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TJ-II:Experimental proposals (view source)

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== Updated TJ-II timeline ==
== Updated TJ-II timeline ==
[[Media:TJ-II_timeline_-_Yearly_planning_2022-2023.pdf|TJ-II yearly planning 2022-2023]]
[[Media:TJ-II_timeline_-_Yearly_planning_2022-2023.pdf|TJ-II yearly planning 2022-2023]]


== Creation of a new proposal ==
== Creation of a new proposal ==
 
To submit an experimental proposal, please use [https://forms.gle/aNHbrRyVjpQS7MJt7 this form].
'''PLEASE READ these brief instructions!!!'''
The table below is updated manually.
<!--'''PLEASE READ these brief instructions!!!'''
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# <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' (without the apostrophes). Note the 'TJ-II:' at the beginning!
# <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' (without the apostrophes). Note the 'TJ-II:' at the beginning!
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Your proposal will automatically be included in the lists below ('''provided''' you don't delete the relevant lines at the end of your proposal). You may need to reload this page to update the lists.
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== Experimental proposals, Spring 2023 ==


Your proposal will automatically be included in the lists below ('''provided''' you don't delete the relevant lines at the end of your proposal). You may need to reload this page to update the lists.
Creation date: 14/03/2023 13:30
 
{| class="wikitable"
! Title !! Main proponent !! Main proponent's affiliation !! Other proponents  !! Specific objectives of the experiment
|-
| Injection of cryogenic pellets in TJ-II operated with an inverted magnetic field || McCarthy, Kieran Joseph || Ciemat || García Cortés, Isabel || When a pellet is injected, it is ablated by plasma and clouds that detach from it should drift down the B-field gradient. In tokamaks, drifting facilitates efficient pellet fuelling for high-field side injection. However, in helical devices, the effect of such drifting is not clear. Thus, the inversion of the TJ-II B field provides a unique opportunity to compare cloud drifting and particle deposition in a helical device. No differences are expected but this needs experimental confirmation.
|-
| Rational surfaces, flows and radial structure in the TJ-II stellarator: Part II || van Milligen, Boudewijn || CIEMAT || Igor Voldiner (CIEMAT), Benjamin Carreras (UC3M) || We will expand the iota scan of Day 17/03/2022, reported in B.Ph.van Milligen et al., Plasma Phys. Control. Fusion 64 (2023), p. 055006. It revealed an interesting pattern of the poloidal flow velocity, v_theta, linked to low order rational surfaces. Using turbulence modelling, this pattern was shown to be due, likely, to the formation of a staircase pattern in the profiles. By expanding the scan range, here we will study the effect of several major rational surfaces (3/2, 8/5, 5/3).
|-
| Continuation of studies of pellet plasmoid drift in different magnetic configurations || Panadero, Nerea || CIEMAT || Kieran McCarthy (CIEMAT), Julio Hernández-Sánchez (CIEMAT), Isabel García-Cortés (CIEMAT), Daniel Medina-Roque (CIEMAT) || The main objective of this proposal is to quantify pellet plasmoid drift in the early stages of the homogenization process, and its relationship with rational surfaces for magnetic configurations with an iota profile lower than the standard configuration. In addition, experimental results will be compared with HPI2 predictions, since these experiments will be also part of the current effort to evaluate the stellarator version of HPI2 for the TJ-II, W7-X, LHD and Heliotron-J devices.
|-
| Spectroscopic Gas Puff Imaging (SGPI) for edge plasma characterisation || de la Cal, Eduardo || CIEMAT || Igor Voldiner (CIEMAT), Boudewijn van Milligen (CIEMAT) || Characterise the edge plasma boundary with the new SGPI system, with focus on 2-dimensional (2D) imaging of electron density (ne) and temperature (Te) turbulence and its coupling to neutrals.The SGPI diagnostic has shown in the last campaign the ability to obtain 2D measurements of the edge plasma ne and Te with a spatial resolution of , 4 mm and exposure times down to 10 microseconds.
|-
| Studying fast-ion losses induced by Alfvén Eigenmodes in NBI heated plasmas of the stellarator TJ-II || López-Miranda, Belén || CIEMAT || Baciero,  Alfonso; Cappa, Álvaro; Medina, Francisco; Pons-Villalonga, Pedro || In magnetic confinement fusion, fast-ions constitute a source of particles and free energy that, under certain conditions, drive various unstable MHD instabilities that significantly degrade fusion performance. In particular, the study of the impact of Alfvén Eigenmodes (AEs) is of special importance for controlling fast-ion transport across the magnetic field. The present experiment aims to study the influence of fast-ion losses induced by AEs in pure NBI-heated & combined ECR and NBI plasmas.
|-
| Impact of the rotational transform on pellet-induced enhanced performance in the TJ-II stellarator || Carreras, Benjamin || UC3M || Isabel García Cortés (CIEMAT), Kieran McCarthy (CIEMAT), Boudewijn van Milligen (CIEMAT) || In recent work, we observed pellet-induced enhanced confinement at the TJ-II stellarator [reference]. Analysis suggest that this enhancement could be related to the formation of transport barriers associated with low-order rational surfaces. Using the C-mode, i.e., the continuous variation of the rotational transform, we intend to shed further light on this issue.
|-
| External control of ZF in the TJ-II stellarator || De Pablos, José Luis || LNF || B.P. van Milligen, J.M. Barcala, A. Molinero, O. Kozachok (KIPT), O. Chmyga(KIPT), J. Romero (TAE), C. Hidalgo || The present proposal investigates the possibility of actively stimulating and control  the development of  low-frequency zonal flows through feedback.
|-
| Plasma Characterisation with Deuterium pellet injection || Isabel García Cortés || CIEMAT || Kieran McCarthy (CIEMAT), Daniel Medina-Roque (CIEMAT), Nerea Panadero (CIEMAT) || "Enhanced confinement is seen in TJ-II NBI-heated plasmas after single H pellet injection. In addition to the expected rise of core electron density, the plasma diamagnetic energy content rises by up to 40% with respect to similar discharges without PI. Enhancement is larger (up to 70%) when multi-pellets are used. To date, only H pellets into hydrogen plasmas have been studied. Our proposal is to inject deuterium pellets into deuterium plasmas to explore the isotope effect on this PiEC phase.
|-
| Recommissioning of the CXRS/MSE systems || McCarthy, Kieran Joseph || Ciemat || Jaime de la Riva Villen (Ciemat), Isabel García Cortés (Ciemat) || TJ-II is equipped with a compact NBI for performing CXRS and MSE. The NBI has been non-operative for several years due to a vacuum leak. The leak has been located and repaired. It is intended to recommission the CXRS diagnostic during this campaign. CXRS allows obtaining radial measurements of ion temperature, ion toroidal and poloidal velocity and radial electric field. Once operational, it will be used to measure these parameters during the PiEC phases achieved after pellet injection.
|-
| TJ-II: Calibration of the helical arrays of Mirnov coils || Pons-Villalonga, Pedro || CIEMAT || Álvaro Cappa (CIEMAT) || Calibration of the arrays of Mirnov coils, which is essential to correctly determine the mode numbers of the MHD perturbations.
|-
| NBI1 vs. NBI2 heated plasma comparison under reversed field conditions || Estrada, Teresa || CIEMAT || Arturo Alonso (CIEMAT), Alvaro Cappa (CIEMAT), Belen Lopez-Miranda (CIEMAT), Francisco Medina (CIEMAT), Ignacio Pastor (CIEMAT), Jose Luis Velasco (CIEMAT), NBI team. || A systematic comparison of plasmas heated with co- or ctr-NBI shows differences in the maximum achievable density and stored energy; lower values are generally achieved in co-NBI heated plasmas associated to higher impurity accumulation. A more intense negative Er and a reduction in the turbulence are measured in co-NBI heated plasmas as compared to counter- NBI cases. The interpretation of the experimental observations would benefit from experiments carried out under reversed field conditions.
|-
| Internal density measurements of plasmoid in hydrogen pellet || Gen Motojima || National Institute for Fusion Science (NIFS) || Nerea Panadero, Kieran McCarthy, Shinichiro Kado(Kyoto Univ.) || The objective is to evaluate the plasmoid density in hydrogen pellet to understand the pellet ablation. The measurement of plasmoid density has been conducted in LHD and Heliotron J, there is a difference of plasmoid density in them probably due to the difference of background plasma parameters. If the plasmoid density is evaluated also in TJ-II, it must help the understanding of mechanism of pellet ablation.
|}


== Experimental proposals, Spring 2022 ==
== Experimental proposals, Spring 2022 ==
Arturo
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