A new user facility providing ultracold neutrons for fundamental physics research, based on accelerator driven spallation neutron production and a superthermal converter, has been constructed at the
Paul Scherrer Institut
(PSI), the PSI UCN source. Assembly of the facility finished in December 2010 with the first production of ultracold neutrons.
The source is operated by the
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.
The UCN source will feed an experiment for an improved measurement of the electric dipole
moment of the neutron
(nEDM). A sensitivity of better than 10-27e cm is envisaged,
providing one of the most sensitive tests of the Standard Model of particle physics (see