Stability of Elongated Cross-Section Tokamaks to Axisymmetric Even Poloidal Mode Number Deformations.

摘要

A recent paper by Nakayama, Sato and Matsuoka suggests that elliptical cross section tokamaks with aspect ratio R/a = 3.2 and with elongation kappa = 2.6 are unstable to a splitting (m = 2, n = 0) instability for plasma beta > 5%, and that kappa (> =) 4.0 plasmas are unstable to splitting for beta (> =) 1%. We have tried to reproduce these results using the MHD evolution code TSC, but find these configurations to be stable, not even near a stability boundary. Even a kappa = 3.7 plasma with beta = 23.0% is stable to the splitting mode. However, the addition of pinching coils at the waist will cause the plasma to split if the current in these coils exceeds a critical value I(sub c) which decreases with increasing beta . 8 refs., 11 figs., 1 tab.