Study of MHD activity in the HT-7 superconducting tokamak

摘要

An attempt is made to explain the behavior of the magneto-hydrodynamic (MHD) instabilities observed at values of the edge safety factor 3 < q (a) < 4, on the HT-7 superconducting tokamak. For the poloidal-magnetic-field fluctuations observed at the Mirnov coils, Mirnov-coil analysis shows that the MHD activity consists predominantly of m = 2 mode. Estimates are given for the characteristic growth time of the m = 2 mode, tau(g), and the related rate of island growth, dW/dt. The experimental value of tau(g) is found to be smaller than the linear theoretical one, and thus satisfy the condition tau(A) < tau(g) < tau(S) (where ideal timescale is TA, and the resistive timescale is tau(S)). However, the experimental and theoretical calculation of dW/dt are found to be in reasonable agreement with each other. (c) 2005 Elsevier B.V. All rights reserved.