Initial results of the TRIUMF ultracold advanced neutron source

TUCAN Collaboration; B. Algohi; D. Anthony; L. Barrón-Palos; M. Bossé; M. P. Bradley; A. Brossard; T. Bui; J. Chak; R. Chiba; C. Davis; R. de Vries; K. Drury; B. Franke; D. Fujimoto; R. Fujitani; M. Gericke; D. Georgescu; P. Giampa; C. Gibson; R. Golub; K. Hatanaka; T. Hepworth; T. Higuchi; G. Ichikawa; I. Ide; S. Imajo; A. Jaison; B. Jamieson; K. Jorgensen-Fullam; M. Katotoka; S. Kawasaki; M. Kitaguchi; W. Klassen; E. Korkmaz; E. Korobkina; F. Kuchler; C. Lamb; M. Lavvaf; T. Lightbody; T. Lindner; N. Lo; S. Longo; K. W. Madison; Y. Makida; J. Malcolm; J. Mammei; R. Mammei; Z. Mao; C. Marshall; J. W. Martin; R. Matsumiya; M. McCrea; E. Miller; M. Miller; K. Mishima; T. Mohammadi; T. Momose; M. Nalbandian; T. Okamura; S. Pankratz; R. Patni; R. Picker; V. Purcell; K. Qiao; W. D. Ramsay; W. Rathnakela; T. Reimer; D. Salazar; J. Sato; W. Schreyer; T. Shima; H. M. Shimizu; S. Siddiqui; S. Sidhu; S. Stargardter; R. Stutters; P. Switzer; I. Tanihata; Tushar; M. Uzair; S. Vanbergen; W. T. H. van Oers; N. Yazdandoost; Q. Ye; A. Zahra; M. Zhao

doi:10.1103/g41l-jmdx

Letter

Initial results of the TRIUMF ultracold advanced neutron source

B. Algohi¹, D. Anthony², L. Barrón-Palos³, M. Bossé², M. P. Bradley⁴, A. Brossard², T. Bui¹, J. Chak², R. Chiba⁵ et al. (TUCAN Collaboration)

R. Chiba⁵, C. Davis², R. de Vries⁶, K. Drury², B. Franke^2,7, D. Fujimoto², R. Fujitani^8,9, M. Gericke¹, D. Georgescu², P. Giampa², C. Gibson², R. Golub¹⁰, K. Hatanaka^11,*, T. Hepworth⁶, T. Higuchi^9,11, G. Ichikawa¹², I. Ide¹³, S. Imajo^11,†, A. Jaison¹, B. Jamieson⁶, K. Jorgensen-Fullam², M. Katotoka⁶, S. Kawasaki^12,14, M. Kitaguchi¹³, W. Klassen⁷, E. Korkmaz¹⁵, E. Korobkina¹⁰, F. Kuchler^2,‡, C. Lamb², M. Lavvaf¹, T. Lightbody², T. Lindner^2,6, N. Lo², S. Longo¹, K. W. Madison⁷, Y. Makida^12,14, J. Malcolm², J. Mammei¹, R. Mammei⁶, Z. Mao⁷, C. Marshall², J. W. Martin ⁶, R. Matsumiya^2,11, M. McCrea⁶, E. Miller⁷, M. Miller¹⁶, K. Mishima^11,12,13, T. Mohammadi¹, T. Momose^2,7, M. Nalbandian⁷, T. Okamura^12,14, S. Pankratz⁶, R. Patni², R. Picker^2,5, V. Purcell², K. Qiao^11,17, W. D. Ramsay², W. Rathnakela¹, T. Reimer⁶, D. Salazar⁵, J. Sato¹³, W. Schreyer^2,18, T. Shima¹¹, H. M. Shimizu¹³, S. Siddiqui², S. Sidhu², S. Stargardter¹, R. Stutters², P. Switzer⁶, I. Tanihata¹¹, Tushar¹, M. Uzair², S. Vanbergen^2,7, W. T. H. van Oers², N. Yazdandoost², Q. Ye⁷, A. Zahra¹, and M. Zhao² (TUCAN Collaboration)

¹Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba, Canada
²TRIUMF, Vancouver, British Columbia, Canada
³Instituto de Física, Universidad Nacional Autónoma de México, Mexico City, Mexico
⁴Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
⁵Department of Physics, Simon Fraser University, Burnaby, British Columbia, Canada
⁶Department of Physics, The University of Winnipeg, Winnipeg, Manitoba, Canada
⁷Department of Physics and Astronomy, and Department of Chemistry, The University of British Columbia, Vancouver, British Columbia, Canada
⁸Department of Nuclear Engineering, Kyoto University, Kyoto, Japan
⁹Institute for Integrated Radiation and Nuclear Science (KURNS), Kyoto University, Osaka, Japan
¹⁰Department of Physics and Astronomy, North Carolina State University, Raleigh, North Carolina, USA
¹¹Research Center for Nuclear Physics (RCNP), The University of Osaka, Osaka, Japan
¹²High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki, Japan
¹³Department of Physics, Nagoya University, Nagoya, Aichi, Japan
¹⁴The Graduate University for Advanced Studies (Sokendai), Tsukuba, Ibaraki, Japan
¹⁵Department of Physics, The University of Northern British Columbia, Prince George, British Columbia, Canada
¹⁶Department of Physics, McGill University, Montreal, Quebec, Canada
¹⁷Graduate School of Science, The University of Osaka, Osaka, Japan
¹⁸Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA

^*Deceased.
^†Present address: RIKEN Center for Advanced Photonics, Wako, Saitama, Japan.
^‡Present address: Technical University of Munich, Munich, Germany.

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Phys. Rev. C 114, L012501 – Published 13 July, 2026

DOI: https://doi.org/10.1103/g41l-jmdx

Abstract

We report the first results on ultracold neutron production from a new spallation-driven superfluid ${}^{4}{He}$ (He-II) source at TRIUMF, which is being prepared for a new, precise measurement of the neutron electric dipole moment (nEDM). A total of $(9.3 \pm 0.8) \times 10^{5}$ ultracold neutrons (UCNs) were observed at a proton beam current of $37 µ A$ , when the target was irradiated for a period of $60 s$ . The results are in fair agreement with expectations based on a detailed simulation of neutron transport and ultracold neutron-source cryogenics. There is some indication that the new source might not be as limited by the conduction of heat through the He-II as originally expected. The results indicate that the source is likely to make its ultimate production goals, once the liquid deuterium cold moderator system is completed, with the expectation that $5.7 \times 10^{7}$ UCNs would be detected in the same experiment with full liquid levels. This would, for example, correspond to detection of $1.4 \times 10^{6}$ UCNs each Ramsey cycle, and a statistical uncertainty of $1 \times 10^{- 27} e cm$ on the neutron EDM in 280 days of running.

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