1 TH / P 4 - 5 Mitigation of ELMs and Disruptions by Pellet Injection

Deuterium, impurity and impurity doped pellets are studied in light of their use for ELM and disruption mitigation. Based on ELM pace making studies at ASDEX Upgrade and JET, the minimum pellet size required to cause an ELM, has been estimated in ITER for the foreseen pellet velocities. Concerning disruption mitigation studies the number of runaways is determined for JET like plasmas for deuterium, carbon and carbon-doped deuterium pellets. To calculate the ablation rate and to describe the cloud dynamics we used the Hybrid code which considers the formation of the neutral cloud according to the NGS ablation model and the dynamics of the ionized cloud part is treated by an one-dimensional Lagrangian cell code. Interaction between cold pellet particles and background plasma, radiation, Ohmic heating and heat diffusion are taken into account to calculate the change in the background plasma temperature. The resistive diffusion of the electric field is followed, and the resulting number of Dreicer, hot-tail and avalanche runaway electrons are calculated during the current quench. This way a tool has been created to test the suitability of different pellets for disruption mitigation.