Crystal orientation effects on implantation of low-energy hydrogen, helium and hydrogen/helium mixtures in plasma-facing tungsten surfaces

Abstract

The development of plasma-facing materials (PFM) is one of the major challenges in realizing fusion reactors. Materials deployed in PFMs must be capable of withstanding the high-flux of low-energy hydrogen and helium ions omitted from the plasma while not hindering the plasma. Tungsten is considered a promising candidate material due to desirable material properties including its high melting temperature, good thermal conductivity and relatively low physical and chemical sputtering yields. This thesis uses molecular dynamic simulations to investigate helium and hydrogen bombardment of tungsten and the underlying physical effects (e.g. sputtering, erosion, blistering).

Non-cumulative and cumulative bombardment simulations of helium, hydrogen, and hydrogen/helium bombardment of tungsten were modeled using the molecular dynamics code LAMMPS. Two orientations of monocrystalline bcc tungsten surfaces were considered, (001) and (111). Simulations were performed for temperatures ranging from 600K up to 1500K and helium / hydrogen incident energies of 20eV to 100eV . The results of these simulations showed the effect of temperature and incident particle energy on retention rates and implantation/deposition profiles in tungsten.