Effect of magnetic configuration on frequency of NBI-driven Alfvén modes in TJ-II

Melnikov, A. V.; Ochando, M. A.; Ascasíbar, E.; Castejón, F.; Cappa, Á.; Eliseev, L.G.; Hidalgo, C.; Krupnik, L. I.; Löpez‐Fraguas, A.; Liniers, M.; Лысенко, С. Е.; Pablos, J.L. de; Perfilov, S.V.; Sharapov, S. E.; Spong, D. A.; Jiménez, Javier; Ufimtsev, M. V.; Breǐzman, B. N.

doi:10.1088/0029-5515/54/12/123002

Cited by 34 publications

(68 citation statements)

References 41 publications

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“…The present model was already used to study the AE activity in LHD [86,87], TJ-II [88,89,90] and DIII-D [91] indicating reasonable agreement with the observations. Table 1.…”

Section: Equations and Numerical Schemesupporting

confidence: 78%

Analysis of Alfven eigenmode destabilization in ITER using a Landau closure model

Varela

Garcia

2019

Nucl. Fusion

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Alfvén Eigenmodes (AE) can be destabilized during ITER discharges driven by neutral beam injection (NBI) energetic particles (EP) and alpha particles. The aim of the present study is to analyze the AE stability of different ITER operation scenarios considering multiple energetic particle species. We use the reduced magneto-hydrodynamic (MHD) equations to describe the linear evolution of the poloidal flux and the toroidal component of the vorticity in a full 3D system, coupled with equations of density and parallel velocity moments for the energetic particles species including the effect of the acoustic modes. The AEs driven by the NBI EP and alpha particles are stable in the configurations analyzed, only MHD-like modes with large toroidal couplings are unstable, although both can be destabilized if the EP β increases above a threshold. The threshold is two times the model β value for the NBI EP and alpha particles in the reverse shear case, leading to the destabilization of Beta induced AE (BAE) near the magnetic axis with a frequency of 25 − 35 kHz and Toroidal or Elliptical AE (TAE/EAE) in the reverse shear region with a frequency of 125 − 175 kHz, respectively. On the other hand, the hybrid and steady state configurations show a threshold 3 times larger with respect to the model β for the alpha particle and 40 times for the NBI EP, also destabilizing BAE and TAE between the inner and middle plasma region. In addition, a extended analysis of the reverse shear scenario where the β of both alpha particles and NBI EP are above the AE threshold, multiple EP damping effects are also identified as well as optimization trends regarding the resonance properties of the alpha particle and NBI EP with the bulk plasma.

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“…The present model was already used to study the AE activity in LHD [86,87], TJ-II [88,89,90] and DIII-D [91] indicating reasonable agreement with the observations. Table 1.…”

Section: Equations and Numerical Schemesupporting

confidence: 78%

Analysis of Alfven eigenmode destabilization in ITER using a Landau closure model

Varela

Garcia

2019

Nucl. Fusion

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“…The present model was already used to study the AE activity in LHD [31,61], TJ-II [62,63,64] and DIII-D [65,66,67], indicating reasonable agreement with the observations.…”

Section: Equations and Numerical Schemesupporting

confidence: 78%

Analysis of the MHD stability and energetic particles effects on EIC events in LHD plasma using a Landau-closure model

et al. 2019

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The aim of this study is to perform a theoretical analysis of the magnetohydrodynamic (MHD) stability and energetic particle effects on a LHD equilibria, calculated during a discharge where energetic-ion-driven resistive interchange mode (EIC) events were triggered. We use the reduced MHD equations to describe the linear evolution of the poloidal flux and the toroidal component of the vorticity in a full 3D system, coupled with equations of density and parallel velocity moments for the energetic particles species, including the effect of the acoustic modes, multiple energetic particles (EP) species, helical couplings and helically trapped EP. We add the Landau damping and resonant destabilization effects using a closure relation. The simulations suggest that the helically trapped EP driven by the perpendicular neutral beam injector (NBI) further destabilizes the 1/1 MHD-like mode located at the plasma periphery (r/a = 0.88). If the β of the EP driven by the perpendicular NBI is larger than 0.0025 a 1/1 EIC with a frequency around 3 kHz is destabilized. If the effect of the passing EP driven by the tangential NBI is included on the model, any enhancement of the injection intensity of the tangential NBI below β = 0.025 leads to a decrease of the instability growth rate. The simulations indicate that the EIC in LHD 2 perpendicular NBI EP is the main driver of the EIC events, as it was observed in the experiment. If the effect of the helical couplings are added in the model, an 11/13 EIC is destabilized with a frequency around 9 kHz, inward shifted (r/a = 0.81) compared to the 1/1 EIC. Thus, one possible explanation for the EIC frequency chirping down from 9 to 3 kHz is a transition between the 11/13 to the 1/1 EIC due to a weakening of the destabilizing effect of the high n modes, caused by a decrease of the EP drive due to a loss of helically trapped EP or a change in the EP distribution function after the EIC burst. The experimental data during the EIC bursting phase shows a complex mode structure and an inward shift of the instability, although no direct evidence of the proposed transition has been observed yet.

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“…The present model was already used to study the AE activity in LHD [43,44], TJ-II [45,46,47] and DIII-D [48,49,50,51], showing a reasonable agreement with the observations.…”

Section: Equations and Numerical Schemesupporting

confidence: 75%

Theoretical analysis of energetic-ion-driven resistive interchange mode stabilization strategies using a Landau closure model

et al. 2020

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The aim of the present study is to perform a theoretical analysis of different strategies to stabilize energetic-ion-driven resistive interchange mode (EIC) in LHD plasma. We use a reduced MHD for the thermal plasma coupled with a gyrofluid model for the energetic particles (EP) species. The hellically trapped EP component is introduced through a modification of the drift frequency to include their precessional drift. The stabilization trends of the 1/1 EIC observed experimentally with respect to the thermal plasma density and temperature are reproduced by the simulations, showing a reasonable agreement with the data. The LHD operation scenarios with stable 1/1 EIC are identified, leading to the stabilization of the 1/1 EIC if the thermal plasma density and temperature are above a given threshold. The 1/1 EIC are also stabilized if the rotational transform is modified in a way that the 1/1 rational surface is located further away than 0.9 times the normalized radius, or the magnetic shear in the plasma periphery is enhanced. Also, LHD discharges with large magnetic fields show a higher EIC destabilization threshold with respect to the thermal plasma density. If the perpendicular NBI deposition region is moved further inward than 0.875 times the normalized radius the 1/1 EIC are also stabilized. In addition,

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Effect of magnetic configuration on frequency of NBI-driven Alfvén modes in TJ-II

Cited by 34 publications

References 41 publications

Analysis of Alfven eigenmode destabilization in ITER using a Landau closure model

Analysis of Alfven eigenmode destabilization in ITER using a Landau closure model

Analysis of the MHD stability and energetic particles effects on EIC events in LHD plasma using a Landau-closure model

Theoretical analysis of energetic-ion-driven resistive interchange mode stabilization strategies using a Landau closure model

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