Numerical investigate of tokamak runaway current suppression by massive deuterium-argon/neon mixture gas injection

Abstract: Background Tokamak plasma disruption generate runaway current that, if not suppressed, carry enormous amounts of energy that can cause severe damage to equipment. Purpose Investigate of the effect of injecting deuterium-argon/neon mixture gas on the runaway current during disruption. Methods In this paper, numerical simulations are carried out using a fluid model in the DREAM code, which is capable of self-consistently simulating the evolution of plasma parameters with time during the disruption process. Results It is shown that injection of a deuterium-argon/neon mixture gas suppresses the eventual formation of platform runaway current, but the deuterium-argon/neon mixture gas usually has an optimal content and ratio. In the range of pre-disruption plasma current Ip discussed in this paper, the content of neon/argon in the mixture gas should be in the range of 0.50% ~ 0.70% and the injection amount of deuterium should be in the range of 1020 m-3 ~ 1021 m-3. Outside this range, deuterium-argon/neon mixture gas injection has a diminished effect on the suppression of runaway current and even increases them. Conclusions The pre-disruption plasma current Ip is the key factor influencing the runaway current. The larger Ip is the larger the runaway current is formed and more mixture gas needs to be injected. On fusion reactor-scale tokamak devices with Ip up to 10 MA, the amount of injected mixture gas needs to reach 1022 m-3, which is not achievable with the current massive gas injection (MGI) technique and injection of a deuterium-argon/neon mixture through a shattered pellet would be a more viable approach.