The Impact of the ITER-Like Wall at JET on Disruptions
The new full-metal ITER-like wall at JET was found to have a profound impact on the physics of disruptions. The main difference is a significantly lower fraction (by up to a factor of 5) of energy radiated during the disruption process, yielding higher plasma temperatures after the thermal quench and thus longer current quench times. Thus a larger fraction of the total energy was conducted to the wall resulting in larger heat loads. Active mitigation by means of massive gas injection became a necessity to avoid beryllium melting already at moderate levels of thermal and magnetic energy (i.e. already at plasma currents of 2MA). A slower current quench however reduced the risk of runaway generation. Another beneficial effect of the ITER-like wall is that disruptions have a negligible impact on the formation and performance of the subsequent discharge.