中性束注入在EAST中激发的离散阿尔文不稳定性

摘要

The neutral beam injection (NBI) system is applied to the experimental advanced superconducting tokamak (EAST). It will excite some Alfv´en instabilities when the plasma characteristics are improved. The numerical research on the NBI-induced discrete Alfv´en eigenmode (αTAE) and toroidal effect-induced Alfv´en eigenmode (TAE) in the pedestal region is presented in the paper. The research results show that plenty ofαTAEs appear in this region. TheαTAE is very different from the TAE. These modes are trapped by theα-induced potential wells along the magnetic field line. Due to negligible continuum damping via wave energy tunneling, similar to TAE, theαTAE can also be readily destabilized by energetic particles. Differently,αTAE frequency spectrum is more broad than TAE, and they are existed not only inside the gap but also outside the gap. The growth rate increases with injected power increasing. This instability maybe affects the physical behavior of the tokamak and the confinement of the plasma.%　　中性束加热将应用于先进实验超导托卡马克装置中,在改善等离子性能的同时也会激发起多种阿尔文不稳定性。本文主要采用了数值模拟的方法在理论上研究了中性束注入时在台基区激发的离散阿尔文本征模(αTAE)和环效应阿尔文本征模(TAE),结果表明在这个区域会激发出丰富的离散阿尔文不稳定性,这种离散阿尔文不稳定性不同于传统的TAE,这种模式是俘获在气球模驱动势阱中的束缚态,由于气球模势阱的存在使它和连续谱解耦,从势阱中漏出去的能量可以忽略不计,和TAE类似都很容易被激发,这种模式可以存在于gap内,也可以存在于gap外,频谱更宽泛。注入功率越大这种不稳定性增长率越大。这种不稳定性可能会影响等离子体的物理行为,从而影响等离子体的约束。