Title: Study of the Alfven eigenmodes stability in CFQS plasma using a Landau closure model

Abstract

The aim of this study is to analyze the stability of the Alfven eigenmodes (AE) in the Chinese First Quasi-axisymmetric Stellarator (CFQS). The AE stability is calculated using the code FAR3d that solves 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 moment for the energetic particles (EP) species including the effect of the helical couplings and acoustic modes. The Landau damping and resonant destabilization effects are added in the model by a given closure relation. The simulation results indicate the destabilization of n = 1 to 4 AEs by EP during the slowing down process, particularly n = 1 and n = 2 toroidal AEs (TAE), n = 3 elliptical AE (EAE) and n = 4 non circular AE (NAE). If the resonance is caused by EPs with an energy above 17 keV (weakly thermalized EP), n = 2 EAEs and n = 3 NAEs are unstable. On the other hand, EPs with an energy below 17 keV (late thermalization stage) lead to the destabilization of n = 3 and n = 4 TAEs. Themore » simulations for an off-axis NBI injection indicate the further destabilization of n = 2 to 4 AEs although the growth rate of the n = 1 AEs slightly decreases, so no clear optimization trend with respect to the NBI deposition region is identified. In addition, n = 2, 4 helical AE (HAE) are unstable above an EP β threshold. Also, if the thermal β of the simulation increases (higher thermal plasma density) the AE stability of the plasma improves. Overall, the simulations including the effect of the finite Larmor radius and electron-ion Landau damping show the stabilization of the n = 1 to 4 EAE/NAEs as well as a decrease of the growth rate and frequency of the n = 1 to 4 BAE/TAEs.« less

Authors:

Varela, J.  ^[1];

• Search DOE PAGES for author "Varela, J."
• Search DOE PAGES for ORCID "0000-0002-6114-0539"

Shimizu, A.  ^[2];

• Search DOE PAGES for author "Shimizu, A."
• Search DOE PAGES for ORCID "0000-0003-3764-3184"

Spong, D. A.  ^[3];

• Search DOE PAGES for author "Spong, D. A."
• Search DOE PAGES for ORCID "0000-0003-2370-1873"

Garcia, L.  ^[4];

• Search DOE PAGES for author "Garcia, L."
• Search DOE PAGES for ORCID "0000-0002-0492-7466"

Ghai, Y.  ^[3]

• Search DOE PAGES for author "Ghai, Y."
• Search DOE PAGES for ORCID "0000-0002-8432-0233"

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+ Show Author Affiliations

1. Univ. Carlos III de Madrid (Spain); National Inst. of Natural Science, Toki (Japan). National Inst. for Fusion Science
2. National Inst. of Natural Science, Toki (Japan). National Inst. for Fusion Science
3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
4. Univ. Carlos III de Madrid (Spain)

Publication Date:

Wed Jan 20 00:00:00 EST 2021

Research Org.:

Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE

OSTI Identifier:

1777704

Grant/Contract Number:  

AC05-00OR22725

Resource Type:

Accepted Manuscript

Journal Name:

Nuclear Fusion

Additional Journal Information:

Journal Volume: 61; Journal Issue: 2; Journal ID: ISSN 0029-5515

Publisher:

IOP Science

Country of Publication:

United States

Language:

English

Subject:

70 PLASMA PHYSICS AND FUSION TECHNOLOGY