Study of plasma current ramp-down and runaway generation under massive gas injection into the tokamak for disruption mitigation

Plasma disruptions and their consequences is one of the key questions, which define the construction of large tokamaks with high plasma current. For analysis of the process of plasma current shut down after impurity injection 0D code DIMRUN is developed (Dynamics of IMpurity radiation and RUNaway generation in tokamaks). Code includes equations for plasma power balance, plasma circuit, and it uses noncoronal model for impurity radiation and Dreicer and avalanche electron runaway generation. Code gives good agreement with DIII-D experimental data. Mathematical definition of the problem of plasma cooling and plasma current shut down after impurity injection, realised in DIMRUN code, is also discussed.