Deuterium ion-driven permeation and bulk retention in tungsten

Experiments on deuterium ion-driven permeation through tungsten foils with thicknesses of 50 and 360 μm in the temperature range 820–920 K are described and discussed. The lag time for permeation was four orders of magnitude higher than estimated by extrapolation of Frauenfelder’s diffusion values in undamaged material. The experiments can be described by assuming trapping sites with a detrapping energy of 2.05 ± 0.15 eV in tungsten bulk. We assume that trapping is due chemisorption on the surface of voids in the bulk of tungsten, which, according to literature, have a similar detrapping energy. Two kinds of voids (pores and cracks) were observed by scanning electron microscopy of sample cross-sections prepared by a focused ion beam. The recombination coefficients on the inlet side were also deduced from the permeation experiments and compared with theoretical and experimental data from literature.