Phenomenology of major and minor disruptions in high β deuterium and tritium tokamak fusion test reactor plasma

Abstract

The main subject of this work is the experimental study of the low m and n magnetohydrodynamics (MHD) perturbations during disruptive instability. This work presents the magnetic probe data, electron cyclotron emission (ECE), α-particle losses, and neutron flux data measured during the disruptive instability in high β tokamak fusion test reactor (TFTR) [D. J. Grove and D. M. Meade, Nucl. Fusion 25, 1167 (1985)] plasmas. The major disruptions in high β regimes go through several phases. The first phase is the fast (150–250 μs) minor disruption (predisruption), causing a drop of the central temperature (and possibly, density). In this phase a powerful central $\text{m=1/n=1}$ mode initiates the sequential development of $\text{m=4/n=1,}$ 3/1, 2/1, 3/2 peripheral modes, which lead to a 3/1 locked mode. The second phase is the slow thermal quench (2 ms) in the presence of a locked mode. The third phase is a fast positive current spike generation (5%–10% increase in Ip in less than 0.5 ms) and finally, the current quench occurs with a loss of 2.5 MA in 5 ms.