Arcing studies in the dite tokamak using a time-resolved arc detector

The incidence of arcing in DITE as a function of the plasma parameters has been investigated using a time-resolved arc detector. The arcs are detected by observing the current and the optical emission from a concentric probe at the same minor radius as the fixed limiter. The measured currents are in good agreement with the estimated currents previously obtained from the track dimensions on probes. The arcing signals were correlated with pulses in the loop voltage, MHD activity, and rational values of the safety factor q (a) . Arcing during the initial phase of the discharge was reduced by a factor 5 by reducing the plasma current rise-time from 11 to 3 ms. Simultaneous measurements of the Ti flux and TiII and TiXVIII spectral lines did not, however, show a significant reduction in impurities for most of the discharge.