Neutron velocity distribution from a superthermal solid ²H₂ ultracold neutron source

We have determined for the first time the velocity distribution of neutrons from a solid H-2(2) ultracold neutron (UCN) source: The spectrum rises sharply above 4.5m/s and has a maximum around 7m/s after transport in an 8m long guide. The number of neutrons in the UCN velocity range (< 7m/s) may be increased by a factor of two by placing the experiment I m above the UCN source level.