Particle fueling by shallow pellet injection in JT-60U

Abstract

Effects of the shallow pellet injection on the ELMy H-mode plasma have been investigated in JT-60U for single null open-divertor plasmas. The penetration depth of the pellet was 20–30% of the plasma minor radius from the outermost flux surface with NB heating power of 15–25 MW and the plasma density of 1–2 × 10 19 m −3. (1) A particle stream was generated transiently by the shallow pellet injection from the main plasma to the divertor region without the degradation of the energy confinement, and was accelerated by the enhanced ELM activity. (2) The total power on to the divertor plate (mainly to the inboard divertor region) increased just after the pellet injection by ∼ 100% with ∼ 60% rise of the maximum heat flux density. (3) The screening of the helium influx by the shallow pellet injection has been confirmed from the delayed rise of the helium density in the main plasma, which has been obtained by the helium gas puffing just after the pellet injection.