Fokker-Planck simulation study of hot-tail effect on runaway electron generation in ITER disruptions

奴賀 秀男*; 松山 顕之; 矢木 雅敏; 福山 淳*

Nuga, Hideo*; Matsuyama, Akinobu; Yagi, Masatoshi; Fukuyama, Atsushi*

Three-dimensional Fokker-Planck code TASK/FP, which calculates the evolution of the relativistic momentum distribution function of electrons and the induced toroidal electric field, has been applied to the study of runaway electrons generated in ITER disruptions. The hot-tail effect on the runaway electron generation is investigated. The simulation results show that the hot-tail effect affects the runaway electron current density profile even in the secondary runaway electron dominant case. Seed currents are induced during the thermal quench ahead of the Dreicer generation, which have an impact on the subsequent current and electric field evolution. In spite of the small ratio of the primary electrons, they are multiplied significantly by the avalanche effect. Consequently, the hot-tail effect plays an important role in determining the total runaway electron current density profile after the current quench.