Lagrangian Particle Simulations of Pellets and SPI into Runaway Electron Beam in ITER

Numerical studies of the ablation of pellets and shuttered pellet injection (SPI) fragments into a runaway electron beam in ITER have been performed using the time-dependent pellet ablation code [R. Samulyak at el., Nucl Fusion, 61 (4), 046007 (2021)] based on Lagrangian Particle (LP) method. The code implements low magnetic Reynolds number MHD equations, volumetric heating by runaway electrons, an equation of state with multiple ionization, an ionization by impact model, and a model for grad B drift of the ionized material across the magnetic field. The study of the single fragment ablation quantifies the influence of various factors, in particular the impact ionization by runaway electrons, on long-scale dynamics of the ablated plasma. We show that the grad-B drift prevents the ablated material from penetration deeply into the runaway region. Simulations of the SPI at various values of the tokamak safety factor provide information on global dynamics of the ablated plasma.