10th International workshop on "Stochasticity in Fusion Plasmas (SFP)"-"3D physics in stellarators and tokamaks"

37 / 2021-04-23 16:14:54

Effect of the relative phase between pre-existing 2/1 and 3/1 magnetic islands on the suppression of runaway electrons on J-TEXT

disruption, runaway electrons, resonant magnetic perturbation, multiple modes

In the experiment of actively triggering plasma disruption by massive gas injection (MGI), the method of suppressing runaway current by external resonant magnetic perturbation (RMP) has been applied to many devices. In order to study the effect of the phase difference between multiple modes on the suppression of runaway electrons (REs) during disruption, sufficient cases of different relative phases between m/n = 2/1 and m/n = 3/1 magnetic islands are performed with NIMROD code in this work (Sovinec et al 2004 J. Comput. Phys. 195 355). Results show that the RE confinement is drastically affected by the relative phase between 2/1 and 3/1 magnetic islands, when the “O point” phase of 2/1 magnetic island and 3/1 magnetic island are toroidal 330°, the REs can be suppressed. It is predicted that the fitting curve of the remaining ratio of REs vs the relative toroidal phase approximates a sine-like function dependence. Further comparisons between the magnetic topological structure and the transport of REs, indicating that phase difference between co-existing 2/1 island and 3/1 island can cause different stochasticity degree evolution of normalized radial position, which affects the suppression of REs.