Experimental evidence of nonlinear avalanche dynamics of energetic particle modes

¹ Southwestern Institute of Physics - P.O.Box 432, Chengdu 610041, China
² Center for Nonlinear Plasma Science and ENEA C. R. Frascati - Via E. Fermi 45, 00044 Frascati (Roma), Italy
³ Institute for Fusion Theory and Simulation, Zhejiang University - Hangzhou 310027, China
⁴ Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Physics and Optoelectronic Engineering, Shenzhen University - Shenzhen 518060, China
⁵ School of Physics and Optoelectronic, Dalian University of Technology - Dalian 116024, China

^(a) yulm@swip.ac.cn
^(b) zqiu@zju.edu.cn (corresponding author)
^(c) chenw@swip.ac.cn (corresponding author)

Received: 20 June 2021
Accepted: 24 November 2021

Abstract

Recent observations in HL-2A tokamak give new experimental evidences of energetic particle mode (EPM) avalanche. In a strong EPM burst, the mode structure propagates radially outward within two hundred Alfvén time, while the frequency of the dominant mode changes self-consistently to maximize wave-particle power exchange and mode growth. This suggests that significant energetic particle transport occurs in this avalanche phase, in agreement with theoretical framework of EPM convective amplification. A simplified relay runner model yields satisfactory interpretations of the measurements. The results can help understanding the nonlinear dynamics of energetic particle driven modes in future burning plasmas, such as ITER.