The tritium imaging plate technique was applied to visualize penetration profiles of hydrogen (tritium) loaded in pure tungsten by a dc glow discharge at a temperature ranging from 473 to 673K. The penetration profile consists of two components, i.e. a highly localized one in the near-surface region (sub-mm in depth), and another, deep penetrating one (several mm in depth). An apparent hydrogen diffusion coefficient was determined from the latter to be given by:

D = 3 x 10-7exp[-0.39(eV)/kT]

which agrees well with the extrapolation of Frauenfelder's data obtained at elevated temperatures. The near-surface localized one was attributed to hydrogen trapping with a trapping energy of 0.84eV.

Visualization of Hydrogen Depth Profile by Means of Tritium Imaging Plate Technique - Determination of Hydrogen Diffusion Coefficient in Pure Tungsten. T.Otsuka, T.Hoshihira, T.Tanabe: Physica Scripta, 2009, T138, 014052