Impurity fueling to terminate Tokamak discharges

A model has been developed to investigate the requirements for terminating ITER discharges by introducing large quantities of either hydrogen or impurities to radiate the energy and quench the discharge before the discharge can undergo substantial motion and come into contact with the wall. The results of the model indicate that the injection of impurities will lead to runaway currents as large as 60% of the initial plasma current. Injection of hydrogen or low Z impurities is more hopeful, but even they can cause runaways. Radiation transport effects will likely be very important. (orig.)