Runaway dynamics in ITER-like disruptions in the presence of massive material injection

A runaway avalanche can result in a conversion of the initial plasma current into a relativistic electron beam in high current tokamak disruptions. We investigate the effect of massive material injection on the coupled dynamics of runaway generation and resistive diffusion of the electric field, during disruptions in ITER-like plasmas. Considering deuterium-noble gas mixtures across a wide range of injected concentrations, we find that partial screening effects result in large runaway currents, even in cases where runaway generation would have been suppressed according to previous estimates. The reason is that the cooling associated with the injected material leads to higher electric fields, which, in combination with the recombination associated with the low temperatures, leads to a large avalanche generation.