TRIUMF Achieves Initial Ultracold Neutron Production from New Superfluid Helium Source
Researchers at TRIUMF have successfully produced ultracold neutrons using a new spallation-driven superfluid helium-4 source, detecting 9.3 million neutrons in initial tests. The source is designed to enable precise measurements of the neutron electric dipole moment, a fundamental physics parameter. The results suggest the source will meet its production goals once the liquid deuterium moderator system is completed, potentially achieving sensitivity improvements for neutron EDM measurements.
TRIUMF's new ultracold neutron (UCN) source, based on superfluid helium-4 (He-II) technology, has produced its first results, detecting (9.3 ± 0.8) × 10⁵ ultracold neutrons at a proton beam current of 37 microamperes during a 60-second irradiation period. The production rates align with theoretical predictions from detailed neutron transport and cryogenic simulations. Notably, the source appears less limited by heat conduction through the superfluid helium than originally anticipated. Once the liquid deuterium cold moderator system is fully operational, the collaboration expects to achieve production of 5.7 × 10⁷ UCNs, enabling delivery of 1.4 × 10⁶ UCNs to each of two neutron EDM measurement cells. This capability would allow measurement of the neutron electric dipole moment with a statistical uncertainty of 1 × 10⁻²⁷ e·cm over 280 days of operation, advancing fundamental tests of CP symmetry violation in particle physics.
What's missing
The study does not discuss potential systematic uncertainties in the EDM measurement beyond statistical uncertainty, nor does it address how this measurement compares to existing constraints on the neutron EDM from other experiments or theoretical predictions from beyond-Standard-Model physics.
What different sources said
- arXiv physicsCenter
Initial results of the TRIUMF ultracold advanced neutron source
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