Growing solid deuterium for UCN production

Abstract

We have experimentally studied growing a large (about 1 liter) solid ortho-deuterium crystal in a real UCN source cryostat and recorded the growing process optically using a camera. The best quality was observed when growing the crystal directly from a vapor phase. The crystal was grown at different mass flows of deuterium and annealed at different temperatures. Optimum conditions were found for both, obtaining an optically transparent crystal and cooling it down with minimal damage. We found that the quality, final shape and changes during annealing of the crystal are very much dependent on the temperature profile of the cryostat walls.

HighNESS conceptual design report: Volume I

“…Irradiation of methane leads to the formation of radiolysis-induced radicals -(CH 2 ) n -, followed by polymerization into carbon-based deposits and release of H 2 , both of which have been observed to accumulate in the moderator vessel [18,90]. On the other hand, solid ortho-deuterium, well-established as an in-pile converter medium for UCN sources [12,29,111,115,134,182], has no physical impediment to the VCN production in high radiation fields, despite the many challenges related to keeping such a source at low temperature.…”

“…Growing a perfectly transparent SD 2 crystal is clearly known as a challenge [9,13,29,111,134,165]. The goal of perfect optical transparency is hindered by the crystal defects due to thermal stress.…”