Heat load on the first wall materials and interaction of emitted neutrals with plasma

The relation between the interactions of H2 with electron and plasma heat load to a tungsten target was investigated experimentally in the linear steady edge plasma simulator MAP-II. The heat load shows a large dependence on the density of injected H2 gas (NH2), electron density (ne) and electron temperature (Te) in the region of interactions between H2 and electrons. It was found that increase and decrease of the heat load can be described by characteristic lengths of several types of electron collisions normalized by the mean free paths of the corresponding collisions. In the plasma parameters surveyed in this work (Te of 5–20 eV and ne of 1016–1018/m−3), the increase of the heat load was mainly caused by the ionization of H2 and the decrease was caused by the reduction of the electron energy through the interaction with H2 and by the thermallization of the electrons through electron–electron collision.