LNF:Estudios del confinamiento mejorado y de impurezas en los Stellarators TJ-II y W7-X mediante inyección de pastillas criogénicas (Pellets) y encapsulados de impurezas (TESPEL): Difference between revisions

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'''Programme and date''': Proyectos de Generación de Conocimiento 2023
'''Programme and date''': Proyectos de Generación de Conocimiento 2023


'''Programme type (Modalidad de proyecto)''':  
'''Programme type (Modalidad de proyecto)''': Proyectos investigación orientada


'''Area/subarea (Área temática / subárea)''': Energy & Transport / Energy
'''Area/subarea (Área temática / subárea)''': Energy & Transport / Energy


'''Principal Investigator(s)''': [https://orcid.org/0000-0002-5223-391X Isabel García-Cortés ][https://orcid.org/0000-0002-5881-1442 Kieran Joseph McCarthy]
'''Principal Investigator(s)''': [https://orcid.org/0000-0002-5223-391X Isabel García-Cortés] [https://orcid.org/0000-0002-5881-1442 Kieran Joseph Mc Carthy]
 
'''Research Team (Equipo de investigación)''': [https://orcid.org/0000-0001-9631-9558 Carmen Pastor] [https://orcid.org/0000-0003-1717-3509 Alfonso Baciero] [https://orcid.org/0000-0001-7678-0240 Josep María Fontdecaba]  [https://orcid.org/0000-0002-7638-8772 Daniel López Bruna] [https://orcid.org/0000-0002-5809-5132 Francisco Medina] [https://orcid.org/0009-0005-2938-5463 Ma Carmen Rodríguez]
 
'''Work Team (Equipo de trabajo)''': [https://orcid.org/0000-0003-1682-1519 Naoki Tamura] [https://orcid.org/0000-0001-7644-751X Federico Nespoli] [https://orcid.org/0000-0003-4251-7924 Felix Reimold]


'''Project type''': Proyecto individual
'''Project type''': Proyecto individual
Line 18: Line 22:


'''Financing granted (direct costs)''': 130.000 €
'''Financing granted (direct costs)''': 130.000 €
[[File:Logo_PN.jpg|600px]]


== Description of the project ==
== Description of the project ==


Enter text here
The aim of this project, which falls within the realm of magnetic confinement fusion, is to continue and broaden the research initiated in projects ENE2013-48679-R, FIS2017-89326-R and PID2020-116599RB-I00 on fuelling and impurity control in plasmas created in the stellarators TJ-II (Ciemat, Madrid), W7-X (Greifswald, Germany) and LHD (Toki, Japan). This research aims to investigate issues related to these two issue which are critical for achieving steady-state operation of helical-type fusion reactors. In particular, it is necessary to identify operational scenarios that ensure adequate plasma fuelling and short impurity confinement times, in particular, for heavy ions. It is intended that this work will support the European stellarator programme and contribute to the development and scientific exploitation of stellarators, a priority highlighted in the document "Fusion Electricity: a roadmap to the realization of fusion energy" (EFDA 2012).
 
1. The first aim is to investigate aspects of pellet injection that are still not fully understood as well as to understand better how pellets affect plasma magnetic activity, plasma turbulence and plasma performance. For this, the medium-sized heliac TJ-II will be used. It is equipped with a cryogenic pellet injector (PI) for producing solid hydrogen pellets that can be injected at high velocity into the plasma. During previous projects it was found that pellet injection into TJ-II results in enhanced plasma performance (simultaneously higher electron density and ion temperature, larger stored diamagnetic energy, longer particle confinement, higher plasma beta) <ref>1</ref> <ref>2</ref>. It was also seen how the injection of additional fuel pellets  further increases and maintains this enhanced plasma performance. It is now necessary to understand the underlying physics of these experimental observations. This will be done using available codes to evaluate neoclassical and turbulent contributions.
 
2. The second aim is to continue to support and expand impurity transport studies in TJ-II, W7-X and LHD. Under the umbrella of a trilateral collaboration (2020-2029) with the National Institute for Fusion Science (Japan) and IPP-Max-Planck (Greifswald, Germany), the Tracer-Encapsulated Solid Pellet (TESPEL) method is now employed on TJ-II, W7-X and LHD. TESPELs are polystyrene spheres (diameter <1 mm) loaded with small quantities of selected impurities (atomic elements other than fuel). Thus, TESPEL allows delivering a precise quantify of tracer to a preselected location in the plasma core, after which its transport can be evaluated. An important aspect of previous projects was the establishment of a laboratory to fabricate TESPELs at Ciemat. Since then several hundred TESPELs prepared at Ciemat have been injected successfully into plasmas created in these devices. Thus, key goals of this current project are to continue TESPEL fabrication at this laboratory, thereby allowing Ciemat to maintain its fruitful collaborations with W7-X and LHD, and to expand TESPEL based impurity control studies. For instance, during recent experiments with TESPEL at LHD, project members determined that mid-/high- Z atomic ions can be flushed out of a high-density plasma if Li-granules are dropped continuously into the plasma edge <ref>3</ref>. When results were compared with results from reference plasmas, confinement times of high-Z ions were reduced by a factor 4 or more. It is extend to explore further this new operational scenario for stellarators.
 
== Main results ==
To be completed at the end of the project (final report)
 
== Dissemination of project results (peer-reviewed publications and conference presentations) ==
 
PEER-REVIEWED ARTICLES ASSOCIATED WITH THIS PROJECT (SINCE 2024)
 
[1] The rotational transform and enhanced confinement in the TJ-II stellarator, B. Ph. van Milligen, I. García-Cortés, K. J. McCarthy, B. A. Carreras, L. García, A. Cappa, P. Pons-Villalonga, T. Estrada, D. Medina-Roque, J. Hernández-Sánchez, R. García, O. S. Kozachok, O. O. Chmyga, J. L. de Pablos, J. M. Barcala, A. Molinero, D. Tafalla, I. Pastor, D. Tafalla, A. de la Peña, F. Lapayese and the TJ-II Team, J. Plasma Phys. 90 (2025) E98, https://doi.org/10.1017/S0022377825100433
 
[2] Multi-pellet injection into the NBI-heated phase of TJ-II plasmas, K. J. McCarthy, I. García-Cortés, A. Alonso, A. Arias-Camisón, E. Ascasíbar, A. Baciero, A. Cappa, R. Carrasco, O. O. Chmyga, T. Estrada, R. García, J. Hernández-Sánchez, F. J. Herranz, O. S. Kozachok, B. López Miranda, F. Medina, D. Medina-Roque, B. van Milligen, M. Navarro, M. A. Ochando, J. L. de Pablos, N. Panadero, I. Pastor, J. de la Riva, M. C. Rodríguez, D. Tafalla, V. Tribaldos and TJ-II Team, Nucl. Fusion 64 (2024) 066019, https://doi.org/10.1088/1741-4326/ad4047.


<!-- If applicable: references -->
[3] Observation of Enhanced Core Impurity Transport in a Turbulence-Reduced Stellarator Plasma, D. Medina-Roque, I. García-Cortés, N. Tamura, K. J. McCarthy, F. Nespoli, K. Tanaka, M. Shoji, S. Masuzaki, H. Funaba, C. Suzuki, A. Mollen, R. Lunsford, K. Ida, M. Yoshinuma, M. Goto, T. Kawate, Y. Kawamoto, T. Kawate, T. Tokuzawa, I. Yamada and the LHD experimental team, Phys. Plasmas 33 (2026) 050701, https://doi.org/10.1063/5.0327035.
== References ==
 
<references />
[4] Additional ECRH mitigates thermal quenches induced by tungsten TESPEL injection in LHD, H. Bouvain, A. Dinklage, N. Tamura, K. Mukai, C. Suzuki, T. Tokuzawa, Y. Takemura, Y. Narushima, K. Ida, M. Yoshinuma, H. Igami, H. Kasahara, K. McCarthy, D. Medina Roque, and I. García-Cortés, Phys. Plasmas 33 (2026) 022505. https://doi.org/10.1063/5.0310971.
 
[5] Recent Advances in Plasma Control and Physics Research in the Large Helical Device, K. Tanaka, K. Ida, Y. Morishita, H. Ohtani, D. Medina Roque, T. Tokuzawa, N. Kenmochi, T. Kinoshita, K. Toi, S. Murakami, H. Funaba, G. Ueno, M. Yokoyama, R. Ichikawa, K. Ogawa, A. Kageyama, N. Ohno, K. McCarthy, I. Garcia-Cortes, N. Tamura, F. Nespoli, R. Lunsford, M. Shoji, S. Masuzaki, C. Suzuki, A. Mollen, Y. Yoshinuma, M. Goto, Y. Kawamoto, T. Kawate, I. Yamada, T. Nasu, T. Kobayashi, K. Itoh, Y. Mizuno, R. Yasuhara, H. Uehara, D. Den Hartog, Y. Takemura, H. Igami, R. Yanai, T. Takeuchi, T. Yokoyama, M. Osakabe, S. Morita, A. Shimizu, M. Nishiura, N. Pablant, D. Spong, H. Nuga, K. Nagaoka, R. Sakamoto, H. Yamada, Y. Katoh, accepted for publication by Nucl. Fusion, NF-108651.R1
 
[6] Characterization of an Enhanced Plasma Performance Phase Induced by Pellet Injection in the Stellarator TJ-II, I. García-Cortés, K. McCarthy, B. Van Milligen, A. Kozachek, T. Estrada, V. Tribaldos, A. Baciero, B. Carreras, L. Garcia, D. Medina Roque, I. Pastor, M. C. Rodriguez Fernandez, D. Tafalla, sent to Nucl. Fusion for publication, NF-108859.R1.
 
[7] The radial localization of low-order rational surfaces in the stellarator TJ-II using pellet injection, K. J. McCarthy, I. García-Cortés, B. van Milligen, A. Baciero, R. Carrasco, B. A. Carreras, O. O. Chmyga, T. Estrada, R. García, J. Hernández-Sánchez, F. J. Hernanz, O. S. Kozachok, B. López Miranda, F. Medina, D. Medina-Roque, M. Navarro, N. Panadero, I. Pastor, M. C. Rodríguez, D. Tafalla, and TJ-II Team, sent to Nucl. Fusion for publication: NF-108785.
 
[8] The pump-out effect as a trigger for the electron to ion root transition in TJ-II, B. Ph. van Milligen, I. García-Cortés, K. McCarthy, O.S. Kozachok, O. O. Chmyga, J.L. de Pablos, A. Cappa, and the TJ-II Team, sent to J. Fusion Energy for publication, ID e7e624ed-fe96-4e3e-be5e-cb2ce1112310.
 
[9] Transport in high-performance plasmas of the TJ-II stellarator: From first-principles simulations to experimental validation, J. M. García-Regaña, D. Alegre, … K. J. McCarthy, …, et al., sent to Nucl. Fusion for publication, NF-108797.
 
POSTERS AND TALKS IN CONFERENCES SINCE 2024
 
[1] High performance plasmas of the TJ-II stellarator: Experiments and validation of first-principles models, T. Estrada, J.M. García-Regaña, A. Alonso, A. Cappa, D. Carralero, I. García-Cortés, K. McCarthy, N. Panadero, E. Sánchez, J.L. Velasco and the TJ-II Team, 52nd EPS Conf. on Controlled Fusion and Plasma Physics, Edinburgh, Scotland (2026), Invited talk.
 
[2] Transport in high-performance TJ-II plasmas: insights from first- principles simulations and experimental validation, J. M. García-Regaña, N. Panadero, E. Sánchez, A. Cappa, D. Carralero, H. Thienpondt, T. Estrada, J. A. Alonso, J. L. Velasco, K. McCarthy, I. García-Cortés and the TJ-II Team, 25th International Stellarator and Heliotron Workshop, Cordoba, Spain (2026), Invited talk.
 
[3] A multi-machine study on turbulence suppression by density peaking in stellarators, D. Carralero, B. Stefanoska, E. Maragkoudakis, K. Tanaka, T. Windisch, T. Estrada, A. Alonso, J. M. García-Regaña, A. Knieps, K. McCarthy, E. Sánchez, H. Thienpondt, 25th International Stellarator and Heliotron Workshop, Cordoba, Spain (2026), Oral.
 
[4] The observation of low-frequency oscillations in bolometer and soft X-ray signals after multiple pellet injections into the stellarator TJ-II, K. J. McCarthy, I. García-Cortés, B. van Milligen, N. Panadero, I. Pastor, V. Tribaldos, A. Baciero, R. Carrasco, O. O. Chmyga, T. Estrada, R. García, J. Hernanz, O. S. Kozachok, D. López Bruna, B. López Miranda, F. Medina, D. Medina-Roque, M. Navarro, C. Pastor, M. C. Rodriguez and TJ-II Team, 25th International Stelletator Heliotron Workshop, Cordoba, Spain (2026), Poster.
 
[5] Tungsten erosion and injection investigations in the stellarator Wendelstein 7-X: Results from OP2.1-2.3, B. P. Dhard, S. Brezinsek, Y. Boumendjel, R. Bussiahn, B. Buttenschön, D. Cipciar, T. Dittmar, D. Ennis, J. Fellinger, E. Flom, T. Fornal, Y. Gao, I. García-Cortés, D. Gradic1, M. Gruca, T. Gonda, S. Jabłoński, F. Henke, C. Killer, A. Knieps, P. Kornejew, M. Kubkowska, D. M. Kriete, M. Krychowiak, O. Marchuk, A. Langenberg, F. Maragkos, M. Mayer, K. J. McCarthy, D. Medina-Roque, D. Naujoks, D. Nocolai, N. Pablant, A. Pandey, M. Rasinski, J. Romazanov, J. Schäfer, M. F. Siddiki, L. Syrocki, N. Tamura, S. Thiede, T. Wegner and The W7-X Team, 27th Plasma Surface Interaction Conference, Regensburg, Germany (2026). Poster.
 
[6] Characterization of enhanced plasma performance phase after pellet injections in the TJ-II stellarator, I. García-Cortés, K. J. McCarthy, B. Van Milligen, T. Estrada, D. Medina-Roque, A. Baciero, B. A. Carreras, A. Cappa, A. A. Chmyga, F. Medina, L. Garcia, R. García, J. Hernández-Sánchez, F. J. Hernanz, A. S.  Kozachek, F. Lapayese, B. Lopez-Miranda,  D. Lopez-Bruna, V. Tribaldos, J. L. De Pablos, N. Panadero, I. Pastor, A. de La Peña, P. Pons-Villalonga, M.C. Rodriguez, D. Tafalla and TJ-II team, 30th IAEA Fusion Energy Conference, Chengdu, China (2025) Poster.
 
[7] Interpreting structures observed in pellet ablation profiles in the stellarator TJ-IIInterpreting structures observed in pellet ablation profiles in the stellarator TJ-II, K. J. McCarthy, I. García-Cortés, B. van Milligen, A. Baciero, R. Carrasco, T. Estrada, R. García, J. Hernández-Sánchez, B. López-Miranda, F. Medina, D. Medina-Roque, M. Navarro, N. Panadero, I. Pastor, M. C. Rodríguez and TJ-II Team, 30th IAEA Fusion Energy Conference, Chengdu, China (2025) Poster.
 
[8] Impact of Li-granule injection on the improvement of energy transport and the expulsion of impurities in the LHD heliotron, D. Medina-Roque, K. J. McCarthy, N. Tamura, I. García-Cortés, K. Tanaka, F. Nespoli, M. Shoji, S. Masuzaki, H. Funaba, C. Suzuki, A. Mollen, R. Lunsford, K. Ida, M. Yoshinuma, M. Goto, Y. Kawamoto, T. Kawate, T. Tokuzawa, I. Yamada and the LHD Experimental Team, 30th IAEA Fusion Energy Conference, Chengdu, China (2025) Poster.
 
[9] Confinement modelling pf enhanced plasma performance after multiple pellet injections into the TJ-II stellarator, V. Tribaldos, I. García-Cortés, K. J. McCarthy, D. Medina-Roque, A. Baciero, T. Estrada, D. López-Bruna, F. Medina, B. van Milligen, J. L. de Pablos, N. Panadero, I. Pastor, J. de la Riva and TJ-II Team, J. M. Reynolds-Barredo, O. O. Chmyga, O. S. Kozachok, 30th IAEA Fusion Energy Conference, Chengdu, China (2025).
 
[10] Transport in high-performance plasmas in the TJ-II stellarator: from first-principles simulations to experimental validation, J. M. García-Regaña, …, J. M. Fontdecaba, …, I. García-Cortés, …, J. Hernández-Sánchez, …,  B. López-Miranda, …, K. J. McCarthy, …, D. Medina-Roque, P. Méndez, … N. Panadero, …, N. Tamura et al., 30th IAEA Fusion Energy Conference, Chengdu, China (2025).
 
[11] Tungsten erosion and injection investigations in the stellarator Wendelstein 7-X during OP2.2, D. Chandra-Prakash, N. Tamura, … D. Medina-Roque, … I. García-Cortés, … K. J. McCarthy, et al., 20th International Conference on Plasma-Facing Materials and Components for Fusion Applocations, Ljubljana, Slovenia (2025).
 
[12] Characterization of the pellet cloud drift in stellarators, G. Kocsis, J. Baldzuhn, R. Bussiahn, A. Buzás, G. Cseh, I. García-Cortés, K. J. McCarthy, D. Medina-Roque, N. Panadero, T. Szepesi, N. Tamura, M.B. Vavrik, Th. Wegner, TJ-II Team and W7-X Team, 51st EPS Conference on Plasma Physics, Vilnius, Lituania (2025).
 
[13] Study of the density limit physics for stellarator devices by means of an energy balance model, J. Gallego, A. Alonso, A. Bustos, T. Estrada, B. López-Miranda, A. Baciero, A. Cappa, K. J. McCarthy, I. García-Cortés, J. de la Riva Villén, F. Medina, N. Panadero and the TJ-II Team, 51st EPS Conference on Plasma Physics, Vilnius, Lituania (2025).
 
[14] Magnetic configuration effects on pellet fuelling in stellarators, N. Panadero, K.J. McCarthy, J. Baldzuhn, J. Hernández-Fernández, F. Köchl, G. Kocsis, A. I. Mohammed, N. Tamura, M.B. Vavrik, E. Villalobos Granados, T. Szepesi, and TJ-II and W7-X teams, 51st EPS Conference on Plasma Physics, Vilnius, Lituania (2025).


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[[Category:LNF Nationally Funded Projects]]
[[Category:LNF Nationally Funded Projects]]
The goal of this project, which falls within the realm of magnetic confinement nuclear fusion, is to continue research initiated in projects ENE2013-48679-R and FIS2017-89326-R on fuelling and impurity control in plasmas created in the stellarators TJ-II (Ciemat, Madrid) and W7-X (Greifswald, Germany). Further research to resolve these issues is critical to demonstrate steady-state operation of helical-type fusion reactors, in particular to identify operational scenarios that ensure adequate plasma fuelling and avoidance of impurity accumulation. This project will contribute to the development and scientific exploitation of stellarators, a priority highlighted in the document "Fusion Electricity: a roadmap to the realization of fusion energy" (EFDA 2012).
1. The first aim is to investigate aspects of plasma fuelling that are still not fully understood and the effects of fuel pellets on plasma magnetic activity, plasma turbulence and plasma performance. For this, the medium-sized heliac TJ-II will be used. It is equipped with a cryogenic pellet injector (PI) for producing solid hydrogen pellets that can be injected at high velocity into the plasma. It is intended to investigate pellet fuelling as a means to enhance plasma confinement (higher stored energy, longer particle confinement) and to identify and explore new pellet phenomena. While TJ-II is equipped with a large number of modern diagnostics, it is proposed to develop a new system to measure pellet cloud density and temperature to extend knowledge of pellet physics.
2. The second aim is to continue to support impurity transport and accumulation studies in TJ-II and W7-X. Under the umbrella of a trilateral collaboration (2020-2029) with the National Institute for Fusion Science (Japan) and IPP-Max-Planck (Greifswald, Germany), Tracer-Encapsulated Solid Pellet (TESPEL) injections systems hare now operated on both TJ-II and W7-X. TESPELs are polystyrene spheres (diameter <1 mm) loaded with impurity tracers (atomic elements other than fuel). This allows delivering a precise quantify of tracer to a preselected location in the plasma core, after which its transport and confinement can be studied. An important aspect of the collaboration has been the establishment of a laboratory to fabricate TESPELs at Ciemat for both devices (project FIS2017- 89326-R). Key parts of this current project are to continue TESPEL fabrication for TJ-II and W7-X at this laboratory, thereby allowing Ciemat to maintain this fruitful collaboration, and to upgrade a vacuum ultraviolet spectrometer on TJ-II to provide important spectral line data for impurity identification in W7-X.
The PI and TESPEL systems on TJ-II share a common injection guide lines. This unique set-up allows direct comparative studies of ablation, deposition and plasma response to be made thereby facilitating the understanding of common physics. Given that fuelling and impurity control are critical issues for stellarator steady-state operation, the project will allow us to continue to contribute to, and participate in, research programmes on W7-X, the stellarator of reference. Finally, team members have significant experience in the formation of young researchers at Master and PhD levels and in disseminating research to second level students and to the general public. A PhD student will undertake research in these areas during the project.

Latest revision as of 13:51, 22 May 2026

LNF - Nationally funded project

Title: Estudios del confinamiento mejorado y de impurezas en los Stellarators TJ-II y W7-X mediante inyección de pastillas criogenicas (Pellets) y encapsulados de impurezas (TESPEL)

Reference: PID2023-148697OB-I00

Programme and date: Proyectos de Generación de Conocimiento 2023

Programme type (Modalidad de proyecto): Proyectos investigación orientada

Area/subarea (Área temática / subárea): Energy & Transport / Energy

Principal Investigator(s): Isabel García-Cortés Kieran Joseph Mc Carthy

Research Team (Equipo de investigación): Carmen Pastor Alfonso Baciero Josep María Fontdecaba Daniel López Bruna Francisco Medina Ma Carmen Rodríguez

Work Team (Equipo de trabajo): Naoki Tamura Federico Nespoli Felix Reimold

Project type: Proyecto individual

Start-end dates: 01/09/2024 - 31/08/2027

Financing granted (direct costs): 130.000 €

Description of the project

The aim of this project, which falls within the realm of magnetic confinement fusion, is to continue and broaden the research initiated in projects ENE2013-48679-R, FIS2017-89326-R and PID2020-116599RB-I00 on fuelling and impurity control in plasmas created in the stellarators TJ-II (Ciemat, Madrid), W7-X (Greifswald, Germany) and LHD (Toki, Japan). This research aims to investigate issues related to these two issue which are critical for achieving steady-state operation of helical-type fusion reactors. In particular, it is necessary to identify operational scenarios that ensure adequate plasma fuelling and short impurity confinement times, in particular, for heavy ions. It is intended that this work will support the European stellarator programme and contribute to the development and scientific exploitation of stellarators, a priority highlighted in the document "Fusion Electricity: a roadmap to the realization of fusion energy" (EFDA 2012).

1. The first aim is to investigate aspects of pellet injection that are still not fully understood as well as to understand better how pellets affect plasma magnetic activity, plasma turbulence and plasma performance. For this, the medium-sized heliac TJ-II will be used. It is equipped with a cryogenic pellet injector (PI) for producing solid hydrogen pellets that can be injected at high velocity into the plasma. During previous projects it was found that pellet injection into TJ-II results in enhanced plasma performance (simultaneously higher electron density and ion temperature, larger stored diamagnetic energy, longer particle confinement, higher plasma beta) [1] [2]. It was also seen how the injection of additional fuel pellets further increases and maintains this enhanced plasma performance. It is now necessary to understand the underlying physics of these experimental observations. This will be done using available codes to evaluate neoclassical and turbulent contributions.

2. The second aim is to continue to support and expand impurity transport studies in TJ-II, W7-X and LHD. Under the umbrella of a trilateral collaboration (2020-2029) with the National Institute for Fusion Science (Japan) and IPP-Max-Planck (Greifswald, Germany), the Tracer-Encapsulated Solid Pellet (TESPEL) method is now employed on TJ-II, W7-X and LHD. TESPELs are polystyrene spheres (diameter <1 mm) loaded with small quantities of selected impurities (atomic elements other than fuel). Thus, TESPEL allows delivering a precise quantify of tracer to a preselected location in the plasma core, after which its transport can be evaluated. An important aspect of previous projects was the establishment of a laboratory to fabricate TESPELs at Ciemat. Since then several hundred TESPELs prepared at Ciemat have been injected successfully into plasmas created in these devices. Thus, key goals of this current project are to continue TESPEL fabrication at this laboratory, thereby allowing Ciemat to maintain its fruitful collaborations with W7-X and LHD, and to expand TESPEL based impurity control studies. For instance, during recent experiments with TESPEL at LHD, project members determined that mid-/high- Z atomic ions can be flushed out of a high-density plasma if Li-granules are dropped continuously into the plasma edge [3]. When results were compared with results from reference plasmas, confinement times of high-Z ions were reduced by a factor 4 or more. It is extend to explore further this new operational scenario for stellarators.

Main results

To be completed at the end of the project (final report)

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

PEER-REVIEWED ARTICLES ASSOCIATED WITH THIS PROJECT (SINCE 2024)

[1] The rotational transform and enhanced confinement in the TJ-II stellarator, B. Ph. van Milligen, I. García-Cortés, K. J. McCarthy, B. A. Carreras, L. García, A. Cappa, P. Pons-Villalonga, T. Estrada, D. Medina-Roque, J. Hernández-Sánchez, R. García, O. S. Kozachok, O. O. Chmyga, J. L. de Pablos, J. M. Barcala, A. Molinero, D. Tafalla, I. Pastor, D. Tafalla, A. de la Peña, F. Lapayese and the TJ-II Team, J. Plasma Phys. 90 (2025) E98, https://doi.org/10.1017/S0022377825100433

[2] Multi-pellet injection into the NBI-heated phase of TJ-II plasmas, K. J. McCarthy, I. García-Cortés, A. Alonso, A. Arias-Camisón, E. Ascasíbar, A. Baciero, A. Cappa, R. Carrasco, O. O. Chmyga, T. Estrada, R. García, J. Hernández-Sánchez, F. J. Herranz, O. S. Kozachok, B. López Miranda, F. Medina, D. Medina-Roque, B. van Milligen, M. Navarro, M. A. Ochando, J. L. de Pablos, N. Panadero, I. Pastor, J. de la Riva, M. C. Rodríguez, D. Tafalla, V. Tribaldos and TJ-II Team, Nucl. Fusion 64 (2024) 066019, https://doi.org/10.1088/1741-4326/ad4047.

[3] Observation of Enhanced Core Impurity Transport in a Turbulence-Reduced Stellarator Plasma, D. Medina-Roque, I. García-Cortés, N. Tamura, K. J. McCarthy, F. Nespoli, K. Tanaka, M. Shoji, S. Masuzaki, H. Funaba, C. Suzuki, A. Mollen, R. Lunsford, K. Ida, M. Yoshinuma, M. Goto, T. Kawate, Y. Kawamoto, T. Kawate, T. Tokuzawa, I. Yamada and the LHD experimental team, Phys. Plasmas 33 (2026) 050701, https://doi.org/10.1063/5.0327035.

[4] Additional ECRH mitigates thermal quenches induced by tungsten TESPEL injection in LHD, H. Bouvain, A. Dinklage, N. Tamura, K. Mukai, C. Suzuki, T. Tokuzawa, Y. Takemura, Y. Narushima, K. Ida, M. Yoshinuma, H. Igami, H. Kasahara, K. McCarthy, D. Medina Roque, and I. García-Cortés, Phys. Plasmas 33 (2026) 022505. https://doi.org/10.1063/5.0310971.

[5] Recent Advances in Plasma Control and Physics Research in the Large Helical Device, K. Tanaka, K. Ida, Y. Morishita, H. Ohtani, D. Medina Roque, T. Tokuzawa, N. Kenmochi, T. Kinoshita, K. Toi, S. Murakami, H. Funaba, G. Ueno, M. Yokoyama, R. Ichikawa, K. Ogawa, A. Kageyama, N. Ohno, K. McCarthy, I. Garcia-Cortes, N. Tamura, F. Nespoli, R. Lunsford, M. Shoji, S. Masuzaki, C. Suzuki, A. Mollen, Y. Yoshinuma, M. Goto, Y. Kawamoto, T. Kawate, I. Yamada, T. Nasu, T. Kobayashi, K. Itoh, Y. Mizuno, R. Yasuhara, H. Uehara, D. Den Hartog, Y. Takemura, H. Igami, R. Yanai, T. Takeuchi, T. Yokoyama, M. Osakabe, S. Morita, A. Shimizu, M. Nishiura, N. Pablant, D. Spong, H. Nuga, K. Nagaoka, R. Sakamoto, H. Yamada, Y. Katoh, accepted for publication by Nucl. Fusion, NF-108651.R1

[6] Characterization of an Enhanced Plasma Performance Phase Induced by Pellet Injection in the Stellarator TJ-II, I. García-Cortés, K. McCarthy, B. Van Milligen, A. Kozachek, T. Estrada, V. Tribaldos, A. Baciero, B. Carreras, L. Garcia, D. Medina Roque, I. Pastor, M. C. Rodriguez Fernandez, D. Tafalla, sent to Nucl. Fusion for publication, NF-108859.R1.

[7] The radial localization of low-order rational surfaces in the stellarator TJ-II using pellet injection, K. J. McCarthy, I. García-Cortés, B. van Milligen, A. Baciero, R. Carrasco, B. A. Carreras, O. O. Chmyga, T. Estrada, R. García, J. Hernández-Sánchez, F. J. Hernanz, O. S. Kozachok, B. López Miranda, F. Medina, D. Medina-Roque, M. Navarro, N. Panadero, I. Pastor, M. C. Rodríguez, D. Tafalla, and TJ-II Team, sent to Nucl. Fusion for publication: NF-108785.

[8] The pump-out effect as a trigger for the electron to ion root transition in TJ-II, B. Ph. van Milligen, I. García-Cortés, K. McCarthy, O.S. Kozachok, O. O. Chmyga, J.L. de Pablos, A. Cappa, and the TJ-II Team, sent to J. Fusion Energy for publication, ID e7e624ed-fe96-4e3e-be5e-cb2ce1112310.

[9] Transport in high-performance plasmas of the TJ-II stellarator: From first-principles simulations to experimental validation, J. M. García-Regaña, D. Alegre, … K. J. McCarthy, …, et al., sent to Nucl. Fusion for publication, NF-108797.

POSTERS AND TALKS IN CONFERENCES SINCE 2024

[1] High performance plasmas of the TJ-II stellarator: Experiments and validation of first-principles models, T. Estrada, J.M. García-Regaña, A. Alonso, A. Cappa, D. Carralero, I. García-Cortés, K. McCarthy, N. Panadero, E. Sánchez, J.L. Velasco and the TJ-II Team, 52nd EPS Conf. on Controlled Fusion and Plasma Physics, Edinburgh, Scotland (2026), Invited talk.

[2] Transport in high-performance TJ-II plasmas: insights from first- principles simulations and experimental validation, J. M. García-Regaña, N. Panadero, E. Sánchez, A. Cappa, D. Carralero, H. Thienpondt, T. Estrada, J. A. Alonso, J. L. Velasco, K. McCarthy, I. García-Cortés and the TJ-II Team, 25th International Stellarator and Heliotron Workshop, Cordoba, Spain (2026), Invited talk.

[3] A multi-machine study on turbulence suppression by density peaking in stellarators, D. Carralero, B. Stefanoska, E. Maragkoudakis, K. Tanaka, T. Windisch, T. Estrada, A. Alonso, J. M. García-Regaña, A. Knieps, K. McCarthy, E. Sánchez, H. Thienpondt, 25th International Stellarator and Heliotron Workshop, Cordoba, Spain (2026), Oral.

[4] The observation of low-frequency oscillations in bolometer and soft X-ray signals after multiple pellet injections into the stellarator TJ-II, K. J. McCarthy, I. García-Cortés, B. van Milligen, N. Panadero, I. Pastor, V. Tribaldos, A. Baciero, R. Carrasco, O. O. Chmyga, T. Estrada, R. García, J. Hernanz, O. S. Kozachok, D. López Bruna, B. López Miranda, F. Medina, D. Medina-Roque, M. Navarro, C. Pastor, M. C. Rodriguez and TJ-II Team, 25th International Stelletator Heliotron Workshop, Cordoba, Spain (2026), Poster.

[5] Tungsten erosion and injection investigations in the stellarator Wendelstein 7-X: Results from OP2.1-2.3, B. P. Dhard, S. Brezinsek, Y. Boumendjel, R. Bussiahn, B. Buttenschön, D. Cipciar, T. Dittmar, D. Ennis, J. Fellinger, E. Flom, T. Fornal, Y. Gao, I. García-Cortés, D. Gradic1, M. Gruca, T. Gonda, S. Jabłoński, F. Henke, C. Killer, A. Knieps, P. Kornejew, M. Kubkowska, D. M. Kriete, M. Krychowiak, O. Marchuk, A. Langenberg, F. Maragkos, M. Mayer, K. J. McCarthy, D. Medina-Roque, D. Naujoks, D. Nocolai, N. Pablant, A. Pandey, M. Rasinski, J. Romazanov, J. Schäfer, M. F. Siddiki, L. Syrocki, N. Tamura, S. Thiede, T. Wegner and The W7-X Team, 27th Plasma Surface Interaction Conference, Regensburg, Germany (2026). Poster.

[6] Characterization of enhanced plasma performance phase after pellet injections in the TJ-II stellarator, I. García-Cortés, K. J. McCarthy, B. Van Milligen, T. Estrada, D. Medina-Roque, A. Baciero, B. A. Carreras, A. Cappa, A. A. Chmyga, F. Medina, L. Garcia, R. García, J. Hernández-Sánchez, F. J. Hernanz, A. S. Kozachek, F. Lapayese, B. Lopez-Miranda, D. Lopez-Bruna, V. Tribaldos, J. L. De Pablos, N. Panadero, I. Pastor, A. de La Peña, P. Pons-Villalonga, M.C. Rodriguez, D. Tafalla and TJ-II team, 30th IAEA Fusion Energy Conference, Chengdu, China (2025) Poster.

[7] Interpreting structures observed in pellet ablation profiles in the stellarator TJ-IIInterpreting structures observed in pellet ablation profiles in the stellarator TJ-II, K. J. McCarthy, I. García-Cortés, B. van Milligen, A. Baciero, R. Carrasco, T. Estrada, R. García, J. Hernández-Sánchez, B. López-Miranda, F. Medina, D. Medina-Roque, M. Navarro, N. Panadero, I. Pastor, M. C. Rodríguez and TJ-II Team, 30th IAEA Fusion Energy Conference, Chengdu, China (2025) Poster.

[8] Impact of Li-granule injection on the improvement of energy transport and the expulsion of impurities in the LHD heliotron, D. Medina-Roque, K. J. McCarthy, N. Tamura, I. García-Cortés, K. Tanaka, F. Nespoli, M. Shoji, S. Masuzaki, H. Funaba, C. Suzuki, A. Mollen, R. Lunsford, K. Ida, M. Yoshinuma, M. Goto, Y. Kawamoto, T. Kawate, T. Tokuzawa, I. Yamada and the LHD Experimental Team, 30th IAEA Fusion Energy Conference, Chengdu, China (2025) Poster.

[9] Confinement modelling pf enhanced plasma performance after multiple pellet injections into the TJ-II stellarator, V. Tribaldos, I. García-Cortés, K. J. McCarthy, D. Medina-Roque, A. Baciero, T. Estrada, D. López-Bruna, F. Medina, B. van Milligen, J. L. de Pablos, N. Panadero, I. Pastor, J. de la Riva and TJ-II Team, J. M. Reynolds-Barredo, O. O. Chmyga, O. S. Kozachok, 30th IAEA Fusion Energy Conference, Chengdu, China (2025).

[10] Transport in high-performance plasmas in the TJ-II stellarator: from first-principles simulations to experimental validation, J. M. García-Regaña, …, J. M. Fontdecaba, …, I. García-Cortés, …, J. Hernández-Sánchez, …, B. López-Miranda, …, K. J. McCarthy, …, D. Medina-Roque, P. Méndez, … N. Panadero, …, N. Tamura et al., 30th IAEA Fusion Energy Conference, Chengdu, China (2025).

[11] Tungsten erosion and injection investigations in the stellarator Wendelstein 7-X during OP2.2, D. Chandra-Prakash, N. Tamura, … D. Medina-Roque, … I. García-Cortés, … K. J. McCarthy, et al., 20th International Conference on Plasma-Facing Materials and Components for Fusion Applocations, Ljubljana, Slovenia (2025).

[12] Characterization of the pellet cloud drift in stellarators, G. Kocsis, J. Baldzuhn, R. Bussiahn, A. Buzás, G. Cseh, I. García-Cortés, K. J. McCarthy, D. Medina-Roque, N. Panadero, T. Szepesi, N. Tamura, M.B. Vavrik, Th. Wegner, TJ-II Team and W7-X Team, 51st EPS Conference on Plasma Physics, Vilnius, Lituania (2025).

[13] Study of the density limit physics for stellarator devices by means of an energy balance model, J. Gallego, A. Alonso, A. Bustos, T. Estrada, B. López-Miranda, A. Baciero, A. Cappa, K. J. McCarthy, I. García-Cortés, J. de la Riva Villén, F. Medina, N. Panadero and the TJ-II Team, 51st EPS Conference on Plasma Physics, Vilnius, Lituania (2025).

[14] Magnetic configuration effects on pellet fuelling in stellarators, N. Panadero, K.J. McCarthy, J. Baldzuhn, J. Hernández-Fernández, F. Köchl, G. Kocsis, A. I. Mohammed, N. Tamura, M.B. Vavrik, E. Villalobos Granados, T. Szepesi, and TJ-II and W7-X teams, 51st EPS Conference on Plasma Physics, Vilnius, Lituania (2025).


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