Experimental observation of the geodesic acoustic frequency limit for the NBI-driven Alfvén eigenmodes in TJ-II

Eliseev, L.G.; Melnikov, A. V.; Ascasíbar, E.; Cappa, Á.; Drabinskiy, M.A.; Hidalgo, C.; Khabanov, P.O.; Kharchev, N. K.; Kozachek, A.S.; Liniers, M.; Лысенко, С. Е.; Ochando, M. A.; Pablos, J.L. de; Pastor, I.; Sharapov, S. E.; Spong, D. A.; Breǐzman, B. N.; Varela, J.

doi:10.1063/5.0049225

Cited by 10 publications

(9 citation statements)

References 44 publications

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“…The FAR3d code was already validated with respect to gyro-kinetic and hybrid codes in dedicated benchmarking studies [41]. In addition, the linear simulation performed by the code shows a reasonable agreement with respect to observational data, reproducing the AE stability in LHD [42][43][44][45], DIII-D [46][47][48][49][50], TJ-II [33,51,52] and Heliotron J [53,54] plasma. In addition, the nonlinear version of the code succeeded in analyzing the sawtooth-like internal collapse events and energetic-ion-driven resistive interchange mode (EIC) burst observed in LHD plasma [39,[55][56][57][58] and the AE saturation in DIII-D plasma [59].…”

Section: Numerical Schemementioning

confidence: 79%

Simulation of the TAEs’ saturation phase in the Large Helical Device: MHD burst

Varela¹,

Spong²,

Todo³

et al. 2022

Nucl. Fusion

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The aim of the present study is to analyze the saturation regime of the Toroidal Alfven Eigenmodes (TAE) in the LHD plasma, particularly the MHD burst. The linear and non linear evolution of the TAEs are simulated by the FAR3d code that uses a reduced MHD model for the thermal plasma coupled with a gyrofluid model for the energetic particles (EP) species. The linear simulations indicate the overlapping of $1/2-1/1$, $2/3-2/4$ and $3/5-3/6$ TAEs in the inner-middle plasma region and frequency range of $45-75$ kHz, triggered by EPs with an energy of $T_{f} = 45$ keV and EP $\beta = 0.022 $. The non linear simulations show that $2/3-2/4$ and $3/4-3/5$ TAEs are further destabilized due to the energy transfer from $1/1-1/2$ TAE, leading to a broad TAEs radial overlapping and the MHD burst triggering. The energy of $1/1-1/2$ TAE is also non linearly transferred to the thermal plasma destabilizing the $0/0$ and $0/1$ modes, inducing the generation of shear flows and zonal currents as well as large deformations in the thermal pressure and EP density radial profiles. The non linear simulation reproduces the same succession of instabilities and the same frequency range with respect to the experiment. The instability propagates outward during the bursting phase, showing a large decrease of the EP density profile between the middle-outer plasma, pointing out the loss of part of the EP population that explains the decrease of the plasma heating efficiency observed during the MHD burst.

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Section: Numerical Schemementioning

confidence: 79%

Simulation of the TAEs’ saturation phase in the Large Helical Device: MHD burst

Varela¹,

Spong²,

Todo³

et al. 2022

Nucl. Fusion

Self Cite

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“…FAR3d code participated in benchmarking studies validating the model results with respect to gyro-kinetic and hybrid codes [52]. Previous studies performed using FAR3d show a reasonable agreement with the experimental data, for example reproducing the AE stability in Heliotron J [53], LHD [54,55], TJ-II [8,44,56] and DIII-D [57,58] plasma. Likewise, nonlinear simulations reproduced the sawtooth-like events, internal collapse and EIC burst observed in LHD [59][60][61][62][63] and the AE saturation in DIII-D [64].…”

Section: Numerical Schemementioning

confidence: 81%

Analysis of the ECH effect on EPM/AE stability in Heliotron J plasma using a Landau closure model

et al. 2022

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The aim of the present study is to analyze the effect of the electron cyclotron heating (ECH) on the linear stability of Alfven Eigenmodes (AE) and energetic particle modes (EPM) triggered by energetic ions in Heliotron J plasma. The analysis is performed using the FAR3d code that solves a reduced MHD model to describe the thermal plasma coupled with a gyrofluid model for the energetic particles (EP) species. The simulations reproduce the AE/EPM stability trends observed in the experiments as the electron temperature (Te) increases, modifying the thermal plasma β, EP β and EP slowing down time. Particularly, the n/m=1/2 EPM and 2/4 Global AE (GAE) are stabilized in the low bumpiness (LB) configuration due to an enhancement of the continuum, Finite Larmor radius (FLR) and e-i Landau damping effects as the thermal β increases. On the other hand, a larger ECH injection power cannot stabilize the AE/EPM in Medium (MB) and High bumpiness (HB) configurations because the damping effects are weaker compared to the LB case, unable to balance the further destabilization induced by an enhanced EP resonance as the EP slowing down time and EP β increases with Te.

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“…The FAR3d code has been verified through participation in benchmarking studies of gyro-kinetic and hybrid codes [72] and show a reasonable agreement with the experimental data. FAR3d has been validated against linear AE stability in LHD [73][74][75][76], TJ-II [50,77,78] and DIII-D [56,58]. The nonlinear version of the code has analyzed successfully the sawtoothlike, internal collapse events, EIC and TAE burst observed in LHD plasma [79][80][81][82][83][84] and the AE saturation in DIII-D plasma [85].…”

Section: Numerical Modelmentioning

confidence: 99%

Study of Alfvén eigenmode stability in Quasi-Poloidal Stellarator (QPS) plasma using a Landau closure model

Luengo

Varela²,

Spong³

et al. 2023

Nucl. Fusion

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The aim of this study is to analyze the linear stability of Alfvén Eigenmodes (AE) in QPS device heated by a tangential NBI. The analysis is performed using the gyro-fluid code FAR3d, that solves the reduced MHD equations for the thermal plasma coupled with moments of the kinetic equation for the energetic particles (EP). The AE stability is calculated in several operational regimes of the tangential NBI: EP β between 0.001 − 0.1, EP energy between 12−180 keV and different radial locations of the beam. The analysis is performed for vacuum and finite β equilibria as well as QPS configurations with 2 and 3 periods. The EP β threshold in the vacuum case is 0.001 and the AE frequency is lower as the energy of the EP population decreases. Toroidal Alfvén Eigenmodes (TAEs) with f = 80 − 120 kHz and Elliptical AE (EAEs) between f = 120 − 350 kHz are triggered between the middle-outer plasma region (r/a > 0.5). The AE stability improves in the simulations with finite β equilibria and 3 period configurations with respect to the vacuum case with 2 periods because the continuum gaps are slender, leading to a higher threshold of the EP β, above 0.03 for the AEs triggered by the helical mode families. Helical effects are not strong enough to destabilize Helical Alfvén Eigenmodes (HAEs), the AEs with the largest growth rates are triggered by the n = 1 and n = 2 toroidal families.

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Experimental observation of the geodesic acoustic frequency limit for the NBI-driven Alfvén eigenmodes in TJ-II

Cited by 10 publications

References 44 publications

Simulation of the TAEs’ saturation phase in the Large Helical Device: MHD burst

Simulation of the TAEs’ saturation phase in the Large Helical Device: MHD burst

Analysis of the ECH effect on EPM/AE stability in Heliotron J plasma using a Landau closure model

Study of Alfvén eigenmode stability in Quasi-Poloidal Stellarator (QPS) plasma using a Landau closure model

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