American Physical Society (APS) Acta Medica Okayama 2470-0010 113 5 2026 Analytical study of birefringent cavities for axionlike dark matter search 055009 EN Tadashi Kuramoto Research Institute for Interdisciplinary Science, Okayama University Yasutaka Imai Research Institute for Interdisciplinary Science, Okayama University Takahiko Masuda Research Institute for Interdisciplinary Science, Okayama University Yutaka Shikano Institute of Systems and Information Engineering, University of Tsukuba Sayuri Takatori Research Institute for Interdisciplinary Science, Okayama University Satoshi Uetake Research Institute for Interdisciplinary Science, Okayama University Light polarization plays a crucial role in optical-cavity experiments; however, mirror birefringence presents a significant challenge that must be addressed carefully. In this study, a rigorous, nonperturbative framework is developed to quantify birefringence effects by incorporating variations in reflectance and polarization misalignment. We analyze the impact of this framework on the sensitivity of axionlike particle (ALP) dark matter searches. The results show that both birefringence and misalignment contribute to sensitivity degradation in the low-mass regime; however, the adverse effects of misalignment can be mitigated by selecting a postselection angle greater than the misalignment angle. Furthermore, birefringence produces an additional resonance peak in the high-mass region, which remains largely unaffected by misalignment and postselection variations. This rigorous framework underscores the importance of considering birefringence in high-precision optical-cavity experiments for ALP detection. No potential conflict of interest relevant to this article was reported.

American Physical Society (APS) Acta Medica Okayama 3070-2240 1 2026 Cryogenic buffer gas beam source with in situ ablation target replacement 000016 EN Zhen Han Department of Physics, University of Chicago Zack Lasner Department of Physics, Harvard University Collin Diver Center for Fundamental Physics, Northwestern University Peiran Hu Department of Physics, University of Chicago Takahiko Masuda Research Institute for Interdisciplinary Science, Okayama University Xing Wu Facility for Rare Isotope Beams, Michigan State University Ayami Hiramoto Research Institute for Interdisciplinary Science, Okayama University Maya Watts Center for Fundamental Physics, Northwestern University Satoshi Uetake Research Institute for Interdisciplinary Science, Okayama University Koji Yoshimura Research Institute for Interdisciplinary Science, Okayama University Xing Fan Department of Physics, Harvard University Gerald Gabrielse Center for Fundamental Physics, Northwestern University John M. Doyle Department of Physics, Harvard University David DeMille Department of Physics, University of Chicago The design and performance of a cryogenic buffer gas beam source with a load-lock system is presented. The third generation of advanced cold molecule electric dipole moment search (ACME III) uses this source to produce a beam of cold, slow thorium monoxide (ThO) molecules. A feature of the apparatus is the capability of replacing the ablation targets without interrupting the vacuum or cryogenic conditions, thus increasing the average signal in the eEDM search. The beam source produces 1.3×1011 ground-state ThO molecules per pulse on average, with rotational temperature of 4.8K, molecular beam solid angle of 0.31sr, and forward velocity of 200ms−1, parameters that are consistent with the performance of a traditional source (without a load lock) requiring time-consuming thermal cycles for target replacement. Long-term yield improvement of ∼40% is achieved when the load-lock system is employed to replace targets every two weeks. No potential conflict of interest relevant to this article was reported.

Nature Portfolio Acta Medica Okayama 2041-1723 15 1 2024 Controlling 229Th isomeric state population in a VUV transparent crystal 5536 EN Takahiro Hiraki Research Institute for Interdisciplinary Science, Okayama University Koichi Okai Research Institute for Interdisciplinary Science, Okayama University Michael Bartokos Institute for Atomic and Subatomic Physics, TU Wien Kjeld Beeks Institute for Atomic and Subatomic Physics, TU Wien Hiroyuki Fujimoto National Institute of Advanced Industrial Science and Technology (AIST) Yuta Fukunaga Research Institute for Interdisciplinary Science, Okayama University Hiromitsu Haba RIKEN Yoshitaka Kasamatsu Graduate School of Science, Osaka University Shinji Kitao Institute for Integrated Radiation and Nuclear Science, Kyoto University Adrian Leitner Institute for Atomic and Subatomic Physics, TU Wien Takahiko Masuda Research Institute for Interdisciplinary Science, Okayama University Ming Guan Research Institute for Interdisciplinary Science, Okayama University Nobumoto Nagasawa Japan Synchrotron Radiation Research Institute Ryoichiro Ogake Research Institute for Interdisciplinary Science, Okayama University Martin Pimon Institute for Atomic and Subatomic Physics, TU Wien Martin Pressler Institute for Atomic and Subatomic Physics, TU Wien Noboru Sasao Research Institute for Interdisciplinary Science, Okayama University Fabian Schaden Institute for Atomic and Subatomic Physics, TU Wien Thorsten Schumm Institute for Atomic and Subatomic Physics, TU Wien Makoto Seto Institute for Integrated Radiation and Nuclear Science, Kyoto University Yudai Shigekawa RIKEN Kotaro Shimizu Research Institute for Interdisciplinary Science, Okayama University Tomas Sikorsky Institute for Atomic and Subatomic Physics, TU Wien Kenji Tamasaku RIKEN SPring-8 Center Sayuri Takatori Research Institute for Interdisciplinary Science, Okayama University Tsukasa Watanabe National Institute of Advanced Industrial Science and Technology (AIST) Atsushi Yamaguchi RIKEN Yoshitaka Yoda Japan Synchrotron Radiation Research Institute Akihiro Yoshimi Research Institute for Interdisciplinary Science, Okayama University Koji Yoshimura Research Institute for Interdisciplinary Science, Okayama University The radioisotope thorium-229 (Th-229) is renowned for its extraordinarily low-energy, long-lived nuclear first-excited state. This isomeric state can be excited by vacuum ultraviolet (VUV) lasers and Th-229 has been proposed as a reference transition for ultra-precise nuclear clocks. To assess the feasibility and performance of the nuclear clock concept, time-controlled excitation and depopulation of the Th-229 isomer are imperative. Here we report the population of the Th-229 isomeric state through resonant X-ray pumping and detection of the radiative decay in a VUV transparent Th-229-doped CaF2 crystal. The decay half-life is measured to 447(25) s, with a transition wavelength of 148.18(42) nm and a radiative decay fraction consistent with unity. Furthermore, we report a new "X-ray quenching" effect which allows to de-populate the isomer on demand and effectively reduce the half-life. Such controlled quenching can be used to significantly speed up the interrogation cycle in future nuclear clock schemes. No potential conflict of interest relevant to this article was reported.

Optica Publishing Group Acta Medica Okayama 1094-4087 31 2 2023 High-sensitivity low-noise photodetector using a large-area silicon photomultiplier 1943 1957 EN Takahiko Masuda Research Institute for Interdisciplinary Science, Okayama University Ayami Hiramoto Research Institute for Interdisciplinary Science, Okayama University Daniel G. Ang Department of Physics, Harvard University Cole Meisenhelder Department of Physics, Harvard University Cristian D. Panda Department of Physics, University of California Noboru Sasao Research Institute for Interdisciplinary Science, Okayama University Satoshi Uetake Research Institute for Interdisciplinary Science, Okayama University Xing Wu 2Department of Physics, Harvard University David P. DeMille James Franck Institute and Department of Physics, University of Chicago John M. Doyle Research Institute for Interdisciplinary Science, Okayama University Gerald Gabrielse Center for Fundamental Physics, Department of Physics and Astronomy, Northwestern University Koji Yoshimura Research Institute for Interdisciplinary Science, Okayama University The application of silicon photomultiplier (SiPM) technology for weak-light detection at a single photon level has expanded thanks to its better photon detection efficiency in comparison to a conventional photomultiplier tube (PMT). SiPMs with large detection area have recently become commercially available, enabling applications where the photon flux is low both temporarily and spatially. On the other hand, several drawbacks exist in the usage of SiPMs such as a higher dark count rate, many readout channels, slow response time, and optical crosstalk; therefore, users need to carefully consider the trade-offs. This work presents a SiPM-embedded compact large-area photon detection module. Various techniques are adopted to overcome the disadvantages of SiPMs so that it can be generally utilized as an upgrade from a PMT. A simple cooling component and recently developed optical crosstalk suppression method are adopted to reduce the noise which is more serious for larger-area SiPMs. A dedicated readout circuit increases the response frequency and reduces the number of readout channels. We favorably compare this design with a conventional PMT and obtain both higher photon detection efficiency and larger-area acceptance. No potential conflict of interest relevant to this article was reported.

International Union of Crystallography Acta Medica Okayama 0909-0495 28 1 2021 Absolute X-ray energy measurement using a high-accuracy angle encoder 111 119 EN Takahiko Masuda Research Institute for Interdisciplinary Science, Okayama University Tsukasa Watanabe National Institute of Advanced Industrial Science and Technology Kjeld Beeks Institute for Atomic and Subatomic Physics – Atominstitut Hiroyuki Fujimoto National Institute of Advanced Industrial Science and Technology Takahiro Hiraki Research Institute for Interdisciplinary Science, Okayama University Hiroyuki Kaino Research Institute for Interdisciplinary Science, Okayama University Shinji Kitao National Institute of Advanced Industrial Science and Technology Yuki Miyamoto Research Institute for Interdisciplinary Science, Okayama University Koichi Okai Research Institute for Interdisciplinary Science, Okayama University Noboru Sasao Research Institute for Interdisciplinary Science, Okayama University Makoto Seto Institute for Integrated Radiation and Nuclear Science, Kyoto University Thorsten Schumm Institute for Atomic and Subatomic Physics – Atominstitut Yudai Shigekawa RIKEN Kenji Tamasaku RIKEN, SPring-8 Center Satoshi Uetake Research Institute for Interdisciplinary Science, Okayama University Atsushi Yamaguchi RIKEN Yoshitaka Yoda Japan Synchrotron Radiation Research Institute Akihiro Yoshimi Research Institute for Interdisciplinary Science, Okayama University Koji Yoshimura Research Institute for Interdisciplinary Science, Okayama University This paper presents an absolute X-ray photon energy measurement method that uses a Bond diffractometer. The proposed system enables the prompt and rapid in situ measurement of photon energies over a wide energy range. The diffractometer uses a reference silicon single-crystal plate and a highly accurate angle encoder called SelfA. The performance of the system is evaluated by repeatedly measuring the energy of the first excited state of the potassium-40 nuclide. The excitation energy is determined as 29829.39 (6) eV, and this is one order of magnitude more accurate than the previous measurement. The estimated uncertainty of the photon energy measurement was 0.7 p.p.m. as a standard deviation and the maximum observed deviation was 2 p.p.m. No potential conflict of interest relevant to this article was reported.

Elsevier Science Acta Medica Okayama 01689002 913 2019 Energy response of X-rays under high flux conditions using a thin APD for the energy range of 6–33 keV 72 77 EN T. Masuda Research Institute for Interdisciplinary Science, Okayama University T. Hiraki Research Institute for Interdisciplinary Science, Okayama University H. Kaino Research Institute for Interdisciplinary Science, Okayama University S. Kishimoto High Energy Accelerator Research Organization Y. Miyamoto Research Institute for Interdisciplinary Science, Okayama University K. Okai Research Institute for Interdisciplinary Science, Okayama University S. Okubo Research Institute for Interdisciplinary Science, Okayama University R. Ozaki Research Institute for Interdisciplinary Science, Okayama University N. Sasao Research Institute for Interdisciplinary Science, Okayama University K. Suzuki Research Institute for Interdisciplinary Science, Okayama University S. Uetake Research Institute for Interdisciplinary Science, Okayama University A. Yoshimi Research Institute for Interdisciplinary Science, Okayama University K. Yoshimura Research Institute for Interdisciplinary Science, Okayama University This paper reports on the demonstration of a high-rate energy measurement technique using a thin depletion layer silicon avalanche photodiode (Si-APD). A dedicated amplitude-to-time converter is developed to realize simultaneous energy and timing measurement in a high rate condition. The energy response of the system is systematically studied by using monochromatic X-ray beam with an incident energy ranging from 6 to 33 keV. The obtained energy spectra contain clear peaks and tail distributions. The peak fraction monotonously decreases as the incident photon energy increases. This phenomenon can be explained by considering the distribution of the energy deposit in silicon, which is investigated by using a Monte Carlo simulation. No potential conflict of interest relevant to this article was reported.