Time resolved metal impurity fluxes in the dite tokamak

Abstract Measurements are presented of the time resolved flux of metallic impurities to a carbon probe placed at the limiter radius of the DITE tokamak. Average fluxes of titanium and molybdenum of the order 4 × 10 12 mm −2 s −1 are measured. It is concluded that peaks in the metal flux are correlated with arcing and with disruptions initiated by neutral beam injection. The decrease in flux by almost one order of magnitude compared with earlier studies may be related to a recent redesign of the molybdenum limiters which reduces the minor radius of the plasma. It is observed that the deposit density on the probe is not a linear function of exposure to the plasma and also that insertion of the probe causes a change to the local plasma environment.