Speaker
Description
The ultracold neutron (UCN) source at PSI converts fast neutrons from a spallation target into UCN via thermalization in D$_{2}$O, subsequent moderation in solid ortho-deuterium (sD$_{2}$), and finally down-scattering on the sD$_{2}$ lattice. However, during normal operation a decline in UCN output is observed. A conditioning process allows to recover the original performance, and in many cases even increases the UCN output. This process consists of reducing the sD$_{2}$ vessel cooling power and heating its lid for a short period. Investigations to pinpoint the reasons for the decreasing UCN rate and the beneficial impact of the conditioning process, together with monitoring HD and para-deuterium concentrations to exclude UCN losses through these, will be presented.
