Pellet Ablation in the Large Helical Device

摘要

In the program of physical studies on the Large Helical Device (LHD) injection ofseveral hydrogen and deuterium pellets is foreseen. Injection of impurity pellets also may be useful for the plasma diagnostics. The pellet penetration into the LHD plasma is analyzed. In part 1, the present status of the ablation theory and experiment is discussed and an ablation model is formulated. It takes into account the energy distribution of the particles (both electrons and ions) participating in the ablation process, electrostatic effects of the cloud charging and changes of the pellet form during ablation. Plasma shielding effects are not significant in the ablation. The ablation model is compared with the experiments on T-10, JET, TFTR, Heliotron-E, and Tore Supra in part 2. Finally, in part 3, several regimes of the pellet injection into the LHD plasma are simulated including multiple-pellet sequence injection. Optimization of the injection regime is discussed.