Modelling of hydrogen reflection on tungsten fuzzy surface in an erosive hydrogen plasma

Modelling of the reflection of energetic hydrogen atoms from tungsten fuzz under hydrogen plasma exposure has been performed using the three-dimensional kinetic Monte Carlo program SURO-FUZZ. The simulation results show that the hydrogen reflection coefficient on a porous tungsten fuzzy surface is 50% lower in comparison with a smooth tungsten surface, which shows good agreement with the measurements. The time evolution of the tungsten fuzzy structure has been investigated under energetic hydrogen bombardment. A sustained removal of the porous tungsten fuzzy structure is obtained, which results in a reduced height of tungsten fuzz with exposure time and finally a smoothing of the tungsten fuzz. The erosion-induced degradation of the tungsten fuzzy structure leads to a high hydrogen reflection coefficient with exposure time. The simulated temporal evolution of the hydrogen reflection coefficient is in reasonable agreement with the experimental data. The simulation results show that the reflection coefficient of hydrogen atoms on fuzzy surfaces is decreased with increasing porosity. Parametric studies with varying porous structures have been performed to gain insights into hydrogen reflection characteristics on tungsten fuzzy surfaces. (paper)