HT-7托卡马克中逃逸电子和磁场波纹的共振作用

The resonance between runaway electrons and magnetic ripple in HT-7 Tokamak

为抑制托卡马克等离子体中逃逸电子的能量,在2009年秋HT-7托卡马克物理实验中,分析了逃逸电子在不同放电条件下的能量演化信息,发现逃逸电子和磁场波纹的共振现象。尽管在等离子体的芯部,逃逸电子的能量可高达数十MeV,但在逃逸电子输运到边界的过程中,通过和磁场波纹不同阶的谐波共振,逃逸电子的能量被限制在一个范围内,而不会再继续增加。高环电压下,逃逸电子可和低阶谐波共振,最终可获得的能量较高;在低环电压下,逃逸电子和高阶谐波共振,最终可获得的能量较低。通过这个机制的作用,逃逸电子的能量被限制在一个很低水平,这将大大减轻装置第一壁的负荷,减小逃逸电子对装置的负面影响。

For suppressing the energy of runaway electrons in tokamak plasma, we analyzed the X-ray energy spectra by runaway electrons in different discharges of the HT-7 tokamak experiment performed in the autumn of 2009. The resonant phenomenon between runaway electrons and magnetic ripple was found. Although, the energy of runaway electrons in the plasma core can be as high as several tens of MeV, but when they are transported to the edge, the electron energy are limited to a certain range by resonance with the magnetic ripple of different harmonic numbers. The runaway electrons under high loop voltage resonate with low step magnetic perturbations, with high energy gain; whereas the runaway electrons under low loop voltage resonate with high level magnetic perturbations, with low energy gain. Using this mechanism, the energy of runaway electrons can be restricted to a low level, and this will significantly mitigate the damage effect on the equipment caused by runaway electrons.