Avalanche electron heat transport events triggered by non-linear mode couplings in HL-2A neutral beam injection heated L-mode plasmas

Abstract

Understanding cross-field anomalous transport is a central issue in the magnetic confinement fusion research. Recently, a long range large avalanche electron heat transport event has been observed in HL-2A neutral beam injection heated low-confinement mode (L-mode) plasmas. It is found and identified firstly that the non-linear mode couplings between high-frequency core-localized toroidal Alfvén eigenmodes and low-frequency fishbone mode with , where m and n are poloidal and toroidal mode-numbers, respectively, trigger the avalanche transport event within several hundred Alfvén times. This finding can help to understand the generation mechanism of avalanche transport events, and is also expected to shed light on the importance of the non-linear multiple mode couplings in fusion and burning plasmas.