Simulations of runaway electron generation including the hot-tail effect

Abstract

The hot-tail (H-T) effect in disruptions with impurity injection is considered. The contribution of H-T effect on runaway electron (RE) current, which arises from fast thermal quench, is studied using two-dimensional Fokker-Planck simulation. It is found that in a high density plasma, the total RE current is reduced owing to its high collisionality. We also found that if the thermal quench is fast enough to invoke the H-T effect, the effect produces more seed REs than that excluding H-T effect even in high density plasmas. In high density region (n e ∼ 10 21 m −3 ) with fast thermal quench, nevertheless the increment of the seed REs due to H-T effect is generally small (tens of mili amperes), the increment of the total RE current reached to 2 MA owing to the avalanche effect.

Runaway current suppression by secondary massive gas injection during the disruption mitigation phase on J-TEXT

“…The fall of T e during TQ will also decrease the primary RE generation rate, and the primary RE generation is mainly concentrated in TQ. This has been confirmed with some simulations [14,15]. Thus, the primary RE generation is hard to be affected by the electron density increase after TQ.…”