Experimental measurements and modeling of the deuterium release from tungsten co-deposited layers

The release of deuterium from sputter magnetron produced tungsten co-deposit layers is studied by thermal desorption mass spectrometry and modelled with the diffusion reaction codes TESSIM and FACE. Layers up to similar to 2 mu m thick, produced at substrate deposition temperatures up to 513 K are modeled. TESSIM simulations are found to require activity from at least nine traps in the range 1.0 - 2.5 eV in order to reproduce the experimentally observed desorption. FACE simulations, which utilize a quasi-continuous distribution of traps, suggest some discreteness in trapping energy above similar to 1.5 eV, but smoothness in the distribution below. Both codes indicate a quasi-exponential decrease in trap concentration with trap energy. When examined for predictive capability, the developed tungsten co-deposit models accurately reproduce experimental changes in the desorption heating rate from 0.3 to 3 Ks(-1), and give reasonable agreement with experimentally different layer thicknesses and deposition temperatures in the parameter ranges explored. Measured D/W ratios in the codeposits are also found to be in good agreement with literature based predictive scalings.