Simulation of deuterium pellet ablation and deposition in the EAST tokamak with HPI2 code

Abstract

Pellet injection is a primary method for fueling the plasma in magnetic confinement devices. For that goal the knowledges of pellet ablation and deposition profiles are critical. In the present study, the pellet fueling code HPI2 was used to predict the ablation and deposition profiles of deuterium pellets injected into a typical H-mode discharge on the EAST tokamak. Pellet ablation and deposition profiles were evaluated for various pellet injection locations, with the aim at optimizing the pellet injection to obtain a deep fueling depth. In this study, we investigate the effect of the injection angle on the deposition depth of the pellet at different velocities and sizes. The ablation and deposition of the injected pellet are mainly studied at each injection position for three different injection angles: 0°, 45°, and 60°. The pellet injection on the high field side (HFS) can achieve a more ideal deposition depth than on the low field side (LFS). Among these angles, horizontal injection on the middle plane is relatively better on either the HFS or the LFS. When the injection location is 0.468 m below the middle plane on the HFS or 0.40 m above the middle plane of the LFS, it can achieve a similar deposition depth to the one of its corresponding side. When the pre-cooling effect is taken into account, the deposition depth is predicted to increase only slightly when the pellet is launched from the HFS. The findings of this study will serve as a reference for the update of pellet injection systems for the EAST tokamak.