Analysis of Alfven eigenmode destabilization in DIII-D high poloidal <i>β</i> discharges using a Landau closure model

Varela, J.; Spong, D. A.; Garcia, L.; Huang, Juan; Murakami, M.; Garofalo, A. M.; Qian, Jing; Holcomb, C.T.; Hyatt, A.W.; Ferron, J. R.; Collins, C.; Ren, Q.; McClenaghan, J.; Guo, Wenfeng

doi:10.1088/1741-4326/aac33f

Cited by 22 publications

(21 citation statements)

References 68 publications

(95 reference statements)

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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: 79%

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 [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: 79%

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 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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“…The model was applied in the AE stability analysis of high poloidal β and reverse shear discharges in DIII-D [38,47], LHD [48] and TJ-II [49] plasma, indicating reasonable agreement with the observations.…”

Section: Numerical Schemesupporting

confidence: 57%

“…Such performance deterioration is observed in several devices such as DIII-D and EAST tokamaks or LHD and W7-X stellarators [31][32][33][34] if the mode frequency resonates with the drift, bounce or transit frequencies of the EP. Experimental and theoretical studies of high poloidal β discharges in DIII-D and EAST show the destabilization of AEs [35][36][37][38], thus AEs could be also triggered in CFETR steady state operations. Consequently, a detailed analysis of the AE stability in CFETR steady state scenarios is mandatory to identify optimized operational regimes.…”

Section: Introductionmentioning

confidence: 99%

Theoretical study of the Alfven eigenmode stability in CFETR steady state discharges

Varela¹,

Huang²,

Spong³

et al. 2022

Nucl. Fusion

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The aim of this study is to analyze the stability of Alfven Eigenmodes (AE) in the China Fusion Engineering Test Reactor (CFETR) plasma for steady state operations. The analysis is done using the gyro-fluid code FAR3d including the effect of the acoustic modes, EP Finite Larmor radius damping effects and multiple energetic particle populations. Two high poloidal β scenarios are studied with respect to the location of the internal transport barrier (ITB) at r/a ≈ 0.45 (case A) and r/a ≈ 0.6 (case B). Both operation scenarios show a narrow TAE gap between the inner-middle plasma region and a wide EAE gap all along the plasma radius. The AE stability of CFETR plasmas improves if the ITB is located inwards, case A, showing AEs with lower growth rates with respect to the case B. The AEs growth rate is smaller in the case A because the modes are located in the inner-middle plasma region where the stabilizing effect of the magnetic shear is stronger with respect to the case B. Multiple EP populations effects (NBI driven EP + alpha articles) are negligible for the case A, although the simulations for the case B show a stabilizing effect of the NBI EP on the n=1 BAE caused by alpha particles during the thermalization process. If the FLR damping effects are included in the simulations, the growth rate of the EAE/NAE decreases up to 70 %, particularly for n > 3 toroidal families. Low n AEs (n<6) show the largest growth rates. On the other hand, high n modes (n=6 to 15) are triggered in the frequency range of the NAE, strongly damped by the FLR effects.

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Analysis of Alfven eigenmode destabilization in DIII-D high poloidal β discharges using a Landau closure model

Cited by 22 publications

References 68 publications

Analysis of the MHD stability and energetic particles effects on EIC events in LHD plasma 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

Theoretical study of the Alfven eigenmode stability in CFETR steady state discharges

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