A MODEL FOR DISRUPTION GENERATED RUNAWAY ELECTRONS

One of the possible consequences of disruptions in tokamaks is the gen eration of runaway electrons which can impact plasma facing components and cause damage, owing to high local energy deposition. This problem becomes more serious as the machine size and plasma current increase. Since large size and high currents are characteristics of proposed fu ture machines, control of runaway generation is an important design co nsideration. A lumped circuit model for disruption runaway electron ge neration indicates that impurity concentration and type, as well as pl asma motion, can strongly influence runaway behaviour. A comparison of disruption data from several runs on JET and DIII-D with model result s demonstrate the effects of impurities, and plasma motion, on runaway number density and energy. The model is also applied to the calculati on of runaway currents for ITER.