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Ultracold Neutrons

LANSCE is home to one of the most intense sources of some of the coldest subatomic particles: ultracold neutrons.


  • Neutron Team Leader
  • Takeyasu Ito
  • Email
  • Neutron Team Leader
  • Mark Makela
  • Email

UCN Facility at LANSCEThe LANSCE Ultracold Neutron (UCN) source is a unique facility that produces high energy spallation neutrons and uses solid deuterium to cool the neutrons by one million billion-fold.

The resulting UCNs have some unique properties that allow them to be studied precisely: they move at speeds of only a few meters per second, and are completely confined by magnetic fields and material bottles for many hundreds of seconds at a time. These properties lead to very precise low energy particle physics experiments that search for small differences between measurement and prediction, and these precision measurements are a powerful tool for investigating new physical processes which can complement and rival experiments at high energy colliders such as CERN.

There are several new and on-going experiments at the UCN source that measure decay correlations and other properties of the neutron. This program of measurements probes the particle physics underlying neutron decay, and has important implications for high energy physics and cosmology.

In addition, because of the interaction between UCNs and material surfaces, the facility is used to study materials relevant to high precision experiments, and will provide a detailed understanding of neutron induced fission on actinides.