Temperature programmed desorption of 1 keV deuterium implanted into clean beryllium

Beryllium is planned as a plasma-facing material for ITER covering most of the inner wall of the plasma vessel. It is thus subjected to intense fluxes of escaping hydrogen ions from the plasma, which are implanted and retained in the plasma-facing material. As beryllium reacts very quickly with oxygen and especially with water, forming a surface oxide layer even under good vacuum conditions, previous studies of the interaction of deuterium and beryllium had to deal with oxygen contamination as a factor of uncertainty. To rule out the influence of a BeO-covered surface, the retention and release of 1 keV deuterium ions implanted in clean beryllium at room temperature are investigated by temperature programmed desorption (TPD). The surface composition is measured by x-ray photoelectron spectroscopy (XPS). The outline of a retention mechanism is developed by discussing the thermal release behaviour as a function of increasing deuterium fluence.