Magnetic Probe Investigation of the Disruptive Instability in Tokamak LT-3

A multicoil, internal magnetic probe is used to follow the development of the plasma current profile through the disruptive instability. The initial perturbation of the current channel is localized between the singular surfaces $q=1, 2$ present within the plasma. Subsequently, during the main disruption, peak toroidal electric fields ≳10 times the quiescent value are observed near axis. It is suggested that microturbulence is responsible for this extreme resistivity anomaly.