Abstract
The neutron electric dipole moment (EDM) is a sensitive probe for currently undiscovered sources of charge-parity symmetry violation. As part of the TRIUMF Ultracold Advanced Neutron (TUCAN) collaboration, we are developing spin analyzers for ultracold neutrons (UCNs) to be used for a next-generation experiment to measure the neutron EDM with unprecedented precision. Spin-state analysis of UCNs constitutes an essential part of the neutron EDM measurement sequence. Magnetized iron films used as spin filters of UCNs are crucial experimental components, whose performance directly influences the statistical sensitivity of the measurement. To test such iron film spin filters, we propose the use of polarized cold-neutron reflectometry, in addition to conventional UCN transmission experiments. The new method provides information on iron film samples complementary to the UCN tests and accelerates the development cycles. We developed a collaborative effort to produce iron film spin filters and test them with cold and ultracold neutrons available at JRR-3=MINE2 and J-PARC=MLF BL05. In this article, we review the methods of neutron EDM measurements, discuss the complementarity of this new approach to test UCN spin filters, provide an overview of our related activities, and present the first results of polarized cold-neutron reflectometry recently conducted at the MINE2 beamline.
| Original language | English |
|---|---|
| Article number | 091009 |
| Journal | Journal of the Physical Society of Japan |
| Volume | 93 |
| Issue number | 9 |
| DOIs | |
| State | Published - Sep 15 2024 |
Funding
We thank K. Ohno and the Research Fabrication Support Division of the Osaka University Core Facility Center for their engineering support of the UCN experiment, and C. Marshall and T. Lightbody (TRIUMF) for their valuable advice on apparatus design. We thank the assistance of D. Georgescu (the University of Edinburgh) in the UCN apparatus design, and I. Press (the University of Winnipeg) for experimental assembly, and J. Sato (Nagoya University) for an important remark on the neutron reflectivity model. We also thank H. Tsukahara (Osaka University & Tohoku University) and T. Hawai (CROSS) for valuable discussions at an early stage of this project. The neutron experiments at the Materials and Life Science Experimental Facility of J-PARC were performed under a user program (Proposal Nos. 2021B0272, 2022B0329) and S-type project of KEK (Proposal No. 2019S03). The neutron experiment at JRR-3 was carried out by the JRR-3 general user program managed by the Institute for Solid State Physics, the University of Tokyo (Proposal No. 22589). The iron film fabrication work has been carried out under the visiting researcher’s program of the Institute for Integrated Radiation and Nuclear Science, Kyoto University (Proposal Nos. R3137, R4099). This work is financially supported by JSPS KAKENHI (Grant Nos. 18H05230, 19K23442, 20KK0069, 20K14487, and 22H01236), JSPS Bilateral Program (Grant No. JSPSBP120239940), JST FOREST Program (Grant No. JPMJFR2237), the Natural Sciences and Engineering Research Council of Canada (NSERC) SAPPJ-2023-00029, the Canada Foundation for Innovation, the Canada Research Chairs Program, International Joint Research Promotion Program of Osaka University, RCNP COREnet, the Yamada Science Foundation and the Murata Science Foundation.