Abstract

Understanding the physics of energetic particles (EP) is crucial for the burning plasmas in next generation fusion devices such as ITER. In this work, three types of internal kink modes (a saturated internal kink mode (SK), a resonant internal kink mode (RK), and a double e-fishbone) excited by energetic particles in the low density discharges during ECRH/ECCD heating have been studied by the newly developed 24(poloidal) × 16(radial) = 384 channel ECEI system on the HL-2A tokamak. The SK and RK rotate in the electron diamagnetic direction poloidally and are destabilized by the energetic trapped electrons. The SK is destabilized in the case of q min > 1, while the RK is destabilized in the case of q min = 1/1 modes propagating in the opposite directions poloidally, has been observed during plasma current ramp-up with counter-ECCD. Strong thermal transfer and mode coupling between the two m/n = 1/1 modes have been studied.

Highlights

  • The MHD activities induced by energetic particles (EP), which may cause severe confinement degradation in the burning plasma devices such as ITER and future fusion reactor, have been concerned by many scientists [1]

  • Three types of internal kink modes (an electron saturated internal kink mode, an electron resonant internal kink mode (RK), and a double efishbone) excited by energetic particles during ECRH/electron cyclotron current drive (ECCD) heating have been studied by the 24×16 = 384 channel electron cyclotron emission imaging (ECEI) system on the HL-2A tokamak. These modes have been found in the low density discharges and their frequencies are close to the precessional frequency of the trapped fast electrons

  • The e-saturated internal kink mode (SK) and electron RK (e-RK) rotate in the electron diamagnetic direction poloidally and are destabilized by the energetic trapped electrons

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Summary

Introduction

The MHD activities induced by energetic particles (EP), which may cause severe confinement degradation in the burning plasma devices such as ITER and future fusion reactor, have been concerned by many scientists [1]. One of those is the fishbone instability, which was first observed in 1983 in PDX tokamak with nearly perpendicular neutral beam injection (NBI) heating [2]. The SKs have been observed and investigated on MAST [12], NSTX [13] and HL-2A [14,15] When these modes appear, there are strong damping of the toroidal rotation, degradation of stored energy and significant losses of fast particles.

Arrangement of the experiment
Resonant internal kink mode and saturated internal kink mode
Double e-fishbone
Summary

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