Non-linear MHD simulations of the plasma instabilities by pellet injection in LHD plasma

The effect of pellets on the global magnetohydrodynamic (MHD) dynamics of the Large Helical Device (LHD), which is a large superconducting heliotron in Japan, has been analyzed with the MIPS code. A pellet ablation model based on the neutral gas shielding model has been implemented. Excitation of MHD modes by the three-dimensionally localized pressure perturbation caused by the pellet injection has been observed. The dependence of the MHD-instabilities on the pellet size has been analyzed.