Atomic re-emission of hydrogen from pure and boronized graphites at temperatures above 1000 K

Abstract

D + ions were implanted in pure and boronized graphites at temperatures between 1000 and 1600 K. The re-emitted deuterium during implantation (D 2 and HD), observed by residual gas analysis, was observed to decrease with increasing sample temperature. The amount of trapped D, as measured by thermal desorption spectrometry, subsequent to the implantation process, was also found to decrease with increasing sample temperature, and thus could not account for the decrease in the deuterium re-emission signal. Experimental evidence, obtained at the University of Toronto, led to the proposed hypothesis that the observed decrease in the re-emitted deuterium was due to increasing atomic D re-emission with increasing target temperature and effective pumping of these atoms by the chamber walls. The hypothesis of atom re-emission was confirmed with the use of direct line-of-sight mass spectrometry at the KFA Forschungszentrum in Julich. At 1850 K, ≈95% of the re-emitted hydrogen is in the form of atoms.