Numerical simulation of lithium granule injection in tokamak edge plasma

To understand how a Li pellet affects the background plasma, the edge plasma code SOLPS combined with a neutral-gas-shield ablation model has been employed to simulate the transport of Li species in the edge plasma during Li pellet injections in a typical EAST H-mode plasma. The simulation results show that a Li pellet 0.5 mm with velocity ∼100 m/s can penetrate the separatrix, and that the electron temperature drops quickly where the pellet passes by while the electron density needs a longer time to respond. The plasma pressure in the pedestal region grows significantly with the pellet size; the pressure gradient changes even more drastically. This work indicates that without accumulative contributions, a pellet 0.7 mm or above in diameter at an injection velocity of 100 m/s is likely to provide a pressure perturbation enough to trigger ELMs in the typical EAST H-mode plasmas used in this work.