Effects of impurities on deuterium retention in single crystal tungsten.
Published: 2005
Language: eng
Number of pages: 79
Description: The role of impurities in the retention of deuterium in single crystal tungsten implanted at room temperature has been investigated. To avoid the effects of air exposure, the D+ implantation and the subsequent D retention measurement using thermal desorption spectroscopy were performed in the same vacuum system without breaking vacuum. For fluences of 1 x 1023 D/m2 prominent desorption peaks were observed during TDS, one at &sim;400 K and one at &sim;600 K. The use of liquid nitrogen cooling of the ion beam aperture led to a reduction of the background gas impurities (O and C containing molecules) in the vacuum chamber, which consequently almost completely eliminated the post-irradiation TDS peak at &sim;400 K. Reduction of these gas impurities by &sim;50% has led to a reduction of &sim;20% in the total deuterium retention. Furthermore, weakly bound deuterium in the W specimens was released when the vacuum system was  mildly baked to &sim;360 K before TDS, resulting in an approximately 50% reduction in the total amount of retained D. It was also found that post-implantation time delay before performing TDS leads to a significant loss of the implanted deuterium; &sim;25% of the implanted deuterium escapes from the W specimens during the first 24 hours and &sim;55% after about eight weeks.
Notes: Source: Masters Abstracts International, Volume: 44-01, page: 0423.

Thesis (M.A.Sc.)--University of Toronto, 2005.

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