Radiation-induced desorption of hydrogen and deuterium from candidate plasma-facing materials

Samples of high purity Be, C, W, BeO and Al2O3, either implanted with deuterium or loaded with deuterium by heating in a D2 atmosphere, were studied using ion-beam analysis. Whether the samples were deuterium-loaded or as-received, there were large concentrations of surface or near-surface hydrogen, ˜ 1020 at/m2, and concentrations of > 100 appm at depths > 200 nm. The bulk concentration observed was much higher than expected, particularly in Be and W.Sequential analyses showed that hydrogen and deuterium were desorbed by the analysis ions, with release cross-sections from 10−22 to 10−18 m2. There were usually two desorption cross-sections, one dominant at fluences ≤ 1019 ions/m2, and another, one or two orders of magnitude smaller, dominant at greater fluences.The desorption cross-sections can be interpreted simply as detrapping cross-sections. Another approach is to model the process and fit an effective radiation-enhanced difflisivity to the data. The effective diffusivities of deuterium in BeO and WESGO-995 alumina during ion-beam analysis were found to be ˜ 10−18 m2/s at 300 K.