Isotope exchange experiments in tungsten with sequential deuterium and protium plasmas in PISCES

Abstract Hydrogen isotope exchange experiments in tungsten samples were conducted in the PISCES linear plasma device to examine this technique as a means of tritium removal. Tungsten samples were first exposed to deuterium plasma in typical divertor conditions to a fluence of 1026 ions/m2 while maintaining a sample temperature below 373 K and subsequently exposed to hydrogen plasma at varying fluences (1023–1026 ions/m2). Bulk retention was measured by thermal desorption spectroscopy (TDS), and the D(3He, p)4He reaction was used to obtain concentration profiles of deuterium. The effects of neutron damage were simulated by exposing some samples to 2.5 MeV Cu ions. Ion induced damage increases deuterium inventory in the near surface region and decreases diffusion into the bulk. Although displacement damage allows more deuterium to be retained near the surface where much of the isotope exchange takes place, the efficiency of isotope exchange in the bulk was reduced.