A New Disruption Mitigation System for Deuterium Tritium Operation at JET
Disruptions, the fast accidental losses of the plasma current and stored energy in Tokamaks, represent a significant risk to the mechanical structure as well as the plasma facing components of reactor-scale fusion facilities like ITER. At JET, the Tokamak experiment closest to ITER in terms of operating parameters and size, massive gas injection, has been established as a disruption mitigation method. As a "last resort" measure it reduces thermal and electromagnetic loads during disruptions which can potentially have a serious impact on the beryllium and tungsten plasmafacing materials of the main chamber and divertor. For the planned deuterium-tritium experiments, a new Disruption Mitigation System (DMS) has been designed and installed and is presented in this article. The new DMS at JET consists of an all metal gate valve compatible with pressure injections, a fast high pressure eddy current driven valve, a high voltage power supply and an all metal gas handling system providing six supply lines for pure and mixed noble and flammable gases (Ar, Ne, Kr, D2 etc.). The valve throughput varies with the injection pressure and gas type (efficiency 50­97%); the maximum injected amount of gas is approximately 4.6 ¥kPa·m3 (at maximum system pressure of 5.0MPa).