Stability Analysis of Alfvén Eigenmodes in the Experimental Advanced Superconducting Tokamak

Abstract

The stability of Alfvén eigenmodes (AEs) driven by fast ions is investigated in the Experimental Advanced Superconducting Tokamak (EAST). It is demonstrated that all AEs found in toroidal AE gaps are stable and that the least stable mode is a reversed shear Alfvén eigenmode (RSAE) with $n=9$. The calculation results show that collisional damping is the main damping mechanism for toroidal mode number $n<11$. The excitation threshold for the RSAE is about β_crit,b = 3.33%, bigger than the value of the central beam ion beta β_b = 1.01%. The results show that AEs driven by fast ions are stable in EAST, at least for the parameters shown in this work. The effect of beam ion pressure and energy on AE stability is also presented. The drive coming from fast ions increases with the pressure gradient, and the drive mainly comes from ${\upsilon }_A/$3 resonance.

Keywords:

• Alfvén eigenmode
• fast ion
• NOVA/NOVA-K
• EAST

Acknowledgments

The authors would like to acknowledge useful discussions with G. Y. Fu and V. S. Chan. Numerical computations were performed on the ShenMa High Performance Computing Cluster in Institute of Plasma Physics, Chinese Academy of Sciences. This work was supported by the National MCF Energy R&D Program (grant number 2018YFE0309101); the National Natural Science Foundation of China (grant number 12005100); and the Opening Project of Cooperative Innovation Center for Nuclear Fuel Cycle Technology and Equipment, University of South China (grant number 2019KFY15).

Disclosure Statement

No potential conflict of interest was reported by the author(s).