UCNs like those produced at TRIUMF move slow enough (~5 m/s, compared to ~500 m/s for air molecules) and with such low energy that they actually can be trapped and contained inside special bottles. This makes UCNs ideal for a variety of important fundamental physics measurements, including determining the neutron electric dipole moment (nEDM). The nEDM is currently predicted to be vanishingly small, but if it is measured to be larger than expected, it could aid in solving the puzzle of why there is much more matter than antimatter in the universe!
The Japanese-Canadian TUCAN (TRIUMF Ultra Cold Advanced Neutron source) collaboration formed in 2010 with the goal of creating the world's most intense UCN source to measure the nEDM with unprecedented precision. Between 2014 and 2016, a new proton beamline at TRIUMF was constructed to supply a spallation target for neutron production. During the most recent TRIUMF's annual cyclotron shutdown period, the UCN source prototype from Japan was installed above the target. The secret behind creating UCNs lies in superfluid helium, which is cooled down to a temperature of less than 1 degree above absolute zero (<1K).
The TUCAN collaboration celebrated its first major milestone in November 2016 when it achieved its first beam-on-target; just a year later, the newly-installed UCN cryostat reached its design temperature of approximately 0.8K. Now, the first Canadian UCNs have been created from hot spallation neutrons produced using a 1 microamp, 480 MeV proton beam. The approximate 50000 UCNs counted per “shot” (pulse of protons on target) were well within expectation, enabling the planned experimental program to be carried out. This will include characterizing the source to aid in the development of the next-generation source, with which TUCAN hopes to achieve orders of magnitude more UCNs. The upgraded source will be deployed for the flagship nEDM experiment, which TUCAN hopes to run by 2020.
This project is led by the University of Winnipeg under principal investigator Prof. Jeff Martin and is supported by TRIUMF, CFI, BCKDF, MRF, and NSERC in Canada, and by KEK and RCNP in Japan.
Congratulations to the TUCAN and UCN facility teams!
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