The influence of D2 pressure on D retention and release from Be co-deposits

Abstract

Beryllium co-deposit thermal desorption studies are reported that focus on the effect of D2pressure during layer formation, as pressure has been linked in prior work to the formation of a high-retention-capacity sharp-release-feature. A pressure range from 0.3 to 13.3 Pa is explored. Additional insight into what drives the formation of T0is established through co-deposit formation parameter variations including deposition temperature spanning 373 K to 608 K, and ion impact energy in the range 10–100 eV. It is found that the formation of the sharp release feature exhibits a multi-parameter dependence, but is predominately favoured by low deposition temperature, higher D2pressure, and to a small degree, increased ion impact energy, during deposition. TESSIM simulations of the D2thermal release at the ITER bake temperatures of Tb1(513 K) and Tb2(623 K), show that the best efficacy for D removal (defined as the ratio of post to pre bake inventory) is found when the sharp release feature is present. However, when this feature is present, the total retained D inventory tends to be significantly increased.

Keywords

• Beryllium
• Co-deposits
• Retention
• Thermal desorption
• Pisces