A user facility providing ultracold neutrons for fundamental physics research, based on accelerator driven spallation neutron production and a superthermal converter, was built at the Paul Scherrer Institut and has been in operation since 2011 (UCN Source).
Detailed studies of all system components were conducted in order to understand the performance of the source with respect to UCN output. Neutron production and thermalization were checked to match detailed simulations (Becker et al. 2015). The transport of UCN from production to detection via the UCN source setup was studied in detail (Bison et al. 2020). The occurence of snow on top of the solid deutrium moderator during source operation was found to be limiting (Anghel et al. 2018), however, can be overcome with a ‘conditioning ‘ method conducted daily during operation.
We have defined a standard measurement (Bison et al. 2016) to determine the performance of a UCN source via characterization of the UCN density at several operating UCN sources world-wide (Bison et al. 2017).
Figure 1 shows the UCN delivery at a beamport as seen by a UCN detector after a proton beam pulse which can be repeated every 300 seconds (Kirch et al. 2020). A most recent preprint for SciPost Physics Proceedings you can find here B. Lauss and B. Blau 2021.