Emergency discharge quench or rampdown by a noble gas pellet

Abstract

Fast discharge quench in ITER using injection of a krypton pellet is considered. A zero dimensional analysis predicts a hundred milliseconds quench time for a 10 mm pellet injected with a velocity of 3 km/s. No significant runaway electrons are expected in the Parail-Pogutse approach improved by the 'avalanche effect'. Temperature shock due to radiation onto the beryllium first wall is not greater than 850 K for 10 ms close to the start of the current rampdown. This seems acceptable for the wall performance