Plasma facing materials response to repetitive pulses simulating fusion reactor conditions

The performed simulation experiments in quasi-stationary plasma accelerators (QSPA) Kh-50 plasma accelerator were concentrated on studies of plasma surface interaction features under irradiation of different candidate materials for the divertor of fusion reactor with high power plasma loads of variable parameters. Dynamics of erosion products, both in form of droplets and solid dust, from exposed tungsten and carbon surfaces under QSPA plasma exposures have been investigated. Analysis of particles velocity distribution and angular dependencies, as well as their start times from the surface has been performed. Different sources of dust: bifurcation of major cracks, fine cracks along the grains, resolidified microbridges through the cracks, material modification have been recognized and investigated in simulation experiments with QSPA Kh- 50. It is shown that modification of W after the repetitive pulses with development of ordered subμm cellular structures may contribute significantly to the nm droplets and dust that remain on the material surface. Macroscopic erosion of castellated targets has been studied to investigate key plasma surface interactions (PSI) effects in 3D geometry. Edge effects became dominating in target erosion. Emission of the droplets has threshold character and cyclical nature. New erosion mechanism introduced by edge effects, results in extremely growing droplet size and even submillimetre particles. The investigations were aimed to support mainstream fusion research in part of testing of plasma facing materials perspective for large thermonuclear devices of both types (with magnetic and inertial plasma confinement) and for plasma technologies. (author)