Phenomenology of Major and Minor Disruptions in High Beta DT in TFTR Plasma
Authors: S. Mirnov, I. Semenov, E. Fredrickson, R. Budny, Z. Chang, K. McGuire, H. Park, H. Takahashi, S. von Goeler, L. Zakharov, and S. Zweben
This work presents the magnetic probe data, electron cyclotron emission (ECE), alpha-particle losses, and neutron flux data measured during the disruptive instability in high beta TFTR plasmas. It is shown that the major disruptions in high beta regimes go through several phases. The first phase is the fast (150-250 microseconds) minor disruption (predisruption) causing a drop of the central temperature (and possibly, density). In this phase, a powerful central m=1/n=1 mode initiates the sequential development of 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 milliseconds) in the presence of a locked mode. The third phase is a fast positive current spike (5-10% increase in Ip in less then 0.5 millisecond) and finally the current quench occurs with a loss of 2.5 MA in 5 msec.