Instrument for synchronizing plasma diagnostic measurements with tokamak internal disruptions

Abstract

We describe an instrument which detects internal disruptions in real time, providing one pulse at each disruption and another pulse at a selectable phase of the internal disruption cycle (as determined by the interval between the two preceding disruptions). By appropriate gating, this instrument allows diagnostics requiring integration times long compared to the internal disruption period to be used in the study of plasma parameter changes produced by internal disruptions. It also permits selection of the phase of the internal disruption cycle at which diagnostics with short sampling times are used. Several features of the instrument are discussed in light of its performance in firing the Thomson scattering laser on the Alcator-C tokamak.