings. This work was partly summarized in an invited talk presented after the end of OP2.3, in which he summarized the main core physics results of the campaigns.

The stays at Greifswald during the experimental campaigns have been funded by EUROfusion; only a short stay of P. Pons, needed to carry out preparatory work for the campaign, has been included in the expenses of the present project.

== Dissemination of project results (peer-reviewed publications and conference presentations) ==

Peer-reviewed publications:

[1] D. Carralero, T. Estrada, E. Maragkoudakis, T. Windisch, J. A. Alonso, J. L. Velasco, O. Ford, M. Jakubowski, S. Lazerson, M. Beurskens, S. Bozhenkov, I. Calvo, H. Damm, G. Fuchert, J.M. García-Regaña, U. Höfel, N. Marushchenko, N. Pablant, E. Sánchez, H.M. Smith, E. Pasch, and T. Stange. Plasma Phys. Control. Fusion 64, 044006 (2022)

[2] E. Ascasíbar, F. Lapayese, A. Soleto, A. Jiménez-Denche, Á. Cappa, P. Pons-Villalonga, A. B. Portas, G. Martín, J.M. Barcala, R. García-Gómez, M. Chamorro, L. Cebrián, R. Antón, L. Bueno, C. Reynoso, V. Guisse, and A. López-Fraguas. Rev. Sci. Instrum. 93, 093508 (2022)

[3] J. A. Alonso, O.P. Ford, L. Vanó, S. Äkäslompolo,  S. Buller, R. McDermott, H. Smith, J. Balzuhn,  C.D. Beidler, M. Beurskens, S. Bozhenkov, K.J. Brunner, I. Calvo, D. Carralero, A. Dinklage, T. Estrada, G. Füchert, J. Geiger, J. Knauer, A. Langenbert, N. Pablant, E. Pasch, P. Zs Poloskei, J.L. Velasco, T. Windisch and the W7-X team. Nuclear Fusion 62, 106005 (2022)

[4] Sunn Pederdsen, I. Abramovic, P. Agostinetti, ..., A. Alonso, …, E. Ascasíbar, …, A. Cappa, …, D. Carralero, …, T. Estrada, et al. Nuclear Fusion 62, 042022 (2022)

[5] C. Hidalgo, E. Ascasíbar, D. Alegre, A. Alonso, ..., A. Cappa, D. Carralero, …, T. Estrada, et al. Nuclear Fusion 62, 042025 (2022)

[6] E. Maragkoudakis, D. Carralero, T. Estrada, T. Windisch, Y. Gao, C. Killer, M. Jakubowski, A. Puig Sitjes, F. Pisano, H. Sándor, M. Vecsei, S. Zoletnik, A. Cappa, and the Wendelstein 7-X team. Nuclear Fusion 63, 026011 (2023)

[7] I. García-Cortés, K. J. McCarthy, T. Estrada, V. Tribaldos, D. Medina-Roque, B. van Milligen, E. Ascasíbar, R. Carrasco, A.A. Chmyga, R. García, J. Hernández-Sánchez, C. Hidalgo, A.S. Kozachek, F. Medina, M. A. Ochando, J. L. de Pablos, N. Panadero, I. Pastor, and TJ-II Team. Phys. Plasmas 30, 072506 (2023)

[8] A. González-Jerez, J.M. García-Regaña, I. Calvo, D. Carralero, T. Estrada, E. Sánchez, M. Barnes, and the W7-X team. Nuclear Fusion 64, 076029 (2024)

[9] O. Grulke, C. Albert, J.A. Alcusón, …, A. Alonso, …, E. Ascasíbar, …, A. Cappa, …, D. Carralero, …, T. Estrada, … Nuclear Fusion 64, 112002 (2024)

[10] A. Alonso, D. Alegre, J. Alonso, …, E. Ascasíbar, …, A. Cappa, D. Carralero, …, T. Estrada, …, J.M. Fontdecaba, …, J. Martínez, …, A. Pereira, …, P. Pons, A.B. Portas, …, … J. de la Riva, et al., Nuclear Fusion 64, 112018 (2024)

[11] P. Pons-Villalonga, Á. Cappa, J. Martínez-Fernández, O. S. Kozachok, E. Ascasíbar. Review of Scientific Instruments 96 063502 (2025)

[12] D. Carralero, T. Estrada, J M García-Regaña, E Sánchez, T. Windisch, A. Alonso, E. Maragkoudakis, C Brandt, K J Brunner et al. Physical Review Research ,7, L022009 (2025).

[13] J. de la Riva Villén, J A Alonso, O P Ford, T Romba, E Maragkoudakis, D Carralero, T Estrada, T Windisch, J L Velasco, H M Smith, D Gradic, P Poloskei and the W7-X Team. Plasma Phys. Control. Fusion 68 015015 (2026).

Conference presentations:

[1] D. Carralero et al., (Invited talk)
“Recent turbulence investigations in the TJ-II and W7-X stellarators: experimental characterization and 3D code-based interpretation”, 23rd International Stellarator and Helliotron Workshop (ISHW), Warsaw, Poland, June 2022.

[2] A. Cappa et al., (Invited talk)
“Linear Stability Analysis of TJ-II stellarator NBI-driven Alfvén Eigenmodes in ECRH and ECCD experiments”, 23rd International Stellarator and Helliotron Workshop (ISHW), Warsaw, Poland, June 2022.

[3] P. Pons et al. (Poster)
“New in-vessel helical arrays of magnetic coils in TJ-II, calibration and preliminary results”, 23rd International Stellarator and Helliotron Workshop (ISHW), Warsaw, Poland, June 2022.

[4] E. Maragkoudakis et al.(Poster)
“On the SOL radial electric field, divertor heat fluxes and plasma edge turbulence of W7-X”, 23rd International Stellarator and Helliotron Workshop (ISHW), Warsaw, Poland, June 2022.

[5] T. Estrada, et al. (Invited talk)
“Radial electric fields, turbulence and transport studies in W7-X and TJ-II”, 48th EPS Conference on Plasma Physics, June 27 - July 1, on-line conference (2022)

[6] T. Estrada, et al. (Oral)
“Effect of internal magnetic islands on turbulence and flows in W7-X and TJ-II”, 15th International Reflectometry Workshop IRW15, ITER, St Paul Lez Durance Cedex, France (2022)

[7] E. Maragkoudakis, et al. (Oral)
“Use of the field line tracing code for the interpretation of Doppler reflectometry measurements in W7-X”, 15th International Reflectometry Workshop IRW15, ITER, St Paul Lez Durance Cedex, France (2022)

[8] D.Carralero and C. Killer (Oral)
“Task Force-III: Wendelstein 7-X optimization” OP2.1 Program Planning Workshop, IPP Greifswald, September, 2022

[9] D.Carralero and M. Nunami (Oral)
“Core transport in a stellarator reactor. Learning from present-day experiments and main questions ahead”,
23rd Coordinated Working Group Meeting, Kyoto, Japan, June, 2023

[10] P. Pons et al., (Poster)
“Measurements of spatial periodicity and radial structure of NBI-driven Alfvén Eigenmodes in the TJ-II stellarator”, 49th EPS conference on Plasma Physics, Bordeaux, France, July 2023.

[11] J. de la Riva et al. (Poster)
“Characteristic profiles of radial electric field and parallel velocity obtained in W7-X using charge exchange recombination spectroscopy”, 49th EPS conference on Plasma Physics, Bordeaux, France, July 2023.

[12] A. Cappa et al., (Poster)
“Fast ion physics in the TJ-II stellarator: experiments and model validation activities”
29th IAEA Fusion Energy Conference (IAEA-FEC), London, October 2023.

[13] E. Maragkoudakis, D. Carralero, T. Estrada, T. Windisch et al (Oral).
“Characterization of Doppler Reflectometry profiles for various Wendelstein 7-X scenarios” 16th International Reflectometry Workshop, Greifswald, Germany, May 2024.

[14] D. Carralero, T. Estrada, J. M. García-Regaña, E. Sánchez et al. (Invited)
“First experimental observation of zonal flows in the optimized stellarator Wendelstein 7-X” 50th EPS Conference on Plasma Physics, Salamanca, Spain, July 2024

[15] T. Estrada, Á. Cappa, ..., J. de la Riva et al (Invited).
“Impact of radial electric field, turbulence and impurity transport on plasma performance in co- and counter-NBI heating scenarios in TJ-II”, 24th International Stellarator and Heliotron Workshop (ISHW), Hiroshima, Japan, September 2024.

[16] D. Carralero, T. Estrada, J. M. García-Regaña, E. Sánchez et al (Invited).
“First experimental observation of zonal flows in the optimized stellarator Wendelstein 7-X” 24th International Stellarator and Heliotron Workshop, Hiroshima, Japan, September 2024.

[17] P. Pons et al, "Characterization of the spatial structure of NBI driven shear Alfven waves in the TJ-II stellarator". 18th Technical Meeting on Energetic Particles (TMEP2025), Seville, Spain, March 2025.

[18] D. Carralero, on behalf of the W7-X team (invited)
“Machine report: W7-X Core Transport after OP2.3” 25th Coordinated Working Group Meeting, Princeton, USA, June, 2025.

[19] S. Vaz Mendez, ...,Á. Cappa, P. Pons villalonga, et al. (Poster)
“Discovering Alfvén Mode Excitation by ITG Turbulence”, 51st EPS conference on Plasma Physics, Vilnius, Lithuania, July 2025.

[20] Á. Cappa, P. Pons villalonga et al (Oral),
“Spatial structure of NBI-driven shear Alfvén waves in the TJ-II stellarator: modeling vs. experimental results” 51st EPS conference on Plasma Physics, Vilnius, Lithuania, July 2025.

[21] J. de la Riva et al. (Oral)
“Systematic study of CXRS ion flow measurements in the W7-X stellarator towards a validation of neoclassical theory”, 51th EPS conference on Plasma Physics, Vilnius, Lithuania, July 2025.

[22] J. M. García-Regaña, J. A. Alonso, …, E. Ascasíbar1, …, A. Cappa, D. Carralero, et al. (Overview)
“Transport in high-performance plasmas of the TJ-II stellarator: from first-principles simulations to experimental validation”, 30th IAEA Fusion Energy Conference (FEC2025), Chendu, China, October, 2025

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<hr>
[[LNF:Nationally Funded Projects|Back to list of nationally funded projects]]

[[Category:LNF Nationally Funded Projects - finished]]

LNF: (2022-2024) Estudio experimental de flujos, turbulencia y modos MHD, y su impacto en confinamiento en los stellarators TJ-II y W7-X

2026-02-26T16:57:06Z

Teresa.estrada:

== LNF - Nationally funded project ==

'''Title''': '''Estudio experimental de flujos, turbulencia y modos MHD, y su impacto en confinamiento en los stellarators TJ-II y W7-X'''

'''Reference''': PID2021-125607NB-I00

'''Programme and date''': Proyectos de Generación de Conocimiento Año 2021

'''Programme type (Modalidad de proyecto)''': Proyectos de investigación no orientada

'''Area/subarea (Área temática / subárea)''': Ciencias Físicas / Física y sus aplicaciones

'''Principal Investigators''': [https://orcid.org/0000-0001-6205-2656 Teresa Estrada] and [https://orcid.org/0000-0002-7824-3307 Daniel Carralero]

'''Project type''': Proyecto individual

'''Start-end dates''': 01/01/2022 - 31/12/2024

'''Financing granted (direct costs)''': 160.000,00 €

== Description of the project ==

The main objective of the present proposal is to study a family of instabilities present in the strongly magnetized plasmas required for the development of a practical nuclear fusion reactor, which range from the electrostatic drift turbulence typically dominating transport among thermal populations of confined species, to magneto-hydrodynamic modes destabilized by fast ion populations, such as the Alfvèn Eigenmodes, as well as the potential interactions between them. Finding mechanisms by which these instabilities can be suppressed or controlled in reactor-relevant conditions is critical for the achievement of the high plasma confinement required for an economical exploitation of nuclear fusion. With this aim, we propose the experimental characterization of these instabilities and the plasma conditions driving them, followed by its interpretation under the best available theoretical frameworks. This project can be seen as a continuation and expansion of the previous FIS2017-88892-P grant, in which related research was carried out in the TJ-II and Wendelstein 7-X (W7-X) stellarators, including the commissioning and operation of several relevant diagnostics. From there, our work plan assesses the current state of the research and defines several lines of work such as turbulence stabilization during post-pellet phases, fluctuation and potential asymmetries, flow departure from neoclassical theory, NBI destabilization of AE modes, detection and characterization of zonal flows, etc.

TJ-II is the flagship of the National Laboratory for Fusion (LNF) and part of the Spanish ICTS catalogue. As members of the LNF, the proponents have full access to TJ-II, where the several diagnostics relevant for the study are available. In particular, a steerable Doppler reflectometry (DR) system provides the simultaneous measurement of fluctuations and flows, allowing for very detailed studies of turbulence, critical for the characterization of drift modes. As well, a helical array of Mirnov coils has been recently added to TJ-II, allowing for a detailed study of AEs, including their complex 3D structure in non-axisymmetric devices. W7-X is sited in the Max-Planck-Institut für Plasmaphysik (IPP) in Greifswald. W7X is the largest stellarator in the world and was built to reproduce a number of reactor-relevant features such as optimized magnetic field, high beta operation or actively cooled island divertor. Since 2015, the LNF has collaborated with IPP in the development of a DR system, which has already been successfully operated in previous experimental campaigns. Presently, this system is being refurbished including a number of improvements which will greatly expand the scope of the experimental measurements which can be carried out. As well, a new diagnostic has been included in the proposal: A Charge eXchange Recombination Spectroscopy (CXRS) system, which will complement the investigation of plasma flows carried out by the DR. These diagnostics will ensure access to experimental data in reactor-relevant conditions during the forthcoming OP2.1-OP2.3 campaigns, scheduled for the 2022-2024 period. On top of these purely experimental activities, we outline the data analysis and comparison of physical results to numerical simulations of turbulence (gyrokinetic codes), AE stability (gyrofluid codes), plasma profiles (neoclassical codes) or synthetic DR response to plasma conditions (2D full wave code).

== Main Results ==

This project advanced the experimental and theoretical understanding of plasma turbulence, flows, and magnetohydrodynamic (MHD) activity in the stellarators W7-X and TJ-II through coordinated diagnostic upgrades, systematic experimentation, and integrated modeling.
At W7-X, upgraded Doppler Reflectometer (DR) systems were installed, commissioned, and successfully operated during the OP2 experimental campaigns. Two systems delivered optimal performance, providing high-resolution measurements of turbulence amplitude, perpendicular flows, and long-range correlations, while a third enabled correlation studies despite alignment limitations. A wide range of magnetic configurations—including reduced mirror, low rotational transform, low magnetic shear, and island-chain scenarios—was explored using standardized density and heating power scans. Turbulence levels were found to increase with plasma density and ECH power, while edge turbulence decreased with increasing rotational transform. A clear correlation emerged between reduced edge turbulence, enhanced radial electric field shear, and improved global energy confinement time. Post-pellet enhanced confinement regimes were successfully reproduced, showing turbulence stabilization and increased plasma flow. Dedicated correlation experiments enabled the first direct measurement of zonal flows in a large stellarator, confirming their dependence on density and heating power and validating gyrokinetic predictions. CXRS flow measurements, refined through improved self-calibration, showed significantly better agreement with neoclassical calculations.
In TJ-II, three experimental campaigns ensured full operation of the DR and the helical Mirnov coil array. Dedicated calibration experiments and advanced numerical tools supported reliable magnetic fluctuation analysis. A comprehensive database of NBI-driven Alfvén Eigenmodes was obtained under varying heating and rotational transform conditions. Synthetic magnetic diagnostics and linear MHD simulations improved mode interpretation. While no direct impact of Alfvén activity on turbulence was confirmed, indirect effects linked to injection direction and fast-ion losses were identified. Pellet experiments reproduced enhanced confinement regimes similar to W7-X, though modeling suggests different underlying mechanisms. Overall, the project achieved near-complete fulfillment of its objectives and delivered substantial advances in stellarator turbulence and flow physics.

== Collaborations with other research groups directly related to the project ==

A Collaboration Agreement between the Max-Planck Institute and CIEMAT for the development of Doppler reflectometry in the W7-X stellarator (Germany) was signed in 2013, renewed in 2021 and in force until 2025.

A collaboration with the X-ray Imaging Chrystal Spectroscopy (XICS) team at W7-X (IPP, PPPL) was formalized to include the plasma flow model and assess the influence of fast parallel rotation in the XICS inversions.

Under a more global framework within EUROfusion, the collaboration with the IPP group of the Max-Planck Institute of Greifswald has allowed us to participate in the experiments carried out in the W7-X stellarator. W7-X is the largest stellarator in the world whose objective is to demonstrate the viability of this type of magnetic configuration for a future fusion reactor. Our group has participated in all experimental campaigns since the beginning of the operation of this stellarator back in 2016, with our engagement being reflected in the co-authorship of many scientific publications of the W7-X group over the last decade. During the campaigns the direct part of this participation has included the manning of the Doppler reflectometer and CXRS systems. Besides, our group has adopted a very active stance in the design and supervision of the experimental program, directly participating in its design through the submission of experimental proposals, taking charge of some experimental sessions and generally taking part in the public discussion about the objectives and conduction of the campaigns. This last part was substantially enhanced by the appointment of D. Carralero and A. Alonso as Task Force Leaders of the experimental campaigns, which allowed them a much more direct access to the decision-making process. As well, D. Carralero was part of the team in charge of the supervision of the experimental program realization, its reorganizations as a response to different operational issues and the periodic communication of the campaign status to the W7-X team through a series of regular physics meetings. This work was partly summarized in an invited talk presented after the end of OP2.3, in which he summarized the main core physics results of the campaigns.

The stays at Greifswald during the experimental campaigns have been funded by EUROfusion; only a short stay of P. Pons, needed to carry out preparatory work for the campaign, has been included in the expenses of the present project.

== Dissemination of project results (peer-reviewed publications and conference presentations) ==

Peer-reviewed publications:

[1] D. Carralero, T. Estrada, E. Maragkoudakis, T. Windisch, J. A. Alonso, J. L. Velasco, O. Ford, M. Jakubowski, S. Lazerson, M. Beurskens, S. Bozhenkov, I. Calvo, H. Damm, G. Fuchert, J.M. García-Regaña, U. Höfel, N. Marushchenko, N. Pablant, E. Sánchez, H.M. Smith, E. Pasch, and T. Stange. Plasma Phys. Control. Fusion 64, 044006 (2022)

[2] E. Ascasíbar, F. Lapayese, A. Soleto, A. Jiménez-Denche, Á. Cappa, P. Pons-Villalonga, A. B. Portas, G. Martín, J.M. Barcala, R. García-Gómez, M. Chamorro, L. Cebrián, R. Antón, L. Bueno, C. Reynoso, V. Guisse, and A. López-Fraguas. Rev. Sci. Instrum. 93, 093508 (2022)

[3] J. A. Alonso, O.P. Ford, L. Vanó, S. Äkäslompolo,  S. Buller, R. McDermott, H. Smith, J. Balzuhn,  C.D. Beidler, M. Beurskens, S. Bozhenkov, K.J. Brunner, I. Calvo, D. Carralero, A. Dinklage, T. Estrada, G. Füchert, J. Geiger, J. Knauer, A. Langenbert, N. Pablant, E. Pasch, P. Zs Poloskei, J.L. Velasco, T. Windisch and the W7-X team. Nuclear Fusion 62, 106005 (2022)

[4] Sunn Pederdsen, I. Abramovic, P. Agostinetti, ..., A. Alonso, …, E. Ascasíbar, …, A. Cappa, …, D. Carralero, …, T. Estrada, et al. Nuclear Fusion 62, 042022 (2022)

[5] C. Hidalgo, E. Ascasíbar, D. Alegre, A. Alonso, ..., A. Cappa, D. Carralero, …, T. Estrada, et al. Nuclear Fusion 62, 042025 (2022)

[6] E. Maragkoudakis, D. Carralero, T. Estrada, T. Windisch, Y. Gao, C. Killer, M. Jakubowski, A. Puig Sitjes, F. Pisano, H. Sándor, M. Vecsei, S. Zoletnik, A. Cappa, and the Wendelstein 7-X team. Nuclear Fusion 63, 026011 (2023)

[7] I. García-Cortés, K. J. McCarthy, T. Estrada, V. Tribaldos, D. Medina-Roque, B. van Milligen, E. Ascasíbar, R. Carrasco, A.A. Chmyga, R. García, J. Hernández-Sánchez, C. Hidalgo, A.S. Kozachek, F. Medina, M. A. Ochando, J. L. de Pablos, N. Panadero, I. Pastor, and TJ-II Team. Phys. Plasmas 30, 072506 (2023)

[8] A. González-Jerez, J.M. García-Regaña, I. Calvo, D. Carralero, T. Estrada, E. Sánchez, M. Barnes, and the W7-X team. Nuclear Fusion 64, 076029 (2024)

[9] O. Grulke, C. Albert, J.A. Alcusón, …, A. Alonso, …, E. Ascasíbar, …, A. Cappa, …, D. Carralero, …, T. Estrada, … Nuclear Fusion 64, 112002 (2024)

[10] A. Alonso, D. Alegre, J. Alonso, …, E. Ascasíbar, …, A. Cappa, D. Carralero, …, T. Estrada, …, J.M. Fontdecaba, …, J. Martínez, …, A. Pereira, …, P. Pons, A.B. Portas, …, … J. de la Riva, et al., Nuclear Fusion 64, 112018 (2024)

[11] P. Pons-Villalonga, Á. Cappa, J. Martínez-Fernández, O. S. Kozachok, E. Ascasíbar. Review of Scientific Instruments 96 063502 (2025)

[12] D. Carralero, T. Estrada, J M García-Regaña, E Sánchez, T. Windisch, A. Alonso, E. Maragkoudakis, C Brandt, K J Brunner et al. Physical Review Research ,7, L022009 (2025).

[13] J. de la Riva Villén, J A Alonso, O P Ford, T Romba, E Maragkoudakis, D Carralero, T Estrada, T Windisch, J L Velasco, H M Smith, D Gradic, P Poloskei and the W7-X Team. Plasma Phys. Control. Fusion 68 015015 (2026).

Conference presentations:

[1] D. Carralero et al., (Invited talk)
“Recent turbulence investigations in the TJ-II and W7-X stellarators: experimental characterization and 3D code-based interpretation”, 23rd International Stellarator and Helliotron Workshop (ISHW), Warsaw, Poland, June 2022.

[2] A. Cappa et al., (Invited talk)
“Linear Stability Analysis of TJ-II stellarator NBI-driven Alfvén Eigenmodes in ECRH and ECCD experiments”, 23rd International Stellarator and Helliotron Workshop (ISHW), Warsaw, Poland, June 2022.

[3] P. Pons et al. (Poster)
“New in-vessel helical arrays of magnetic coils in TJ-II, calibration and preliminary results”, 23rd International Stellarator and Helliotron Workshop (ISHW), Warsaw, Poland, June 2022.

[4] E. Maragkoudakis et al.(Poster)
“On the SOL radial electric field, divertor heat fluxes and plasma edge turbulence of W7-X”, 23rd International Stellarator and Helliotron Workshop (ISHW), Warsaw, Poland, June 2022.

[5] T. Estrada, et al. (Invited talk)
“Radial electric fields, turbulence and transport studies in W7-X and TJ-II”, 48th EPS Conference on Plasma Physics, June 27 - July 1, on-line conference (2022)

[6] T. Estrada, et al. (Oral)
“Effect of internal magnetic islands on turbulence and flows in W7-X and TJ-II”, 15th International Reflectometry Workshop IRW15, ITER, St Paul Lez Durance Cedex, France (2022)

[7] E. Maragkoudakis, et al. (Oral)
“Use of the field line tracing code for the interpretation of Doppler reflectometry measurements in W7-X”, 15th International Reflectometry Workshop IRW15, ITER, St Paul Lez Durance Cedex, France (2022)

[8] D.Carralero and C. Killer (Oral)
“Task Force-III: Wendelstein 7-X optimization” OP2.1 Program Planning Workshop, IPP Greifswald, September, 2022

[9] D.Carralero and M. Nunami (Oral)
“Core transport in a stellarator reactor. Learning from present-day experiments and main questions ahead”,
23rd Coordinated Working Group Meeting, Kyoto, Japan, June, 2023

[10] P. Pons et al., (Poster)
“Measurements of spatial periodicity and radial structure of NBI-driven Alfvén Eigenmodes in the TJ-II stellarator”, 49th EPS conference on Plasma Physics, Bordeaux, France, July 2023.

[11] J. de la Riva et al. (Poster)
“Characteristic profiles of radial electric field and parallel velocity obtained in W7-X using charge exchange recombination spectroscopy”, 49th EPS conference on Plasma Physics, Bordeaux, France, July 2023.

[12] A. Cappa et al., (Poster)
“Fast ion physics in the TJ-II stellarator: experiments and model validation activities”
29th IAEA Fusion Energy Conference (IAEA-FEC), London, October 2023.

[13] E. Maragkoudakis, D. Carralero, T. Estrada, T. Windisch et al (Oral).
“Characterization of Doppler Reflectometry profiles for various Wendelstein 7-X scenarios” 16th International Reflectometry Workshop, Greifswald, Germany, May 2024.

[14] D. Carralero, T. Estrada, J. M. García-Regaña, E. Sánchez et al. (Invited)
“First experimental observation of zonal flows in the optimized stellarator Wendelstein 7-X” 50th EPS Conference on Plasma Physics, Salamanca, Spain, July 2024

[15] T. Estrada, Á. Cappa, ..., J. de la Riva et al (Invited).
“Impact of radial electric field, turbulence and impurity transport on plasma performance in co- and counter-NBI heating scenarios in TJ-II”, 24th International Stellarator and Heliotron Workshop (ISHW), Hiroshima, Japan, September 2024.

[16] D. Carralero, T. Estrada, J. M. García-Regaña, E. Sánchez et al (Invited).
“First experimental observation of zonal flows in the optimized stellarator Wendelstein 7-X” 24th International Stellarator and Heliotron Workshop, Hiroshima, Japan, September 2024.

[17] P. Pons et al, "Characterization of the spatial structure of NBI driven shear Alfven waves in the TJ-II stellarator". 18th Technical Meeting on Energetic Particles (TMEP2025), Seville, Spain, March 2025.

[18] D. Carralero, on behalf of the W7-X team (invited)
“Machine report: W7-X Core Transport after OP2.3” 25th Coordinated Working Group Meeting, Princeton, USA, June, 2025.

[19] S. Vaz Mendez, ...,Á. Cappa, P. Pons villalonga, et al. (Poster)
“Discovering Alfvén Mode Excitation by ITG Turbulence”, 51st EPS conference on Plasma Physics, Vilnius, Lithuania, July 2025.

[20] Á. Cappa, P. Pons villalonga et al (Oral),
“Spatial structure of NBI-driven shear Alfvén waves in the TJ-II stellarator: modeling vs. experimental results” 51st EPS conference on Plasma Physics, Vilnius, Lithuania, July 2025.

[21] J. de la Riva et al. (Oral)
“Systematic study of CXRS ion flow measurements in the W7-X stellarator towards a validation of neoclassical theory”, 51th EPS conference on Plasma Physics, Vilnius, Lithuania, July 2025.

[22] J. M. García-Regaña, J. A. Alonso, …, E. Ascasíbar1, …, A. Cappa, D. Carralero, et al. (Overview)
“Transport in high-performance plasmas of the TJ-II stellarator: from first-principles simulations to experimental validation”, 30th IAEA Fusion Energy Conference (FEC2025), Chendu, China, October, 2025

<references />


<hr>
[[LNF:Nationally Funded Projects|Back to list of nationally funded projects]]

[[Category:LNF Nationally Funded Projects - finished]]

LNF: (2022-2024) Estudio experimental de flujos, turbulencia y modos MHD, y su impacto en confinamiento en los stellarators TJ-II y W7-X

2026-02-26T16:53:50Z

Teresa.estrada:

== LNF - Nationally funded project ==

'''Title''': '''Estudio experimental de flujos, turbulencia y modos MHD, y su impacto en confinamiento en los stellarators TJ-II y W7-X'''

'''Reference''': PID2021-125607NB-I00

'''Programme and date''': Proyectos de Generación de Conocimiento Año 2021

'''Programme type (Modalidad de proyecto)''': Proyectos de investigación no orientada

'''Area/subarea (Área temática / subárea)''': Ciencias Físicas / Física y sus aplicaciones

'''Principal Investigators''': [https://orcid.org/0000-0001-6205-2656 Teresa Estrada] and [https://orcid.org/0000-0002-7824-3307 Daniel Carralero]

'''Project type''': Proyecto individual

'''Start-end dates''': 01/01/2022 - 31/12/2024

'''Financing granted (direct costs)''': 160.000,00 €

== Description of the project ==

The main objective of the present proposal is to study a family of instabilities present in the strongly magnetized plasmas required for the development of a practical nuclear fusion reactor, which range from the electrostatic drift turbulence typically dominating transport among thermal populations of confined species, to magneto-hydrodynamic modes destabilized by fast ion populations, such as the Alfvèn Eigenmodes, as well as the potential interactions between them. Finding mechanisms by which these instabilities can be suppressed or controlled in reactor-relevant conditions is critical for the achievement of the high plasma confinement required for an economical exploitation of nuclear fusion. With this aim, we propose the experimental characterization of these instabilities and the plasma conditions driving them, followed by its interpretation under the best available theoretical frameworks. This project can be seen as a continuation and expansion of the previous FIS2017-88892-P grant, in which related research was carried out in the TJ-II and Wendelstein 7-X (W7-X) stellarators, including the commissioning and operation of several relevant diagnostics. From there, our work plan assesses the current state of the research and defines several lines of work such as turbulence stabilization during post-pellet phases, fluctuation and potential asymmetries, flow departure from neoclassical theory, NBI destabilization of AE modes, detection and characterization of zonal flows, etc.

TJ-II is the flagship of the National Laboratory for Fusion (LNF) and part of the Spanish ICTS catalogue. As members of the LNF, the proponents have full access to TJ-II, where the several diagnostics relevant for the study are available. In particular, a steerable Doppler reflectometry (DR) system provides the simultaneous measurement of fluctuations and flows, allowing for very detailed studies of turbulence, critical for the characterization of drift modes. As well, a helical array of Mirnov coils has been recently added to TJ-II, allowing for a detailed study of AEs, including their complex 3D structure in non-axisymmetric devices. W7-X is sited in the Max-Planck-Institut für Plasmaphysik (IPP) in Greifswald. W7X is the largest stellarator in the world and was built to reproduce a number of reactor-relevant features such as optimized magnetic field, high beta operation or actively cooled island divertor. Since 2015, the LNF has collaborated with IPP in the development of a DR system, which has already been successfully operated in previous experimental campaigns. Presently, this system is being refurbished including a number of improvements which will greatly expand the scope of the experimental measurements which can be carried out. As well, a new diagnostic has been included in the proposal: A Charge eXchange Recombination Spectroscopy (CXRS) system, which will complement the investigation of plasma flows carried out by the DR. These diagnostics will ensure access to experimental data in reactor-relevant conditions during the forthcoming OP2.1-OP2.3 campaigns, scheduled for the 2022-2024 period. On top of these purely experimental activities, we outline the data analysis and comparison of physical results to numerical simulations of turbulence (gyrokinetic codes), AE stability (gyrofluid codes), plasma profiles (neoclassical codes) or synthetic DR response to plasma conditions (2D full wave code).

== Main Results ==

This project advanced the experimental and theoretical understanding of plasma turbulence, flows, and magnetohydrodynamic (MHD) activity in the stellarators W7-X and TJ-II through coordinated diagnostic upgrades, systematic experimentation, and integrated modeling.
At W7-X, upgraded Doppler Reflectometer (DR) systems were installed, commissioned, and successfully operated during the OP2 experimental campaigns. Two systems delivered optimal performance, providing high-resolution measurements of turbulence amplitude, perpendicular flows, and long-range correlations, while a third enabled correlation studies despite alignment limitations. A wide range of magnetic configurations—including reduced mirror, low rotational transform, low magnetic shear, and island-chain scenarios—was explored using standardized density and heating power scans. Turbulence levels were found to increase with plasma density and ECH power, while edge turbulence decreased with increasing rotational transform. A clear correlation emerged between reduced edge turbulence, enhanced radial electric field shear, and improved global energy confinement time. Post-pellet enhanced confinement regimes were successfully reproduced, showing turbulence stabilization and increased plasma flow. Dedicated correlation experiments enabled the first direct measurement of zonal flows in a large stellarator, confirming their dependence on density and heating power and validating gyrokinetic predictions. CXRS flow measurements, refined through improved self-calibration, showed significantly better agreement with neoclassical calculations.
In TJ-II, three experimental campaigns ensured full operation of the DR and the helical Mirnov coil array. Dedicated calibration experiments and advanced numerical tools supported reliable magnetic fluctuation analysis. A comprehensive database of NBI-driven Alfvén Eigenmodes was obtained under varying heating and rotational transform conditions. Synthetic magnetic diagnostics and linear MHD simulations improved mode interpretation. While no direct impact of Alfvén activity on turbulence was confirmed, indirect effects linked to injection direction and fast-ion losses were identified. Pellet experiments reproduced enhanced confinement regimes similar to W7-X, though modeling suggests different underlying mechanisms. Overall, the project achieved near-complete fulfillment of its objectives and delivered substantial advances in stellarator turbulence and flow physics.

== Dissemination of project results (peer-reviewed publications and conference presentations) ==

Peer-reviewed publications:

[1] D. Carralero, T. Estrada, E. Maragkoudakis, T. Windisch, J. A. Alonso, J. L. Velasco, O. Ford, M. Jakubowski, S. Lazerson, M. Beurskens, S. Bozhenkov, I. Calvo, H. Damm, G. Fuchert, J.M. García-Regaña, U. Höfel, N. Marushchenko, N. Pablant, E. Sánchez, H.M. Smith, E. Pasch, and T. Stange. Plasma Phys. Control. Fusion 64, 044006 (2022)

[2] E. Ascasíbar, F. Lapayese, A. Soleto, A. Jiménez-Denche, Á. Cappa, P. Pons-Villalonga, A. B. Portas, G. Martín, J.M. Barcala, R. García-Gómez, M. Chamorro, L. Cebrián, R. Antón, L. Bueno, C. Reynoso, V. Guisse, and A. López-Fraguas. Rev. Sci. Instrum. 93, 093508 (2022)

[3] J. A. Alonso, O.P. Ford, L. Vanó, S. Äkäslompolo,  S. Buller, R. McDermott, H. Smith, J. Balzuhn,  C.D. Beidler, M. Beurskens, S. Bozhenkov, K.J. Brunner, I. Calvo, D. Carralero, A. Dinklage, T. Estrada, G. Füchert, J. Geiger, J. Knauer, A. Langenbert, N. Pablant, E. Pasch, P. Zs Poloskei, J.L. Velasco, T. Windisch and the W7-X team. Nuclear Fusion 62, 106005 (2022)

[4] Sunn Pederdsen, I. Abramovic, P. Agostinetti, ..., A. Alonso, …, E. Ascasíbar, …, A. Cappa, …, D. Carralero, …, T. Estrada, et al. Nuclear Fusion 62, 042022 (2022)

[5] C. Hidalgo, E. Ascasíbar, D. Alegre, A. Alonso, ..., A. Cappa, D. Carralero, …, T. Estrada, et al. Nuclear Fusion 62, 042025 (2022)

[6] E. Maragkoudakis, D. Carralero, T. Estrada, T. Windisch, Y. Gao, C. Killer, M. Jakubowski, A. Puig Sitjes, F. Pisano, H. Sándor, M. Vecsei, S. Zoletnik, A. Cappa, and the Wendelstein 7-X team. Nuclear Fusion 63, 026011 (2023)

[7] I. García-Cortés, K. J. McCarthy, T. Estrada, V. Tribaldos, D. Medina-Roque, B. van Milligen, E. Ascasíbar, R. Carrasco, A.A. Chmyga, R. García, J. Hernández-Sánchez, C. Hidalgo, A.S. Kozachek, F. Medina, M. A. Ochando, J. L. de Pablos, N. Panadero, I. Pastor, and TJ-II Team. Phys. Plasmas 30, 072506 (2023)

[8] A. González-Jerez, J.M. García-Regaña, I. Calvo, D. Carralero, T. Estrada, E. Sánchez, M. Barnes, and the W7-X team. Nuclear Fusion 64, 076029 (2024)

[9] O. Grulke, C. Albert, J.A. Alcusón, …, A. Alonso, …, E. Ascasíbar, …, A. Cappa, …, D. Carralero, …, T. Estrada, … Nuclear Fusion 64, 112002 (2024)

[10] A. Alonso, D. Alegre, J. Alonso, …, E. Ascasíbar, …, A. Cappa, D. Carralero, …, T. Estrada, …, J.M. Fontdecaba, …, J. Martínez, …, A. Pereira, …, P. Pons, A.B. Portas, …, … J. de la Riva, et al., Nuclear Fusion 64, 112018 (2024)

[11] P. Pons-Villalonga, Á. Cappa, J. Martínez-Fernández, O. S. Kozachok, E. Ascasíbar. Review of Scientific Instruments 96 063502 (2025)

[12] D. Carralero, T. Estrada, J M García-Regaña, E Sánchez, T. Windisch, A. Alonso, E. Maragkoudakis, C Brandt, K J Brunner et al. Physical Review Research ,7, L022009 (2025).

[13] J. de la Riva Villén, J A Alonso, O P Ford, T Romba, E Maragkoudakis, D Carralero, T Estrada, T Windisch, J L Velasco, H M Smith, D Gradic, P Poloskei and the W7-X Team. Plasma Phys. Control. Fusion 68 015015 (2026).

Conference presentations:

[1] D. Carralero et al., (Invited talk)
“Recent turbulence investigations in the TJ-II and W7-X stellarators: experimental characterization and 3D code-based interpretation”, 23rd International Stellarator and Helliotron Workshop (ISHW), Warsaw, Poland, June 2022.

[2] A. Cappa et al., (Invited talk)
“Linear Stability Analysis of TJ-II stellarator NBI-driven Alfvén Eigenmodes in ECRH and ECCD experiments”, 23rd International Stellarator and Helliotron Workshop (ISHW), Warsaw, Poland, June 2022.

[3] P. Pons et al. (Poster)
“New in-vessel helical arrays of magnetic coils in TJ-II, calibration and preliminary results”, 23rd International Stellarator and Helliotron Workshop (ISHW), Warsaw, Poland, June 2022.

[4] E. Maragkoudakis et al.(Poster)
“On the SOL radial electric field, divertor heat fluxes and plasma edge turbulence of W7-X”, 23rd International Stellarator and Helliotron Workshop (ISHW), Warsaw, Poland, June 2022.

[5] T. Estrada, et al. (Invited talk)
“Radial electric fields, turbulence and transport studies in W7-X and TJ-II”, 48th EPS Conference on Plasma Physics, June 27 - July 1, on-line conference (2022)

[6] T. Estrada, et al. (Oral)
“Effect of internal magnetic islands on turbulence and flows in W7-X and TJ-II”, 15th International Reflectometry Workshop IRW15, ITER, St Paul Lez Durance Cedex, France (2022)

[7] E. Maragkoudakis, et al. (Oral)
“Use of the field line tracing code for the interpretation of Doppler reflectometry measurements in W7-X”, 15th International Reflectometry Workshop IRW15, ITER, St Paul Lez Durance Cedex, France (2022)

[8] D.Carralero and C. Killer (Oral)
“Task Force-III: Wendelstein 7-X optimization” OP2.1 Program Planning Workshop, IPP Greifswald, September, 2022

[9] D.Carralero and M. Nunami (Oral)
“Core transport in a stellarator reactor. Learning from present-day experiments and main questions ahead”,
23rd Coordinated Working Group Meeting, Kyoto, Japan, June, 2023

[10] P. Pons et al., (Poster)
“Measurements of spatial periodicity and radial structure of NBI-driven Alfvén Eigenmodes in the TJ-II stellarator”, 49th EPS conference on Plasma Physics, Bordeaux, France, July 2023.

[11] J. de la Riva et al. (Poster)
“Characteristic profiles of radial electric field and parallel velocity obtained in W7-X using charge exchange recombination spectroscopy”, 49th EPS conference on Plasma Physics, Bordeaux, France, July 2023.

[12] A. Cappa et al., (Poster)
“Fast ion physics in the TJ-II stellarator: experiments and model validation activities”
29th IAEA Fusion Energy Conference (IAEA-FEC), London, October 2023.

[13] E. Maragkoudakis, D. Carralero, T. Estrada, T. Windisch et al (Oral).
“Characterization of Doppler Reflectometry profiles for various Wendelstein 7-X scenarios” 16th International Reflectometry Workshop, Greifswald, Germany, May 2024.

[14] D. Carralero, T. Estrada, J. M. García-Regaña, E. Sánchez et al. (Invited)
“First experimental observation of zonal flows in the optimized stellarator Wendelstein 7-X” 50th EPS Conference on Plasma Physics, Salamanca, Spain, July 2024

[15] T. Estrada, Á. Cappa, ..., J. de la Riva et al (Invited).
“Impact of radial electric field, turbulence and impurity transport on plasma performance in co- and counter-NBI heating scenarios in TJ-II”, 24th International Stellarator and Heliotron Workshop (ISHW), Hiroshima, Japan, September 2024.

[16] D. Carralero, T. Estrada, J. M. García-Regaña, E. Sánchez et al (Invited).
“First experimental observation of zonal flows in the optimized stellarator Wendelstein 7-X” 24th International Stellarator and Heliotron Workshop, Hiroshima, Japan, September 2024.

[17] P. Pons et al, "Characterization of the spatial structure of NBI driven shear Alfven waves in the TJ-II stellarator". 18th Technical Meeting on Energetic Particles (TMEP2025), Seville, Spain, March 2025.

[18] D. Carralero, on behalf of the W7-X team (invited)
“Machine report: W7-X Core Transport after OP2.3” 25th Coordinated Working Group Meeting, Princeton, USA, June, 2025.

[19] S. Vaz Mendez, ...,Á. Cappa, P. Pons villalonga, et al. (Poster)
“Discovering Alfvén Mode Excitation by ITG Turbulence”, 51st EPS conference on Plasma Physics, Vilnius, Lithuania, July 2025.

[20] Á. Cappa, P. Pons villalonga et al (Oral),
“Spatial structure of NBI-driven shear Alfvén waves in the TJ-II stellarator: modeling vs. experimental results” 51st EPS conference on Plasma Physics, Vilnius, Lithuania, July 2025.

[21] J. de la Riva et al. (Oral)
“Systematic study of CXRS ion flow measurements in the W7-X stellarator towards a validation of neoclassical theory”, 51th EPS conference on Plasma Physics, Vilnius, Lithuania, July 2025.

[22] J. M. García-Regaña, J. A. Alonso, …, E. Ascasíbar1, …, A. Cappa, D. Carralero, et al. (Overview)
“Transport in high-performance plasmas of the TJ-II stellarator: from first-principles simulations to experimental validation”, 30th IAEA Fusion Energy Conference (FEC2025), Chendu, China, October, 2025

<references />


<hr>
[[LNF:Nationally Funded Projects|Back to list of nationally funded projects]]

[[Category:LNF Nationally Funded Projects - finished]]

LNF: (2022-2024) Estudio experimental de flujos, turbulencia y modos MHD, y su impacto en confinamiento en los stellarators TJ-II y W7-X

2026-02-26T16:53:18Z

Teresa.estrada:

== LNF - Nationally funded project ==

'''Title''': '''Estudio experimental de flujos, turbulencia y modos MHD, y su impacto en confinamiento en los stellarators TJ-II y W7-X'''

'''Reference''': PID2021-125607NB-I00

'''Programme and date''': Proyectos de Generación de Conocimiento Año 2021

'''Programme type (Modalidad de proyecto)''': Proyectos de investigación no orientada

'''Area/subarea (Área temática / subárea)''': Ciencias Físicas / Física y sus aplicaciones

'''Principal Investigators''': [https://orcid.org/0000-0001-6205-2656 Teresa Estrada] and [https://orcid.org/0000-0002-7824-3307 Daniel Carralero]

'''Project type''': Proyecto individual

'''Start-end dates''': 01/01/2022 - 31/12/2024

'''Financing granted (direct costs)''': 160.000,00 €

== Description of the project ==

The main objective of the present proposal is to study a family of instabilities present in the strongly magnetized plasmas required for the development of a practical nuclear fusion reactor, which range from the electrostatic drift turbulence typically dominating transport among thermal populations of confined species, to magneto-hydrodynamic modes destabilized by fast ion populations, such as the Alfvèn Eigenmodes, as well as the potential interactions between them. Finding mechanisms by which these instabilities can be suppressed or controlled in reactor-relevant conditions is critical for the achievement of the high plasma confinement required for an economical exploitation of nuclear fusion. With this aim, we propose the experimental characterization of these instabilities and the plasma conditions driving them, followed by its interpretation under the best available theoretical frameworks. This project can be seen as a continuation and expansion of the previous FIS2017-88892-P grant, in which related research was carried out in the TJ-II and Wendelstein 7-X (W7-X) stellarators, including the commissioning and operation of several relevant diagnostics. From there, our work plan assesses the current state of the research and defines several lines of work such as turbulence stabilization during post-pellet phases, fluctuation and potential asymmetries, flow departure from neoclassical theory, NBI destabilization of AE modes, detection and characterization of zonal flows, etc.

TJ-II is the flagship of the National Laboratory for Fusion (LNF) and part of the Spanish ICTS catalogue. As members of the LNF, the proponents have full access to TJ-II, where the several diagnostics relevant for the study are available. In particular, a steerable Doppler reflectometry (DR) system provides the simultaneous measurement of fluctuations and flows, allowing for very detailed studies of turbulence, critical for the characterization of drift modes. As well, a helical array of Mirnov coils has been recently added to TJ-II, allowing for a detailed study of AEs, including their complex 3D structure in non-axisymmetric devices. W7-X is sited in the Max-Planck-Institut für Plasmaphysik (IPP) in Greifswald. W7X is the largest stellarator in the world and was built to reproduce a number of reactor-relevant features such as optimized magnetic field, high beta operation or actively cooled island divertor. Since 2015, the LNF has collaborated with IPP in the development of a DR system, which has already been successfully operated in previous experimental campaigns. Presently, this system is being refurbished including a number of improvements which will greatly expand the scope of the experimental measurements which can be carried out. As well, a new diagnostic has been included in the proposal: A Charge eXchange Recombination Spectroscopy (CXRS) system, which will complement the investigation of plasma flows carried out by the DR. These diagnostics will ensure access to experimental data in reactor-relevant conditions during the forthcoming OP2.1-OP2.3 campaigns, scheduled for the 2022-2024 period. On top of these purely experimental activities, we outline the data analysis and comparison of physical results to numerical simulations of turbulence (gyrokinetic codes), AE stability (gyrofluid codes), plasma profiles (neoclassical codes) or synthetic DR response to plasma conditions (2D full wave code).

== Main Results ==

This project advanced the experimental and theoretical understanding of plasma turbulence, flows, and magnetohydrodynamic (MHD) activity in the stellarators W7-X and TJ-II through coordinated diagnostic upgrades, systematic experimentation, and integrated modeling.
At W7-X, upgraded Doppler Reflectometer (DR) systems were installed, commissioned, and successfully operated during the OP2 experimental campaigns. Two systems delivered optimal performance, providing high-resolution measurements of turbulence amplitude, perpendicular flows, and long-range correlations, while a third enabled correlation studies despite alignment limitations. A wide range of magnetic configurations—including reduced mirror, low rotational transform, low magnetic shear, and island-chain scenarios—was explored using standardized density and heating power scans. Turbulence levels were found to increase with plasma density and ECH power, while edge turbulence decreased with increasing rotational transform. A clear correlation emerged between reduced edge turbulence, enhanced radial electric field shear, and improved global energy confinement time. Post-pellet enhanced confinement regimes were successfully reproduced, showing turbulence stabilization and increased plasma flow. Dedicated correlation experiments enabled the first direct measurement of zonal flows in a large stellarator, confirming their dependence on density and heating power and validating gyrokinetic predictions. CXRS flow measurements, refined through improved self-calibration, showed significantly better agreement with neoclassical calculations.
In TJ-II, three experimental campaigns ensured full operation of the DR and the helical Mirnov coil array. Dedicated calibration experiments and advanced numerical tools supported reliable magnetic fluctuation analysis. A comprehensive database of NBI-driven Alfvén Eigenmodes was obtained under varying heating and rotational transform conditions. Synthetic magnetic diagnostics and linear MHD simulations improved mode interpretation. While no direct impact of Alfvén activity on turbulence was confirmed, indirect effects linked to injection direction and fast-ion losses were identified. Pellet experiments reproduced enhanced confinement regimes similar to W7-X, though modeling suggests different underlying mechanisms. Overall, the project achieved near-complete fulfillment of its objectives and delivered substantial advances in stellarator turbulence and flow physics.

== Dissemination of project results (peer-reviewed publications and conference presentations) ==

Peer-reviewed publications:

[1] D. Carralero, T. Estrada, E. Maragkoudakis, T. Windisch, J. A. Alonso, J. L. Velasco, O. Ford, M. Jakubowski, S. Lazerson, M. Beurskens, S. Bozhenkov, I. Calvo, H. Damm, G. Fuchert, J.M. García-Regaña, U. Höfel, N. Marushchenko, N. Pablant, E. Sánchez, H.M. Smith, E. Pasch, and T. Stange. Plasma Phys. Control. Fusion 64, 044006 (2022)

[2] E. Ascasíbar, F. Lapayese, A. Soleto, A. Jiménez-Denche, Á. Cappa, P. Pons-Villalonga, A. B. Portas, G. Martín, J.M. Barcala, R. García-Gómez, M. Chamorro, L. Cebrián, R. Antón, L. Bueno, C. Reynoso, V. Guisse, and A. López-Fraguas. Rev. Sci. Instrum. 93, 093508 (2022)

[3] J. A. Alonso, O.P. Ford, L. Vanó, S. Äkäslompolo,  S. Buller, R. McDermott, H. Smith, J. Balzuhn,  C.D. Beidler, M. Beurskens, S. Bozhenkov, K.J. Brunner, I. Calvo, D. Carralero, A. Dinklage, T. Estrada, G. Füchert, J. Geiger, J. Knauer, A. Langenbert, N. Pablant, E. Pasch, P. Zs Poloskei, J.L. Velasco, T. Windisch and the W7-X team. Nuclear Fusion 62, 106005 (2022)

[4] Sunn Pederdsen, I. Abramovic, P. Agostinetti, ..., A. Alonso, …, E. Ascasíbar, …, A. Cappa, …, D. Carralero, …, T. Estrada, et al. Nuclear Fusion 62, 042022 (2022)

[5] C. Hidalgo, E. Ascasíbar, D. Alegre, A. Alonso, ..., A. Cappa, D. Carralero, …, T. Estrada, et al. Nuclear Fusion 62, 042025 (2022)

[6] E. Maragkoudakis, D. Carralero, T. Estrada, T. Windisch, Y. Gao, C. Killer, M. Jakubowski, A. Puig Sitjes, F. Pisano, H. Sándor, M. Vecsei, S. Zoletnik, A. Cappa, and the Wendelstein 7-X team. Nuclear Fusion 63, 026011 (2023)

[7] I. García-Cortés, K. J. McCarthy, T. Estrada, V. Tribaldos, D. Medina-Roque, B. van Milligen, E. Ascasíbar, R. Carrasco, A.A. Chmyga, R. García, J. Hernández-Sánchez, C. Hidalgo, A.S. Kozachek, F. Medina, M. A. Ochando, J. L. de Pablos, N. Panadero, I. Pastor, and TJ-II Team. Phys. Plasmas 30, 072506 (2023)

[8] A. González-Jerez, J.M. García-Regaña, I. Calvo, D. Carralero, T. Estrada, E. Sánchez, M. Barnes, and the W7-X team. Nuclear Fusion 64, 076029 (2024)

[9] O. Grulke, C. Albert, J.A. Alcusón, …, A. Alonso, …, E. Ascasíbar, …, A. Cappa, …, D. Carralero, …, T. Estrada, … Nuclear Fusion 64, 112002 (2024)

[10] A. Alonso, D. Alegre, J. Alonso, …, E. Ascasíbar, …, A. Cappa, D. Carralero, …, T. Estrada, …, J.M. Fontdecaba, …, J. Martínez, …, A. Pereira, …, P. Pons, A.B. Portas, …, … J. de la Riva, et al., Nuclear Fusion 64, 112018 (2024)

[11] P. Pons-Villalonga, Á. Cappa, J. Martínez-Fernández, O. S. Kozachok, E. Ascasíbar. Review of Scientific Instruments 96 063502 (2025)

[12] D. Carralero, T. Estrada, J M García-Regaña, E Sánchez, T. Windisch, A. Alonso, E. Maragkoudakis, C Brandt, K J Brunner et al. Physical Review Research ,7, L022009 (2025).

[13] J. de la Riva Villén, J A Alonso, O P Ford, T Romba, E Maragkoudakis, D Carralero, T Estrada, T Windisch, J L Velasco, H M Smith, D Gradic, P Poloskei and the W7-X Team. Plasma Phys. Control. Fusion 68 015015 (2026).

Conference presentations:

[1] D. Carralero et al., (Invited talk)
“Recent turbulence investigations in the TJ-II and W7-X stellarators: experimental characterization and 3D code-based interpretation”, 23rd International Stellarator and Helliotron Workshop (ISHW), Warsaw, Poland, June 2022.

[2] A. Cappa et al., (Invited talk)
“Linear Stability Analysis of TJ-II stellarator NBI-driven Alfvén Eigenmodes in ECRH and ECCD experiments”, 23rd International Stellarator and Helliotron Workshop (ISHW), Warsaw, Poland, June 2022.

[3] P. Pons et al. (Poster)
“New in-vessel helical arrays of magnetic coils in TJ-II, calibration and preliminary results”, 23rd International Stellarator and Helliotron Workshop (ISHW), Warsaw, Poland, June 2022.

[4] E. Maragkoudakis et al.(Poster)
“On the SOL radial electric field, divertor heat fluxes and plasma edge turbulence of W7-X”, 23rd International Stellarator and Helliotron Workshop (ISHW), Warsaw, Poland, June 2022.

[5] T. Estrada, et al. (Invited talk)
“Radial electric fields, turbulence and transport studies in W7-X and TJ-II”, 48th EPS Conference on Plasma Physics, June 27 - July 1, on-line conference (2022)

[6] T. Estrada, et al. (Oral)
“Effect of internal magnetic islands on turbulence and flows in W7-X and TJ-II”, 15th International Reflectometry Workshop IRW15, ITER, St Paul Lez Durance Cedex, France (2022)

[7] E. Maragkoudakis, et al. (Oral)
“Use of the field line tracing code for the interpretation of Doppler reflectometry measurements in W7-X”, 15th International Reflectometry Workshop IRW15, ITER, St Paul Lez Durance Cedex, France (2022)

[8] D.Carralero and C. Killer (Oral)
“Task Force-III: Wendelstein 7-X optimization” OP2.1 Program Planning Workshop, IPP Greifswald, September, 2022

[9] D.Carralero and M. Nunami (Oral)
“Core transport in a stellarator reactor. Learning from present-day experiments and main questions ahead”,
23rd Coordinated Working Group Meeting, Kyoto, Japan, June, 2023

[10] P. Pons et al., (Poster)
“Measurements of spatial periodicity and radial structure of NBI-driven Alfvén Eigenmodes in the TJ-II stellarator”, 49th EPS conference on Plasma Physics, Bordeaux, France, July 2023.

[11] J. de la Riva et al. (Poster)
“Characteristic profiles of radial electric field and parallel velocity obtained in W7-X using charge exchange recombination spectroscopy”, 49th EPS conference on Plasma Physics, Bordeaux, France, July 2023.

[12] A. Cappa et al., (Poster)
“Fast ion physics in the TJ-II stellarator: experiments and model validation activities”
29th IAEA Fusion Energy Conference (IAEA-FEC), London, October 2023.

[13] E. Maragkoudakis, D. Carralero, T. Estrada, T. Windisch et al (Oral).
“Characterization of Doppler Reflectometry profiles for various Wendelstein 7-X scenarios” 16th International Reflectometry Workshop, Greifswald, Germany, May 2024.

[14] D. Carralero, T. Estrada, J. M. García-Regaña, E. Sánchez et al. (Invited)
“First experimental observation of zonal flows in the optimized stellarator Wendelstein 7-X” 50th EPS Conference on Plasma Physics, Salamanca, Spain, July 2024

[15] T. Estrada, Á. Cappa, ..., J. de la Riva et al (Invited).
“Impact of radial electric field, turbulence and impurity transport on plasma performance in co- and counter-NBI heating scenarios in TJ-II”, 24th International Stellarator and Heliotron Workshop (ISHW), Hiroshima, Japan, September 2024.

[16] D. Carralero, T. Estrada, J. M. García-Regaña, E. Sánchez et al (Invited).
“First experimental observation of zonal flows in the optimized stellarator Wendelstein 7-X” 24th International Stellarator and Heliotron Workshop, Hiroshima, Japan, September 2024.

[17] P. Pons et al, Characterization of the spatial structure of NBI driven shear Alfven waves in the TJ-II stellarator. 18th Technical Meeting on Energetic Particles (TMEP2025), Seville, Spain, March 2025.

[18] D. Carralero, on behalf of the W7-X team (invited)
“Machine report: W7-X Core Transport after OP2.3” 25th Coordinated Working Group Meeting, Princeton, USA, June, 2025.

[19] S. Vaz Mendez, ...,Á. Cappa, P. Pons villalonga, et al. (Poster)
“Discovering Alfvén Mode Excitation by ITG Turbulence”, 51st EPS conference on Plasma Physics, Vilnius, Lithuania, July 2025.

[20] Á. Cappa, P. Pons villalonga et al (Oral),
“Spatial structure of NBI-driven shear Alfvén waves in the TJ-II stellarator: modeling vs. experimental results” 51st EPS conference on Plasma Physics, Vilnius, Lithuania, July 2025.

[21] J. de la Riva et al. (Oral)
“Systematic study of CXRS ion flow measurements in the W7-X stellarator towards a validation of neoclassical theory”, 51th EPS conference on Plasma Physics, Vilnius, Lithuania, July 2025.

[22] J. M. García-Regaña, J. A. Alonso, …, E. Ascasíbar1, …, A. Cappa, D. Carralero, et al. (Overview)
“Transport in high-performance plasmas of the TJ-II stellarator: from first-principles simulations to experimental validation”, 30th IAEA Fusion Energy Conference (FEC2025), Chendu, China, October, 2025

<references />


<hr>
[[LNF:Nationally Funded Projects|Back to list of nationally funded projects]]

[[Category:LNF Nationally Funded Projects - finished]]

LNF: (2022-2024) Estudio experimental de flujos, turbulencia y modos MHD, y su impacto en confinamiento en los stellarators TJ-II y W7-X

2026-02-26T16:52:01Z

Teresa.estrada:

== LNF - Nationally funded project ==

'''Title''': '''Estudio experimental de flujos, turbulencia y modos MHD, y su impacto en confinamiento en los stellarators TJ-II y W7-X'''

'''Reference''': PID2021-125607NB-I00

'''Programme and date''': Proyectos de Generación de Conocimiento Año 2021

'''Programme type (Modalidad de proyecto)''': Proyectos de investigación no orientada

'''Area/subarea (Área temática / subárea)''': Ciencias Físicas / Física y sus aplicaciones

'''Principal Investigators''': [https://orcid.org/0000-0001-6205-2656 Teresa Estrada] and [https://orcid.org/0000-0002-7824-3307 Daniel Carralero]

'''Project type''': Proyecto individual

'''Start-end dates''': 01/01/2022 - 31/12/2024

'''Financing granted (direct costs)''': 160.000,00 €

== Description of the project ==

The main objective of the present proposal is to study a family of instabilities present in the strongly magnetized plasmas required for the development of a practical nuclear fusion reactor, which range from the electrostatic drift turbulence typically dominating transport among thermal populations of confined species, to magneto-hydrodynamic modes destabilized by fast ion populations, such as the Alfvèn Eigenmodes, as well as the potential interactions between them. Finding mechanisms by which these instabilities can be suppressed or controlled in reactor-relevant conditions is critical for the achievement of the high plasma confinement required for an economical exploitation of nuclear fusion. With this aim, we propose the experimental characterization of these instabilities and the plasma conditions driving them, followed by its interpretation under the best available theoretical frameworks. This project can be seen as a continuation and expansion of the previous FIS2017-88892-P grant, in which related research was carried out in the TJ-II and Wendelstein 7-X (W7-X) stellarators, including the commissioning and operation of several relevant diagnostics. From there, our work plan assesses the current state of the research and defines several lines of work such as turbulence stabilization during post-pellet phases, fluctuation and potential asymmetries, flow departure from neoclassical theory, NBI destabilization of AE modes, detection and characterization of zonal flows, etc.

TJ-II is the flagship of the National Laboratory for Fusion (LNF) and part of the Spanish ICTS catalogue. As members of the LNF, the proponents have full access to TJ-II, where the several diagnostics relevant for the study are available. In particular, a steerable Doppler reflectometry (DR) system provides the simultaneous measurement of fluctuations and flows, allowing for very detailed studies of turbulence, critical for the characterization of drift modes. As well, a helical array of Mirnov coils has been recently added to TJ-II, allowing for a detailed study of AEs, including their complex 3D structure in non-axisymmetric devices. W7-X is sited in the Max-Planck-Institut für Plasmaphysik (IPP) in Greifswald. W7X is the largest stellarator in the world and was built to reproduce a number of reactor-relevant features such as optimized magnetic field, high beta operation or actively cooled island divertor. Since 2015, the LNF has collaborated with IPP in the development of a DR system, which has already been successfully operated in previous experimental campaigns. Presently, this system is being refurbished including a number of improvements which will greatly expand the scope of the experimental measurements which can be carried out. As well, a new diagnostic has been included in the proposal: A Charge eXchange Recombination Spectroscopy (CXRS) system, which will complement the investigation of plasma flows carried out by the DR. These diagnostics will ensure access to experimental data in reactor-relevant conditions during the forthcoming OP2.1-OP2.3 campaigns, scheduled for the 2022-2024 period. On top of these purely experimental activities, we outline the data analysis and comparison of physical results to numerical simulations of turbulence (gyrokinetic codes), AE stability (gyrofluid codes), plasma profiles (neoclassical codes) or synthetic DR response to plasma conditions (2D full wave code).

== Main Results ==

This project advanced the experimental and theoretical understanding of plasma turbulence, flows, and magnetohydrodynamic (MHD) activity in the stellarators W7-X and TJ-II through coordinated diagnostic upgrades, systematic experimentation, and integrated modeling.
At W7-X, upgraded Doppler Reflectometer (DR) systems were installed, commissioned, and successfully operated during the OP2 experimental campaigns. Two systems delivered optimal performance, providing high-resolution measurements of turbulence amplitude, perpendicular flows, and long-range correlations, while a third enabled correlation studies despite alignment limitations. A wide range of magnetic configurations—including reduced mirror, low rotational transform, low magnetic shear, and island-chain scenarios—was explored using standardized density and heating power scans. Turbulence levels were found to increase with plasma density and ECH power, while edge turbulence decreased with increasing rotational transform. A clear correlation emerged between reduced edge turbulence, enhanced radial electric field shear, and improved global energy confinement time. Post-pellet enhanced confinement regimes were successfully reproduced, showing turbulence stabilization and increased plasma flow. Dedicated correlation experiments enabled the first direct measurement of zonal flows in a large stellarator, confirming their dependence on density and heating power and validating gyrokinetic predictions. CXRS flow measurements, refined through improved self-calibration, showed significantly better agreement with neoclassical calculations.
In TJ-II, three experimental campaigns ensured full operation of the DR and the helical Mirnov coil array. Dedicated calibration experiments and advanced numerical tools supported reliable magnetic fluctuation analysis. A comprehensive database of NBI-driven Alfvén Eigenmodes was obtained under varying heating and rotational transform conditions. Synthetic magnetic diagnostics and linear MHD simulations improved mode interpretation. While no direct impact of Alfvén activity on turbulence was confirmed, indirect effects linked to injection direction and fast-ion losses were identified. Pellet experiments reproduced enhanced confinement regimes similar to W7-X, though modeling suggests different underlying mechanisms. Overall, the project achieved near-complete fulfillment of its objectives and delivered substantial advances in stellarator turbulence and flow physics.

== Dissemination of project results (peer-reviewed publications and conference presentations) ==

Peer-reviewed publications:

[1] D. Carralero, T. Estrada, E. Maragkoudakis, T. Windisch, J. A. Alonso, J. L. Velasco, O. Ford, M. Jakubowski, S. Lazerson, M. Beurskens, S. Bozhenkov, I. Calvo, H. Damm, G. Fuchert, J.M. García-Regaña, U. Höfel, N. Marushchenko, N. Pablant, E. Sánchez, H.M. Smith, E. Pasch, and T. Stange. Plasma Phys. Control. Fusion 64, 044006 (2022)

[2] E. Ascasíbar, F. Lapayese, A. Soleto, A. Jiménez-Denche, Á. Cappa, P. Pons-Villalonga, A. B. Portas, G. Martín, J.M. Barcala, R. García-Gómez, M. Chamorro, L. Cebrián, R. Antón, L. Bueno, C. Reynoso, V. Guisse, and A. López-Fraguas. Rev. Sci. Instrum. 93, 093508 (2022)

[3] J. A. Alonso, O.P. Ford, L. Vanó, S. Äkäslompolo,  S. Buller, R. McDermott, H. Smith, J. Balzuhn,  C.D. Beidler, M. Beurskens, S. Bozhenkov, K.J. Brunner, I. Calvo, D. Carralero, A. Dinklage, T. Estrada, G. Füchert, J. Geiger, J. Knauer, A. Langenbert, N. Pablant, E. Pasch, P. Zs Poloskei, J.L. Velasco, T. Windisch and the W7-X team. Nuclear Fusion 62, 106005 (2022)

[4] Sunn Pederdsen, I. Abramovic, P. Agostinetti, ..., A. Alonso, …, E. Ascasíbar, …, A. Cappa, …, D. Carralero, …, T. Estrada, et al. Nuclear Fusion 62, 042022 (2022)

[5] C. Hidalgo, E. Ascasíbar, D. Alegre, A. Alonso, ..., A. Cappa, D. Carralero, …, T. Estrada, et al. Nuclear Fusion 62, 042025 (2022)

[6] E. Maragkoudakis, D. Carralero, T. Estrada, T. Windisch, Y. Gao, C. Killer, M. Jakubowski, A. Puig Sitjes, F. Pisano, H. Sándor, M. Vecsei, S. Zoletnik, A. Cappa, and the Wendelstein 7-X team. Nuclear Fusion 63, 026011 (2023)

[7] I. García-Cortés, K. J. McCarthy, T. Estrada, V. Tribaldos, D. Medina-Roque, B. van Milligen, E. Ascasíbar, R. Carrasco, A.A. Chmyga, R. García, J. Hernández-Sánchez, C. Hidalgo, A.S. Kozachek, F. Medina, M. A. Ochando, J. L. de Pablos, N. Panadero, I. Pastor, and TJ-II Team. Phys. Plasmas 30, 072506 (2023)

[8] A. González-Jerez, J.M. García-Regaña, I. Calvo, D. Carralero, T. Estrada, E. Sánchez, M. Barnes, and the W7-X team. Nuclear Fusion 64, 076029 (2024)

[9] O. Grulke, C. Albert, J.A. Alcusón, …, A. Alonso, …, E. Ascasíbar, …, A. Cappa, …, D. Carralero, …, T. Estrada, … Nuclear Fusion 64, 112002 (2024)

[10] A. Alonso, D. Alegre, J. Alonso, …, E. Ascasíbar, …, A. Cappa, D. Carralero, …, T. Estrada, …, J.M. Fontdecaba, …, J. Martínez, …, A. Pereira, …, P. Pons, A.B. Portas, …, … J. de la Riva, et al., Nuclear Fusion 64, 112018 (2024)

[11] P. Pons-Villalonga, Á. Cappa, J. Martínez-Fernández, O. S. Kozachok, E. Ascasíbar. Review of Scientific Instruments 96 063502 (2025)

[12] D. Carralero, T. Estrada, J M García-Regaña, E Sánchez, T. Windisch, A. Alonso, E. Maragkoudakis, C Brandt, K J Brunner et al. Physical Review Research ,7, L022009 (2025).

[13] J. de la Riva Villén, J A Alonso, O P Ford, T Romba, E Maragkoudakis, D Carralero, T Estrada, T Windisch, J L Velasco, H M Smith, D Gradic, P Poloskei and the W7-X Team. Plasma Phys. Control. Fusion 68 015015 (2026).

Conference presentations:

[1] D. Carralero et al., (Invited talk)
“Recent turbulence investigations in the TJ-II and W7-X stellarators: experimental characterization and 3D code-based interpretation”, 23rd International Stellarator and Helliotron Workshop (ISHW), Warsaw, Poland, June 2022.

[2] A. Cappa et al., (Invited talk)
“Linear Stability Analysis of TJ-II stellarator NBI-driven Alfvén Eigenmodes in ECRH and ECCD experiments”, 23rd International Stellarator and Helliotron Workshop (ISHW), Warsaw, Poland, June 2022.

[3] P. Pons et al. (Poster)
“New in-vessel helical arrays of magnetic coils in TJ-II, calibration and preliminary results”, 23rd International Stellarator and Helliotron Workshop (ISHW), Warsaw, Poland, June 2022.

[4] E. Maragkoudakis et al.(Poster)
“On the SOL radial electric field, divertor heat fluxes and plasma edge turbulence of W7-X”, 23rd International Stellarator and Helliotron Workshop (ISHW), Warsaw, Poland, June 2022.

[5] T. Estrada, et al. (Invited talk)
“Radial electric fields, turbulence and transport studies in W7-X and TJ-II”, 48th EPS Conference on Plasma Physics, June 27 - July 1, on-line conference (2022)

[6] T. Estrada, et al. (Oral)
“Effect of internal magnetic islands on turbulence and flows in W7-X and TJ-II”, 15th International Reflectometry Workshop IRW15, ITER, St Paul Lez Durance Cedex, France (2022)

[7] E. Maragkoudakis, et al. (Oral)
“Use of the field line tracing code for the interpretation of Doppler reflectometry measurements in W7-X”, 15th International Reflectometry Workshop IRW15, ITER, St Paul Lez Durance Cedex, France (2022)

[8] D.Carralero and C. Killer (Oral)
“Task Force-III: Wendelstein 7-X optimization” OP2.1 Program Planning Workshop, IPP Greifswald, September, 2022

[9] D.Carralero and M. Nunami (Oral)
“Core transport in a stellarator reactor. Learning from present-day experiments and main questions ahead”,
23rd Coordinated Working Group Meeting, Kyoto, Japan, June, 2023

[10] P. Pons et al., (Poster)
“Measurements of spatial periodicity and radial structure of NBI-driven Alfvén Eigenmodes in the TJ-II stellarator”, 49th EPS conference on Plasma Physics, Bordeaux, France, July 2023.

[11] J. de la Riva et al. (Poster)
“Characteristic profiles of radial electric field and parallel velocity obtained in W7-X using charge exchange recombination spectroscopy”, 49th EPS conference on Plasma Physics, Bordeaux, France, July 2023.

[12] A. Cappa et al., (Poster)
“Fast ion physics in the TJ-II stellarator: experiments and model validation activities”
29th IAEA Fusion Energy Conference (IAEA-FEC), London, October 2023.

[13] E. Maragkoudakis, D. Carralero, T. Estrada, T. Windisch et al (Oral).
“Characterization of Doppler Reflectometry profiles for various Wendelstein 7-X scenarios” 16th International Reflectometry Workshop, Greifswald, Germany, May 2024.

[14] D. Carralero, T. Estrada, J. M. García-Regaña, E. Sánchez et al. (Invited)
“First experimental observation of zonal flows in the optimized stellarator Wendelstein 7-X” 50th EPS Conference on Plasma Physics, Salamanca, Spain, July 2024

[15] T. Estrada, Á. Cappa, ..., J. de la Riva et al (Invited).
“Impact of radial electric field, turbulence and impurity transport on plasma performance in co- and counter-NBI heating scenarios in TJ-II”, 24th International Stellarator and Heliotron Workshop (ISHW), Hiroshima, Japan, September 2024.

[16] D. Carralero, T. Estrada, J. M. García-Regaña, E. Sánchez et al (Invited).
“First experimental observation of zonal flows in the optimized stellarator Wendelstein 7-X” 24th International Stellarator and Heliotron Workshop, Hiroshima, Japan, September 2024.

[17] P. Pons et al,
“Characterization of the spatial structure of NBI-driven shear Alfvén waves in the TJ-II Stellarator”, 18th Technical Meeting on Energetic Particles (TMEP2025), Seville, Spain, March 2025.

[18] D. Carralero, on behalf of the W7-X team (invited)
“Machine report: W7-X Core Transport after OP2.3” 25th Coordinated Working Group Meeting, Princeton, USA, June, 2025.

[19] S. Vaz Mendez, ...,Á. Cappa, P. Pons villalonga, et al. (Poster)
“Discovering Alfvén Mode Excitation by ITG Turbulence”, 51st EPS conference on Plasma Physics, Vilnius, Lithuania, July 2025.

[20] Á. Cappa, P. Pons villalonga et al (Oral),
“Spatial structure of NBI-driven shear Alfvén waves in the TJ-II stellarator: modeling vs. experimental results” 51st EPS conference on Plasma Physics, Vilnius, Lithuania, July 2025.

[21] J. de la Riva et al. (Oral)
“Systematic study of CXRS ion flow measurements in the W7-X stellarator towards a validation of neoclassical theory”, 51th EPS conference on Plasma Physics, Vilnius, Lithuania, July 2025.

[22] J. M. García-Regaña, J. A. Alonso, …, E. Ascasíbar1, …, A. Cappa, D. Carralero, et al. (Overview)
“Transport in high-performance plasmas of the TJ-II stellarator: from first-principles simulations to experimental validation”, 30th IAEA Fusion Energy Conference (FEC2025), Chendu, China, October, 2025

<references />


<hr>
[[LNF:Nationally Funded Projects|Back to list of nationally funded projects]]

[[Category:LNF Nationally Funded Projects - finished]]

LNF: (2022-2024) Estudio experimental de flujos, turbulencia y modos MHD, y su impacto en confinamiento en los stellarators TJ-II y W7-X

2026-02-26T16:50:44Z

Teresa.estrada:

== LNF - Nationally funded project ==

'''Title''': '''Estudio experimental de flujos, turbulencia y modos MHD, y su impacto en confinamiento en los stellarators TJ-II y W7-X'''

'''Reference''': PID2021-125607NB-I00

'''Programme and date''': Proyectos de Generación de Conocimiento Año 2021

'''Programme type (Modalidad de proyecto)''': Proyectos de investigación no orientada

'''Area/subarea (Área temática / subárea)''': Ciencias Físicas / Física y sus aplicaciones

'''Principal Investigators''': [https://orcid.org/0000-0001-6205-2656 Teresa Estrada] and [https://orcid.org/0000-0002-7824-3307 Daniel Carralero]

'''Project type''': Proyecto individual

'''Start-end dates''': 01/01/2022 - 31/12/2024

'''Financing granted (direct costs)''': 160.000,00 €

== Description of the project ==

The main objective of the present proposal is to study a family of instabilities present in the strongly magnetized plasmas required for the development of a practical nuclear fusion reactor, which range from the electrostatic drift turbulence typically dominating transport among thermal populations of confined species, to magneto-hydrodynamic modes destabilized by fast ion populations, such as the Alfvèn Eigenmodes, as well as the potential interactions between them. Finding mechanisms by which these instabilities can be suppressed or controlled in reactor-relevant conditions is critical for the achievement of the high plasma confinement required for an economical exploitation of nuclear fusion. With this aim, we propose the experimental characterization of these instabilities and the plasma conditions driving them, followed by its interpretation under the best available theoretical frameworks. This project can be seen as a continuation and expansion of the previous FIS2017-88892-P grant, in which related research was carried out in the TJ-II and Wendelstein 7-X (W7-X) stellarators, including the commissioning and operation of several relevant diagnostics. From there, our work plan assesses the current state of the research and defines several lines of work such as turbulence stabilization during post-pellet phases, fluctuation and potential asymmetries, flow departure from neoclassical theory, NBI destabilization of AE modes, detection and characterization of zonal flows, etc.

TJ-II is the flagship of the National Laboratory for Fusion (LNF) and part of the Spanish ICTS catalogue. As members of the LNF, the proponents have full access to TJ-II, where the several diagnostics relevant for the study are available. In particular, a steerable Doppler reflectometry (DR) system provides the simultaneous measurement of fluctuations and flows, allowing for very detailed studies of turbulence, critical for the characterization of drift modes. As well, a helical array of Mirnov coils has been recently added to TJ-II, allowing for a detailed study of AEs, including their complex 3D structure in non-axisymmetric devices. W7-X is sited in the Max-Planck-Institut für Plasmaphysik (IPP) in Greifswald. W7X is the largest stellarator in the world and was built to reproduce a number of reactor-relevant features such as optimized magnetic field, high beta operation or actively cooled island divertor. Since 2015, the LNF has collaborated with IPP in the development of a DR system, which has already been successfully operated in previous experimental campaigns. Presently, this system is being refurbished including a number of improvements which will greatly expand the scope of the experimental measurements which can be carried out. As well, a new diagnostic has been included in the proposal: A Charge eXchange Recombination Spectroscopy (CXRS) system, which will complement the investigation of plasma flows carried out by the DR. These diagnostics will ensure access to experimental data in reactor-relevant conditions during the forthcoming OP2.1-OP2.3 campaigns, scheduled for the 2022-2024 period. On top of these purely experimental activities, we outline the data analysis and comparison of physical results to numerical simulations of turbulence (gyrokinetic codes), AE stability (gyrofluid codes), plasma profiles (neoclassical codes) or synthetic DR response to plasma conditions (2D full wave code).

== Main Results ==

This project advanced the experimental and theoretical understanding of plasma turbulence, flows, and magnetohydrodynamic (MHD) activity in the stellarators W7-X and TJ-II through coordinated diagnostic upgrades, systematic experimentation, and integrated modeling.
At W7-X, upgraded Doppler Reflectometer (DR) systems were installed, commissioned, and successfully operated during the OP2 experimental campaigns. Two systems delivered optimal performance, providing high-resolution measurements of turbulence amplitude, perpendicular flows, and long-range correlations, while a third enabled correlation studies despite alignment limitations. A wide range of magnetic configurations—including reduced mirror, low rotational transform, low magnetic shear, and island-chain scenarios—was explored using standardized density and heating power scans. Turbulence levels were found to increase with plasma density and ECH power, while edge turbulence decreased with increasing rotational transform. A clear correlation emerged between reduced edge turbulence, enhanced radial electric field shear, and improved global energy confinement time. Post-pellet enhanced confinement regimes were successfully reproduced, showing turbulence stabilization and increased plasma flow. Dedicated correlation experiments enabled the first direct measurement of zonal flows in a large stellarator, confirming their dependence on density and heating power and validating gyrokinetic predictions. CXRS flow measurements, refined through improved self-calibration, showed significantly better agreement with neoclassical calculations.
In TJ-II, three experimental campaigns ensured full operation of the DR and the helical Mirnov coil array. Dedicated calibration experiments and advanced numerical tools supported reliable magnetic fluctuation analysis. A comprehensive database of NBI-driven Alfvén Eigenmodes was obtained under varying heating and rotational transform conditions. Synthetic magnetic diagnostics and linear MHD simulations improved mode interpretation. While no direct impact of Alfvén activity on turbulence was confirmed, indirect effects linked to injection direction and fast-ion losses were identified. Pellet experiments reproduced enhanced confinement regimes similar to W7-X, though modeling suggests different underlying mechanisms. Overall, the project achieved near-complete fulfillment of its objectives and delivered substantial advances in stellarator turbulence and flow physics.

== Dissemination of project results (peer-reviewed publications and conference presentations) ==

Peer-reviewed publications:

[1] D. Carralero, T. Estrada, E. Maragkoudakis, T. Windisch, J. A. Alonso, J. L. Velasco, O. Ford, M. Jakubowski, S. Lazerson, M. Beurskens, S. Bozhenkov, I. Calvo, H. Damm, G. Fuchert, J.M. García-Regaña, U. Höfel, N. Marushchenko, N. Pablant, E. Sánchez, H.M. Smith, E. Pasch, and T. Stange. Plasma Phys. Control. Fusion 64, 044006 (2022)

[2] E. Ascasíbar, F. Lapayese, A. Soleto, A. Jiménez-Denche, Á. Cappa, P. Pons-Villalonga, A. B. Portas, G. Martín, J.M. Barcala, R. García-Gómez, M. Chamorro, L. Cebrián, R. Antón, L. Bueno, C. Reynoso, V. Guisse, and A. López-Fraguas. Rev. Sci. Instrum. 93, 093508 (2022)

[3] J. A. Alonso, O.P. Ford, L. Vanó, S. Äkäslompolo,  S. Buller, R. McDermott, H. Smith, J. Balzuhn,  C.D. Beidler, M. Beurskens, S. Bozhenkov, K.J. Brunner, I. Calvo, D. Carralero, A. Dinklage, T. Estrada, G. Füchert, J. Geiger, J. Knauer, A. Langenbert, N. Pablant, E. Pasch, P. Zs Poloskei, J.L. Velasco, T. Windisch and the W7-X team. Nuclear Fusion 62, 106005 (2022)

[4] Sunn Pederdsen, I. Abramovic, P. Agostinetti, ..., A. Alonso, …, E. Ascasíbar, …, A. Cappa, …, D. Carralero, …, T. Estrada, et al. Nuclear Fusion 62, 042022 (2022)

[5] C. Hidalgo, E. Ascasíbar, D. Alegre, A. Alonso, ..., A. Cappa, D. Carralero, …, T. Estrada, et al. Nuclear Fusion 62, 042025 (2022)

[6] E. Maragkoudakis, D. Carralero, T. Estrada, T. Windisch, Y. Gao, C. Killer, M. Jakubowski, A. Puig Sitjes, F. Pisano, H. Sándor, M. Vecsei, S. Zoletnik, A. Cappa, and the Wendelstein 7-X team. Nuclear Fusion 63, 026011 (2023)

[7] I. García-Cortés, K. J. McCarthy, T. Estrada, V. Tribaldos, D. Medina-Roque, B. van Milligen, E. Ascasíbar, R. Carrasco, A.A. Chmyga, R. García, J. Hernández-Sánchez, C. Hidalgo, A.S. Kozachek, F. Medina, M. A. Ochando, J. L. de Pablos, N. Panadero, I. Pastor, and TJ-II Team. Phys. Plasmas 30, 072506 (2023)

[8] A. González-Jerez, J.M. García-Regaña, I. Calvo, D. Carralero, T. Estrada, E. Sánchez, M. Barnes, and the W7-X team. Nuclear Fusion 64, 076029 (2024)

[9] O. Grulke, C. Albert, J.A. Alcusón, …, A. Alonso, …, E. Ascasíbar, …, A. Cappa, …, D. Carralero, …, T. Estrada, … Nuclear Fusion 64, 112002 (2024)

[10] A. Alonso, D. Alegre, J. Alonso, …, E. Ascasíbar, …, A. Cappa, D. Carralero, …, T. Estrada, …, J.M. Fontdecaba, …, J. Martínez, …, A. Pereira, …, P. Pons, A.B. Portas, …, … J. de la Riva, et al., Nuclear Fusion 64, 112018 (2024)

[11] P. Pons-Villalonga, Á. Cappa, J. Martínez-Fernández, O. S. Kozachok, E. Ascasíbar. Review of Scientific Instruments 96 063502 (2025)

[12] D. Carralero, T. Estrada, J M García-Regaña, E Sánchez, T. Windisch, A. Alonso, E. Maragkoudakis, C Brandt, K J Brunner et al. Physical Review Research ,7, L022009 (2025).

[13] J. de la Riva Villén, J A Alonso, O P Ford, T Romba, E Maragkoudakis, D Carralero, T Estrada, T Windisch, J L Velasco, H M Smith, D Gradic, P Poloskei and the W7-X Team. Plasma Phys. Control. Fusion 68 015015 (2026).

Conference presentations:

[1] D. Carralero et al., (Invited talk)
“Recent turbulence investigations in the TJ-II and W7-X stellarators: experimental characterization and 3D code-based interpretation”, 23rd International Stellarator and Helliotron Workshop (ISHW), Warsaw, Poland, June 2022.

[2] A. Cappa et al., (Invited talk)
“Linear Stability Analysis of TJ-II stellarator NBI-driven Alfvén Eigenmodes in ECRH and ECCD experiments”, 23rd International Stellarator and Helliotron Workshop (ISHW), Warsaw, Poland, June 2022.

[3] P. Pons et al. (Poster)
“New in-vessel helical arrays of magnetic coils in TJ-II, calibration and preliminary results”, 23rd International Stellarator and Helliotron Workshop (ISHW), Warsaw, Poland, June 2022.

[4] E. Maragkoudakis et al.(Poster)
“On the SOL radial electric field, divertor heat fluxes and plasma edge turbulence of W7-X”, 23rd International Stellarator and Helliotron Workshop (ISHW), Warsaw, Poland, June 2022.

[5] T. Estrada, et al. (Invited talk)
“Radial electric fields, turbulence and transport studies in W7-X and TJ-II”, 48th EPS Conference on Plasma Physics, June 27 - July 1, on-line conference (2022)

[6] T. Estrada, et al. (Oral)
“Effect of internal magnetic islands on turbulence and flows in W7-X and TJ-II”, 15th International Reflectometry Workshop IRW15, ITER, St Paul Lez Durance Cedex, France (2022)

[7] E. Maragkoudakis, et al. (Oral)
“Use of the field line tracing code for the interpretation of Doppler reflectometry measurements in W7-X”, 15th International Reflectometry Workshop IRW15, ITER, St Paul Lez Durance Cedex, France (2022)

[8] D.Carralero and C. Killer (Oral)
“Task Force-III: Wendelstein 7-X optimization” OP2.1 Program Planning Workshop, IPP Greifswald, September, 2022

[9] D.Carralero and M. Nunami (Oral)
“Core transport in a stellarator reactor. Learning from present-day experiments and main questions ahead”,
23rd Coordinated Working Group Meeting, Kyoto, Japan, June, 2023

[10] P. Pons et al., (Poster)
“Measurements of spatial periodicity and radial structure of NBI-driven Alfvén Eigenmodes in the TJ-II stellarator”, 49th EPS conference on Plasma Physics, Bordeaux, France, July 2023.

[11] J. de la Riva et al. (Poster)
“Characteristic profiles of radial electric field and parallel velocity obtained in W7-X using charge exchange recombination spectroscopy”, 49th EPS conference on Plasma Physics, Bordeaux, France, July 2023.

[12] A. Cappa et al., (Poster)
“Fast ion physics in the TJ-II stellarator: experiments and model validation activities”
29th IAEA Fusion Energy Conference (IAEA-FEC), London, October 2023.

[13] E. Maragkoudakis, D. Carralero, T. Estrada, T. Windisch et al (Oral).
“Characterization of Doppler Reflectometry profiles for various Wendelstein 7-X scenarios” 16th International Reflectometry Workshop, Greifswald, Germany, May 2024.

[14] D. Carralero, T. Estrada, J. M. García-Regaña, E. Sánchez et al. (Invited)
“First experimental observation of zonal flows in the optimized stellarator Wendelstein 7-X” 50th EPS Conference on Plasma Physics, Salamanca, Spain, July 2024

[15] T. Estrada, Á. Cappa, ..., J. de la Riva et al (Invited).
“Impact of radial electric field, turbulence and impurity transport on plasma performance in co- and counter-NBI heating scenarios in TJ-II”, 24th International Stellarator and Heliotron Workshop (ISHW), Hiroshima, Japan, September 2024.

[16] D. Carralero, T. Estrada, J. M. García-Regaña, E. Sánchez et al (Invited).
“First experimental observation of zonal flows in the optimized stellarator Wendelstein 7-X” 24th International Stellarator and Heliotron Workshop, Hiroshima, Japan, September 2024.

[17] P. Pons et al,
“Characterization of the spatial structure of NBI-driven shear Alfvén waves in the TJ-II Stellarator”, 18th Technical Meeting on Energetic Particles (TMEP2025), Seville, Spain, March 2025.

[18] D. Carralero, on behalf of the W7-X team (invited)
“Machine report: W7-X Core Transport after OP2.3” 25th Coordinated Working Group Meeting, Princeton, USA, June, 2025.

[19] S. Vaz Mendez, ...,Á. Cappa, P. Pons villalonga, et al. (Poster)
“Discovering Alfvén Mode Excitation by ITG Turbulence”, 51st EPS conference on Plasma Physics, Vilnius, Lithuania, July 2025.

[20] Á. Cappa, P. Pons villalonga et al (Oral),
“Spatial structure of NBI-driven shear Alfvén waves in the TJ-II stellarator: modeling vs. experimental results” 51st EPS conference on Plasma Physics, Vilnius, Lithuania, July 2025.

[21] J. de la Riva et al. (Oral)
“Systematic study of CXRS ion flow measurements in the W7-X stellarator towards a validation of neoclassical theory”, 51th EPS conference on Plasma Physics, Vilnius, Lithuania, July 2025.

[22] J. M. García-Regaña, J. A. Alonso, …, E. Ascasíbar1, …, A. Cappa, D. Carralero, et al. (Overview)
“Transport in high-performance plasmas of the TJ-II stellarator: from first-principles simulations to experimental validation”, 30th IAEA Fusion Energy Conference (FEC2025), Chendu, China, October, 2025

<references />


<hr>
[[LNF:Nationally Funded Projects|Back to list of nationally funded projects]]

[[Category:LNF Nationally Funded Projects - finished]]

LNF: (2022-2024) Estudio experimental de flujos, turbulencia y modos MHD, y su impacto en confinamiento en los stellarators TJ-II y W7-X

2026-02-26T16:49:18Z

Teresa.estrada:

LNF: (2022-2024) Estudio experimental de flujos, turbulencia y modos MHD, y su impacto en confinamiento en los stellarators TJ-II y W7-X

2026-02-26T16:43:44Z

Teresa.estrada:

TJ-II:Turbulence and flow measured at the 3/2 magnetic island using Doppler reflectometry

2022-01-19T16:54:01Z

Teresa.estrada: /* Description of the activity */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''Turbulence and flow measured at the 3/2 magnetic island using Doppler reflectometry '''

== Name and affiliation of proponent ==
T. Estrada (1), E. Ascasíbar, E. Maragkoudakis, C. Hidalgo, A. de la Peña, F. Lapayese

CIEMAT

(1) https://orcid.org/0000-0001-6205-2656

== Details of contact person at LNF ==
N/A

== Description of the activity ==
The impact of magnetic island on turbulence and flows has been studied in different fusion devices finding differences that depend, among other parameters, on the island width. A vortex-like flow has been measured at large magnetic islands in several devices (e.g. LHD [1] and TJ-II [2]). Narrower islands however show a different flow pattern without signatures of flow reversal at the island O-point (e.g. LHD [1] and W7-X [3]). These observations are qualitatively reproduced by gyrokinetic simulations [4]. Regarding the impact on the turbulence, a turbulence reduction associated to the island has been found localized nearby the island O-point, both in experiments and simulations [3, 4]. The minimum in the turbulence level nearby the island O-point may be consequence of the strong flow-shear developed at the island boundaries that precludes the spreading of the turbulence into the island.

On the other hand, differences in the flow measured across the island O-point and the island X-point have been found in HL-2A [5], with stronger flow-shear at the island boundaries at the O-point and a nearly flat flow profile at the X-point. This difference has been also studied theoretically [6] showing that the flow-shearing near the X-point is important for the turbulence penetration into the island. Such a turbulence spreading into the island has been demonstrated experimentally in several devices: DIII-D [7], HL-2A [8], and KSTAR [9].

In this proposal, we would like to extend the characterization of the turbulence and flow associated to a low order magnetic island carried out in TJ-II [2]. In those experiments, the radial position of the 3/2 magnetic island was scanned along the plasma discharge tailoring the rotational transform profile by means of OH current external induction. The characteristic signatures of the magnetic island were detected as it crossed the Doppler reflectometer measurement position. In the present proposal however, we will try to fix the radial position of the magnetic island by using the operational mode called C-mode; this mode allows sweeping the radial position of the magnetic island up to a given position in a controlled way (see experiments in [10]). This scheme would allow the comparison of the turbulence and flow measured across the island at the two poloidal regions accessible by the Doppler reflectometer.

[1] K. Ida et al., Phys. Rev. Lett. 88, 015002 (2001)

[2] T. Estrada et al., Nucl. Fusion 56, 026011 (2016)

[3] T. Estrada et al., Nucl. Fusion 61, 096011 (2021)

[4] A. Bañón-Navarro et al., Plasma Phys. Control. Fusion 59, 034004 (2017)

[5] M. Jiang et al., Nucl. Fusion 58, 026002 (2017)

[6] T.S. Hahm et al., Phys. Plasmas 28, 022302 (2021)

[7] K. Ida et al., Phys. Rev. Lett. 120, 245001 (2018)

[8] M. Jiang et al., Nucl. Fusion 59, 066019 (2019)

[9] M.J. Choi et al., Nat. Commun. 12, 375 (2021)

[10] F. Fernández-Marina et al., Phys. Plasmas 24, 072513 (2017)

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: one experimental day is required as several attempts will be needed in order to get the desired evolution of the plasma current. Then, reproducible discharges are needed in order to properly characterize the magnetic island at the two separate poloidal positions accessible by the Doppler reflectometer.
* Essential diagnostic systems: Microwave interferometer, Rogosky coils, Doppler reflectometer, Thomson scattering, diamagnetic loop , bolometers, Hα detectors, Mirnov coils, SXR.
* Type of plasmas (heating configuration): ECH plasmas in the standard magnetic configuration with OH current programmed using C-mode operation.
* Specific requirements on wall conditioning if any: Fresh Li is required for a good density control.
* External users: need a local computer account for data access: no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II:Turbulence and flow measured at the 3/2 magnetic island using Doppler reflectometry

2022-01-19T16:47:39Z

Teresa.estrada: /* Description of the activity */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''Turbulence and flow measured at the 3/2 magnetic island using Doppler reflectometry '''

== Name and affiliation of proponent ==
T. Estrada (1), E. Ascasíbar, E. Maragkoudakis, C. Hidalgo, A. de la Peña, F. Lapayese

CIEMAT

(1) https://orcid.org/0000-0001-6205-2656

== Details of contact person at LNF ==
N/A

== Description of the activity ==
The impact of magnetic island on turbulence and flows has been studied in different fusion devices finding differences that depend, among other parameters, on the island width. A vortex-like flow has been measured at large magnetic islands in several devices (e.g. LHD [1] and TJ-II [2]). Narrower islands however show a different flow pattern without signatures of flow reversal at the island O-point (e.g. LHD [1] and W7-X [3]). These observations are qualitatively reproduced by gyrokinetic simulations [4]. Regarding the impact on the turbulence, a turbulence reduction associated to the island has been found localized nearby the island O-point, both in experiments and simulations [3, 4]. The minimum in the turbulence level nearby the island O-point may be consequence of the strong flow-shear developed at the island boundaries that precludes the spreading of the turbulence into the island.
On the other hand, differences in the flow measured across the island O-point and the island X-point have been found in HL-2A [5], with stronger flow-shear at the island boundaries at the O-point and a nearly flat flow profile at the X-point. This difference has been also studied theoretically [6] showing that the flow-shearing near the X-point is important for the turbulence penetration into the island. Such a turbulence spreading into the island has been demonstrated experimentally in several devices: DIII-D [7], HL-2A [8], and KSTAR [9].
In this proposal, we would like to extend the characterization of the turbulence and flow associated to a low order magnetic island carried out in TJ-II [2]. In those experiments, the radial position of the 3/2 magnetic island was scanned along the plasma discharge tailoring the rotational transform profile by means of OH current external induction. The characteristic signatures of the magnetic island were detected as it crossed the Doppler reflectometer measurement position. In the present proposal however, we will try to fix the radial position of the magnetic island by using the operational mode called C-mode; this mode allows sweeping the radial position of the magnetic island up to a given position in a controlled way (see experiments in [10]). This scheme would allow the comparison of the turbulence and flow measured across the island at the two poloidal regions accessible by the Doppler reflectometer.

[1] K. Ida et al., Phys. Rev. Lett. 88, 015002 (2001)

[2] T. Estrada et al., Nucl. Fusion 56, 026011 (2016)

[3] T. Estrada et al., Nucl. Fusion 61, 096011 (2021)

[4] A. Bañón-Navarro et al., Plasma Phys. Control. Fusion 59, 034004 (2017)

[5] M. Jiang et al., Nucl. Fusion 58, 026002 (2017)

[6] T.S. Hahm et al., Phys. Plasmas 28, 022302 (2021)

[7] K. Ida et al., Phys. Rev. Lett. 120, 245001 (2018)

[8] M. Jiang et al., Nucl. Fusion 59, 066019 (2019)

[9] M.J. Choi et al., Nat. Commun. 12, 375 (2021)

[10] F. Fernández-Marina et al., Phys. Plasmas 24, 072513 (2017)

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: one experimental day is required as several attempts will be needed in order to get the desired evolution of the plasma current. Then, reproducible discharges are needed in order to properly characterize the magnetic island at the two separate poloidal positions accessible by the Doppler reflectometer.
* Essential diagnostic systems: Microwave interferometer, Rogosky coils, Doppler reflectometer, Thomson scattering, diamagnetic loop , bolometers, Hα detectors, Mirnov coils, SXR.
* Type of plasmas (heating configuration): ECH plasmas in the standard magnetic configuration with OH current programmed using C-mode operation.
* Specific requirements on wall conditioning if any: Fresh Li is required for a good density control.
* External users: need a local computer account for data access: no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II:Turbulence and flow measured at the 3/2 magnetic island using Doppler reflectometry

2022-01-19T16:42:39Z

Teresa.estrada: /* Name and affiliation of proponent */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''Turbulence and flow measured at the 3/2 magnetic island using Doppler reflectometry '''

== Name and affiliation of proponent ==
T. Estrada (1), E. Ascasíbar, E. Maragkoudakis, C. Hidalgo, A. de la Peña, F. Lapayese

CIEMAT

(1) https://orcid.org/0000-0001-6205-2656

== Details of contact person at LNF ==
N/A

== Description of the activity ==
The impact of magnetic island on turbulence and flows has been studied in different fusion devices finding differences that depend, among other parameters, on the island width. A vortex-like flow has been measured at large magnetic islands in several devices (e.g. LHD [1] and TJ-II [2]). Narrower islands however show a different flow pattern without signatures of flow reversal at the island O-point (e.g. LHD [1] and W7-X [3]). These observations are qualitatively reproduced by gyrokinetic simulations [4]. Regarding the impact on the turbulence, a turbulence reduction associated to the island has been found localized nearby the island O-point, both in experiments and simulations [3, 4]. The minimum in the turbulence level nearby the island O-point may be consequence of the strong flow-shear developed at the island boundaries that precludes the spreading of the turbulence into the island.
On the other hand, differences in the flow measured across the island O-point and the island X-point have been found in HL-2A [5], with stronger flow-shear at the island boundaries at the O-point and a nearly flat flow profile at the X-point. This difference has been also studied theoretically [6] showing that the flow-shearing near the X-point is important for the turbulence penetration into the island. Such a turbulence spreading into the island has been demonstrated experimentally in several devices: DIII-D [7], HL-2A [8], and KSTAR [9].
In this proposal, we would like to extend the characterization of the turbulence and flow associated to a low order magnetic island carried out in TJ-II [2]. In those experiments, the radial position of the 3/2 magnetic island was scanned along the plasma discharge tailoring the rotational transform profile by means of OH current external induction. The characteristic signatures of the magnetic island were detected as it crossed the Doppler reflectometer measurement position. In the present proposal however, we will try to fix the radial position of the magnetic island by using the operational mode called C-mode; this mode allows sweeping the radial position of the magnetic island up to a given position in a controlled way (see experiments in [10]). This scheme would allow the comparison of the turbulence and flow measured across the island at the two poloidal regions accessible by the Doppler reflectometer.

[1] K. Ida et al., Phys. Rev. Lett. 88, 015002 (2001)

[2] T. Estrada et al., Nucl. Fusion 56, 026011 (2016)

[3] T. Estrada et al., Nucl. Fusion 61, 096011 (2021)

[4] A. Bañón-Navarro et al., Plasma Phys. Control. Fusion 59, 034004 (2017)

[5] M. Jiang et al., Nucl. Fusion 58, 026002 (2017)

[6] T.S. Hahm et al., Phys. Plasmas 28, 022302 (2021)

[6] K. Ida et al., Phys. Rev. Lett. 120, 245001 (2018)

[8] M. Jiang et al., Nucl. Fusion 59, 066019 (2019)

[9] M.J. Choi et al., Nat. Commun. 12, 375 (2021)

[10] F. Fernández-Marina et al., Phys. Plasmas 24, 072513 (2017)

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: one experimental day is required as several attempts will be needed in order to get the desired evolution of the plasma current. Then, reproducible discharges are needed in order to properly characterize the magnetic island at the two separate poloidal positions accessible by the Doppler reflectometer.
* Essential diagnostic systems: Microwave interferometer, Rogosky coils, Doppler reflectometer, Thomson scattering, diamagnetic loop , bolometers, Hα detectors, Mirnov coils, SXR.
* Type of plasmas (heating configuration): ECH plasmas in the standard magnetic configuration with OH current programmed using C-mode operation.
* Specific requirements on wall conditioning if any: Fresh Li is required for a good density control.
* External users: need a local computer account for data access: no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II:Turbulence and flow measured at the 3/2 magnetic island using Doppler reflectometry

2022-01-19T16:34:42Z

Teresa.estrada:

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''Turbulence and flow measured at the 3/2 magnetic island using Doppler reflectometry '''

== Name and affiliation of proponent ==
T. Estrada (1), E. Ascasíbar, E. Maragkoudakis, A. de la Peña, F. Lapayese

CIEMAT

(1) https://orcid.org/0000-0001-6205-2656

== Details of contact person at LNF ==
N/A

== Description of the activity ==
The impact of magnetic island on turbulence and flows has been studied in different fusion devices finding differences that depend, among other parameters, on the island width. A vortex-like flow has been measured at large magnetic islands in several devices (e.g. LHD [1] and TJ-II [2]). Narrower islands however show a different flow pattern without signatures of flow reversal at the island O-point (e.g. LHD [1] and W7-X [3]). These observations are qualitatively reproduced by gyrokinetic simulations [4]. Regarding the impact on the turbulence, a turbulence reduction associated to the island has been found localized nearby the island O-point, both in experiments and simulations [3, 4]. The minimum in the turbulence level nearby the island O-point may be consequence of the strong flow-shear developed at the island boundaries that precludes the spreading of the turbulence into the island.
On the other hand, differences in the flow measured across the island O-point and the island X-point have been found in HL-2A [5], with stronger flow-shear at the island boundaries at the O-point and a nearly flat flow profile at the X-point. This difference has been also studied theoretically [6] showing that the flow-shearing near the X-point is important for the turbulence penetration into the island. Such a turbulence spreading into the island has been demonstrated experimentally in several devices: DIII-D [7], HL-2A [8], and KSTAR [9].
In this proposal, we would like to extend the characterization of the turbulence and flow associated to a low order magnetic island carried out in TJ-II [2]. In those experiments, the radial position of the 3/2 magnetic island was scanned along the plasma discharge tailoring the rotational transform profile by means of OH current external induction. The characteristic signatures of the magnetic island were detected as it crossed the Doppler reflectometer measurement position. In the present proposal however, we will try to fix the radial position of the magnetic island by using the operational mode called C-mode; this mode allows sweeping the radial position of the magnetic island up to a given position in a controlled way (see experiments in [10]). This scheme would allow the comparison of the turbulence and flow measured across the island at the two poloidal regions accessible by the Doppler reflectometer.

[1] K. Ida et al., Phys. Rev. Lett. 88, 015002 (2001)

[2] T. Estrada et al., Nucl. Fusion 56, 026011 (2016)

[3] T. Estrada et al., Nucl. Fusion 61, 096011 (2021)

[4] A. Bañón-Navarro et al., Plasma Phys. Control. Fusion 59, 034004 (2017)

[5] M. Jiang et al., Nucl. Fusion 58, 026002 (2017)

[6] T.S. Hahm et al., Phys. Plasmas 28, 022302 (2021)

[6] K. Ida et al., Phys. Rev. Lett. 120, 245001 (2018)

[8] M. Jiang et al., Nucl. Fusion 59, 066019 (2019)

[9] M.J. Choi et al., Nat. Commun. 12, 375 (2021)

[10] F. Fernández-Marina et al., Phys. Plasmas 24, 072513 (2017)

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: one experimental day is required as several attempts will be needed in order to get the desired evolution of the plasma current. Then, reproducible discharges are needed in order to properly characterize the magnetic island at the two separate poloidal positions accessible by the Doppler reflectometer.
* Essential diagnostic systems: Microwave interferometer, Rogosky coils, Doppler reflectometer, Thomson scattering, diamagnetic loop , bolometers, Hα detectors, Mirnov coils, SXR.
* Type of plasmas (heating configuration): ECH plasmas in the standard magnetic configuration with OH current programmed using C-mode operation.
* Specific requirements on wall conditioning if any: Fresh Li is required for a good density control.
* External users: need a local computer account for data access: no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II:NBI1 vs. NBI2 heated plasma comparison

2022-01-19T14:34:02Z

Teresa.estrada: /* Description of required resources */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''NBI1 vs. NBI2 heated plasma comparison'''

== Name and affiliation of proponent ==
T. Estrada (1), M. Liniers, S. Mulas, M.A. Ochando, E. Ascasíbar, J. Hernández, A. Cappa, I. Pastor

CIEMAT

Suggested format:

(1) https://orcid.org/0000-0001-6205-2656

== Details of contact person at LNF ==
N/A

== Description of the activity ==
At TJ-II, NBI heated plasmas show differences that depend on the injection direction, co- or counter-injection (NBI1 or NBI2, respectively). Whereas the evolution of the electron temperature and density profiles are alike in the two heating schemes, the radial electric field and density turbulence profiles evolve differently, ending up in a higher density limit and higher energy content in plasmas heated with counter-NBI (NBI2). Besides, some differences in the plasma radiation profiles are detected whose evolution is presently being studied.
The experimental characterization of the beams indicates that both present similar re-ionization losses and transmission [1], while NBI heating simulations performed using ASCOT [2, 3] show more direct ion losses using co-NBI heating and better efficiency using counter-NBI for the same plasma profiles.
Previous experiments indicate that the differences become more noticeable as the heating power increases.
In this proposal we would like to proceed with the co- vs. counter-NBI comparison aiming at the identification of the relevant physical mechanisms responsible for the experimental observations.

[1] M. Liniers et al., FED 123, 259 (2017)

[2] J.Guasp, M.Liniers, Informe técnico 761 "Comportamiento de las pérdidas instantáneas y retardadas en la inyección de neutros del TJ-II"

[3] S.Mulas et al., 1st HPC fusion workshop 2020, ''Simulations of neutral beam injection in TJ-II stellarator using ASCOT5"

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: one experimental day is required as several reproducible discharges at each heating scheme are needed in order to properly characterize plasma profiles (electron density, electron and ion temperature, radial electric field, radiation, etc.)
* Essential diagnostic systems: Microwave interferometer, Thomson scattering, diamagnetic loop, Doppler reflectometer, bolometers, Hα detectors, Rogosky and Mirnov coils, SXR, IR camera at NBI2.
* Type of plasmas (heating configuration): co-and counter-NBI heated plasmas with plasma target created by ECH in the standard magnetic configuration.
* Specific requirements on wall conditioning if any: fresh Li is required for a good density control during the NBI phase.
* External users: need a local computer account for data access: no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II:NBI1 vs. NBI2 heated plasma comparison

2022-01-19T14:33:11Z

Teresa.estrada: /* Description of the activity */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''NBI1 vs. NBI2 heated plasma comparison'''

== Name and affiliation of proponent ==
T. Estrada (1), M. Liniers, S. Mulas, M.A. Ochando, E. Ascasíbar, J. Hernández, A. Cappa, I. Pastor

CIEMAT

Suggested format:

(1) https://orcid.org/0000-0001-6205-2656

== Details of contact person at LNF ==
N/A

== Description of the activity ==
At TJ-II, NBI heated plasmas show differences that depend on the injection direction, co- or counter-injection (NBI1 or NBI2, respectively). Whereas the evolution of the electron temperature and density profiles are alike in the two heating schemes, the radial electric field and density turbulence profiles evolve differently, ending up in a higher density limit and higher energy content in plasmas heated with counter-NBI (NBI2). Besides, some differences in the plasma radiation profiles are detected whose evolution is presently being studied.
The experimental characterization of the beams indicates that both present similar re-ionization losses and transmission [1], while NBI heating simulations performed using ASCOT [2, 3] show more direct ion losses using co-NBI heating and better efficiency using counter-NBI for the same plasma profiles.
Previous experiments indicate that the differences become more noticeable as the heating power increases.
In this proposal we would like to proceed with the co- vs. counter-NBI comparison aiming at the identification of the relevant physical mechanisms responsible for the experimental observations.

[1] M. Liniers et al., FED 123, 259 (2017)

[2] J.Guasp, M.Liniers, Informe técnico 761 "Comportamiento de las pérdidas instantáneas y retardadas en la inyección de neutros del TJ-II"

[3] S.Mulas et al., 1st HPC fusion workshop 2020, ''Simulations of neutral beam injection in TJ-II stellarator using ASCOT5"

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: one experimental day is required as several reproducible discharges at each heating scheme are needed in order to properly characterize plasma profiles (electron density, electron and ion temperature, radial electric field, radiation, etc.)
* Essential diagnostic systems: Microwave interferometer, Thomson scattering, diamagnetic loop, Doppler reflectometer, bolometers, Hα detectors, , Rogosky and Mirnov coils, SXR.
* Type of plasmas (heating configuration): co-and counter-NBI heated plasmas with plasma target created by ECH in the standard magnetic configuration.
* Specific requirements on wall conditioning if any: fresh Li is required for a good density control during the NBI phase.
* External users: need a local computer account for data access: no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II:Turbulence and flow measured at the 3/2 magnetic island using Doppler reflectometry

2022-01-18T13:33:38Z

Teresa.estrada: /* Name and affiliation of proponent */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''Turbulence and flow measured at the 3/2 magnetic island using Doppler reflectometry '''

== Name and affiliation of proponent ==
T. Estrada (1), E. Ascasíbar

CIEMAT

(1) https://orcid.org/0000-0001-6205-2656

== Details of contact person at LNF ==
N/A

== Description of the activity ==
The impact of magnetic island on turbulence and flows has been studied in different fusion devices finding differences that depend, among other parameters, on the island width. A vortex-like flow has been measured at large magnetic islands in several devices (e.g. LHD [1] and TJ-II [2]). Narrower islands however show a different flow pattern without signatures of flow reversal at the island O-point [1, 3]. These observations are qualitatively reproduced by gyrokinetic simulations [4]. Regarding the impact on the turbulence, a turbulence reduction associated to the island is found ......

[1] K. Ida et al.,

[2] T. Estrada et al.,

[3] T. Estrada et al.,

[4] A. Bañón-Navarro et al.,

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
* Essential diagnostic systems:
* Type of plasmas (heating configuration):
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II:Turbulence and flow measured at the 3/2 magnetic island using Doppler reflectometry

2022-01-18T13:29:56Z

Teresa.estrada: Created page with "== Experimental campaign == Spring 2022 == Proposal title == '''Turbulence and flow measured at the 3/2 magnetic island using Doppler reflectometry ''' == Name and affiliati..."

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''Turbulence and flow measured at the 3/2 magnetic island using Doppler reflectometry '''

== Name and affiliation of proponent ==
T. Estrada (1), E. Ascasíbar

(1) https://orcid.org/0000-0001-6205-2656

== Details of contact person at LNF ==
N/A

== Description of the activity ==
The impact of magnetic island on turbulence and flows has been studied in different fusion devices finding differences that depend, among other parameters, on the island width. A vortex-like flow has been measured at large magnetic islands in several devices (e.g. LHD [1] and TJ-II [2]). Narrower islands however show a different flow pattern without signatures of flow reversal at the island O-point [1, 3]. These observations are qualitatively reproduced by gyrokinetic simulations [4]. Regarding the impact on the turbulence, a turbulence reduction associated to the island is found ......

[1] K. Ida et al.,

[2] T. Estrada et al.,

[3] T. Estrada et al.,

[4] A. Bañón-Navarro et al.,

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
* Essential diagnostic systems:
* Type of plasmas (heating configuration):
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II:NBI1 vs. NBI2 heated plasma comparison

2022-01-18T13:04:03Z

Teresa.estrada: /* Name and affiliation of proponent */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''NBI1 vs. NBI2 heated plasma comparison'''

== Name and affiliation of proponent ==
T. Estrada (1), M. Liniers, S. Mulas, M.A. Ochando, E. Ascasíbar, J. Hernández, A. Cappa, I. Pastor

CIEMAT

Suggested format:

(1) https://orcid.org/0000-0001-6205-2656

== Details of contact person at LNF ==
N/A

== Description of the activity ==
At TJ-II, NBI heated plasmas show differences that depend on the injection direction, co- or counter-injection (NBI1 or NBI2, respectively). Whereas the evolution of the electron temperature and density profiles are alike in the two heating schemes, the radial electric field and density turbulence profiles evolve differently, ending up in a higher density limit and higher energy content in plasmas heated with counter-NBI (NBI2). Besides, some differences in the plasma radiation profiles are detected whose evolution is presently being studied.
The experimental characterization of the beams indicates that both present similar re-ionization losses and transmission [1], while NBI heating simulations performed using ASCOT [2] show more direct ion losses using co-NBI heating and better efficiency using counter-NBI for the same plasma profiles.
Previous experiments indicate that the differences become more noticeable as the heating power increases.
In this proposal we would like to proceed with the co- vs. counter-NBI comparison aiming at the identification of the relevant physical mechanisms responsible for the experimental observations.

[1] M. Liniers et al., FED 123, 259 (2017)

[2] S. Mulas et al.,

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: one experimental day is required as several reproducible discharges at each heating scheme are needed in order to properly characterize plasma profiles (electron density, electron and ion temperature, radial electric field, radiation, etc.)
* Essential diagnostic systems: Microwave interferometer, Thomson scattering, diamagnetic loop, Doppler reflectometer, bolometers, Hα detectors, , Rogosky and Mirnov coils, SXR.
* Type of plasmas (heating configuration): co-and counter-NBI heated plasmas with plasma target created by ECH in the standard magnetic configuration.
* Specific requirements on wall conditioning if any: fresh Li is required for a good density control during the NBI phase.
* External users: need a local computer account for data access: no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II:NBI1 vs. NBI2 heated plasma comparison

2022-01-18T13:03:38Z

Teresa.estrada: Created page with "== Experimental campaign == Spring 2022 == Proposal title == '''NBI1 vs. NBI2 heated plasma comparison''' == Name and affiliation of proponent == T. Estrada(1), M. Liniers, ..."

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''NBI1 vs. NBI2 heated plasma comparison'''

== Name and affiliation of proponent ==
T. Estrada(1), M. Liniers, S. Mulas, M.A. Ochando, E. Ascasíbar, J. Hernández, A. Cappa, I. Pastor

CIEMAT

Suggested format:

(1) https://orcid.org/0000-0001-6205-2656

== Details of contact person at LNF ==
N/A

== Description of the activity ==
At TJ-II, NBI heated plasmas show differences that depend on the injection direction, co- or counter-injection (NBI1 or NBI2, respectively). Whereas the evolution of the electron temperature and density profiles are alike in the two heating schemes, the radial electric field and density turbulence profiles evolve differently, ending up in a higher density limit and higher energy content in plasmas heated with counter-NBI (NBI2). Besides, some differences in the plasma radiation profiles are detected whose evolution is presently being studied.
The experimental characterization of the beams indicates that both present similar re-ionization losses and transmission [1], while NBI heating simulations performed using ASCOT [2] show more direct ion losses using co-NBI heating and better efficiency using counter-NBI for the same plasma profiles.
Previous experiments indicate that the differences become more noticeable as the heating power increases.
In this proposal we would like to proceed with the co- vs. counter-NBI comparison aiming at the identification of the relevant physical mechanisms responsible for the experimental observations.

[1] M. Liniers et al., FED 123, 259 (2017)

[2] S. Mulas et al.,

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: one experimental day is required as several reproducible discharges at each heating scheme are needed in order to properly characterize plasma profiles (electron density, electron and ion temperature, radial electric field, radiation, etc.)
* Essential diagnostic systems: Microwave interferometer, Thomson scattering, diamagnetic loop, Doppler reflectometer, bolometers, Hα detectors, , Rogosky and Mirnov coils, SXR.
* Type of plasmas (heating configuration): co-and counter-NBI heated plasmas with plasma target created by ECH in the standard magnetic configuration.
* Specific requirements on wall conditioning if any: fresh Li is required for a good density control during the NBI phase.
* External users: need a local computer account for data access: no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II:L-H transition studies: characterization of plasma turbulence using Gas Puff Imaging, Probes, Doppler reflectometry and HIBP diagnostics

2022-01-18T10:32:48Z

Teresa.estrada: /* Name and affiliation of proponent */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''L-H transition studies: characterization of plasma turbulence using Gas Puff Imaging, Probes, Doppler reflectometry and HIBP diagnostics'''

== Name and affiliation of proponent ==
HIBP Kurchatov team, Russia

HIBP Kharkov team, Ukraine

M. Koepke UWV, USA

T. Estrada, E. de la Cal, I. Voldiner, M.A. Ochando, CIEMAT

== Details of contact person at LNF ==
Teresa Estrada

https://orcid.org/0000-0001-6205-2656

== Description of the activity ==
At TJ-II, spontaneous L-H transitions are achieved in neutral beam injection (NBI) heated plasma. Abrupt as well as gradual transitions are achieved depending, among other plasma parameters, on the heating power and magnetic configuration topology. Doppler reflectometry (DR) measurements show an increase in the negative radial electric field (Er) together with a reduction in plasma turbulence at the transition [1]. These measurements together with measurements obtained using a dual Langmuir probe system [2] indicate that the trigger of the L-H transition is more correlated with the development of fluctuating radial electric fields than steady-state Er effects. This conclusion is further stressed when operating close to the L-H transition threshold conditions, where pronounced oscillations in both, Er and density turbulence measured by DR show a characteristic predator-prey relation [3]. These experimental observations are consistent with L-H transition models based on turbulence-induced sheared/zonal flows. In addition, HIBP measurements show a reduction in the plasma turbulence and associated flux not only in the plasma edge region but also in the plasma core [4].
Recently a Gas Puff Imaging system (GPI) has been installed and tested at TJ-II. The new gas injection system is used with a camera system that allows 3 simultaneous filtered frames to apply the He I ratio technique, getting 2D measurements of the edge plasma electron density ne and temperature Te with spatial resolution of 3 mm and temporal resolution down to 10 microseconds [5]. This new diagnostic will permit the 2-D characterization of edge and SOL plasma turbulence and is expected to provide additional valuable information on the behaviour of the turbulence during the L-H transition.
The whole set of diagnostics operating simultaneously will allow the characterization of the plasma turbulence evolution from the SOL (GPI and probes) to the plasma gradient (DR) and plasma core (HIBP) regions at the L-H transition.

[1] T. Estrada et al., Plasma Phys. Control. Fusion 51, 124015 (2009)

[2] C. Hidalgo et al., EPL 87, 55002 (2009)

[3] T. Estrada et al., Phys. Rev. Lett. 107, 245004 (2011) 

[4] A. Melnikov et al., Nucl. Fusion 53, 092002 (2013)

[5] E. de la Cal and TJ-II Team, Nucl. Fusion 56, 106031 (2016)

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
Experiments in March 2022 focussed on GPI & DR: To prepare the experiment we need first to reproduce the conditions for L-H transitions. Once the proper conditions are found, He puffing will be introduced for GPI measurements.

Experiments in May 2022 focussed on HIBP & DR & Probes

Experiments in June 2022 focussed on simultaneous measurements using the whole set of TJ-II diagnostics

* Essential diagnostic systems: GPI, Doppler reflectometer, Langmuir probes, HIBP, microwave interferometer, Thomson scattering, Hα detectors, diamagnetic, Rogosky and Mirnov coils, SXR, bolometry

* Type of plasmas (heating configuration): NBI plasmas with plasma target created by ECH in the standard (or 101_42_64) magnetic configuration.

* Specific requirements on wall conditioning if any: Fresh Li is required for a good density control during the NBI phase.

* External users: need a local computer account for data access: no

* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: experiments splitted in three blocks in March (DR and GPI), May and June (availability of HIBP)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II:L-H transition studies: characterization of plasma turbulence using Gas Puff Imaging, Probes, Doppler reflectometry and HIBP diagnostics

2022-01-18T10:31:03Z

Teresa.estrada: /* Details of contact person at LNF */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''L-H transition studies: characterization of plasma turbulence using Gas Puff Imaging, Probes, Doppler reflectometry and HIBP diagnostics'''

== Name and affiliation of proponent ==
Teresa Estrada

CIEMAT

https://orcid.org/0000-0001-6205-2656

== Details of contact person at LNF ==
Teresa Estrada

https://orcid.org/0000-0001-6205-2656

== Description of the activity ==
At TJ-II, spontaneous L-H transitions are achieved in neutral beam injection (NBI) heated plasma. Abrupt as well as gradual transitions are achieved depending, among other plasma parameters, on the heating power and magnetic configuration topology. Doppler reflectometry (DR) measurements show an increase in the negative radial electric field (Er) together with a reduction in plasma turbulence at the transition [1]. These measurements together with measurements obtained using a dual Langmuir probe system [2] indicate that the trigger of the L-H transition is more correlated with the development of fluctuating radial electric fields than steady-state Er effects. This conclusion is further stressed when operating close to the L-H transition threshold conditions, where pronounced oscillations in both, Er and density turbulence measured by DR show a characteristic predator-prey relation [3]. These experimental observations are consistent with L-H transition models based on turbulence-induced sheared/zonal flows. In addition, HIBP measurements show a reduction in the plasma turbulence and associated flux not only in the plasma edge region but also in the plasma core [4].
Recently a Gas Puff Imaging system (GPI) has been installed and tested at TJ-II. The new gas injection system is used with a camera system that allows 3 simultaneous filtered frames to apply the He I ratio technique, getting 2D measurements of the edge plasma electron density ne and temperature Te with spatial resolution of 3 mm and temporal resolution down to 10 microseconds [5]. This new diagnostic will permit the 2-D characterization of edge and SOL plasma turbulence and is expected to provide additional valuable information on the behaviour of the turbulence during the L-H transition.
The whole set of diagnostics operating simultaneously will allow the characterization of the plasma turbulence evolution from the SOL (GPI and probes) to the plasma gradient (DR) and plasma core (HIBP) regions at the L-H transition.

[1] T. Estrada et al., Plasma Phys. Control. Fusion 51, 124015 (2009)

[2] C. Hidalgo et al., EPL 87, 55002 (2009)

[3] T. Estrada et al., Phys. Rev. Lett. 107, 245004 (2011) 

[4] A. Melnikov et al., Nucl. Fusion 53, 092002 (2013)

[5] E. de la Cal and TJ-II Team, Nucl. Fusion 56, 106031 (2016)

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
Experiments in March 2022 focussed on GPI & DR: To prepare the experiment we need first to reproduce the conditions for L-H transitions. Once the proper conditions are found, He puffing will be introduced for GPI measurements.

Experiments in May 2022 focussed on HIBP & DR & Probes

Experiments in June 2022 focussed on simultaneous measurements using the whole set of TJ-II diagnostics

* Essential diagnostic systems: GPI, Doppler reflectometer, Langmuir probes, HIBP, microwave interferometer, Thomson scattering, Hα detectors, diamagnetic, Rogosky and Mirnov coils, SXR, bolometry

* Type of plasmas (heating configuration): NBI plasmas with plasma target created by ECH in the standard (or 101_42_64) magnetic configuration.

* Specific requirements on wall conditioning if any: Fresh Li is required for a good density control during the NBI phase.

* External users: need a local computer account for data access: no

* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: experiments splitted in three blocks in March (DR and GPI), May and June (availability of HIBP)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II:L-H transition studies: characterization of plasma turbulence using Gas Puff Imaging, Probes, Doppler reflectometry and HIBP diagnostics

2022-01-18T10:30:46Z

Teresa.estrada: /* Details of contact person at LNF */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''L-H transition studies: characterization of plasma turbulence using Gas Puff Imaging, Probes, Doppler reflectometry and HIBP diagnostics'''

== Name and affiliation of proponent ==
Teresa Estrada

CIEMAT

https://orcid.org/0000-0001-6205-2656

== Details of contact person at LNF ==
Teresa Estrada

CIEMAT

https://orcid.org/0000-0001-6205-2656

== Description of the activity ==
At TJ-II, spontaneous L-H transitions are achieved in neutral beam injection (NBI) heated plasma. Abrupt as well as gradual transitions are achieved depending, among other plasma parameters, on the heating power and magnetic configuration topology. Doppler reflectometry (DR) measurements show an increase in the negative radial electric field (Er) together with a reduction in plasma turbulence at the transition [1]. These measurements together with measurements obtained using a dual Langmuir probe system [2] indicate that the trigger of the L-H transition is more correlated with the development of fluctuating radial electric fields than steady-state Er effects. This conclusion is further stressed when operating close to the L-H transition threshold conditions, where pronounced oscillations in both, Er and density turbulence measured by DR show a characteristic predator-prey relation [3]. These experimental observations are consistent with L-H transition models based on turbulence-induced sheared/zonal flows. In addition, HIBP measurements show a reduction in the plasma turbulence and associated flux not only in the plasma edge region but also in the plasma core [4].
Recently a Gas Puff Imaging system (GPI) has been installed and tested at TJ-II. The new gas injection system is used with a camera system that allows 3 simultaneous filtered frames to apply the He I ratio technique, getting 2D measurements of the edge plasma electron density ne and temperature Te with spatial resolution of 3 mm and temporal resolution down to 10 microseconds [5]. This new diagnostic will permit the 2-D characterization of edge and SOL plasma turbulence and is expected to provide additional valuable information on the behaviour of the turbulence during the L-H transition.
The whole set of diagnostics operating simultaneously will allow the characterization of the plasma turbulence evolution from the SOL (GPI and probes) to the plasma gradient (DR) and plasma core (HIBP) regions at the L-H transition.

[1] T. Estrada et al., Plasma Phys. Control. Fusion 51, 124015 (2009)

[2] C. Hidalgo et al., EPL 87, 55002 (2009)

[3] T. Estrada et al., Phys. Rev. Lett. 107, 245004 (2011) 

[4] A. Melnikov et al., Nucl. Fusion 53, 092002 (2013)

[5] E. de la Cal and TJ-II Team, Nucl. Fusion 56, 106031 (2016)

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
Experiments in March 2022 focussed on GPI & DR: To prepare the experiment we need first to reproduce the conditions for L-H transitions. Once the proper conditions are found, He puffing will be introduced for GPI measurements.

Experiments in May 2022 focussed on HIBP & DR & Probes

Experiments in June 2022 focussed on simultaneous measurements using the whole set of TJ-II diagnostics

* Essential diagnostic systems: GPI, Doppler reflectometer, Langmuir probes, HIBP, microwave interferometer, Thomson scattering, Hα detectors, diamagnetic, Rogosky and Mirnov coils, SXR, bolometry

* Type of plasmas (heating configuration): NBI plasmas with plasma target created by ECH in the standard (or 101_42_64) magnetic configuration.

* Specific requirements on wall conditioning if any: Fresh Li is required for a good density control during the NBI phase.

* External users: need a local computer account for data access: no

* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: experiments splitted in three blocks in March (DR and GPI), May and June (availability of HIBP)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II:L-H transition studies: characterization of plasma turbulence using Gas Puff Imaging, Probes, Doppler reflectometry and HIBP diagnostics

2022-01-18T10:27:06Z

Teresa.estrada: /* Name and affiliation of proponent */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''L-H transition studies: characterization of plasma turbulence using Gas Puff Imaging, Probes, Doppler reflectometry and HIBP diagnostics'''

== Name and affiliation of proponent ==
Teresa Estrada

CIEMAT

https://orcid.org/0000-0001-6205-2656

== Details of contact person at LNF ==
N/A

== Description of the activity ==
At TJ-II, spontaneous L-H transitions are achieved in neutral beam injection (NBI) heated plasma. Abrupt as well as gradual transitions are achieved depending, among other plasma parameters, on the heating power and magnetic configuration topology. Doppler reflectometry (DR) measurements show an increase in the negative radial electric field (Er) together with a reduction in plasma turbulence at the transition [1]. These measurements together with measurements obtained using a dual Langmuir probe system [2] indicate that the trigger of the L-H transition is more correlated with the development of fluctuating radial electric fields than steady-state Er effects. This conclusion is further stressed when operating close to the L-H transition threshold conditions, where pronounced oscillations in both, Er and density turbulence measured by DR show a characteristic predator-prey relation [3]. These experimental observations are consistent with L-H transition models based on turbulence-induced sheared/zonal flows. In addition, HIBP measurements show a reduction in the plasma turbulence and associated flux not only in the plasma edge region but also in the plasma core [4].
Recently a Gas Puff Imaging system (GPI) has been installed and tested at TJ-II. The new gas injection system is used with a camera system that allows 3 simultaneous filtered frames to apply the He I ratio technique, getting 2D measurements of the edge plasma electron density ne and temperature Te with spatial resolution of 3 mm and temporal resolution down to 10 microseconds [5]. This new diagnostic will permit the 2-D characterization of edge and SOL plasma turbulence and is expected to provide additional valuable information on the behaviour of the turbulence during the L-H transition.
The whole set of diagnostics operating simultaneously will allow the characterization of the plasma turbulence evolution from the SOL (GPI and probes) to the plasma gradient (DR) and plasma core (HIBP) regions at the L-H transition.

[1] T. Estrada et al., Plasma Phys. Control. Fusion 51, 124015 (2009)

[2] C. Hidalgo et al., EPL 87, 55002 (2009)

[3] T. Estrada et al., Phys. Rev. Lett. 107, 245004 (2011) 

[4] A. Melnikov et al., Nucl. Fusion 53, 092002 (2013)

[5] E. de la Cal and TJ-II Team, Nucl. Fusion 56, 106031 (2016)

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
Experiments in March 2022 focussed on GPI & DR: To prepare the experiment we need first to reproduce the conditions for L-H transitions. Once the proper conditions are found, He puffing will be introduced for GPI measurements.

Experiments in May 2022 focussed on HIBP & DR & Probes

Experiments in June 2022 focussed on simultaneous measurements using the whole set of TJ-II diagnostics

* Essential diagnostic systems: GPI, Doppler reflectometer, Langmuir probes, HIBP, microwave interferometer, Thomson scattering, Hα detectors, diamagnetic, Rogosky and Mirnov coils, SXR, bolometry

* Type of plasmas (heating configuration): NBI plasmas with plasma target created by ECH in the standard (or 101_42_64) magnetic configuration.

* Specific requirements on wall conditioning if any: Fresh Li is required for a good density control during the NBI phase.

* External users: need a local computer account for data access: no

* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: experiments splitted in three blocks in March (DR and GPI), May and June (availability of HIBP)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II:L-H transition studies: characterization of plasma turbulence using Gas Puff Imaging, Probes, Doppler reflectometry and HIBP diagnostics

2022-01-18T10:22:42Z

Teresa.estrada: /* Description of required resources */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''L-H transition studies: characterization of plasma turbulence using Gas Puff Imaging, Probes, Doppler reflectometry and HIBP diagnostics'''

== Name and affiliation of proponent ==
Teresa Estrada, CIEMAT
https://orcid.org/0000-0001-6205-2656

== Details of contact person at LNF ==
N/A

== Description of the activity ==
At TJ-II, spontaneous L-H transitions are achieved in neutral beam injection (NBI) heated plasma. Abrupt as well as gradual transitions are achieved depending, among other plasma parameters, on the heating power and magnetic configuration topology. Doppler reflectometry (DR) measurements show an increase in the negative radial electric field (Er) together with a reduction in plasma turbulence at the transition [1]. These measurements together with measurements obtained using a dual Langmuir probe system [2] indicate that the trigger of the L-H transition is more correlated with the development of fluctuating radial electric fields than steady-state Er effects. This conclusion is further stressed when operating close to the L-H transition threshold conditions, where pronounced oscillations in both, Er and density turbulence measured by DR show a characteristic predator-prey relation [3]. These experimental observations are consistent with L-H transition models based on turbulence-induced sheared/zonal flows. In addition, HIBP measurements show a reduction in the plasma turbulence and associated flux not only in the plasma edge region but also in the plasma core [4].
Recently a Gas Puff Imaging system (GPI) has been installed and tested at TJ-II. The new gas injection system is used with a camera system that allows 3 simultaneous filtered frames to apply the He I ratio technique, getting 2D measurements of the edge plasma electron density ne and temperature Te with spatial resolution of 3 mm and temporal resolution down to 10 microseconds [5]. This new diagnostic will permit the 2-D characterization of edge and SOL plasma turbulence and is expected to provide additional valuable information on the behaviour of the turbulence during the L-H transition.
The whole set of diagnostics operating simultaneously will allow the characterization of the plasma turbulence evolution from the SOL (GPI and probes) to the plasma gradient (DR) and plasma core (HIBP) regions at the L-H transition.

[1] T. Estrada et al., Plasma Phys. Control. Fusion 51, 124015 (2009)

[2] C. Hidalgo et al., EPL 87, 55002 (2009)

[3] T. Estrada et al., Phys. Rev. Lett. 107, 245004 (2011) 

[4] A. Melnikov et al., Nucl. Fusion 53, 092002 (2013)

[5] E. de la Cal and TJ-II Team, Nucl. Fusion 56, 106031 (2016)

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
Experiments in March 2022 focussed on GPI & DR: To prepare the experiment we need first to reproduce the conditions for L-H transitions. Once the proper conditions are found, He puffing will be introduced for GPI measurements.

Experiments in May 2022 focussed on HIBP & DR & Probes

Experiments in June 2022 focussed on simultaneous measurements using the whole set of TJ-II diagnostics

* Essential diagnostic systems: GPI, Doppler reflectometer, Langmuir probes, HIBP, microwave interferometer, Thomson scattering, Hα detectors, diamagnetic, Rogosky and Mirnov coils, SXR, bolometry

* Type of plasmas (heating configuration): NBI plasmas with plasma target created by ECH in the standard (or 101_42_64) magnetic configuration.

* Specific requirements on wall conditioning if any: Fresh Li is required for a good density control during the NBI phase.

* External users: need a local computer account for data access: no

* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: experiments splitted in three blocks in March (DR and GPI), May and June (availability of HIBP)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II:L-H transition studies: characterization of plasma turbulence using Gas Puff Imaging, Probes, Doppler reflectometry and HIBP diagnostics

2022-01-18T10:20:45Z

Teresa.estrada: /* Description of the activity */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''L-H transition studies: characterization of plasma turbulence using Gas Puff Imaging, Probes, Doppler reflectometry and HIBP diagnostics'''

== Name and affiliation of proponent ==
Teresa Estrada, CIEMAT
https://orcid.org/0000-0001-6205-2656

== Details of contact person at LNF ==
N/A

== Description of the activity ==
At TJ-II, spontaneous L-H transitions are achieved in neutral beam injection (NBI) heated plasma. Abrupt as well as gradual transitions are achieved depending, among other plasma parameters, on the heating power and magnetic configuration topology. Doppler reflectometry (DR) measurements show an increase in the negative radial electric field (Er) together with a reduction in plasma turbulence at the transition [1]. These measurements together with measurements obtained using a dual Langmuir probe system [2] indicate that the trigger of the L-H transition is more correlated with the development of fluctuating radial electric fields than steady-state Er effects. This conclusion is further stressed when operating close to the L-H transition threshold conditions, where pronounced oscillations in both, Er and density turbulence measured by DR show a characteristic predator-prey relation [3]. These experimental observations are consistent with L-H transition models based on turbulence-induced sheared/zonal flows. In addition, HIBP measurements show a reduction in the plasma turbulence and associated flux not only in the plasma edge region but also in the plasma core [4].
Recently a Gas Puff Imaging system (GPI) has been installed and tested at TJ-II. The new gas injection system is used with a camera system that allows 3 simultaneous filtered frames to apply the He I ratio technique, getting 2D measurements of the edge plasma electron density ne and temperature Te with spatial resolution of 3 mm and temporal resolution down to 10 microseconds [5]. This new diagnostic will permit the 2-D characterization of edge and SOL plasma turbulence and is expected to provide additional valuable information on the behaviour of the turbulence during the L-H transition.
The whole set of diagnostics operating simultaneously will allow the characterization of the plasma turbulence evolution from the SOL (GPI and probes) to the plasma gradient (DR) and plasma core (HIBP) regions at the L-H transition.

[1] T. Estrada et al., Plasma Phys. Control. Fusion 51, 124015 (2009)

[2] C. Hidalgo et al., EPL 87, 55002 (2009)

[3] T. Estrada et al., Phys. Rev. Lett. 107, 245004 (2011) 

[4] A. Melnikov et al., Nucl. Fusion 53, 092002 (2013)

[5] E. de la Cal and TJ-II Team, Nucl. Fusion 56, 106031 (2016)

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
Experiments in March 2022 focussed on GPI & DR: To prepare the experiment we need first to reproduce the conditions for L-H transitions. Once the proper conditions are found, He puffing will be introduced for GPI measurements.
Experiments in May 2022 focussed on HIBP & DR & Probes
Experiments in June 2022 focussed on simultaneous measurements using the whole set of TJ-II diagnostics

* Essential diagnostic systems: GPI, Doppler reflectometer, Langmuir probes, HIBP, microwave interferometer, Thomson scattering, Hα detectors, diamagnetic, Rogosky and Mirnov coils, SXR, bolometry

* Type of plasmas (heating configuration): NBI plasmas with plasma target created by ECH in the standard (or 101_42_64) magnetic configuration.

* Specific requirements on wall conditioning if any: Fresh Li is required for a good density control during the NBI phase.

* External users: need a local computer account for data access: no

* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: experiments splitted in three blocks in March (DR and GPI), May and June (availability of HIBP)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II:L-H transition studies: characterization of plasma turbulence using Gas Puff Imaging, Probes, Doppler reflectometry and HIBP diagnostics

2022-01-18T10:18:55Z

Teresa.estrada: /* Description of the activity */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''L-H transition studies: characterization of plasma turbulence using Gas Puff Imaging, Probes, Doppler reflectometry and HIBP diagnostics'''

== Name and affiliation of proponent ==
Teresa Estrada, CIEMAT
https://orcid.org/0000-0001-6205-2656

== Details of contact person at LNF ==
N/A

== Description of the activity ==
At TJ-II, spontaneous L-H transitions are achieved in neutral beam injection (NBI) heated plasma. Abrupt as well as gradual transitions are achieved depending, among other plasma parameters, on the heating power and magnetic configuration topology. Doppler reflectometry (DR) measurements show an increase in the negative radial electric field (Er) together with a reduction in plasma turbulence at the transition [1]. These measurements together with measurements obtained using a dual Langmuir probe system [2] show that the trigger of the L-H transition is more correlated with the development of fluctuating radial electric fields than steady-state Er effects. This conclusion is further stressed when operating close to the L-H transition threshold conditions, where pronounced oscillations in both, Er and density turbulence measured by DR show a characteristic predator-prey relation [3]. These experimental observations are consistent with L-H transition models based on turbulence-induced sheared/zonal flows. In addition, HIBP measurements show a reduction in the plasma turbulence and associated flux not only in the plasma edge region but also in the plasma core [4].
Recently a Gas Puff Imaging system (GPI) has been installed and tested at TJ-II. The new gas injection system is used with a camera system that allows 3 simultaneous filtered frames to apply the He I ratio technique, getting 2D measurements of the edge plasma electron density ne and temperature Te with spatial resolution of 3 mm and temporal resolution down to 10 microseconds [5]. This new diagnostic will permit the 2-D characterization of edge and SOL plasma turbulence and is expected to provide additional valuable information on the behaviour of the turbulence during the L-H transition.
The whole set of diagnostics operating simultaneously will allow the characterization of the plasma turbulence evolution from the SOL (GPI and probes) to the plasma gradient (DR) and plasma core (HIBP) regions at the L-H transition.

[1] T. Estrada et al., Plasma Phys. Control. Fusion 51, 124015 (2009)

[2] C. Hidalgo et al., EPL 87, 55002 (2009)

[3] T. Estrada et al., Phys. Rev. Lett. 107, 245004 (2011) 

[4] A. Melnikov et al., Nucl. Fusion 53, 092002 (2013)

[5] E. de la Cal and TJ-II Team, Nucl. Fusion 56, 106031 (2016)

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
Experiments in March 2022 focussed on GPI & DR: To prepare the experiment we need first to reproduce the conditions for L-H transitions. Once the proper conditions are found, He puffing will be introduced for GPI measurements.
Experiments in May 2022 focussed on HIBP & DR & Probes
Experiments in June 2022 focussed on simultaneous measurements using the whole set of TJ-II diagnostics

* Essential diagnostic systems: GPI, Doppler reflectometer, Langmuir probes, HIBP, microwave interferometer, Thomson scattering, Hα detectors, diamagnetic, Rogosky and Mirnov coils, SXR, bolometry

* Type of plasmas (heating configuration): NBI plasmas with plasma target created by ECH in the standard (or 101_42_64) magnetic configuration.

* Specific requirements on wall conditioning if any: Fresh Li is required for a good density control during the NBI phase.

* External users: need a local computer account for data access: no

* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: experiments splitted in three blocks in March (DR and GPI), May and June (availability of HIBP)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II:L-H transition studies: characterization of plasma turbulence using Gas Puff Imaging, Probes, Doppler reflectometry and HIBP diagnostics

2022-01-18T10:17:09Z

Teresa.estrada: /* Description of the activity */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''L-H transition studies: characterization of plasma turbulence using Gas Puff Imaging, Probes, Doppler reflectometry and HIBP diagnostics'''

== Name and affiliation of proponent ==
Teresa Estrada, CIEMAT
https://orcid.org/0000-0001-6205-2656

== Details of contact person at LNF ==
N/A

== Description of the activity ==
At TJ-II, spontaneous L-H transitions are achieved in neutral beam injection (NBI) heated plasma. Abrupt as well as gradual transitions are achieved depending, among other plasma parameters, on the heating power and magnetic configuration topology. Doppler reflectometry (DR) measurements show an increase in the negative radial electric field (Er) together with a reduction in plasma turbulence at the transition [1]. These measurements together with measurements obtained using a dual Langmuir probe system [2] show that the trigger of the L-H transition is more correlated with the development of fluctuating radial electric fields than steady-state Er effects. This conclusion is further stressed when operating close to the L-H transition threshold conditions, where pronounced oscillations in both, Er and density turbulence measured by DR show a characteristic predator-prey relation [3]. These experimental observations are consistent with L-H transition models based on turbulence-induced sheared/zonal flows. In addition, HIBP measurements have shown a reduction in the plasma turbulence and associated flux not only in the plasma edge region but also in the plasma core [4].
Recently a Gas Puff Imaging system (GPI) has been installed and tested at TJ-II. The new gas injection system is used with a camera system that allows 3 simultaneous filtered frames to apply the He I ratio technique, getting 2D measurements of the edge plasma electron density ne and temperature Te with spatial resolution of 3 mm and temporal resolution down to 10 microseconds [5]. This new diagnostic will permit the 2-D characterization of edge and SOL plasma turbulence and is expected to provide additional valuable information on the behaviour of the turbulence during the L-H transition.
The whole set of diagnostics operating simultaneously will allow the characterization of the plasma turbulence evolution from the SOL (GPI and probes) to the plasma gradient (DR) and plasma core (HIBP) regions at the L-H transition.

[1] T. Estrada et al., Plasma Phys. Control. Fusion 51, 124015 (2009)

[2] C. Hidalgo et al., EPL 87, 55002 (2009)

[3] T. Estrada et al., Phys. Rev. Lett. 107, 245004 (2011) 

[4] A. Melnikov et al., Nucl. Fusion 53, 092002 (2013)

[5] E. de la Cal and TJ-II Team, Nucl. Fusion 56, 106031 (2016)

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
Experiments in March 2022 focussed on GPI & DR: To prepare the experiment we need first to reproduce the conditions for L-H transitions. Once the proper conditions are found, He puffing will be introduced for GPI measurements.
Experiments in May 2022 focussed on HIBP & DR & Probes
Experiments in June 2022 focussed on simultaneous measurements using the whole set of TJ-II diagnostics

* Essential diagnostic systems: GPI, Doppler reflectometer, Langmuir probes, HIBP, microwave interferometer, Thomson scattering, Hα detectors, diamagnetic, Rogosky and Mirnov coils, SXR, bolometry

* Type of plasmas (heating configuration): NBI plasmas with plasma target created by ECH in the standard (or 101_42_64) magnetic configuration.

* Specific requirements on wall conditioning if any: Fresh Li is required for a good density control during the NBI phase.

* External users: need a local computer account for data access: no

* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: experiments splitted in three blocks in March (DR and GPI), May and June (availability of HIBP)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II:L-H transition studies: characterization of plasma turbulence using Gas Puff Imaging, Probes, Doppler reflectometry and HIBP diagnostics

2022-01-18T10:16:35Z

Teresa.estrada: Created page with "== Experimental campaign == Spring 2022 == Proposal title == '''L-H transition studies: characterization of plasma turbulence using Gas Puff Imaging, Probes, Doppler reflecto..."

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''L-H transition studies: characterization of plasma turbulence using Gas Puff Imaging, Probes, Doppler reflectometry and HIBP diagnostics'''

== Name and affiliation of proponent ==
Teresa Estrada, CIEMAT
https://orcid.org/0000-0001-6205-2656

== Details of contact person at LNF ==
N/A

== Description of the activity ==
At TJ-II, spontaneous L-H transitions are achieved in neutral beam injection (NBI) heated plasma. Abrupt as well as gradual transitions are achieved depending, among other plasma parameters, on the heating power and magnetic configuration topology. Doppler reflectometry (DR) measurements show an increase in the negative radial electric field (Er) together with a reduction in plasma turbulence at the transition [1]. These measurements together with measurements obtained using a dual Langmuir probe system [2] show that the trigger of the L-H transition is more correlated with the development of fluctuating radial electric fields than steady-state Er effects. This conclusion is further stressed when operating close to the L-H transition threshold conditions, where pronounced oscillations in both, Er and density turbulence measured by DR show a characteristic predator-prey relation [3]. These experimental observations are consistent with L-H transition models based on turbulence-induced sheared/zonal flows. In addition, HIBP measurements have shown a reduction in the plasma turbulence and associated flux not only in the plasma edge region but also in the plasma core [4].
Recently a Gas Puff Imaging system (GPI) has been installed and tested at TJ-II. The new gas injection system is used with a camera system that allows 3 simultaneous filtered frames to apply the He I ratio technique, getting 2D measurements of the edge plasma electron density ne and temperature Te with spatial resolution of 3 mm and temporal resolution down to 10 microseconds [5]. This new diagnostic will permit the 2-D characterization of edge and SOL plasma turbulence and is expected to provide additional valuable information on the behaviour of the turbulence during the L-H transition.
The whole set of diagnostics operating simultaneously will allow the characterization of the plasma turbulence evolution from the SOL (GPI and probes) to the plasma gradient (DR) and plasma core (HIBP) regions at the L-H transition.

[1] T. Estrada et al., Plasma Phys. Control. Fusion 51, 124015 (2009)
[2] C. Hidalgo et al., EPL 87, 55002 (2009)
[3] T. Estrada et al., Phys. Rev. Lett. 107, 245004 (2011) 
[4] A. Melnikov et al., Nucl. Fusion 53, 092002 (2013)
[5] E. de la Cal and TJ-II Team, Nucl. Fusion 56, 106031 (2016)

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
Experiments in March 2022 focussed on GPI & DR: To prepare the experiment we need first to reproduce the conditions for L-H transitions. Once the proper conditions are found, He puffing will be introduced for GPI measurements.
Experiments in May 2022 focussed on HIBP & DR & Probes
Experiments in June 2022 focussed on simultaneous measurements using the whole set of TJ-II diagnostics

* Essential diagnostic systems: GPI, Doppler reflectometer, Langmuir probes, HIBP, microwave interferometer, Thomson scattering, Hα detectors, diamagnetic, Rogosky and Mirnov coils, SXR, bolometry

* Type of plasmas (heating configuration): NBI plasmas with plasma target created by ECH in the standard (or 101_42_64) magnetic configuration.

* Specific requirements on wall conditioning if any: Fresh Li is required for a good density control during the NBI phase.

* External users: need a local computer account for data access: no

* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: experiments splitted in three blocks in March (DR and GPI), May and June (availability of HIBP)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: Perpendicular plasma flow asymmetries in different iota magnetic configurations measured by Doppler reflectometry

2021-04-29T09:34:30Z

Teresa.estrada: /* Description of the activity */

== Experimental campaign ==
Spring 2021

== Proposal title ==
'''Perpendicular plasma flow asymmetries in different iota magnetic configurations measured by Doppler reflectometry'''

== Name and affiliation of proponent ==

T. Estrada, E. Maragkoudakis, D. Carralero, J. Martínez

Laboratorio Nacional de Fusión, CIEMAT

== Details of contact person at LNF ==
N/A

== Description of the activity ==
Enter description here <ref>A. Einstein, Journal of Exceptional Results (2017)</ref>, including motivation/objectives and experience of the proponent (typically one-two pages)

Experimental studies have been performed in TJ-II aiming at the verification of the spatial localization of instabilities predicted by the Gyrokinetic simulations in stellarators and the verification of the electrostatic potential variation on the flux surface as calculated by Neoclassical codes and its possible impact on the radial electric field. The experimental technique used to measure these quantities, Doppler reflectometry, allows the measurement of the density turbulence and its perpendicular rotation velocity at different turbulence scales and with good spatial and temporal resolution [1]. It can cover the radial region from ρ ≈ 0.6 to 0.9, at different perpendicular wave-numbers of the turbulence in the range k⊥ ≈ 1-14 cm-1, and at two plasma regions poloidally separated.
Poloidal asymmetries in the k⊥ spectrum were found [2] and compared with linear gyrokinetic simulations obtained using the code EUTERPE [3]. Model and experiment agree in showing a poloidal asymmetry that depends on the magnetic configuration. The agreement is good in the high iota configuration but not in the standard one. Besides, poloidal asymmetries in the Er profile were found in low density plasmas [2] and compared with the contribution to the local radial electric field arising from −φ′1, φ1 being the component of the neoclassical electrostatic potential that varies over the flux surface [4].
Recently, poloidal asymmetries in the rotation velocity have been detected at low k⊥. This effect appears to be more pronounced at the plasma edge under ion-root conditions and could be related to the tilt of the turbulent structures produced by sheared flows [5]. In order to investigate the possible link between this asymmetry and the tilt of turbulent structures, further experiments are needed to characterize the asymmetry and tilt angle simultaneously.
We propose to study high density ECH plasmas or NBI discharges with density control, in the standard magnetic configuration and in a higher iota configuration.
To properly measure with the Doppler reflectometry at different k⊥ at the two poloidally separated positions a series of 16-20 similar discharges is needed in each scenario.

[1] T. Happel, et al., Rev. Sci. Instrum. 80 (2009) 073502

[2] T. Estrada, et al., Nucl. Fusion 59 (2019) 076021

[3] E. Sánchez, et al., Nucl. Fusion 59 (2019) 076029

[4] J.M. García-Regaña, et al., Plasma Phys. Control. Fusion 60 (2018) 104002

[5] J. Pinzón, et al., Plasma Phys. Control. Fusion 61 (2019) 105009

== International or National funding project or entity ==
FIS2017-88892-P

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: 3 days
* Essential diagnostic systems: Doppler reflectometer, microwave interferometer, Thomson scattering, ECE, Hα detectors, diamagnetic loop, Rogosky and Mirnov coils
* Type of plasmas (heating configuration): high density ECH plasmas or NBI discharges with density control
* Specific requirements on wall conditioning if any: fresh Li coating
* External users: need a local computer account for data access: no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2021]]

TJ-II: Perpendicular plasma flow asymmetries in different iota magnetic configurations measured by Doppler reflectometry

2021-03-05T09:58:51Z

Teresa.estrada: Created page with "== Experimental campaign == Spring 2021 == Proposal title == '''Perpendicular plasma flow asymmetries in different iota magnetic configurations measured by Doppler reflectome..."

== Experimental campaign ==
Spring 2021

== Proposal title ==
'''Perpendicular plasma flow asymmetries in different iota magnetic configurations measured by Doppler reflectometry'''

== Name and affiliation of proponent ==

T. Estrada, E. Maragkoudakis, D. Carralero, J. Martínez

Laboratorio Nacional de Fusión, CIEMAT

== Details of contact person at LNF ==
N/A

== Description of the activity ==
Enter description here <ref>A. Einstein, Journal of Exceptional Results (2017)</ref>, including motivation/objectives and experience of the proponent (typically one-two pages)

Experimental studies have been performed in TJ-II aiming at the verification of the spatial localization of instabilities predicted by the Gyrokinetic simulations in stellarators and the verification of the electrostatic potential variation on the flux surface as calculated by Neoclassical codes and its possible impact on the radial electric field. The experimental technique used to measure these quantities, Doppler reflectometry, allows the measurement of the density turbulence and its perpendicular rotation velocity at different turbulence scales and with good spatial and temporal resolution [1]. It can cover the radial region from ρ ≈ 0.6 to 0.9, at different perpendicular wave-numbers of the turbulence in the range k⊥ ≈ 1-14 cm-1, and at two plasma regions poloidally separated.
Poloidal asymmetries in the k⊥ spectrum were found [2] and compared with linear gyrokinetic simulations obtained using the code EUTERPE [3]. Model and experiment agree in showing a poloidal asymmetry that depends on the magnetic configuration. The agreement is good in the high iota configuration but not in the standard one. Besides, poloidal asymmetries in the Er profile were found in low density plasmas [2] and compared with the contribution to the local radial electric field arising from −φ′1, φ1 being the component of the neoclassical electrostatic potential that varies over the flux surface [4].
Recently, poloidal asymmetries in the rotation velocity have been detected at low k⊥. This effect appears to be more pronounced at the plasma edge under ion-root conditions and could be related to the tilt of the turbulent structures produced by sheared flows [5]. In order to investigate the possible link between this asymmetry and the tilt of turbulent structures, further experiments are needed to characterize the asymmetry and tilt angle simultaneously.
We propose to study high density ECH plasmas or NBI discharges with density control, in the standard magnetic configuration and in a higher iota configuration.
To properly measure with the Doppler reflectometry at different k⊥ at the two poloidally separated positions a series of 16-20 similar discharges is needed in each scenario.

[1] T. Happel, et al., Rev. Sci. Instrum. 80 (2009) 073502
[2] T. Estrada, et al., Nucl. Fusion 59 (2019) 076021
[3] E. Sánchez, et al., Nucl. Fusion 59 (2019) 076029
[4] J.M. García-Regaña, et al., Plasma Phys. Control. Fusion 60 (2018) 104002
[5] J. Pinzón, et al., Plasma Phys. Control. Fusion 61 (2019) 105009

== International or National funding project or entity ==
FIS2017-88892-P

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: 3 days
* Essential diagnostic systems: Doppler reflectometer, microwave interferometer, Thomson scattering, ECE, Hα detectors, diamagnetic loop, Rogosky and Mirnov coils
* Type of plasmas (heating configuration): high density ECH plasmas or NBI discharges with density control
* Specific requirements on wall conditioning if any: fresh Li coating
* External users: need a local computer account for data access: no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2021]]

TJ-II:Turbulence and radial electric field asymmetries in different iota magnetic configurations measured by Doppler reflectometry

2019-10-24T08:53:41Z

Teresa.estrada:

== Experimental campaign ==
2019 Autumn

== Proposal title ==
'''Turbulence and radial electric field asymmetries in different iota magnetic configurations measured by Doppler reflectometry'''

== Name and affiliation of proponent ==
Teresa Estrada CIEMAT

== Details of contact person at LNF ==
N/A

== Description of the activity ==
Experimental studies have been performed in TJ-II aiming at the verification of the spatial localization of instabilities predicted by the Gyrokinetic simulations in stellarators and the verification of the electrostatic potential variation on the flux surface as calculated by Neoclassical codes and its possible impact on the radial electric field. The experimental technique used to measure these quantities, Doppler reflectometry, allows the measurement of the density turbulence and its perpendicular rotation velocity at different turbulence scales and with good spatial and temporal resolution [1]. It can cover the radial region from ρ ≈ 0.6 to 0.9, at different perpendicular wave-numbers of the turbulence in the range k⊥ ≈ 1-14 cm-1, and at two plasma regions poloidally separated.
Poloidal asymmetries in the k⊥ spectrum were found [2] and compared with linear gyrokinetic simulations obtained using the code EUTERPE [3]. Model and experiment agree in showing a poloidal asymmetry that depends on the magnetic configuration. The agreement is good in the high iota configuration but not in the standard one. Besides, poloidal asymmetries in the Er profile were found in low density plasmas [2] and compared with the contribution to the local radial electric field arising from −φ′1, φ1 being the component of the neoclassical electrostatic potential that varies over the flux surface [4]. The simulation results show variations in Er comparable to those found in the experiments, but there is a disagreement regarding the sign of the Er correction when the effect of kinetic electrons on φ1 is not considered as shown in recent simulations performed with the newly developed NC code KNOSOS [5].
In order to further investigate the impact of the magnetic configuration on the turbulence and Er asymmetries we propose to explore additional magnetic configurations covering different rotational transform values.
We propose to explore magnetic configurations between the standard 100_44_64 and the high iota 42_102_69 in electron root confinement regime plasmas, heated with ECH full power on-axis at densities 0.5-0.6 1019 m-3. To properly measured the k⊥ spectra at the two poloidally separated positions a series of 16-20 similar discharges is needed in each scenario.

[1] T. Happel, et al., Rev. Sci. Instrum. 80 (2009) 073502

[2] T. Estrada, et al., Nucl. Fusion 59 (2019) 076021

[3] E. Sánchez, et al., Nucl. Fusion 59 (2019) 076029

[4] J.M. García-Regaña, et al., Plasma Phys. Control. Fusion 60 (2018) 104002

[5] J. L. Velasco, I. Calvo, F. I. Parra, and J. M. García-Regaña, Submitted, arXiv:1908.11615

== International or National funding project or entity ==
FIS2017-88892-P

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: 2-3 days
* Essential diagnostic systems: Doppler reflectometer, microwave interferometer, Thomson scattering, ECE
* Type of plasmas (heating configuration): ECH full power on-axis
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Autumn 2019]]

TJ-II:Turbulence and radial electric field asymmetries in different iota magnetic configurations measured by Doppler reflectometry

2019-10-24T08:52:50Z

Teresa.estrada: Created page with "== Experimental campaign == 2019 Autumn == Proposal title == '''Turbulence and radial electric field asymmetries in different iota magnetic configurations measured by Doppler..."

== Experimental campaign ==
2019 Autumn

== Proposal title ==
'''Turbulence and radial electric field asymmetries in different iota magnetic configurations measured by Doppler reflectometry'''

== Name and affiliation of proponent ==
Teresa Estrada CIEMAT

== Details of contact person at LNF ==
N/A

== Description of the activity ==
Experimental studies have been performed in TJ-II aiming at the verification of the spatial localization of instabilities predicted by the Gyrokinetic simulations in stellarators and the verification of the electrostatic potential variation on the flux surface as calculated by Neoclassical codes and its possible impact on the radial electric field. The experimental technique used to measure these quantities, Doppler reflectometry, allows the measurement of the density turbulence and its perpendicular rotation velocity at different turbulence scales and with good spatial and temporal resolution [1]. It can cover the radial region from ρ ≈ 0.6 to 0.9, at different perpendicular wave-numbers of the turbulence in the range k⊥ ≈ 1-14 cm-1, and at two plasma regions poloidally separated.
Poloidal asymmetries in the k⊥ spectrum were found [2] and compared with linear gyrokinetic simulations obtained using the code EUTERPE [3]. Model and experiment agree in showing a poloidal asymmetry that depends on the magnetic configuration. The agreement is good in the high iota configuration but not in the standard one. Besides, poloidal asymmetries in the Er profile were found in low density plasmas [2] and compared with the contribution to the local radial electric field arising from −φ′1, φ1 being the component of the neoclassical electrostatic potential that varies over the flux surface [4]. The simulation results show variations in Er comparable to those found in the experiments, but there is a disagreement regarding the sign of the Er correction when the effect of kinetic electrons on φ1 is not considered as shown in recent simulations performed with the newly developed NC code KNOSOS [5].
In order to further investigate the impact of the magnetic configuration on the turbulence and Er asymmetries we propose to explore additional magnetic configurations covering different rotational transform values.
We propose to explore magnetic configurations between the standard 100_44_64 and the high iota 42_102_69 in electron root confinement regime plasmas, heated with ECH full power on-axis at densities 0.5-0.6 1019 m-3. To properly measured the k⊥ spectra at the two poloidally separated positions a series of 16-20 similar discharges is needed in each scenario.

[1] T. Happel, et al., Rev. Sci. Instrum. 80 (2009) 073502
[2] T. Estrada, et al., Nucl. Fusion 59 (2019) 076021
[3] E. Sánchez, et al., Nucl. Fusion 59 (2019) 076029
[4] J.M. García-Regaña, et al., Plasma Phys. Control. Fusion 60 (2018) 104002
[5] J. L. Velasco, I. Calvo, F. I. Parra, and J. M. García-Regaña, Submitted, arXiv:1908.11615

== International or National funding project or entity ==
FIS2017-88892-P

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: 2-3 days
* Essential diagnostic systems: Doppler reflectometer, microwave interferometer, Thomson scattering, ECE
* Type of plasmas (heating configuration): ECH full power on-axis
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Autumn 2019]]

TJ-II:Er and turbulence asymmetries in low ripple configurations measured by Doppler reflectometry

2018-10-16T13:59:35Z

Teresa.estrada: /* If applicable, International or National funding project or entity */

== Experimental campaign ==
2018 Autumn

== Proposal title ==
'''Er and turbulence asymmetries in low ripple configurations measured by Doppler reflectometry'''

== Name and affiliation of proponent ==

T. Estrada, J. M. García-Regaña, E. Sánchez, D. Carralero, C. Hidalgo, J.L. Velasco

CIEMAT

== Details of contact person at LNF (if applicable) ==
N/A

== Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages)==

Motivation

Experimental studies have been performed in TJ-II aiming at the verification of the spatial localization of instabilities predicted by the Gyrokinetic simulations in stellarators [1-3] and the verification of the electrostatic potential variation on the flux surface, φ1, as calculated by Neoclassical codes and its possible impact on the radial electric field [4]. The experimental technique used to measure these quantities, Doppler reflectometry, allows the measurement of the density turbulence and its perpendicular rotation velocity at different turbulence scales and with good spatial and temporal resolution [5]. It can cover the radial region from ρ ≈ 0.6 to 0.9, at different perpendicular wave-numbers of the turbulence in the range k⊥ ≈ 1-14 cm-1, and at two plasma regions poloidally separated.
The main results, discussed in [6], can be summarized as follows:
• Er profiles measured at poloidally separated positions in the same flux-surfaces show pronounced differences in low density plasmas, i.e. plasmas in neoclassical electron root confinement. At higher plasma densities the Er asymmetry gradually decreases and almost disappears in ion root plasmas. The asymmetry in the Er profile can be explained to be due to the radial dependence of electrostatic potential varying over the flux surface, φ1 [7].
• Differences in the turbulence intensity have been found when comparing the k⊥ spectra measured at poloidally separated positions in the same flux-surface. The results are in good qualitative agreement with the spatial localization of instabilities as calculated using the global gyrokinetic code EUTERPE [8].
• Experiments performed in a magnetic configuration with high rotational transform show a less pronounced and reversed poloidal asymmetry.

Proposal

We propose to explore the influence of the magnetic ripple on the poloidal asymmetry of Er and compare with the Neoclassical expectations. To that end, we propose to explore configurations with different plasma volume, and therefore different magnetic ripple, while keeping the rotational transform profile fixed (as in the standard magnetic configuration). The main properties of the proposed magnetic configurations are summarized in the table.
We propose to measure the asymmetry properties of the Er profiles in the four magnetic configurations in low density (0.5 1019 m-3), ECH heated plasmas at maximum power (≈ 500 kW) on-axis. Besides, the asymmetry properties of the k⊥ spectra will be measured in the lowest ripple configuration for comparison with the asymmetry found in the standard one.

Config. Rax (0º) -Zlim(m) ι0 ιa Well(%) ripp_axis ripp_edge a(cm) V(m3)

100_44_64 1.739 0.362 1.551 1.650 2.390 1.900 37.600 20.64 1.0976

071_44_52 1.722 0.319 1.549 1.649 3.200 1.500 29.400 17.37 0.7575

054_43_45 1.709 0.288 1.543 1.648 3.200 ------- ------- 14.63 0.5315

039_42_38 1.699 0.261 1.549 1.674 3.000 2.900 20.000 12.35 0.3741

[1] M. Nadeem, et al., Phys. Plasmas 8 (2001) 4375

[2] P. Xanthopoulos, et al., Phys. Rev. X 6 (2016) 021033

[3] E. Sánchez, et al., 21st ISHW (2017) Kyoto, Japan

[4] J.M. García-Regaña, et al., Nucl. Fusion 57 (2017) 056004

[5] T. Happel, et al., Rev. Sci. Instrum. 80 (2009) 073502

[6] T. Estrada, et al., IAEA FEC (2018)

[7] J.M. García-Regaña, et al., PPCF 60 (2018) 10402

[8] E. Sánchez, et al., IAEA FEC (2018)

== If applicable, International or National funding project or entity ==

Proyecto del Plan Nacional, referencia: FIS2017-88892-P

EUROfusion WP.S1

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
The characterization of the Er profiles will required four reproducible discharges in each magnetic configuration (4 shots x 4 configurations: 16 discharges); and to properly measured the k⊥ spectra at the two poloidally separated positions a series of about 20 similar discharges is needed in in the lowest ripple configuration.
* Essential diagnostic systems:
Doppler reflectometer, microwave interferometer, Thomson scattering, ECE, Hα detectors, diamagnetic loop, Rogosky and Mirnov coils, SXR, bolometry, etc.
* Type of plasmas (heating configuration):
ECH on-axis, full power
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
December

== References ==
<references /> 

<hr> 
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Autumn 2018]]

TJ-II:Er and turbulence asymmetries in low ripple configurations measured by Doppler reflectometry

2018-10-16T13:58:24Z

Teresa.estrada: /* If applicable, International or National funding project or entity */

== Experimental campaign ==
2018 Autumn

== Proposal title ==
'''Er and turbulence asymmetries in low ripple configurations measured by Doppler reflectometry'''

== Name and affiliation of proponent ==

T. Estrada, J. M. García-Regaña, E. Sánchez, D. Carralero, C. Hidalgo, J.L. Velasco

CIEMAT

== Details of contact person at LNF (if applicable) ==
N/A

== Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages)==

Motivation

Experimental studies have been performed in TJ-II aiming at the verification of the spatial localization of instabilities predicted by the Gyrokinetic simulations in stellarators [1-3] and the verification of the electrostatic potential variation on the flux surface, φ1, as calculated by Neoclassical codes and its possible impact on the radial electric field [4]. The experimental technique used to measure these quantities, Doppler reflectometry, allows the measurement of the density turbulence and its perpendicular rotation velocity at different turbulence scales and with good spatial and temporal resolution [5]. It can cover the radial region from ρ ≈ 0.6 to 0.9, at different perpendicular wave-numbers of the turbulence in the range k⊥ ≈ 1-14 cm-1, and at two plasma regions poloidally separated.
The main results, discussed in [6], can be summarized as follows:
• Er profiles measured at poloidally separated positions in the same flux-surfaces show pronounced differences in low density plasmas, i.e. plasmas in neoclassical electron root confinement. At higher plasma densities the Er asymmetry gradually decreases and almost disappears in ion root plasmas. The asymmetry in the Er profile can be explained to be due to the radial dependence of electrostatic potential varying over the flux surface, φ1 [7].
• Differences in the turbulence intensity have been found when comparing the k⊥ spectra measured at poloidally separated positions in the same flux-surface. The results are in good qualitative agreement with the spatial localization of instabilities as calculated using the global gyrokinetic code EUTERPE [8].
• Experiments performed in a magnetic configuration with high rotational transform show a less pronounced and reversed poloidal asymmetry.

Proposal

We propose to explore the influence of the magnetic ripple on the poloidal asymmetry of Er and compare with the Neoclassical expectations. To that end, we propose to explore configurations with different plasma volume, and therefore different magnetic ripple, while keeping the rotational transform profile fixed (as in the standard magnetic configuration). The main properties of the proposed magnetic configurations are summarized in the table.
We propose to measure the asymmetry properties of the Er profiles in the four magnetic configurations in low density (0.5 1019 m-3), ECH heated plasmas at maximum power (≈ 500 kW) on-axis. Besides, the asymmetry properties of the k⊥ spectra will be measured in the lowest ripple configuration for comparison with the asymmetry found in the standard one.

Config. Rax (0º) -Zlim(m) ι0 ιa Well(%) ripp_axis ripp_edge a(cm) V(m3)

100_44_64 1.739 0.362 1.551 1.650 2.390 1.900 37.600 20.64 1.0976

071_44_52 1.722 0.319 1.549 1.649 3.200 1.500 29.400 17.37 0.7575

054_43_45 1.709 0.288 1.543 1.648 3.200 ------- ------- 14.63 0.5315

039_42_38 1.699 0.261 1.549 1.674 3.000 2.900 20.000 12.35 0.3741

[1] M. Nadeem, et al., Phys. Plasmas 8 (2001) 4375

[2] P. Xanthopoulos, et al., Phys. Rev. X 6 (2016) 021033

[3] E. Sánchez, et al., 21st ISHW (2017) Kyoto, Japan

[4] J.M. García-Regaña, et al., Nucl. Fusion 57 (2017) 056004

[5] T. Happel, et al., Rev. Sci. Instrum. 80 (2009) 073502

[6] T. Estrada, et al., IAEA FEC (2018)

[7] J.M. García-Regaña, et al., PPCF 60 (2018) 10402

[8] E. Sánchez, et al., IAEA FEC (2018)

== If applicable, International or National funding project or entity ==

Proyecto del Plan Nacional, referencia: FIS2017-88892-P

EUROfusion S!

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
The characterization of the Er profiles will required four reproducible discharges in each magnetic configuration (4 shots x 4 configurations: 16 discharges); and to properly measured the k⊥ spectra at the two poloidally separated positions a series of about 20 similar discharges is needed in in the lowest ripple configuration.
* Essential diagnostic systems:
Doppler reflectometer, microwave interferometer, Thomson scattering, ECE, Hα detectors, diamagnetic loop, Rogosky and Mirnov coils, SXR, bolometry, etc.
* Type of plasmas (heating configuration):
ECH on-axis, full power
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
December

== References ==
<references /> 

<hr> 
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Autumn 2018]]

TJ-II:Er and turbulence asymmetries in low ripple configurations measured by Doppler reflectometry

2018-10-16T13:56:18Z

Teresa.estrada: /* Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages) */

== Experimental campaign ==
2018 Autumn

== Proposal title ==
'''Er and turbulence asymmetries in low ripple configurations measured by Doppler reflectometry'''

== Name and affiliation of proponent ==

T. Estrada, J. M. García-Regaña, E. Sánchez, D. Carralero, C. Hidalgo, J.L. Velasco

CIEMAT

== Details of contact person at LNF (if applicable) ==
N/A

== Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages)==

Motivation

Experimental studies have been performed in TJ-II aiming at the verification of the spatial localization of instabilities predicted by the Gyrokinetic simulations in stellarators [1-3] and the verification of the electrostatic potential variation on the flux surface, φ1, as calculated by Neoclassical codes and its possible impact on the radial electric field [4]. The experimental technique used to measure these quantities, Doppler reflectometry, allows the measurement of the density turbulence and its perpendicular rotation velocity at different turbulence scales and with good spatial and temporal resolution [5]. It can cover the radial region from ρ ≈ 0.6 to 0.9, at different perpendicular wave-numbers of the turbulence in the range k⊥ ≈ 1-14 cm-1, and at two plasma regions poloidally separated.
The main results, discussed in [6], can be summarized as follows:
• Er profiles measured at poloidally separated positions in the same flux-surfaces show pronounced differences in low density plasmas, i.e. plasmas in neoclassical electron root confinement. At higher plasma densities the Er asymmetry gradually decreases and almost disappears in ion root plasmas. The asymmetry in the Er profile can be explained to be due to the radial dependence of electrostatic potential varying over the flux surface, φ1 [7].
• Differences in the turbulence intensity have been found when comparing the k⊥ spectra measured at poloidally separated positions in the same flux-surface. The results are in good qualitative agreement with the spatial localization of instabilities as calculated using the global gyrokinetic code EUTERPE [8].
• Experiments performed in a magnetic configuration with high rotational transform show a less pronounced and reversed poloidal asymmetry.

Proposal

We propose to explore the influence of the magnetic ripple on the poloidal asymmetry of Er and compare with the Neoclassical expectations. To that end, we propose to explore configurations with different plasma volume, and therefore different magnetic ripple, while keeping the rotational transform profile fixed (as in the standard magnetic configuration). The main properties of the proposed magnetic configurations are summarized in the table.
We propose to measure the asymmetry properties of the Er profiles in the four magnetic configurations in low density (0.5 1019 m-3), ECH heated plasmas at maximum power (≈ 500 kW) on-axis. Besides, the asymmetry properties of the k⊥ spectra will be measured in the lowest ripple configuration for comparison with the asymmetry found in the standard one.

Config. Rax (0º) -Zlim(m) ι0 ιa Well(%) ripp_axis ripp_edge a(cm) V(m3)

100_44_64 1.739 0.362 1.551 1.650 2.390 1.900 37.600 20.64 1.0976

071_44_52 1.722 0.319 1.549 1.649 3.200 1.500 29.400 17.37 0.7575

054_43_45 1.709 0.288 1.543 1.648 3.200 ------- ------- 14.63 0.5315

039_42_38 1.699 0.261 1.549 1.674 3.000 2.900 20.000 12.35 0.3741

[1] M. Nadeem, et al., Phys. Plasmas 8 (2001) 4375

[2] P. Xanthopoulos, et al., Phys. Rev. X 6 (2016) 021033

[3] E. Sánchez, et al., 21st ISHW (2017) Kyoto, Japan

[4] J.M. García-Regaña, et al., Nucl. Fusion 57 (2017) 056004

[5] T. Happel, et al., Rev. Sci. Instrum. 80 (2009) 073502

[6] T. Estrada, et al., IAEA FEC (2018)

[7] J.M. García-Regaña, et al., PPCF 60 (2018) 10402

[8] E. Sánchez, et al., IAEA FEC (2018)

== If applicable, International or National funding project or entity ==
Proyecto del Plan NAcional, referencia: FIS2017-88892-P

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
The characterization of the Er profiles will required four reproducible discharges in each magnetic configuration (4 shots x 4 configurations: 16 discharges); and to properly measured the k⊥ spectra at the two poloidally separated positions a series of about 20 similar discharges is needed in in the lowest ripple configuration.
* Essential diagnostic systems:
Doppler reflectometer, microwave interferometer, Thomson scattering, ECE, Hα detectors, diamagnetic loop, Rogosky and Mirnov coils, SXR, bolometry, etc.
* Type of plasmas (heating configuration):
ECH on-axis, full power
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
December

== References ==
<references /> 

<hr> 
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Autumn 2018]]

TJ-II:Er and turbulence asymmetries in low ripple configurations measured by Doppler reflectometry

2018-10-16T13:55:55Z

Teresa.estrada: /* Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages) */

== Experimental campaign ==
2018 Autumn

== Proposal title ==
'''Er and turbulence asymmetries in low ripple configurations measured by Doppler reflectometry'''

== Name and affiliation of proponent ==

T. Estrada, J. M. García-Regaña, E. Sánchez, D. Carralero, C. Hidalgo, J.L. Velasco

CIEMAT

== Details of contact person at LNF (if applicable) ==
N/A

== Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages)==

Motivation

Experimental studies have been performed in TJ-II aiming at the verification of the spatial localization of instabilities predicted by the Gyrokinetic simulations in stellarators [1-3] and the verification of the electrostatic potential variation on the flux surface, φ1, as calculated by Neoclassical codes and its possible impact on the radial electric field [4]. The experimental technique used to measure these quantities, Doppler reflectometry, allows the measurement of the density turbulence and its perpendicular rotation velocity at different turbulence scales and with good spatial and temporal resolution [5]. It can cover the radial region from ρ ≈ 0.6 to 0.9, at different perpendicular wave-numbers of the turbulence in the range k⊥ ≈ 1-14 cm-1, and at two plasma regions poloidally separated.
The main results, discussed in [6], can be summarized as follows:
• Er profiles measured at poloidally separated positions in the same flux-surfaces show pronounced differences in low density plasmas, i.e. plasmas in neoclassical electron root confinement. At higher plasma densities the Er asymmetry gradually decreases and almost disappears in ion root plasmas. The asymmetry in the Er profile can be explained to be due to the radial dependence of electrostatic potential varying over the flux surface, φ1 [7].
• Differences in the turbulence intensity have been found when comparing the k⊥ spectra measured at poloidally separated positions in the same flux-surface. The results are in good qualitative agreement with the spatial localization of instabilities as calculated using the global gyrokinetic code EUTERPE [8].
• Experiments performed in a magnetic configuration with high rotational transform show a less pronounced and reversed poloidal asymmetry.

Proposal

We propose to explore the influence of the magnetic ripple on the poloidal asymmetry of Er and compare with the Neoclassical expectations. To that end, we propose to explore configurations with different plasma volume, and therefore different magnetic ripple, while keeping the rotational transform profile fixed (as in the standard magnetic configuration). The main properties of the proposed magnetic configurations are summarized in the table.
We propose to measure the asymmetry properties of the Er profiles in the four magnetic configurations in low density (0.5 1019 m-3), ECH heated plasmas at maximum power (≈ 500 kW) on-axis. Besides, the asymmetry properties of the k⊥ spectra will be measured in the lowest ripple configuration for comparison with the asymmetry found in the standard one.

Config. Rax (0º) -Zlim(m) ι0 ιa Well(%) ripp_axis ripp_edge a(cm) V(m3)

100_44_64 1.739 0.362 1.551 1.650 2.390 1.900 37.600 20.64 1.0976

071_44_52 1.722 0.319 1.549 1.649 3.200 1.500 29.400 17.37 0.7575

054_43_45 1.709 0.288 1.543 1.648 3.200 ------- ------- 14.63 0.5315

039_42_38 1.699 0.261 1.549 1.674 3.000 2.900 20.000 12.35 0.3741

[1] M. Nadeem, et al., Phys. Plasmas 8 (2001) 4375

[2] P. Xanthopoulos, et al., Phys. Rev. X 6 (2016) 021033

[3] E. Sánchez, et al., 21st ISHW (2017) Kyoto, Japan

[4] J.M. García-Regaña, et al., Nucl. Fusion 57 (2017) 056004

[5] T. Happel, et al., Rev. Sci. Instrum. 80 (2009) 073502

[6] T. Estrada, et al., IAEA FEC (2018)

[7] J.M. García-Regaña, et al., PPCF 60 (2018) 10402

[8] E. Sánchez, et al., IAEA FEC (2018)

== If applicable, International or National funding project or entity ==
Proyecto del Plan NAcional, referencia: FIS2017-88892-P

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
The characterization of the Er profiles will required four reproducible discharges in each magnetic configuration (4 shots x 4 configurations: 16 discharges); and to properly measured the k⊥ spectra at the two poloidally separated positions a series of about 20 similar discharges is needed in in the lowest ripple configuration.
* Essential diagnostic systems:
Doppler reflectometer, microwave interferometer, Thomson scattering, ECE, Hα detectors, diamagnetic loop, Rogosky and Mirnov coils, SXR, bolometry, etc.
* Type of plasmas (heating configuration):
ECH on-axis, full power
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
December

== References ==
<references /> 

<hr> 
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Autumn 2018]]

TJ-II:Er and turbulence asymmetries in low ripple configurations measured by Doppler reflectometry

2018-10-16T13:55:11Z

Teresa.estrada: /* Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages) */

== Experimental campaign ==
2018 Autumn

== Proposal title ==
'''Er and turbulence asymmetries in low ripple configurations measured by Doppler reflectometry'''

== Name and affiliation of proponent ==

T. Estrada, J. M. García-Regaña, E. Sánchez, D. Carralero, C. Hidalgo, J.L. Velasco

CIEMAT

== Details of contact person at LNF (if applicable) ==
N/A

== Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages)==

Motivation

Experimental studies have been performed in TJ-II aiming at the verification of the spatial localization of instabilities predicted by the Gyrokinetic simulations in stellarators [1-3] and the verification of the electrostatic potential variation on the flux surface, φ1, as calculated by Neoclassical codes and its possible impact on the radial electric field [4]. The experimental technique used to measure these quantities, Doppler reflectometry, allows the measurement of the density turbulence and its perpendicular rotation velocity at different turbulence scales and with good spatial and temporal resolution [5]. It can cover the radial region from ρ ≈ 0.6 to 0.9, at different perpendicular wave-numbers of the turbulence in the range k⊥ ≈ 1-14 cm-1, and at two plasma regions poloidally separated.
The main results, discussed in [6], can be summarized as follows:
• Er profiles measured at poloidally separated positions in the same flux-surfaces show pronounced differences in low density plasmas, i.e. plasmas in neoclassical electron root confinement. At higher plasma densities the Er asymmetry gradually decreases and almost disappears in ion root plasmas. The asymmetry in the Er profile can be explained to be due to the radial dependence of electrostatic potential varying over the flux surface, φ1 [7].
• Differences in the turbulence intensity have been found when comparing the k⊥ spectra measured at poloidally separated positions in the same flux-surface. The results are in good qualitative agreement with the spatial localization of instabilities as calculated using the global gyrokinetic code EUTERPE [8].
• Experiments performed in a magnetic configuration with high rotational transform show a less pronounced and reversed poloidal asymmetry.

Proposal

We propose to explore the influence of the magnetic ripple on the poloidal asymmetry of Er and compare with the Neoclassical expectations. To that end, we propose to explore configurations with different plasma volume, and therefore different magnetic ripple, while keeping the rotational transform profile fixed (as in the standard magnetic configuration). The main properties of the proposed magnetic configurations are summarized in the table.
We propose to measure the asymmetry properties of the Er profiles in the four magnetic configurations in low density (0.5 1019 m-3), ECH heated plasmas at maximum power (≈ 500 kW) on-axis. Besides, the asymmetry properties of the k⊥ spectra will be measured in the lowest ripple configuration for comparison with the asymmetry found in the standard one.

Config. Rax (0º) -Zlim(m) ι0 ιa Well(%) ripp_axis ripp_edge a(cm) V(m3)

100_44_64 1.739 0.362 1.551 1.650 2.390 1.900 37.600 20.64 1.0976

071_44_52 1.722 0.319 1.549 1.649 3.200 1.500 29.400 17.37 0.7575

054_43_45 1.709 0.288 1.543 1.648 3.200 ------- ------- 14.63 0.5315

039_42_38 1.699 0.261 1.549 1.674 3.000 2.900 20.000 12.35 0.3741

[1] M. Nadeem, et al., Phys. Plasmas 8 (2001) 4375

[2] P. Xanthopoulos, et al., Phys. Rev. X 6 (2016) 021033

[3] E. Sánchez, et al., 21st ISHW (2017) Kyoto, Japan

[4] J.M. García-Regaña, et al., Nucl. Fusion 57 (2017) 056004

[5] T. Happel, et al., Rev. Sci. Instrum. 80 (2009) 073502

[6] T. Estrada, et al., IAEA FEC (2018)

[7] J.M. García-Regaña, et al., PPCF 60 (2018) 10402

[8] E. Sánchez, et al., IAEA FEC (2018)

== If applicable, International or National funding project or entity ==
Proyecto del Plan NAcional, referencia: FIS2017-88892-P

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
The characterization of the Er profiles will required four reproducible discharges in each magnetic configuration (4 shots x 4 configurations: 16 discharges); and to properly measured the k⊥ spectra at the two poloidally separated positions a series of about 20 similar discharges is needed in in the lowest ripple configuration.
* Essential diagnostic systems:
Doppler reflectometer, microwave interferometer, Thomson scattering, ECE, Hα detectors, diamagnetic loop, Rogosky and Mirnov coils, SXR, bolometry, etc.
* Type of plasmas (heating configuration):
ECH on-axis, full power
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
December

== References ==
<references /> 

<hr> 
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Autumn 2018]]

TJ-II:Er and turbulence asymmetries in low ripple configurations measured by Doppler reflectometry

2018-10-16T13:53:58Z

Teresa.estrada: /* Name and affiliation of proponent */

== Experimental campaign ==
2018 Autumn

== Proposal title ==
'''Er and turbulence asymmetries in low ripple configurations measured by Doppler reflectometry'''

== Name and affiliation of proponent ==

T. Estrada, J. M. García-Regaña, E. Sánchez, D. Carralero, C. Hidalgo, J.L. Velasco

CIEMAT

== Details of contact person at LNF (if applicable) ==
N/A

== Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages)==

Motivation

Experimental studies have been performed in TJ-II aiming at the verification of the spatial localization of instabilities predicted by the Gyrokinetic simulations in stellarators [1-3] and the verification of the electrostatic potential variation on the flux surface, φ1, as calculated by Neoclassical codes and its possible impact on the radial electric field [4]. The experimental technique used to measure these quantities, Doppler reflectometry, allows the measurement of the density turbulence and its perpendicular rotation velocity at different turbulence scales and with good spatial and temporal resolution [5]. It can cover the radial region from ρ ≈ 0.6 to 0.9, at different perpendicular wave-numbers of the turbulence in the range k⊥ ≈ 1-14 cm-1, and at two plasma regions poloidally separated.
The main results, discussed in [6], can be summarized as follows:
• Er profiles measured at poloidally separated positions in the same flux-surfaces show pronounced differences in low density plasmas, i.e. plasmas in neoclassical electron root confinement. At higher plasma densities the Er asymmetry gradually decreases and almost disappears in ion root plasmas. The asymmetry in the Er profile can be explained to be due to the radial dependence of electrostatic potential varying over the flux surface, φ1 [7].
• Differences in the turbulence intensity have been found when comparing the k⊥ spectra measured at poloidally separated positions in the same flux-surface. The results are in good qualitative agreement with the spatial localization of instabilities as calculated using the global gyrokinetic code EUTERPE [8].
• Experiments performed in a magnetic configuration with high rotational transform show a less pronounced and reversed poloidal asymmetry.

Proposal

We propose to explore the influence of the magnetic ripple on the poloidal asymmetry of Er and compare with the Neoclassical expectations. To that end, we propose to explore configurations with different plasma volume, and therefore different magnetic ripple, while keeping the rotational transform profile fixed (as in the standard magnetic configuration). The main properties of the proposed magnetic configurations are summarized in the table.
We propose to measure the asymmetry properties of the Er profiles in the four magnetic configurations in low density (0.5 1019 m-3), ECH heated plasmas at maximum power (≈ 500 kW) on-axis. Besides, the asymmetry properties of the k⊥ spectra will be measured in the lowest ripple configuration for comparison with the asymmetry found in the standard one.

Config. Rax (0º) -Zlim(m) ι0 ιa Well(%) ripp_axis ripp_edge a(cm) V(m3)

100_44_64 1.739 0.362 1.551 1.650 2.390 1.900 37.600 20.64 1.0976

71_44_52 1.722 0.319 1.549 1.649 3.200 1.500 29.400 17.37 0.7575

54_43_45 1.709 0.288 1.543 1.648 3.200 ------- ------- 14.63 0.5315

39_42_38 1.699 0.261 1.549 1.674 3.000 2.900 20.000 12.35 0.3741

[1] M. Nadeem, et al., Phys. Plasmas 8 (2001) 4375

[2] P. Xanthopoulos, et al., Phys. Rev. X 6 (2016) 021033

[3] E. Sánchez, et al., 21st ISHW (2017) Kyoto, Japan

[4] J.M. García-Regaña, et al., Nucl. Fusion 57 (2017) 056004

[5] T. Happel, et al., Rev. Sci. Instrum. 80 (2009) 073502

[6] T. Estrada, et al., IAEA FEC (2018)

[7] J.M. García-Regaña, et al., PPCF 60 (2018) 10402

[8] E. Sánchez, et al., IAEA FEC (2018)

== If applicable, International or National funding project or entity ==
Proyecto del Plan NAcional, referencia: FIS2017-88892-P

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
The characterization of the Er profiles will required four reproducible discharges in each magnetic configuration (4 shots x 4 configurations: 16 discharges); and to properly measured the k⊥ spectra at the two poloidally separated positions a series of about 20 similar discharges is needed in in the lowest ripple configuration.
* Essential diagnostic systems:
Doppler reflectometer, microwave interferometer, Thomson scattering, ECE, Hα detectors, diamagnetic loop, Rogosky and Mirnov coils, SXR, bolometry, etc.
* Type of plasmas (heating configuration):
ECH on-axis, full power
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
December

== References ==
<references /> 

<hr> 
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Autumn 2018]]

TJ-II:Er and turbulence asymmetries in low ripple configurations measured by Doppler reflectometry

2018-10-16T13:53:06Z

Teresa.estrada: /* Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages) */

== Experimental campaign ==
2018 Autumn

== Proposal title ==
'''Er and turbulence asymmetries in low ripple configurations measured by Doppler reflectometry'''

== Name and affiliation of proponent ==
Teresa Estrada, CIEMAT

== Details of contact person at LNF (if applicable) ==
N/A

== Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages)==

Motivation

Experimental studies have been performed in TJ-II aiming at the verification of the spatial localization of instabilities predicted by the Gyrokinetic simulations in stellarators [1-3] and the verification of the electrostatic potential variation on the flux surface, φ1, as calculated by Neoclassical codes and its possible impact on the radial electric field [4]. The experimental technique used to measure these quantities, Doppler reflectometry, allows the measurement of the density turbulence and its perpendicular rotation velocity at different turbulence scales and with good spatial and temporal resolution [5]. It can cover the radial region from ρ ≈ 0.6 to 0.9, at different perpendicular wave-numbers of the turbulence in the range k⊥ ≈ 1-14 cm-1, and at two plasma regions poloidally separated.
The main results, discussed in [6], can be summarized as follows:
• Er profiles measured at poloidally separated positions in the same flux-surfaces show pronounced differences in low density plasmas, i.e. plasmas in neoclassical electron root confinement. At higher plasma densities the Er asymmetry gradually decreases and almost disappears in ion root plasmas. The asymmetry in the Er profile can be explained to be due to the radial dependence of electrostatic potential varying over the flux surface, φ1 [7].
• Differences in the turbulence intensity have been found when comparing the k⊥ spectra measured at poloidally separated positions in the same flux-surface. The results are in good qualitative agreement with the spatial localization of instabilities as calculated using the global gyrokinetic code EUTERPE [8].
• Experiments performed in a magnetic configuration with high rotational transform show a less pronounced and reversed poloidal asymmetry.

Proposal

We propose to explore the influence of the magnetic ripple on the poloidal asymmetry of Er and compare with the Neoclassical expectations. To that end, we propose to explore configurations with different plasma volume, and therefore different magnetic ripple, while keeping the rotational transform profile fixed (as in the standard magnetic configuration). The main properties of the proposed magnetic configurations are summarized in the table.
We propose to measure the asymmetry properties of the Er profiles in the four magnetic configurations in low density (0.5 1019 m-3), ECH heated plasmas at maximum power (≈ 500 kW) on-axis. Besides, the asymmetry properties of the k⊥ spectra will be measured in the lowest ripple configuration for comparison with the asymmetry found in the standard one.

Config. Rax (0º) -Zlim(m) ι0 ιa Well(%) ripp_axis ripp_edge a(cm) V(m3)

100_44_64 1.739 0.362 1.551 1.650 2.390 1.900 37.600 20.64 1.0976

71_44_52 1.722 0.319 1.549 1.649 3.200 1.500 29.400 17.37 0.7575

54_43_45 1.709 0.288 1.543 1.648 3.200 ------- ------- 14.63 0.5315

39_42_38 1.699 0.261 1.549 1.674 3.000 2.900 20.000 12.35 0.3741

[1] M. Nadeem, et al., Phys. Plasmas 8 (2001) 4375

[2] P. Xanthopoulos, et al., Phys. Rev. X 6 (2016) 021033

[3] E. Sánchez, et al., 21st ISHW (2017) Kyoto, Japan

[4] J.M. García-Regaña, et al., Nucl. Fusion 57 (2017) 056004

[5] T. Happel, et al., Rev. Sci. Instrum. 80 (2009) 073502

[6] T. Estrada, et al., IAEA FEC (2018)

[7] J.M. García-Regaña, et al., PPCF 60 (2018) 10402

[8] E. Sánchez, et al., IAEA FEC (2018)

== If applicable, International or National funding project or entity ==
Proyecto del Plan NAcional, referencia: FIS2017-88892-P

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
The characterization of the Er profiles will required four reproducible discharges in each magnetic configuration (4 shots x 4 configurations: 16 discharges); and to properly measured the k⊥ spectra at the two poloidally separated positions a series of about 20 similar discharges is needed in in the lowest ripple configuration.
* Essential diagnostic systems:
Doppler reflectometer, microwave interferometer, Thomson scattering, ECE, Hα detectors, diamagnetic loop, Rogosky and Mirnov coils, SXR, bolometry, etc.
* Type of plasmas (heating configuration):
ECH on-axis, full power
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
December

== References ==
<references /> 

<hr> 
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Autumn 2018]]

TJ-II:Er and turbulence asymmetries in low ripple configurations measured by Doppler reflectometry

2018-10-16T13:52:35Z

Teresa.estrada: /* Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages) */

== Experimental campaign ==
2018 Autumn

== Proposal title ==
'''Er and turbulence asymmetries in low ripple configurations measured by Doppler reflectometry'''

== Name and affiliation of proponent ==
Teresa Estrada, CIEMAT

== Details of contact person at LNF (if applicable) ==
N/A

== Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages)==

Motivation

Experimental studies have been performed in TJ-II aiming at the verification of the spatial localization of instabilities predicted by the Gyrokinetic simulations in stellarators [1-3] and the verification of the electrostatic potential variation on the flux surface, φ1, as calculated by Neoclassical codes and its possible impact on the radial electric field [4]. The experimental technique used to measure these quantities, Doppler reflectometry, allows the measurement of the density turbulence and its perpendicular rotation velocity at different turbulence scales and with good spatial and temporal resolution [5]. It can cover the radial region from ρ ≈ 0.6 to 0.9, at different perpendicular wave-numbers of the turbulence in the range k⊥ ≈ 1-14 cm-1, and at two plasma regions poloidally separated.
The main results, discussed in [6], can be summarized as follows:
• Er profiles measured at poloidally separated positions in the same flux-surfaces show pronounced differences in low density plasmas, i.e. plasmas in neoclassical electron root confinement. At higher plasma densities the Er asymmetry gradually decreases and almost disappears in ion root plasmas. The asymmetry in the Er profile can be explained to be due to the radial dependence of electrostatic potential varying over the flux surface, φ1 [7].
• Differences in the turbulence intensity have been found when comparing the k⊥ spectra measured at poloidally separated positions in the same flux-surface. The results are in good qualitative agreement with the spatial localization of instabilities as calculated using the global gyrokinetic code EUTERPE [8].
• Experiments performed in a magnetic configuration with high rotational transform show a less pronounced and reversed poloidal asymmetry.

Proposal

We propose to explore the influence of the magnetic ripple on the poloidal asymmetry of Er and compare with the Neoclassical expectations. To that end, we propose to explore configurations with different plasma volume, and therefore different magnetic ripple, while keeping the rotational transform profile fixed (as in the standard magnetic configuration). The main properties of the proposed magnetic configurations are summarized in the table.
We propose to measure the asymmetry properties of the Er profiles in the four magnetic configurations in low density (0.5 1019 m-3), ECH heated plasmas at maximum power (≈ 500 kW) on-axis. Besides, the asymmetry properties of the k⊥ spectra will be measured in the lowest ripple configuration for comparison with the asymmetry found in the standard one.

Config. Rax (0º) -Zlim(m) ι0 ιa Well(%) ripp_axis ripp_edge a(cm) V(m3)

100_44_64 1.739 0.362 1.551 1.650 2.390 1.900 37.600 20.64 1.0976

71_44_52 1.722 0.319 1.549 1.649 3.200 1.500 29.400 17.37 0.7575

54_43_45 1.709 0.288 1.543 1.648 3.200 ------- ------- 14.63 0.5315

39_42_38 1.699 0.261 1.549 1.674 3.000 2.900 20.000 12.35 0.3741

[1] M. Nadeem, et al., Phys. Plasmas 8 (2001) 4375
[2] P. Xanthopoulos, et al., Phys. Rev. X 6 (2016) 021033
[3] E. Sánchez, et al., 21st ISHW (2017) Kyoto, Japan
[4] J.M. García-Regaña, et al., Nucl. Fusion 57 (2017) 056004
[5] T. Happel, et al., Rev. Sci. Instrum. 80 (2009) 073502
[6] T. Estrada, et al., IAEA FEC (2018)
[7] J.M. García-Regaña, et al., PPCF 60 (2018) 10402
[8] E. Sánchez, et al., IAEA FEC (2018)

== If applicable, International or National funding project or entity ==
Proyecto del Plan NAcional, referencia: FIS2017-88892-P

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
The characterization of the Er profiles will required four reproducible discharges in each magnetic configuration (4 shots x 4 configurations: 16 discharges); and to properly measured the k⊥ spectra at the two poloidally separated positions a series of about 20 similar discharges is needed in in the lowest ripple configuration.
* Essential diagnostic systems:
Doppler reflectometer, microwave interferometer, Thomson scattering, ECE, Hα detectors, diamagnetic loop, Rogosky and Mirnov coils, SXR, bolometry, etc.
* Type of plasmas (heating configuration):
ECH on-axis, full power
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
December

== References ==
<references /> 

<hr> 
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Autumn 2018]]

TJ-II:Er and turbulence asymmetries in low ripple configurations measured by Doppler reflectometry

2018-10-16T13:52:11Z

Teresa.estrada: /* Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages) */

== Experimental campaign ==
2018 Autumn

== Proposal title ==
'''Er and turbulence asymmetries in low ripple configurations measured by Doppler reflectometry'''

== Name and affiliation of proponent ==
Teresa Estrada, CIEMAT

== Details of contact person at LNF (if applicable) ==
N/A

== Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages)==

Motivation

Experimental studies have been performed in TJ-II aiming at the verification of the spatial localization of instabilities predicted by the Gyrokinetic simulations in stellarators [1-3] and the verification of the electrostatic potential variation on the flux surface, φ1, as calculated by Neoclassical codes and its possible impact on the radial electric field [4]. The experimental technique used to measure these quantities, Doppler reflectometry, allows the measurement of the density turbulence and its perpendicular rotation velocity at different turbulence scales and with good spatial and temporal resolution [5]. It can cover the radial region from ρ ≈ 0.6 to 0.9, at different perpendicular wave-numbers of the turbulence in the range k⊥ ≈ 1-14 cm-1, and at two plasma regions poloidally separated.
The main results, discussed in [6], can be summarized as follows:
• Er profiles measured at poloidally separated positions in the same flux-surfaces show pronounced differences in low density plasmas, i.e. plasmas in neoclassical electron root confinement. At higher plasma densities the Er asymmetry gradually decreases and almost disappears in ion root plasmas. The asymmetry in the Er profile can be explained to be due to the radial dependence of electrostatic potential varying over the flux surface, φ1 [7].
• Differences in the turbulence intensity have been found when comparing the k⊥ spectra measured at poloidally separated positions in the same flux-surface. The results are in good qualitative agreement with the spatial localization of instabilities as calculated using the global gyrokinetic code EUTERPE [8].
• Experiments performed in a magnetic configuration with high rotational transform show a less pronounced and reversed poloidal asymmetry.

Proposal

We propose to explore the influence of the magnetic ripple on the poloidal asymmetry of Er and compare with the Neoclassical expectations. To that end, we propose to explore configurations with different plasma volume, and therefore different magnetic ripple, while keeping the rotational transform profile fixed (as in the standard magnetic configuration). The main properties of the proposed magnetic configurations are summarized in the table.
We propose to measure the asymmetry properties of the Er profiles in the four magnetic configurations in low density (0.5 1019 m-3), ECH heated plasmas at maximum power (≈ 500 kW) on-axis. Besides, the asymmetry properties of the k⊥ spectra will be measured in the lowest ripple configuration for comparison with the asymmetry found in the standard one.

Config. Rax (0º) -Zlim(m) ι0 ιa Well(%) ripp_axis ripp_edge a(cm) V(m3)

100_44_64 1.739 0.362 1.551 1.650 2.390 1.900 37.600 20.64 1.0976

71_44_52 1.722 0.319 1.549 1.649 3.200 1.500 29.400 17.37 0.7575

54_43_45 1.709 0.288 1.543 1.648 3.200 ---- ---- 14.63 0.5315

39_42_38 1.699 0.261 1.549 1.674 3.000 2.900 20.000 12.35 0.3741

[1] M. Nadeem, et al., Phys. Plasmas 8 (2001) 4375
[2] P. Xanthopoulos, et al., Phys. Rev. X 6 (2016) 021033
[3] E. Sánchez, et al., 21st ISHW (2017) Kyoto, Japan
[4] J.M. García-Regaña, et al., Nucl. Fusion 57 (2017) 056004
[5] T. Happel, et al., Rev. Sci. Instrum. 80 (2009) 073502
[6] T. Estrada, et al., IAEA FEC (2018)
[7] J.M. García-Regaña, et al., PPCF 60 (2018) 10402
[8] E. Sánchez, et al., IAEA FEC (2018)

== If applicable, International or National funding project or entity ==
Proyecto del Plan NAcional, referencia: FIS2017-88892-P

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
The characterization of the Er profiles will required four reproducible discharges in each magnetic configuration (4 shots x 4 configurations: 16 discharges); and to properly measured the k⊥ spectra at the two poloidally separated positions a series of about 20 similar discharges is needed in in the lowest ripple configuration.
* Essential diagnostic systems:
Doppler reflectometer, microwave interferometer, Thomson scattering, ECE, Hα detectors, diamagnetic loop, Rogosky and Mirnov coils, SXR, bolometry, etc.
* Type of plasmas (heating configuration):
ECH on-axis, full power
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
December

== References ==
<references /> 

<hr> 
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Autumn 2018]]

TJ-II:Er and turbulence asymmetries in low ripple configurations measured by Doppler reflectometry

2018-10-16T13:50:37Z

Teresa.estrada: /* Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages) */

== Experimental campaign ==
2018 Autumn

== Proposal title ==
'''Er and turbulence asymmetries in low ripple configurations measured by Doppler reflectometry'''

== Name and affiliation of proponent ==
Teresa Estrada, CIEMAT

== Details of contact person at LNF (if applicable) ==
N/A

== Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages)==

Motivation

Experimental studies have been performed in TJ-II aiming at the verification of the spatial localization of instabilities predicted by the Gyrokinetic simulations in stellarators [1-3] and the verification of the electrostatic potential variation on the flux surface, φ1, as calculated by Neoclassical codes and its possible impact on the radial electric field [4]. The experimental technique used to measure these quantities, Doppler reflectometry, allows the measurement of the density turbulence and its perpendicular rotation velocity at different turbulence scales and with good spatial and temporal resolution [5]. It can cover the radial region from ρ ≈ 0.6 to 0.9, at different perpendicular wave-numbers of the turbulence in the range k⊥ ≈ 1-14 cm-1, and at two plasma regions poloidally separated.
The main results, discussed in [6], can be summarized as follows:
• Er profiles measured at poloidally separated positions in the same flux-surfaces show pronounced differences in low density plasmas, i.e. plasmas in neoclassical electron root confinement. At higher plasma densities the Er asymmetry gradually decreases and almost disappears in ion root plasmas. The asymmetry in the Er profile can be explained to be due to the radial dependence of electrostatic potential varying over the flux surface, φ1 [7].
• Differences in the turbulence intensity have been found when comparing the k⊥ spectra measured at poloidally separated positions in the same flux-surface. The results are in good qualitative agreement with the spatial localization of instabilities as calculated using the global gyrokinetic code EUTERPE [8].
• Experiments performed in a magnetic configuration with high rotational transform show a less pronounced and reversed poloidal asymmetry.

Proposal

We propose to explore the influence of the magnetic ripple on the poloidal asymmetry of Er and compare with the Neoclassical expectations. To that end, we propose to explore configurations with different plasma volume, and therefore different magnetic ripple, while keeping the rotational transform profile fixed (as in the standard magnetic configuration). The main properties of the proposed magnetic configurations are summarized in the table.
We propose to measure the asymmetry properties of the Er profiles in the four magnetic configurations in low density (0.5 1019 m-3), ECH heated plasmas at maximum power (≈ 500 kW) on-axis. Besides, the asymmetry properties of the k⊥ spectra will be measured in the lowest ripple configuration for comparison with the asymmetry found in the standard one.

Config. Rax (0º) -Zlim(m) ι0 ιa Well(%) ripp_axis ripp_edge a(cm) V(m3)

100_44_64 1.739 0.362 1.551 1.650 2.390 1.900 37.600 20.64 1.0976

71_44_52 1.722 0.319 1.549 1.649 3.200 1.500 29.400 17.37 0.7575

54_43_45 1.709 0.288 1.543 1.648 3.200 14.63 0.5315

39_42_38 1.699 0.261 1.549 1.674 3.000 2.900 20.000 12.35 0.3741

[1] M. Nadeem, et al., Phys. Plasmas 8 (2001) 4375
[2] P. Xanthopoulos, et al., Phys. Rev. X 6 (2016) 021033
[3] E. Sánchez, et al., 21st ISHW (2017) Kyoto, Japan
[4] J.M. García-Regaña, et al., Nucl. Fusion 57 (2017) 056004
[5] T. Happel, et al., Rev. Sci. Instrum. 80 (2009) 073502
[6] T. Estrada, et al., IAEA FEC (2018)
[7] J.M. García-Regaña, et al., PPCF 60 (2018) 10402
[8] E. Sánchez, et al., IAEA FEC (2018)

== If applicable, International or National funding project or entity ==
Proyecto del Plan NAcional, referencia: FIS2017-88892-P

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
The characterization of the Er profiles will required four reproducible discharges in each magnetic configuration (4 shots x 4 configurations: 16 discharges); and to properly measured the k⊥ spectra at the two poloidally separated positions a series of about 20 similar discharges is needed in in the lowest ripple configuration.
* Essential diagnostic systems:
Doppler reflectometer, microwave interferometer, Thomson scattering, ECE, Hα detectors, diamagnetic loop, Rogosky and Mirnov coils, SXR, bolometry, etc.
* Type of plasmas (heating configuration):
ECH on-axis, full power
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
December

== References ==
<references /> 

<hr> 
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Autumn 2018]]

TJ-II:Er and turbulence asymmetries in low ripple configurations measured by Doppler reflectometry

2018-10-16T13:50:13Z

Teresa.estrada: /* Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages) */

== Experimental campaign ==
2018 Autumn

== Proposal title ==
'''Er and turbulence asymmetries in low ripple configurations measured by Doppler reflectometry'''

== Name and affiliation of proponent ==
Teresa Estrada, CIEMAT

== Details of contact person at LNF (if applicable) ==
N/A

== Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages)==

Motivation

Experimental studies have been performed in TJ-II aiming at the verification of the spatial localization of instabilities predicted by the Gyrokinetic simulations in stellarators [1-3] and the verification of the electrostatic potential variation on the flux surface, φ1, as calculated by Neoclassical codes and its possible impact on the radial electric field [4]. The experimental technique used to measure these quantities, Doppler reflectometry, allows the measurement of the density turbulence and its perpendicular rotation velocity at different turbulence scales and with good spatial and temporal resolution [5]. It can cover the radial region from ρ ≈ 0.6 to 0.9, at different perpendicular wave-numbers of the turbulence in the range k⊥ ≈ 1-14 cm-1, and at two plasma regions poloidally separated.
The main results, discussed in [6], can be summarized as follows:
• Er profiles measured at poloidally separated positions in the same flux-surfaces show pronounced differences in low density plasmas, i.e. plasmas in neoclassical electron root confinement. At higher plasma densities the Er asymmetry gradually decreases and almost disappears in ion root plasmas. The asymmetry in the Er profile can be explained to be due to the radial dependence of electrostatic potential varying over the flux surface, φ1 [7].
• Differences in the turbulence intensity have been found when comparing the k⊥ spectra measured at poloidally separated positions in the same flux-surface. The results are in good qualitative agreement with the spatial localization of instabilities as calculated using the global gyrokinetic code EUTERPE [8].
• Experiments performed in a magnetic configuration with high rotational transform show a less pronounced and reversed poloidal asymmetry.

Proposal

We propose to explore the influence of the magnetic ripple on the poloidal asymmetry of Er and compare with the Neoclassical expectations. To that end, we propose to explore configurations with different plasma volume, and therefore different magnetic ripple, while keeping the rotational transform profile fixed (as in the standard magnetic configuration). The main properties of the proposed magnetic configurations are summarized in the table.
We propose to measure the asymmetry properties of the Er profiles in the four magnetic configurations in low density (0.5 1019 m-3), ECH heated plasmas at maximum power (≈ 500 kW) on-axis. Besides, the asymmetry properties of the k⊥ spectra will be measured in the lowest ripple configuration for comparison with the asymmetry found in the standard one.

Config. Rax (0º) -Zlim(m) ι0 ιa Well(%) ripp_axis ripp_edge a(cm) V(m3)

100_44_64 1.739 0.362 1.551 1.650 2.390 1.900 37.600 20.64 1.0976
71_44_52 1.722 0.319 1.549 1.649 3.200 1.500 29.400 17.37 0.7575
54_43_45 1.709 0.288 1.543 1.648 3.200 14.63 0.5315
39_42_38 1.699 0.261 1.549 1.674 3.000 2.900 20.000 12.35 0.3741

[1] M. Nadeem, et al., Phys. Plasmas 8 (2001) 4375
[2] P. Xanthopoulos, et al., Phys. Rev. X 6 (2016) 021033
[3] E. Sánchez, et al., 21st ISHW (2017) Kyoto, Japan
[4] J.M. García-Regaña, et al., Nucl. Fusion 57 (2017) 056004
[5] T. Happel, et al., Rev. Sci. Instrum. 80 (2009) 073502
[6] T. Estrada, et al., IAEA FEC (2018)
[7] J.M. García-Regaña, et al., PPCF 60 (2018) 10402
[8] E. Sánchez, et al., IAEA FEC (2018)

== If applicable, International or National funding project or entity ==
Proyecto del Plan NAcional, referencia: FIS2017-88892-P

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
The characterization of the Er profiles will required four reproducible discharges in each magnetic configuration (4 shots x 4 configurations: 16 discharges); and to properly measured the k⊥ spectra at the two poloidally separated positions a series of about 20 similar discharges is needed in in the lowest ripple configuration.
* Essential diagnostic systems:
Doppler reflectometer, microwave interferometer, Thomson scattering, ECE, Hα detectors, diamagnetic loop, Rogosky and Mirnov coils, SXR, bolometry, etc.
* Type of plasmas (heating configuration):
ECH on-axis, full power
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
December

== References ==
<references /> 

<hr> 
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Autumn 2018]]

TJ-II:Er and turbulence asymmetries in low ripple configurations measured by Doppler reflectometry

2018-10-16T13:49:31Z

Teresa.estrada: /* Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages) */

== Experimental campaign ==
2018 Autumn

== Proposal title ==
'''Er and turbulence asymmetries in low ripple configurations measured by Doppler reflectometry'''

== Name and affiliation of proponent ==
Teresa Estrada, CIEMAT

== Details of contact person at LNF (if applicable) ==
N/A

== Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages)==

Motivation

Experimental studies have been performed in TJ-II aiming at the verification of the spatial localization of instabilities predicted by the Gyrokinetic simulations in stellarators [1-3] and the verification of the electrostatic potential variation on the flux surface, φ1, as calculated by Neoclassical codes and its possible impact on the radial electric field [4]. The experimental technique used to measure these quantities, Doppler reflectometry, allows the measurement of the density turbulence and its perpendicular rotation velocity at different turbulence scales and with good spatial and temporal resolution [5]. It can cover the radial region from ρ ≈ 0.6 to 0.9, at different perpendicular wave-numbers of the turbulence in the range k⊥ ≈ 1-14 cm-1, and at two plasma regions poloidally separated.
The main results, discussed in [6], can be summarized as follows:
• Er profiles measured at poloidally separated positions in the same flux-surfaces show pronounced differences in low density plasmas, i.e. plasmas in neoclassical electron root confinement. At higher plasma densities the Er asymmetry gradually decreases and almost disappears in ion root plasmas. The asymmetry in the Er profile can be explained to be due to the radial dependence of electrostatic potential varying over the flux surface, φ1 [7].
• Differences in the turbulence intensity have been found when comparing the k⊥ spectra measured at poloidally separated positions in the same flux-surface. The results are in good qualitative agreement with the spatial localization of instabilities as calculated using the global gyrokinetic code EUTERPE [8].
• Experiments performed in a magnetic configuration with high rotational transform show a less pronounced and reversed poloidal asymmetry.

Proposal

We propose to explore the influence of the magnetic ripple on the poloidal asymmetry of Er and compare with the Neoclassical expectations. To that end, we propose to explore configurations with different plasma volume, and therefore different magnetic ripple, while keeping the rotational transform profile fixed (as in the standard magnetic configuration). The main properties of the proposed magnetic configurations are summarized in the table.
We propose to measure the asymmetry properties of the Er profiles in the four magnetic configurations in low density (0.5 1019 m-3), ECH heated plasmas at maximum power (≈ 500 kW) on-axis. Besides, the asymmetry properties of the k⊥ spectra will be measured in the lowest ripple configuration for comparison with the asymmetry found in the standard one.

Config. Rax (0º) -Zlim(m) ι0 ιa Well(%) ripp_axis ripp_edge a(cm) V(m3)

100_44_64 1.739 0.362 1.551 1.650 2.390 1.900 37.600 20.64 1.0976
71_44_52 1.722 0.319 1.549 1.649 3.200 1.500 29.400 17.37 0.7575
54_43_45 1.709 0.288 1.543 1.648 3.200 14.63 0.5315
39_42_38 1.699 0.261 1.549 1.674 3.000 2.900 20.000 12.35 0.3741

[1] M. Nadeem, et al., Phys. Plasmas 8 (2001) 4375
[2] P. Xanthopoulos, et al., Phys. Rev. X 6 (2016) 021033
[3] E. Sánchez, et al., 21st ISHW (2017) Kyoto, Japan
[4] J.M. García-Regaña, et al., Nucl. Fusion 57 (2017) 056004
[5] T. Happel, et al., Rev. Sci. Instrum. 80 (2009) 073502
[6] T. Estrada, et al., IAEA FEC (2018)
[7] J.M. García-Regaña, et al., PPCF 60 (2018) 10402
[8] E. Sánchez, et al., IAEA FEC (2018)

== If applicable, International or National funding project or entity ==
Proyecto del Plan NAcional, referencia: FIS2017-88892-P

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
The characterization of the Er profiles will required four reproducible discharges in each magnetic configuration (4 shots x 4 configurations: 16 discharges); and to properly measured the k⊥ spectra at the two poloidally separated positions a series of about 20 similar discharges is needed in in the lowest ripple configuration.
* Essential diagnostic systems:
Doppler reflectometer, microwave interferometer, Thomson scattering, ECE, Hα detectors, diamagnetic loop, Rogosky and Mirnov coils, SXR, bolometry, etc.
* Type of plasmas (heating configuration):
ECH on-axis, full power
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
December

== References ==
<references /> 

<hr> 
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Autumn 2018]]

TJ-II:Er and turbulence asymmetries in low ripple configurations measured by Doppler reflectometry

2018-10-16T13:48:54Z

Teresa.estrada: /* Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages) */

== Experimental campaign ==
2018 Autumn

== Proposal title ==
'''Er and turbulence asymmetries in low ripple configurations measured by Doppler reflectometry'''

== Name and affiliation of proponent ==
Teresa Estrada, CIEMAT

== Details of contact person at LNF (if applicable) ==
N/A

== Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages)==

Motivation

Experimental studies have been performed in TJ-II aiming at the verification of the spatial localization of instabilities predicted by the Gyrokinetic simulations in stellarators [1-3] and the verification of the electrostatic potential variation on the flux surface, φ1, as calculated by Neoclassical codes and its possible impact on the radial electric field [4]. The experimental technique used to measure these quantities, Doppler reflectometry, allows the measurement of the density turbulence and its perpendicular rotation velocity at different turbulence scales and with good spatial and temporal resolution [5]. It can cover the radial region from ρ ≈ 0.6 to 0.9, at different perpendicular wave-numbers of the turbulence in the range k⊥ ≈ 1-14 cm-1, and at two plasma regions poloidally separated.
The main results, discussed in [6], can be summarized as follows:
• Er profiles measured at poloidally separated positions in the same flux-surfaces show pronounced differences in low density plasmas, i.e. plasmas in neoclassical electron root confinement. At higher plasma densities the Er asymmetry gradually decreases and almost disappears in ion root plasmas. The asymmetry in the Er profile can be explained to be due to the radial dependence of electrostatic potential varying over the flux surface, φ1 [7].
• Differences in the turbulence intensity have been found when comparing the k⊥ spectra measured at poloidally separated positions in the same flux-surface. The results are in good qualitative agreement with the spatial localization of instabilities as calculated using the global gyrokinetic code EUTERPE [8].
• Experiments performed in a magnetic configuration with high rotational transform show a less pronounced and reversed poloidal asymmetry.

Proposal

We propose to explore the influence of the magnetic ripple on the poloidal asymmetry of Er and compare with the Neoclassical expectations. To that end, we propose to explore configurations with different plasma volume, and therefore different magnetic ripple, while keeping the rotational transform profile fixed (as in the standard magnetic configuration). The main properties of the proposed magnetic configurations are summarized in the table.
We propose to measure the asymmetry properties of the Er profiles in the four magnetic configurations in low density (0.5 1019 m-3), ECH heated plasmas at maximum power (≈ 500 kW) on-axis. Besides, the asymmetry properties of the k⊥ spectra will be measured in the lowest ripple configuration for comparison with the asymmetry found in the standard one.

Config. Rax (0º) -Zlim(m) ι0 ιa Well(%) ripp_axis ripp_edge a(cm) V(m3)

100_44_64 1.739 0.362 1.551 1.650 2.390 1.900 37.600 20.64 1.0976
71_44_52 1.722 0.319 1.549 1.649 3.200 1.500 29.400 17.37 0.7575
54_43_45 1.709 0.288 1.543 1.648 3.200 14.63 0.5315
39_42_38 1.699 0.261 1.549 1.674 3.000 2.900 20.000 12.35 0.3741

[1] M. Nadeem, et al., Phys. Plasmas 8 (2001) 4375
[2] P. Xanthopoulos, et al., Phys. Rev. X 6 (2016) 021033
[3] E. Sánchez, et al., 21st ISHW (2017) Kyoto, Japan
[4] J.M. García-Regaña, et al., Nucl. Fusion 57 (2017) 056004
[5] T. Happel, et al., Rev. Sci. Instrum. 80 (2009) 073502
[6] T. Estrada, et al., IAEA FEC (2018)
[7] J.M. García-Regaña, et al., PPCF 60 (2018) 10402
[8] E. Sánchez, et al., IAEA FEC (2018)

== If applicable, International or National funding project or entity ==
Proyecto del Plan NAcional, referencia: FIS2017-88892-P

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
The characterization of the Er profiles will required four reproducible discharges in each magnetic configuration (4 shots x 4 configurations: 16 discharges); and to properly measured the k⊥ spectra at the two poloidally separated positions a series of about 20 similar discharges is needed in in the lowest ripple configuration.
* Essential diagnostic systems:
Doppler reflectometer, microwave interferometer, Thomson scattering, ECE, Hα detectors, diamagnetic loop, Rogosky and Mirnov coils, SXR, bolometry, etc.
* Type of plasmas (heating configuration):
ECH on-axis, full power
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
December

== References ==
<references /> 

<hr> 
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Autumn 2018]]

TJ-II:Er and turbulence asymmetries in low ripple configurations measured by Doppler reflectometry

2018-10-16T13:47:42Z

Teresa.estrada: Created page with "== Experimental campaign == 2018 Autumn == Proposal title == '''Er and turbulence asymmetries in low ripple configurations measured by Doppler reflectometry''' == Name and a..."

== Experimental campaign ==
2018 Autumn

== Proposal title ==
'''Er and turbulence asymmetries in low ripple configurations measured by Doppler reflectometry'''

== Name and affiliation of proponent ==
Teresa Estrada, CIEMAT

== Details of contact person at LNF (if applicable) ==
N/A

== Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages)==

Motivation

Experimental studies have been performed in TJ-II aiming at the verification of the spatial localization of instabilities predicted by the Gyrokinetic simulations in stellarators [1-3] and the verification of the electrostatic potential variation on the flux surface, φ1, as calculated by Neoclassical codes and its possible impact on the radial electric field [4]. The experimental technique used to measure these quantities, Doppler reflectometry, allows the measurement of the density turbulence and its perpendicular rotation velocity at different turbulence scales and with good spatial and temporal resolution [5]. It can cover the radial region from ρ ≈ 0.6 to 0.9, at different perpendicular wave-numbers of the turbulence in the range k⊥ ≈ 1-14 cm-1, and at two plasma regions poloidally separated.
The main results, discussed in [6], can be summarized as follows:
• Er profiles measured at poloidally separated positions in the same flux-surfaces show pronounced differences in low density plasmas, i.e. plasmas in neoclassical electron root confinement. At higher plasma densities the Er asymmetry gradually decreases and almost disappears in ion root plasmas. The asymmetry in the Er profile can be explained to be due to the radial dependence of electrostatic potential varying over the flux surface, φ1 [7].
• Differences in the turbulence intensity have been found when comparing the k⊥ spectra measured at poloidally separated positions in the same flux-surface. The results are in good qualitative agreement with the spatial localization of instabilities as calculated using the global gyrokinetic code EUTERPE [8].
• Experiments performed in a magnetic configuration with high rotational transform show a less pronounced and reversed poloidal asymmetry.

Proposal

We propose to explore the influence of the magnetic ripple on the poloidal asymmetry of Er and compare with the Neoclassical expectations. To that end, we propose to explore configurations with different plasma volume, and therefore different magnetic ripple, while keeping the rotational transform profile fixed (as in the standard magnetic configuration). The main properties of the proposed magnetic configurations are summarized in the table.
We propose to measure the asymmetry properties of the Er profiles in the four magnetic configurations in low density (0.5 1019 m-3), ECH heated plasmas at maximum power (≈ 500 kW) on-axis. Besides, the asymmetry properties of the k⊥ spectra will be measured in the lowest ripple configuration for comparison with the asymmetry found in the standard one.

Config. Rax (0º) -Zlim(m) ι0 ιa Well(%) ripp_axis ripp_edge a(cm) V(m3)
100_44_64 1.739 0.362 1.551 1.650 2.390 1.900 37.600 20.64 1.0976
71_44_52 1.722 0.319 1.549 1.649 3.200 1.500 29.400 17.37 0.7575
54_43_45 1.709 0.288 1.543 1.648 3.200 14.63 0.5315
39_42_38 1.699 0.261 1.549 1.674 3.000 2.900 20.000 12.35 0.3741

[1] M. Nadeem, et al., Phys. Plasmas 8 (2001) 4375
[2] P. Xanthopoulos, et al., Phys. Rev. X 6 (2016) 021033
[3] E. Sánchez, et al., 21st ISHW (2017) Kyoto, Japan
[4] J.M. García-Regaña, et al., Nucl. Fusion 57 (2017) 056004
[5] T. Happel, et al., Rev. Sci. Instrum. 80 (2009) 073502
[6] T. Estrada, et al., IAEA FEC (2018)
[7] J.M. García-Regaña, et al., PPCF 60 (2018) 10402
[8] E. Sánchez, et al., IAEA FEC (2018)

== If applicable, International or National funding project or entity ==
Proyecto del Plan NAcional, referencia: FIS2017-88892-P

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
The characterization of the Er profiles will required four reproducible discharges in each magnetic configuration (4 shots x 4 configurations: 16 discharges); and to properly measured the k⊥ spectra at the two poloidally separated positions a series of about 20 similar discharges is needed in in the lowest ripple configuration.
* Essential diagnostic systems:
Doppler reflectometer, microwave interferometer, Thomson scattering, ECE, Hα detectors, diamagnetic loop, Rogosky and Mirnov coils, SXR, bolometry, etc.
* Type of plasmas (heating configuration):
ECH on-axis, full power
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
December

== References ==
<references /> 

<hr> 
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Autumn 2018]]

TJ-II:Experimental proposals

2018-03-06T13:22:42Z

Teresa.estrada: /* Experimental proposals, 2018 Spring */

[[File:TJII_model.jpg|400px|thumb|right|TJ-II Model]]

== Creation of a new proposal ==

# Log in to the FusionWiki. If you don't have an account, request one by clicking 'Create account' in the left-hand menu.
# <font color="#FF0000">''Type the name of your proposal page in the field below''</font>. The required format is: 'TJ-II:Title of my proposal'. Note the 'TJ-II:' at the beginning!
# Click 'Create new proposal'. Your proposal page will be created. Edit and save (please use 'Show preview' before saving the final version).

<inputbox>
type=create
default=TJ-II:Title of my proposal
buttonlabel=Create new proposal with this title
preload=TJ-II:Proposal_template
</inputbox>

The proposal page is created on the basis of this [[TJ-II:Proposal template|Proposal template]]. You do not need to view or modify it.

== Inclusion of your proposal in the proposal list ==

* Edit the table below and add your proposal (instructions in the table).
* The link to your proposal is as follows: <nowiki>[[TJ-II:Title of your proposal|]]</nowiki> (the final character before the closing brackets <nowiki>]]</nowiki> is a vertical slash).

== Experimental proposals, 2018 Spring==
Deadline: March 7, 2018

{| class="wikitable sortable" width="100%" border="1" cellpadding="5" cellspacing="0" style="text-align:left"
|- style="background:#FFDEAD;"
! width="10%"| '''Nr.'''
! width="60%"| '''Title'''
! width="30%"| '''Proponent(s)'''




|-
 | 1
 | [[TJ-II:Observation of suprathermal ions with Neutral Particle Analyzers during electron cyclotron heating in the TJ-II stellarator|Observation of suprathermal ions with Neutral Particle Analyzers during electron cyclotron heating in the TJ-II stellarator]]
 | [mailto:josepmaria.fontdecaba@ciemat.es J.M. Fontdecaba]



|-
 | 2
 | [[TJ-II:Poloidal 2D scans to investigate potential and density profiles in the TJ-II stellarator using dual Heavy ion beam probe diagnostic|Poloidal 2D scans to investigate potential and density profiles in the TJ-II stellarator using dual Heavy ion beam probe diagnostic]]
 | [mailto:ridhimas757@gmail.com R. Sharma]

|-
 | 3
 | [[TJ-II:Validation of bootstrap predictions|Validation of bootstrap predictions]]
 | [mailto:joseluis.velasco@ciemat.es J.L.Velasco]

|-
 | 4
 | [[TJ-II:Transport analysis by means of the Transfer Entropy|Transport analysis by means of the Transfer Entropy]]
 | [mailto:boudewijn.vanmilligen@ciemat.es B.Ph. van Milligen]

|-
 | 5
 | [[TJ-II:Understanding an often observed transient rise in core electron temperature during pellet injection into TJ-II plasmas|Understanding an often observed transient rise in core electron temperature during pellet injection into TJ-II plasmas]]
 | [mailto:kieran.mccarthy@ciemat.es K J McCarthy]

|-
 | 6
 | [[TJ-II:Improving fuelling efficiency in TJ-II ECRH plasmas|Improving fuelling efficiency in TJ-II ECRH plasmas]]
 | [mailto:kieran.mccarthy@ciemat.es M Calvo]

|-
 | 7
 | [[TJ-II:The influence of a core fast electron population on pellet fuelling efficiency in TJ-II|The influence of a core fast electron population on pellet fuelling efficiency in TJ-II]]
 | [mailto:nerea.panadero@externos.ciemat.es N Panadero]

|-
 | 8
 | [[TJ-II:Studies of LIquid Metal insertion in TJ-II|Studies of LIquid Metal insertion in TJ-II]]
 | [mailto:tabares@ciemat.es P.Tabares]

|-
 | 9
 | [[TJ-II:Fast Camera studies with triple bundle|Fast Camera studies with triple bundle]]
 | [mailto:e.delacal@ciemat.es E. de la Cal]

|-
 | 10
 | [[TJ-II:Validation of ECCD predictions in TJ-II ECRH plasmas|Validation of ECCD predictions in TJ-II ECRH plasmas]]
 | [mailto:jose.reganal@ciemat.es J. M. García-Regaña]

|-
 | 11
 | [[TJ-II:Radiation asymmetries and potential variations|Radiation asymmetries and potential variations]]
 | [mailto:jose.reganal@ciemat.es J. M. García-Regaña]

|-
 | 11
 | [[TJ-II:Turbulence and radial electric field asymmetries in high iota magnetic configuration measured by Doppler reflectometry|Turbulence and radial electric field asymmetries in high iota magnetic configuration measured by Doppler reflectometry]]
 | [mailto:teresa.estrada@ciemat.es Teresa Estrada]

|
|}

== Experimental proposals, 2017 Spring==
Deadline: January 26, 2017

{| class="wikitable sortable" width="100%" border="1" cellpadding="5" cellspacing="0" style="text-align:left"
|- style="background:#FFDEAD;"
! width="10%"| '''Nr.'''
! width="60%"| '''Title'''
! width="30%"| '''Proponent(s)'''




|-
 | 1
 | [[TJ-II:Search for physical mechanisms that lead to increase of turbulence following pellet injection|Search for physical mechanisms that lead to increase of turbulence following pellet injection]]
 | [mailto:kieran.mccarthy@ciemat.es Kieran McCarthy]


|-
 | 2
 | [[TJ-II:Effect of pellet injection on the radial electric field profile of stellarators|Effect of pellet injection on the radial electric field profile of stellarators]]
 | [mailto:silvagnidavide1@gmail.com,joseluis.velasco@ciemat.es Davide Silvagni, José L. Velasco]


|-
 | 3
 | [[TJ-II:Excitation of zonal flow oscillations by energetic particles|Excitation of zonal flow oscillations by energetic particles]]
 | [mailto:edi.sanchez@ciemat.es Edi Sánchez]


|-
 | 4
 | [[TJ-II:Radial electric field of low-magnetic-field low-collisionality NBI plasmas|Radial electric field of low-magnetic-field low-collisionality NBI plasmas]]
 | [mailto:joseluis.velasco@ciemat.es José L. Velasco]


|-
 | 5
 | [[TJ-II:Comparison of transport of on-axis and off-axis ECH-heated plasmas|Comparison of transport of on-axis and off-axis ECH-heated plasmas]]
 | [mailto:joseluis.velasco@ciemat.es,edi.sanchez@ciemat.es José L. Velasco, Edi Sánchez]
|-

 | 6
 | [[TJ-II:Impurity injection by laser blow-off: influence of main ions charge/mass on impurity confinement and transport|Impurity injection by laser blow-off: influence of main ions charge/mass on impurity confinement and transport]]
 | [mailto:belen.lopez@ciemat.es Belén López-Miranda]

|-

 | 7
 | [[TJ-II:PelletFuelling|PelletFuelling]]
 | [mailto:kieran.mccarthy@ciemat.es Kieran McCarthy]

|-

 | 8
 | [[TJ-II:Impurity density and potential asymmetries|Impurity density and potential asymmetries]]
 | [mailto:jose.regana@ciemat.es José M. García Regaña]

|-

 | 9
 | [[TJ-II:Investigation of turbulence spreading and information transfer in the TJ-II stellarator|Investigation of turbulence spreading and information transfer in the TJ-II stellarator]]
 | [mailto:boudewijn.vanmilligen@ciemat.es Boudewijn van Milligen]

|-

 | 10
 | [[TJ-II:Role of isotope effect on biasing induced transitions in the TJ-II stellarator|Role of isotope effect on biasing induced transitions in the TJ-II stellarator]]
 | [mailto:carlos.hidalgo@ciemat.es S. Ohshima]

|-

 | 11
 | [[TJ-II:Investigation of the mechanism of decoupling between energy and particle transport channels: Proposal for joint experiments in TJ-II and H-J|Investigation of the mechanism of decoupling between energy and particle transport channels: Proposal for joint experiments in TJ-II and H-J]]
 | [mailto:bing.liu@externos.ciemat.es,ulises.losada@ciemat.es Bing Liu, Ulises Losada]

|-

 | 12
 | [[TJ-II: Alfven Eigenmodes and biasing in TJ-II| Alfven Eigenmodes and biasing in TJ-II]]
 | [mailto:melnikov_07@yahoo.com A. Melnikov]

|-

 | 13
 | [[TJ-II: Potential asymmetries at low magnetic field | Potential asymmetries at low magnetic field ]]
 | [mailto:jose.regana@ciemat.es José M. García-Regaña]
|-

 | 14
 | [[TJ-II:NBI contribution to plasma fuelling|NBI contribution to plasma fuelling]]
 | [mailto:macarena.liniers@ciemat.es Macarena Liniers]

|-

 | 15
 | [[TJ-II: Investigation of plasma asymmetries in the TJ-II stellarator and comparison with Gyrokinetic simulations|Investigation of plasma asymmetries in the TJ-II stellarator and comparison with Gyrokinetic simulations]]
 | [mailto:Edi.sanchez@ciemat.es Edi Sanchez]

|-

 | 16
 | [[TJ-II:Effect of ECRH on the characteristics of Alfven Eigenmodes activity|Effect of ECRH on the characteristics of Alfven Eigenmodes activity]]
 | [mailto:alvaro.cappa@ciemat.es,enrique.ascasibar@ciemat.es,francisco.castejon@ciemat.es Álvaro Cappa, Enrique Ascasíbar, Paco Castejón]

|-

 | 17
 | [[TJ-II:Investigating the Alfvén Wave damping|Investigating the Alfvén Wave damping]]
 | [mailto:francisco.castejon@ciemat.es Paco Castejón, Álvaro Cappa, Enrique Ascasíbar]

|-

 | 18
 | [[TJ-II:L-H Transition and Isotope Effect in low magnetic ripple configurations|L-H Transition and Isotope Effect in low magnetic ripple configurations]]
 | [mailto:teresa.estrada@ciemat.es,Ulises.LosadaRodriguez@ciemat.es,Carlos.Hidalgo@ciemat.es Teresa Estrada,Ulises Losada,Carlos Hidalgo]

|-

 | 19
 | [[TJ-II:Measurements of radial correlation length and tilting of turbulent eddies by Radial Correlation Doppler Reflectometry|Measurements of radial correlation length and tilting of turbulent eddies by Radial Correlation Doppler Reflectometry]]
 | [mailto:teresa.estrada@ciemat.es,javier.pinzon@ipp.mpg.de,tim.happel@ipp.mpg.de Javier Pinzon, Tim Happel,Teresa Estrada]

|-

 | 20
 | [[TJ-II:Measurement of Te and ne of Blobs analyzing recycling helium emission in front of a poloidal limiter|Measurement of Te and ne of Blobs analyzing recycling helium emission in front of a poloidal limiter]]
 | [mailto:e.delacal@ciemat.es, Eduardo de la Cal]

|-
|}

== See also ==

* [[TJ-II:Experimental program]] (current)
* [http://intranet-fusion.ciemat.es/document-server/tj-ii-experimental-program/ Experimental programs for earlier years (2002-2016)] (Intranet, password required)

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals]]

TJ-II:Turbulence and radial electric field asymmetries in high iota magnetic configuration measured by Doppler reflectometry

2018-03-06T13:12:27Z

Teresa.estrada: /* Preferred dates and degree of flexibility */

== Experimental campaign ==
2018 Spring

== Proposal title ==
'''Turbulence and radial electric field asymmetries in high iota magnetic configuration measured by Doppler reflectometry'''

== Name and affiliation of proponent ==
Teresa Estrada, Edi Sánchez, Daniel Carralero, Jose Manuel García-Regaña, and the TJ-II team
LNF, CIEMAT

== Details of contact person at LNF (if applicable) ==
Teresa Estrada

== Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages)==
Motivation
Experimental studies have been performed in TJ-II aiming at the verification of the spatial localization of instabilities predicted by the Gyrokinetic simulations in stellarators [1-3] and the verification of the electrostatic potential variation on the flux surface as calculated by Neoclassical codes and its possible impact on the radial electric field [4,5]. The experimental technique used to measure these quantities, Doppler reflectometry, allows the measurement of the density turbulence and its perpendicular rotation velocity at different turbulence scales and with good spatial and temporal resolution [6]. It can cover the radial region from ρ ≈ 0.6 to 0.9, at different perpendicular wave-numbers of the turbulence in the range k⊥ ≈ 1-14 cm-1, and at two plasma regions poloidally separated.
Differences in the turbulence intensity have been found in previous experiments when comparing the k⊥ spectra measured at poloidally separated positions in the same flux-surface, in ECH heated plasmas in the standard magnetic configuration. This behaviour remains almost unchanged in ECH plasmas with higher density and/or lower heating power. On the other hand, Er profiles obtained from the perpendicular rotation velocity measured at the two plasma regions show pronounced differences in low density plasmas, i.e. plasmas in neoclassical electron root confinement. At higher plasma densities the Er asymmetry gradually decreases and almost disappears in ion root plasmas. No asymmetries are found in NBI heated plasmas, i.e. higher density, lower electron temperature, where very similar turbulence intensity, spectral shape and Er profile are measured at both plasma regions. Finally, the asymmetry in the turbulence intensity found in the standard magnetic configuration in ECH plasmas, reverses in the magnetic configuration with high rotation transform. In order to further investigate the impact of the magnetic configuration on the turbulence and Er asymmetries we propose to cover additional plasma scenarios in the high iota magnetic configuration.

Proposal
We propose to explore the magnetic configuration 42_102_69 in plasmas heated with ECH off-axis with high & low input power. To properly measured the k⊥ spectra at the two poloidally separated positions a series of about 20 similar discharges is needed in each scenario.

References

[1] M. Nadeem, et al., Phys. Plasmas 8 (2001) 4375

[2] P. Xanthopoulos, et al., Phys. Rev. X 6 (2016) 021033

[3] E. Sánchez, et al., 21st ISHW (2017) Kyoto, Japan

[4] J.M. García-Regaña, et al., Nucl. Fusion 57 (2017) 056004

[5] J.M. García-Regaña, et al., 21st ISHW (2017) Kyoto, Japan

[6] T. Happel, et al., Rev. Sci. Instrum. 80 (2009) 073502

== If applicable, International or National funding project or entity ==

National: FIS2017-88892-P

International: EUROfusion WP.S1

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: Two experimental days are requested to cover at least two plasma scenarios
* Essential diagnostic systems: Doppler reflectometer, Microwave interferometer, Thomson scattering, AM reflectometer, ECE, Hα detectors, Diamagnetic loop, Rogowski coils, Mirnov coils, SXR, bolometry, CX
* Type of plasmas (heating configuration): ECH heated plasmas in high iota configuration (42_102_69)
* Specific requirements on wall conditioning if any: fresh Li coated wall for a good reproducibility
* External users: need a local computer account for data access: N/A
* Any external equipment to be integrated? Provide description and integration needs: N/A

== Preferred dates and degree of flexibility ==

Preferred dates: (format dd-mm-yyyy) June-2018

Not available in:

April

22-May

24-May

TJ-II:Turbulence and radial electric field asymmetries in high iota magnetic configuration measured by Doppler reflectometry

2018-03-06T13:11:26Z

Teresa.estrada: /* Preferred dates and degree of flexibility */

TJ-II:Turbulence and radial electric field asymmetries in high iota magnetic configuration measured by Doppler reflectometry

2018-03-06T13:11:05Z

Teresa.estrada: /* Description of required resources */

== Experimental campaign ==
2018 Spring

== Proposal title ==
'''Turbulence and radial electric field asymmetries in high iota magnetic configuration measured by Doppler reflectometry'''

== Name and affiliation of proponent ==
Teresa Estrada, Edi Sánchez, Daniel Carralero, Jose Manuel García-Regaña, and the TJ-II team
LNF, CIEMAT

== Details of contact person at LNF (if applicable) ==
Teresa Estrada

== Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages)==
Motivation
Experimental studies have been performed in TJ-II aiming at the verification of the spatial localization of instabilities predicted by the Gyrokinetic simulations in stellarators [1-3] and the verification of the electrostatic potential variation on the flux surface as calculated by Neoclassical codes and its possible impact on the radial electric field [4,5]. The experimental technique used to measure these quantities, Doppler reflectometry, allows the measurement of the density turbulence and its perpendicular rotation velocity at different turbulence scales and with good spatial and temporal resolution [6]. It can cover the radial region from ρ ≈ 0.6 to 0.9, at different perpendicular wave-numbers of the turbulence in the range k⊥ ≈ 1-14 cm-1, and at two plasma regions poloidally separated.
Differences in the turbulence intensity have been found in previous experiments when comparing the k⊥ spectra measured at poloidally separated positions in the same flux-surface, in ECH heated plasmas in the standard magnetic configuration. This behaviour remains almost unchanged in ECH plasmas with higher density and/or lower heating power. On the other hand, Er profiles obtained from the perpendicular rotation velocity measured at the two plasma regions show pronounced differences in low density plasmas, i.e. plasmas in neoclassical electron root confinement. At higher plasma densities the Er asymmetry gradually decreases and almost disappears in ion root plasmas. No asymmetries are found in NBI heated plasmas, i.e. higher density, lower electron temperature, where very similar turbulence intensity, spectral shape and Er profile are measured at both plasma regions. Finally, the asymmetry in the turbulence intensity found in the standard magnetic configuration in ECH plasmas, reverses in the magnetic configuration with high rotation transform. In order to further investigate the impact of the magnetic configuration on the turbulence and Er asymmetries we propose to cover additional plasma scenarios in the high iota magnetic configuration.

Proposal
We propose to explore the magnetic configuration 42_102_69 in plasmas heated with ECH off-axis with high & low input power. To properly measured the k⊥ spectra at the two poloidally separated positions a series of about 20 similar discharges is needed in each scenario.

References

[1] M. Nadeem, et al., Phys. Plasmas 8 (2001) 4375

[2] P. Xanthopoulos, et al., Phys. Rev. X 6 (2016) 021033

[3] E. Sánchez, et al., 21st ISHW (2017) Kyoto, Japan

[4] J.M. García-Regaña, et al., Nucl. Fusion 57 (2017) 056004

[5] J.M. García-Regaña, et al., 21st ISHW (2017) Kyoto, Japan

[6] T. Happel, et al., Rev. Sci. Instrum. 80 (2009) 073502

== If applicable, International or National funding project or entity ==

National: FIS2017-88892-P

International: EUROfusion WP.S1

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: Two experimental days are requested to cover at least two plasma scenarios
* Essential diagnostic systems: Doppler reflectometer, Microwave interferometer, Thomson scattering, AM reflectometer, ECE, Hα detectors, Diamagnetic loop, Rogowski coils, Mirnov coils, SXR, bolometry, CX
* Type of plasmas (heating configuration): ECH heated plasmas in high iota configuration (42_102_69)
* Specific requirements on wall conditioning if any: fresh Li coated wall for a good reproducibility
* External users: need a local computer account for data access: N/A
* Any external equipment to be integrated? Provide description and integration needs: N/A

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy) June-2018
Not available in April, and on 22nd and 24th of May.

TJ-II:Turbulence and radial electric field asymmetries in high iota magnetic configuration measured by Doppler reflectometry

2018-03-06T13:10:36Z

Teresa.estrada: /* Description of required resources */

== Experimental campaign ==
2018 Spring

== Proposal title ==
'''Turbulence and radial electric field asymmetries in high iota magnetic configuration measured by Doppler reflectometry'''

== Name and affiliation of proponent ==
Teresa Estrada, Edi Sánchez, Daniel Carralero, Jose Manuel García-Regaña, and the TJ-II team
LNF, CIEMAT

== Details of contact person at LNF (if applicable) ==
Teresa Estrada

== Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages)==
Motivation
Experimental studies have been performed in TJ-II aiming at the verification of the spatial localization of instabilities predicted by the Gyrokinetic simulations in stellarators [1-3] and the verification of the electrostatic potential variation on the flux surface as calculated by Neoclassical codes and its possible impact on the radial electric field [4,5]. The experimental technique used to measure these quantities, Doppler reflectometry, allows the measurement of the density turbulence and its perpendicular rotation velocity at different turbulence scales and with good spatial and temporal resolution [6]. It can cover the radial region from ρ ≈ 0.6 to 0.9, at different perpendicular wave-numbers of the turbulence in the range k⊥ ≈ 1-14 cm-1, and at two plasma regions poloidally separated.
Differences in the turbulence intensity have been found in previous experiments when comparing the k⊥ spectra measured at poloidally separated positions in the same flux-surface, in ECH heated plasmas in the standard magnetic configuration. This behaviour remains almost unchanged in ECH plasmas with higher density and/or lower heating power. On the other hand, Er profiles obtained from the perpendicular rotation velocity measured at the two plasma regions show pronounced differences in low density plasmas, i.e. plasmas in neoclassical electron root confinement. At higher plasma densities the Er asymmetry gradually decreases and almost disappears in ion root plasmas. No asymmetries are found in NBI heated plasmas, i.e. higher density, lower electron temperature, where very similar turbulence intensity, spectral shape and Er profile are measured at both plasma regions. Finally, the asymmetry in the turbulence intensity found in the standard magnetic configuration in ECH plasmas, reverses in the magnetic configuration with high rotation transform. In order to further investigate the impact of the magnetic configuration on the turbulence and Er asymmetries we propose to cover additional plasma scenarios in the high iota magnetic configuration.

Proposal
We propose to explore the magnetic configuration 42_102_69 in plasmas heated with ECH off-axis with high & low input power. To properly measured the k⊥ spectra at the two poloidally separated positions a series of about 20 similar discharges is needed in each scenario.

References

[1] M. Nadeem, et al., Phys. Plasmas 8 (2001) 4375

[2] P. Xanthopoulos, et al., Phys. Rev. X 6 (2016) 021033

[3] E. Sánchez, et al., 21st ISHW (2017) Kyoto, Japan

[4] J.M. García-Regaña, et al., Nucl. Fusion 57 (2017) 056004

[5] J.M. García-Regaña, et al., 21st ISHW (2017) Kyoto, Japan

[6] T. Happel, et al., Rev. Sci. Instrum. 80 (2009) 073502

== If applicable, International or National funding project or entity ==

National: FIS2017-88892-P

International: EUROfusion WP.S1

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: Two experimental days are requested to cover at least two plasma scenarios
* Essential diagnostic systems: Doppler reflectometer, Microwave interferometer, Thomson scattering, AM reflectometer, ECE, Hα detectors, Diamagnetic loop, Rogowski coils, Mirnov coils, SXR, bolometry, CX
* Type of plasmas (heating configuration): ECH heated plasmas in high iota configuration (42_102_69)
* Specific requirements on wall conditioning if any: fresh Li coates wall for a good reproducibility
* External users: need a local computer account for data access: N/A
* Any external equipment to be integrated? Provide description and integration needs: N/A

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy) June-2018
Not available in April, and on 22nd and 24th of May.