Analysis of disruptive discharges during density limit experiments on the HT-7 Tokamak

Abstract

In this work, we discuss the preliminary analysis of some disruptive plasma discharges with a moveable graphite limiter on the HT-7 tokamak, which has been developed in order to investigate the influence of the horizontal plasma position on the density limit. What we have observed is that the m=2, MHD component dominates during almost the whole discharge duration, when the density limit is approached at values of the edge safety factor 3 < q(a) < 3.5. For the poloidal-magnetic-field fluctuations observed at the Mirnov coils, Mirnov-coil analysis shows that the m = 2 mode is unstable, which finally causes disruption.

Study of Effective Edge Safety Factor Using Analytical Solution of Grad-Shafranov Equation for Circular Cross Section Tokamak

“…, where ( is Shafranov pa- rameter) from magnetic coils measurement [22][23][24][25]30] using following equations…”