Simulation of plasma evolution in the initial phase of inductive tokamak startup

Summary form only given, as follows. In the tokamak startup phase, several conditions should be satisfied for successful discharge. First, null field structure that is related to particle confinement. Second, loop voltage inside the vacuum vessel, which is responsible for neutral gas breakdown. Third, magnetic field decay index that is related to the stability of the null position. In most circumstances, since these conditions are inseparable, a self-consistent approach including eddy currents flowing in various conducting structure materials is needed to find an optimal solution. We studied this optimization problem for enlarging the null field area at the desired position under two constraints, sufficient loop voltage and reliable decay index. Under such circumstances, the evolution of plasma parameters such as density, temperature, and plasma current is investigated through numerical simulation with an exemplary tokamak geometry.