Dynamical calculation of low energy hydrogen reemission off hydrogen covered surfaces

Abstract

The reemission of low energy ( < 100 eV) hydrogen is a critical issue in plasma/first wall recycling. Previous molecular dynamics calculations, using the Embedded Atom Method (EAM), showed a decreasing reflection coefficient at energies below 10 eV for clean nickel surfaces with no surface defects. These calculations have been extended to investigate the influence of chemisorbed hydrogen atoms on the reemission coefficient for typical fusion operating conditions. A hybrid EAM method has been developed to include molecular hydrogen formation. The results of these calculations indicate that, in addition to atomic reflection and atomic penetration into the bulk which occur on a clean surface, hydrogen atom induced atomic and molecular desorption can compete, thereby affecting the reemission coefficient. The results are dependent on the incident hydrogen energy as well as surface coverage.