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. Tn 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 (approximate to 500 degreesC), 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. (C) 2000 Elsevier Science B.V. All rights reserved.