Lagrangian particle simulation of hydrogen pellets and SPI into runaway electron beam in ITER

Abstract

Numerical studies of the ablation of pellets and shattered pellet injection (SPI) fragments into a runaway electron beam in ITER have been performed using a time-dependent pellet ablation code [Samulyak et al., Nucl. Fusion, 61(4), 046007 (2021)]. The code resolves detailed ablation physics near pellet fragments and large-scale expansion of ablated clouds. The study of a single-fragment ablation quantifies the influence of various factors, in particular, the impact ionization by runaway electrons and cross-field transport models, on the dynamics of ablated plasma and its penetration into the runaway beam. Simulations of SPI performed using different numbers of pellet fragments study the formation and evolution of the ablation clouds and their large-scale dynamics in ITER. The penetration depth of the ablation clouds is found to be of the order of 50 cm.

Interpretative 3D MHD modelling of deuterium SPI into a JET H-mode plasma

“…The PELOTON code (the first version was described in [57] as the LP code), is a three-dimensional, scalable, adaptive, massively-parallel particle code for fully-resolved simulations of the ablation of pellets and SPI fragments by hot and runaway plasma electrons based on the Lagrangian particle method [58]. It implements the phase transition (ablation) equations on the pellet surface, the low magnetic Reynolds number MHD equations valid in cold and dense ablation clouds, kinetic models for cloud heating by hot thermal background plasma electrons and volumetric heating by REs, equation of state models atomic processes (dissociation and ionisation), radiation models (for Ne and Ne/D mixtures), and models for the transverse motion of ablation clouds across magnetic field lines, in particular the ∇B drift [59]. The pellet rocket acceleration is driven by the ∇B drift that creates asymmetry and non-uniform heating of the ablation cloud [60].…”