A New High-Intensity Source for Ultracold Neutrons

The TRIUMF UltraCold Advanced Neutron (TUCAN) collaboration has completed a new superthermal source for ultracold neutrons (UCNs) at TRIUMF. It uses neutrons from a spallation target driven by TRIUMF’s main cyclotron. Heavy water and liquid deuterium serve as neutron moderators, and inelastic scattering inside superfluid ${}^4$He at around $1.1$~K slows the neutrons down to become ultracold. During commissioning runs with the completed source, including the deuterium moderator, up to $1.34(1)\times {10}^7$ UCNs were detected in the experimental area after irradiating the target and accumulating UCNs in the source for $60$~s. Up to $6.75(3)\times {10}^5$ UCN/s were detected during continuous operation, more than at any other source in the world.