DIII-D Studies of Massive Gas Injection for Disruption Mitigation

摘要: Experiments with massive (3x10^ 22 particles) argon injection in the DIII-D tokamak have shown that neutral delivery rate is the crucial jet parameter. Nozzle aiming is not crucial, as the neutrals are stopped at the plasma edge. This was demonstrated over a range of plasma thermal energies from W th 1.0 MJ down to W th 0.02 MJ. Calculations suggest that magnetic field pressure is contributing to the observed neutral jet stopping. The subsequent core radiative thermal collapse is greatly accelerated by the onset of low-order (m= 1, 2/n= 1) MHD modes; this was demonstrated by shutting down target plasmas with different q-profiles and observing a delay in the collapse onset as the low order (q= 1 and 2) rational surfaces were buried deeper in the target plasma. Experiments using a new large valve with a 10x higher flow rate will also be presented.