Simulation of the Lithium pellet injection on EAST tokamak using the BOUT++ transport code

A novel model predicting the Lithium pellet injected into the plasmas has been developed to simulate the pellet effects to the background plasma profiles, as well as the Lithium impurity density and temperature profiles. The pellet ablates due to the heat from the background plasma, and the neutral gas shielding (NGS) model has been used to describe this physical process. The shielding factor of the model have been identified by comparing the simulated neutral gas density and the experimental neutral gas measurements using CCD camera.

In the new BOUT++ transport code, the ionization, charge exchange and recombination rates of the lithium ions use the data from the ADAS database. The transport equations have been obtained by reduction of the Braginskii equations with source and sink terms due to the collisional interactions. The scan of the pellet parameters such as the pellet size, injection velocity has been conducted. The comparison of the simulation results and the experimental measurements from both the reflectometry and the POINT interferometer have been done on EAST tokamak.