Deuterium retention of DIII-D DiMES sample

The deuterium retention property of B4C converted graphite and isotropic gr aphite exposed to DIII-D deuterium plasma was examined by using a technique of thermal desorption spectroscopy. Major outgassing species were HD, D-2 and CD4 in both the graphite and the B4C. In the case of the graphite, the ratios of deuterium desorbed in the forms of HD, D-2 and CD4 to the total d esorption amount of deuterium were 40%, 27% and 33%, respectively. In the c ase of the B4C, which was covered by carbon due to redeposition, these rati os were similar to those of the graphite. In a thermal desorption spectrum of deuterium, three desorption peaks appeared in both the graphite and the B4C covered by the redeposition layer. At low temperature region, the desor ption rate of deuterium for the B4C covered by the redeposition layer was l arger than that of the graphite. From two dimensional distribution of deute rium retention, it was seen that the retained amount at the electron drift side was quite large. The amount at the ion drift side and the edge of inwa rd major radius was also observed to be large. The average retained amount of the graphite was almost the same as that of the B4C covered by the redep osition layer. (C) 1999 Elsevier Science B.V. All rights reserved.