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Paul Scherrer Institut

E-Mail: geza.zsigmond@psi.ch

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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 now routinely operated by the NUM department.
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 feeds an experiment for an improved measurement of the electric dipole moment of the neutron (nEDM). A sensitivity of better than 10-27e cm is pursued, providing one of the most sensitive tests of the Standard Model of particle physics (see LTP).


      Ultracold Neutrons - Physics and Production, Nuclear Physics News, 2010
The PSI ultra-cold neutron source, Nucl. Instr. and Meth. A, 2009
Cryogenic system of the Swiss UCN Source, Cryogenics 2008

Characterization of the PSI source of UCN - poster --- Spallation target performance - poster

Components of the PSI UCN Source


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