Correlation of Radiation with Operating Parameters during PLT Neutral Injection

Changes in impurity radiation during injection of neutral beams into the Princeton Large Torus (PLT) tokamak have been studied using both a soft X-ray detector and a scanning bolometer. The direction of injection with respect to the plasma current is found to be the most consistently significant factor. Injection counter to the plasma current gives rise to more central radiation than either injection parallel to the current or simultaneous injection parallel and antiparallel to the current. In addition, injection into ungettered discharges increases the soft X-ray impurity radiation more than does injection into gettered discharges. At least for coinjection, the change in soft X-ray impurity radiation tends to be less at higher preinjection electron densities than at lower ones.