Reflection and Adsorption of Hydrogen Atoms and Molecules on Graphite and Tungsten

Abstract

The reflection coefficients of hydrogen/deuterium atoms and molecules on graphite and tungsten are experimentally determined by using a mixed thermal beam of atoms and molecules with temperatures above 2000 K. The velocity distributions of released atoms and molecules measured by the time-of-flight are used to distinguish the elastically reflected particles from desorbed particles. The released deuterium atoms and the elastically reflected molecules show the energy distribution of the incident beams. Most of the adsorbed deuterium is released as molecules with a Maxwell-Boltzmann velocity distribution of the target temperature. The reflection coefficients for deuterium atoms and molecules (above 2000 K) on graphite and tungsten ranges from 0.7 to 0.9. The reflection coefficient for cold deuterium molecules on hot tungsten is zero.