Outgassing from and deuterium retention in beryllium and Be/C mixed-material plasma-facing components

Thermal desorption spectrometry (TDS) is used to examine the outgassing characteristics of as-received beryllium samples and the deuterium retention and desorption behavior of beryllium following plasma exposure. The samples consist of a hot-pressed powder metallurgy product and a plasma-sprayed product. The number of molecules outgassed from a plasma-sprayed sample is ten times that outgassed from a press-sintered sample and a higher desorption temperature is necessary to outgas a plasma-sprayed sample. The majority of the molecules outgassed from each sample type are in the form of hydrogen molecules and water vapor. In addition, the post-plasma-exposure desorption of deuterium from both products are compared. Following identical plasma exposures at close to room temperature, a factor of ten less deuterium is retained in plasma-sprayed samples, presumably due to the columnar structure of the resultant sprayed material that would have enhanced pathways to the sample surface. After higher surface temperature exposure (≈500°C), the retention in the plasma-sprayed material is a factor of three less than the retention in the pressed-powder material. Finally, the impact on deuterium retention of carbon-containing surface layers formed during the plasma exposure is evaluated.