First operational experience with the cryogenic system of a large solid deuterium moderator for a new ultracold neutron source

The key component of the new ultracold neutron (UCN) source built at PSI, Switzerland is a cold moderator consisting of a 30 liter large crystal of solid ortho-deuterium operating at 5K. In a specially designed coldbox all necessary steps for the condensation of 30Nm3 of high purity D2, the para-ortho conversion and the transfer to the moderator vessel are performed. The latter is an AlMg3 container cooled by supercritical helium circulating in its double-walled structure. An overview of the cryogenic system of the UCN source is given together with some issues of its first year operational performance. (author)