A 0-dimensional simulation of particle balance between plasma and plasma facing components in the LHD

We have developed a new 0-dimensional simulation for investigating the particle balance in the LHD plasma. The hydrogen barrier model (from K.Hanada 2015 J. Nucl. Mater. 463 1084) is adopted for evaluating the number of particles stored on the plasma-facing materials, including the first wall and the divertor tiles, and it is assumed that all the particle reactions only took place in the edge plasma. We attempted a calculation using experimental data, i.e, the electron density and temperature, and the neutral pressure, from an LHD discharge in nearly steady state, and it was confirmed that the steady state condition was actually reproduced. As a result, it was found that the first wall has a certain maximum ability of particle storage (4.8×1022 particles) against certain electron density (3×1019 m-3) and temperature (1.2keV), while the divertor tile has very little effect on the particle balance.

We are now able to estimate the amount of desorption/adsorption from the first wall, and also to judge whether the next discharge will be steady or not by comparing the actual number of wall-stored particles to the estimated maximum ability of storage.