Speaker
Description
The TRIUMF UltraCold Advanced Neutron collaboration recently demonstrated world-leading UCN densities delivered to an external experimental volume using a spallation-driven source. This marks a major milestone toward reaching a statistical sensitivity of 10⁻²⁷ e·cm in the future TUCAN EDM experiment.
Realizing this goal requires transporting the ultracold neutrons (UCNs) from the source to the experiment via UCN guides with minimal UCN losses and UCN depolarization. Diamond-like Carbon (DLC) is an attractive UCN coating material due to its high Fermi potential (~250 neV) and low neutron absorption and depolarization properties. To this end, a dedicated DLC UCN Guide Coating Facility has been built at the University of Winnipeg, where DLC coatings are deposited via UV pulsed laser deposition onto the inner surfaces of aluminum guide tubes. We report our optimized deposition recipe for the TUCAN guides, using a chromium underlayer for adhesion, followed by a carbon plasma deposition in which a voltage bias blocks the lower-energy plasma fraction. Profilometry confirms film thicknesses in the range of 150–170 nm. The coating adhered well under testing.
We will present the current coating status for TUCAN and report on planned UCN transmission measurements using a 1 m DLC-coated aluminum guide tube at J-PARC in fall 2026.