We are pleased to announce that Higuchi has completed the master’s program, and Fukushima, Ueyama, and Hattori have graduated from the undergraduate program in our laboratory. Higuchi will be joining a company, while Hattori will go on to graduate studies at another university. Fukushima and Ueyama will continue on to graduate school at Okayama University and remain in our laboratory to pursue their research. We sincerely commend all of them for their hard work and achievements, and we look forward to their continued success in the future. Congratulations to everyone.
From left: Ueyama, Higuchi, Fukushima, and Hattori
From April 1 to 2, 2026, Mr. Ikuma (D2), Mr. Kakinoki (M2), Mr. Fukushima (M1), and Ms. Ueyama (M1) gave presentations at the Post-C2C Meeting held at Tokyo Midtown Yaesu.
This meeting was organized to strengthen collaboration within the CMB research community in Japan, building on the achievements of the “CMB Core-to-Core Program” conducted from 2020 to 2024. The event also provided valuable opportunities to interact with researchers from various institutions, making it a highly meaningful experience.
In the dark matter search experiment “DOSUE-RR,” a collaborative research team, including Associate Professor Adachi from our laboratory, has carried out a dark photon search using the millimeter-wave receiver developed in the FINER project (link) at the National Astronomical Observatory of Japan (NAOJ).
The FINER (Far-Infrared Nebular Emission Receiver) project is an effort to develop a high-sensitivity millimeter-wave receiver based on superconducting SIS mixers. The receiver is designed to be installed on the Large Millimeter Telescope (LMT, link) in Mexico for spectroscopic observations of distant galaxies. In this study, the receiver (210–350 GHz) enables a search for dark photons in the mass range of 0.9–1.4 meV.
In this experiment, calibration systems and a readout system ( dSpec ), developed in collaboration with Okayama University, the University of Tsukuba, and Kyoto University, were integrated into the FINER receiver at NAOJ, owing to the collaboration with the FINER team from NAOJ, Nagoya University, and UEC. Observations for dark photon detection commenced on April 6, 2026.
If successful, this measurement is expected to achieve the world’s highest sensitivity in this mass range for dark photon searches. We look forward to future results.
Measurement setup after integration of the DOSUE-RR readout system (dSpec) with the FINER receiver. Associate Professor Adachi (Okayama University) is second from the left in the back row on the right.
On March 26, 2026, Professor Ishino delivered a presentation titled “Development and Performance Evaluation of an Indium-Target Superconducting Detector” and Nagano (D3) gave a presentation titled “Study on the impact of scan strategy on beam systematics in CMB satellite observations”.
During the question-and-answer session, we received many valuable comments. In addition, by engaging with research in related fields, we were able to gain new insights and perspectives.
We will make use of the outcomes gained from this conference and continue to pursue our research activities with even greater dedication.
Mahdi Najafi, a PhD student at Sapienza University of Rome, will be visiting our lab under CMB-INFLATE from February 16 through the end of August. During his stay, he plans to work not only on his own research—studying the impact of de-lensing effect on estimation of the inflation model—but also systematics simulation for LiteBIRD. We look forward to working with him over the next six months!
Research led by Associate Professor Shunsuke Adachi and his team as part of the Simons Observatory (SO) international collaboration has been published in the prestigious astronomical journal, The Astrophysical Journal Supplement Series (ApJS).
This paper presents the initial results of the detector antenna angle calibration for the Small Aperture Telescope (SAT) located in the Atacama Desert, Chile. The study utilized a “Sparse Wire Grid” calibrator, a device that is being developed in our laboratory.
To capture the faint polarization signals of the Cosmic Microwave Background (CMB), it is essential to determine the detector angles with extreme precision. This successful demonstration of our calibration technology significantly enhances the accuracy of future observational data. This achievement marks a major step forward in the search for primordial gravitational waves, which hold the key to uncovering the mysteries of the universe’s birth.
Publication Information
Title: The Simons Observatory: Detector Polarization Angle Calibration using Sparse Wire Grid with Initial Data Sets of the Small Aperture Telescope
Authors: H. Nakata, S. Adachi, K. Yamada, M. Randall, et al.
Journal:The Astrophysical Journal Supplement Series
On March 6–7, 2026, Associate Professor Shunsuke Adachi from our laboratory gave an oral presentation at the 11th Workshop on Low-Radioactivity Techniques held at Kobe University. The presentation introduced the DOSUE-RR experiment, which aims to detect ultralight dark matter candidates such as dark photon and axion using a sensitive radio receiver system.
On December 23, our laboratory hosted a year-end party. In addition to members of the Okayama University Astrophysics Laboratory (our laboratory), we were joined by MPA Director Komatsu and by colleagues from Okayama University of Science (the Yamauchi and Nagao groups). Bringing together members who normally work at different sites sparked natural conversations and new momentum for collaborations. Thank you to everyone who attended—we’ll continue to balance research, education, and outreach in the year ahead.
During his stay in Okayama, Director Eiichiro Komatsu led a cosmology seminar. Starting from the Friedmann equations that describe the expansion of space, participants followed the derivation of the cosmic expansion rate and the age of the universe. The sessions benefited not only students working on CMB but also those in other areas.
On December 17, the second Physics Colloquium was held in Building 2 of the Faculty of Science, where our Associate Professor Adachi gave a lecture titled “What am I wandering to search for?” He reflected on his research from student days to the present. The colloquium drew many students and faculty across fields, and the Q&A was lively.
A standing reception afterward fostered cross-disciplinary conversations and meaningful exchange.
