Plasma Cooling During Disruptions of Ohmic Discharges at the T-10 Tokamak

Abstract

Experimental data on plasma cooling during slow discharge disruptions at the T-10 tokamak are analyzed. It is shown that, in the initial phase of thermal quench at T-10, two different scenarios of plasma cooling can take place. The first scenario is associated with energy transport due to heat conduction. It is initiated by the “cooling wave” that arises during the development of the m2/n1 mode instability or other plasma instabilities excited in the presence of the magnetic fields of this mode. The cooling wave rapidly propagates from the region where the instability develops into the plasma core and leaves plasma with enhanced electron thermal conductivity behind its front. The second scenario takes place when the cooling wave is so intense that it causes fast decay of the central helical magnetic structure created in the preliminary disruption phase by the magnetic fields of the m2/n1 mode. This stage is followed by the decay of the m2/n1 mode, after which the last phase of the plasma cooling begins: plasma mixing at the periphery of the plasma column and the beginning of plasma current disruption. Based on these scenarios, a general classification scheme of slow disruptions of ohmic discharges at the T-10 tokamak is proposed.