Massive gas injections in JET - Impact on wall conditions

Disruptions are a critical issue for large scale tokamaks due to the potential damage to plasma facing components. Massive Gas Injection (MGI) is considered as a "last resort" method for disruption mitigation. A MGI system based on the Disruption Mitigation Valve (DMV) has been brought into operation at JET. Injections of neon, argon and its mixtures with deuterium show distinct effects on the machine condition during and after MGI-induced disruptions. MGI with pure argon shows a continuous accumulation in consecutive pulses. Neon on the contrary shows a fast saturation due to trapping in carbon PFCs.