Neutrons are produced in a short pulse of the full 2.2 mA, 590 MeV PSI proton beam on a spallation target. The fast neutrons are moderated, cooled, and finally down-scattered into UCN in solid ortho-deuterium. UCN are extracted from the solid deuterium and guided into a diamond-like carbon (DLC) coated large storage volume from which they can be extracted into experiments. After the proton beam pulse, the production and storage volumes are separated by a shutter, allowing for UCN storage times of the order of magnitude comparable to the lifetime of the free neutron.
See more: Ultracold neutron production at the second spallation target of the Paul Scherrer Institute (web).