JET Disruption Studies in Support of ITER

Disruptions are a key issue for all future large tokamaks, due to the large mechanical and thermal loads they can place on the vacuum vessel and plasma facing components. This paper summarises recent key advances in understanding on JET, in the disruption area. Results will be presented on halo currents and asymmetric disruptions, where large sideways forces may occur (up to ~4MN in JET) ­ which are a significant design issue for ITER. Heat loads arising from disruptions are also a concern and JET data on the location, duration and peaking of these heat loads under various classes of disruptions is discussed. Another disruption consequence is Runaway Electrons (REs). IR imaging shows distinct localised impacts on the upper dump plate by the RE beam leading to an increase of the surface temperature of >1000oC; this localization and nature of the runway beam loss is discussed. Intrinsic to mitigation of disruptions is a means to predict that they are going to occur, and results on understanding of the sequence of events that ultimately leads to disruptive termination are outlined. A fast Disruption Mitigation Valve (DMV) has been recently installed on JET to study disruption mitigation by Massive Gas Injection (MGI) and the results are briefly reviewed.
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