Ion-induced release of deuterium trapped in stainless steel

The release of deuterium atoms which have been trapped in stainless steel, by subsequent bombardment with protrons, has been investigated over the range of incident ion energies from 5 to 30 keV. It is shown that at 77 K ion induced release occurs with "cross sections" for release in the range 10 ^-18 to 10 ^-17 cm ². This mechanism appears to be important in determining the saturation level of surfaces under ion bombardment in cases where diffusion is not important. At 300 K the release cross section is ~5 × 10 ^-17cm² and it is suggested that this is due to a combination of ion induced release and simple diffusion. Some different models, including trap filling and radiation enhanced fissuion, are proposed as the physical mechanisms responsible for ion induced release. Each of the models has some success in explaining the experimental results but there is still insufficient data to decide between them.