Active Control System for Stabilization of Resistive Wall Mode in the Low-aspect-ratio RFP RELAX

Abstract

This paper presents the active control system for Resistive Wall Mode (RWM) stabilization in the low-aspect-ratio Reversed Field Pinch (RFP) machine RELAX. In magnetic confinement fusion research, RWM is MHD instability that degrades plasma confinement, and the stabilization of RWM is an important research issue. In the RFP machine RELAX with the aspect ratio of 2, RWM of m/n = 1/2 mode grows from when the discharge time exceeds 1.5 ms, and limits the discharge time. In RELAX, a control system using saddle coil array and on-off control have applied for RWM stabilization. It is confirmed that the system works as design, and as a result, the discharge time has been extended from ~3.0 ms to ~4.0 ms.