Integrated simulation study of ELM pacing by pellet injection with TOPICS-IB

ペレット入射によるELMペーシングに関するTOPICS-IBを用いた統合シミュレーション研究

林 伸彦; 相羽 信行; 滝塚 知典; 大山 直幸

Hayashi, Nobuhiko; Aiba, Nobuyuki; Takizuka, Tomonori; Oyama, Naoyuki

Simulations of pellet triggered ELM (edge localized mode) have been done by an integrated code TOPICS-IB with various pellet parameters (location (high-magnetic-field side (HFS) or low-field side (LFS)), timing, size and speed) to clarify optimum parameters for ELM pacing by pellet. TOPICS-IB reasonably reproduce the pellet penetration depth measured in JT-60U OH and NB plasmas. In this paper, the pellet energy absorption effect is first considered as an ELM triggering mechanism. An ELM is triggered when a pellet enters more deeply in the pedestal region for earlier pellet injection in the natural ELM cycle, smaller size or faster speed, independent of pellet injection location. The energy loss by the pellet triggered ELM just before next natural ELM onset is almost the same as the natural ELM in wide ranges of parameters, but earlier injection can reduce energy loss depending on parameters. The energy loss by the pellet triggered ELM just after the previous natural ELM becomes smaller for smaller or slower pellet. At the middle timing of pellet injection in the natural ELM cycle, energy loss becomes smaller for larger (smaller) or slower (faster) pellet from HFS (LFS). The reduced energy loss is mainly attributed to the onset of high-n ballooning mode.