Neutral gas and plasma shielding (NGPS) model and cross-field motion of ablated material for hydrogen–neon mixed pellet injection

Abstract

A neutral-gas and plasma shielding (NGPS) model is applied for cryogenic hydrogen–neon mixed pellet injection used for the mitigation of tokamak disruptions. The NGPS model is useful to evaluate the characteristics of ionized plasmoid (size, density, temperature, and radiation), while reproducing the scaling of the neutral gas shielding model. It is found that even if one takes into account the optical thickness for radiation, the energy loss due to line radiation associated with neon is strong enough to limit the temperature and the pressure of the ionized plasmoid for pure neon or hydrogen–neon mixed pellets in the early phase of the material homogenization. Consequently, the ionized plasmoid of the neon mixed pellets is expected to homogenize along the magnetic field line where the ablated material is released—without significantly making the cross-field drift motion—as compared to pure hydrogen pellets.