Neutron EDM Experiment with an Advanced Ultracold Neutron Source at TRIUMF
T. Higuchi, B. Algohi, D. Anthony, L. Barrón-Palos, M. Bradley, A. Brossard, T. Bui, J. Chak, R. Chiba, C. Davis, R. de Vries, K. Drury, D. Fujimoto, R. Fujitani, M. Gericke, P. Giampa, R. Golub, T. Hepworth, G. Ichikawa, S. Imajo, A. Jaison, B. Jamieson, M. Katotoka, S. Kawasaki, M. Kitaguchi, W. Klassen, E. Korkmaz, E. Korobkina, M. Lavvaf, T. Lindner, N. Lo, S. Longo, K. Madison, Y. Makida, J. Malcolm, J. Mammei, R. Mammei, Z. Mao, C. Marshall, J. W. Martin, M. McCrea, E. Miller, M. Miller, K. Mishima, T. Mohammadi, T. Momose, T. Okamura, H. J. Ong, R. Patni, R. Picker, K. Qiao, W. D. Ramsay, W. Rathnakela, D. Salazar, J. Sato, W. Schreyer, T. Shima, H. M. Shimizu, S. Sidhu, S. Stargardter, P. Switzer, I. Tanihata, Tushar, S. Vanbergen, W. T. H. van Oers, Y. Watanabe, N. Yazdandoost, Q. Ye, A. Zahra, M. Zhao
TL;DR
The paper reports progress toward a high-intensity ultracold neutron source at TRIUMF designed to reach a neutron EDM sensitivity of $10^{-27}$ e cm, a two-order-of-magnitude improvement over current limits. It details the commissioning of the upgraded UCN source based on spallation-driven production and a super-thermal converter in He-II, plus a liquid deuterium moderator that is expected to boost yield; initial UCN production has begun following purification steps, with full performance contingent on LD2 integration. It also covers the development of the neutron EDM spectrometer, emphasizing magnetic shielding, Hg co-magnetometry, and Cs-magnetometer arrays to achieve sub-pT stability over measurement cycles, as well as prospects for Lorentz-symmetry tests using multiple spin species. The work outlines a clear path to commissioning in 2026 and data-taking starting in 2027, with LD2-enabled gains and system-level calibration guiding the program toward the targeted EDM sensitivity and potential new constraints on Lorentz-violating processes.
Abstract
The TRIUMF Ultracold Advanced Neutron (TUCAN) collaboration has been developing a high-intensity ultracold neutron (UCN) source aimed at searching for the neutron electric dipole moment (EDM) with a sensitivity goal of $10^{-27}\ e{\rm cm}$. This article reports on recent progress in commissioning of the UCN source and in the development of the neutron EDM spectrometer. In its final configuration, the accelerator-driven super-thermal UCN source will enable a neutron EDM experiment with two orders of magnitude improved statistics compared to the current best experiment. Substantial progress in 2024 allowed the collaboration to operate the complete source system, with the exception of the liquid deuterium cold moderator, resulting in the first production of UCNs. The status of the EDM spectrometer is also presented, with emphasis on UCN handling components and magnetic subsystems relevant to field control, shielding, and magnetometry.