J-PARC News May 2025 (Issue #241)
■Successful Extraction of Muon Beam to H2 Area of H-Line
At the Materials and Life Science Experimental Facility (MLF), researchers successfully extracted the first muon beam to the newly extended "H2 area", which branches off from the high-intensity muon beamline known as the H-Line. The extension of the H-Line underwent a facility inspection related to modification approval and was officially cleared on May 13, 2025.
In the H2 area, the goal is to generate a low-emittance muon beam by decelerating and re-accelerating the high-intensity muon beam supplied by the H-Line. To achieve this, the construction of a muon acceleration system is underway. In the future, the beamline will be further extended to enable precise measurement of the anomalous magnetic moment of muons—potentially leading to the discovery of unexplained physical phenomena beyond the standard model of particle physics. Additionally, efforts will be made to develop a transmission-type muon microscope, which could visualize the distribution of electromagnetic fields within materials, paving the way for industrial applications.
■Recent Awards
(1) Recipient of the 2024 Society of Muon and Meson Science of Japan Technology Award
Dr. KAWAMURA Naritoshi and Dr. YAMAZAKI Takayuki from the Muon Section have received the 2024 Technology Award from the Society of Muon and Meson Science of Japan for their outstanding achievements in the design and development of the H-Line.
The H-Line at the Materials and Life Science Experimental Facility (MLF), J-PARC, was designed and developed as a high-intensity, versatile muon beamline. It enables precision measurements, such as the hyperfine structure of muonium and the anomalous magnetic moment of muon, by providing 108 muons per second. This innovative design has been adopted by new muon facilities such as PSI in Switzerland and CSNS in China, and an advanced version is also being considered in future plans for MLF.
■2024 Society Award of the Society of Muon and Meson Science of Japan
Dr. HIGEMOTO Wataru of the Muon Section has been honored with the 2024 Society Award by the Society for Muon and Meson Science of Japan, in recognition of his outstanding contributions to the advancement of meson science.
Dr. HIGEMOTO has long been engaged in material research using the muon spin rotation and relaxation (µSR) technique, particularly focusing on heavy Fermion superconductors. He has also been actively involved in the development of µSR experimental techniques under extreme conditions such as ultra-low temperatures and high pressures. His award-winning research includes studies on the correlation between superconductivity and magnetism, as well as investigations of superconducting states that break time-reversal symmetry. These studies make full use of the high magnetic sensitivity of the µSR technique. His work is expected to continue playing a vital role in elucidating the mechanisms behind various physical properties.
■Paving the Future of Fuel Cell Technologies: Establishing a New Method for Quantitative Evaluation of "Water" in PEFC Catalyst Layers (April 17)
Polymer Electrolyte Fuel Cells(PEFCs), which use hydrogen as fuel, have power generation characteristics that are closely linked to the behavior of water inside the cell. Controlling this water behavior is critically important. However, methods for elucidating the behavior of water within the ionomer (an ion-conducting polymer) within the catalyst layer have been limited.
In this study, an analytical method was established to quantify the water content in the ionomer within the catalyst layer of PEFCs, using the small and wide angle neutron scattering instrument “TAIKAN” at the Materials and Life Science Experimental Facility (MLF) in J-PARC, and the small-angle neutron scattering diffractometer “SANS-J” at the research reactor (JRR-3). The method revealed that as relative humidity increases, the ionomer within the catalyst layer retains the water more strongly.
This evaluation method developed in this study enables faster and more accurate quantification of the water content in the ionomer within the catalyst layer of PEFC’s. It is expected to contribute to improving PEFC performance by supporting the development of catalyst layer materials and the optimization of operating conditions.
■Successful Measurement of Quantum States Created by Centrifugal Force
— Toward Verification of the Equivalence Principle and Exploration of Hypothetical Short-Range Forces (April 28)
To understand the laws of the universe at the most fundamental level, a unified understanding of general relativity and quantum mechanics is essential. However, due to the vastly different scales these theories address, experimental methods capable of testing both simultaneously have been extremely limited.
In this study, experiments were conducted using pulsed cold neutron beams generated by the neutron optics and fundamental physics “NOP” at the Materials and Life Science Experimental Facility (MLF), along with precisely polished concave mirrors. By comparing the measured results with theoretical calculations, the researchers successfully verified that quantum mechanics holds even under conditions where centrifugal acceleration reaches 7 million times that of the gravity of Earth.
This marks the world’s first observation of quantum-bound states induced by centrifugal acceleration using a pulsed neutron source. The study establishes a new method for high-precision measurements in fundamental physics experiments. By further refining these measurement techniques and comparing them with quantum states influenced by Earth's gravity, it will be possible to test the equivalence principle—the foundation of general relativity—with even greater precision in the quantum regime. Moreover, this precision opens the door to exploring hypothetical interactions at the 10-nanometer scale, which remains poorly understood.
■Hello Science "A Neutron Peek Inside the Micro World of Batteries" (April 22)
Dr. MORI Kazuhiro from the Neutron Science Section introduced his research on materials for storage batteries. The research and development of innovative storage batteries for electric vehicles is a collaborative project involving the Ministry of Economy, Trade and Industry (METI), various domestic companies, universities, and research organizations.
All-solid-state fluoride batteries are gaining attention as an innovative alternative to current lithium-ion batteries, offering high energy density with safe and inexpensive materials. Although fluoride is typically considered to have low ionic conductivity, mixing calcium and barium in a specific ratio increases the conductivity by several orders of magnitude. This increase in conductivity was elucidated at the atomic level using neutron diffraction with "SPICA", the special environment powder diffractometer located in the Materials and Life Science Experimental Facility(MLF). It was determined that the key factor is the distortion of the crystal structure caused by calcium and barium, which have different ionic radii.
Dr. MORI expressed his desire to continue the challenge of research and development of storage batteries as part of an all-Japan effort to achieve carbon neutrality. Participants showed great interest, asking many questions about materials for storage batteries and electric vehicles.
▶ Press release by Dr. Mori (https://j-parc.jp/c/press-release/2024/09/06001392.html) (only in Japanese).
■J-PARC Outreach Lectures
(1) National Institute of Technology, Tsuyama College (April 22)
Dr. OTANI Masashi from the Accelerator Division delivered a lecture titled "How Accelerators Reveal the Microscopic World – Muon Acceleration Technology for Probing from Subatomic Phenomena to Massive Structures" for third- and fourth-year students at the National Institute of Technology, Tsuyama College.
In the lecture, he explained the principles of particle accelerators and introduced their wide-ranging applications in fields such as industry and medicine.
He then discussed muons—subatomic particles used to discover hidden chambers in ancient pyramids and to visualize the interior of volcanoes. He also introduced research conducted at J-PARC using artificially generated high-intensity muons, as well as the latest developments in related technologies.
Toward the end of the lecture, he presented a case study on a collaborative project involving students building a compact accelerator named AxeLatoon (a coined term combining "Accelerator" and "Ratoon," meaning new sprout), as part of a community engagement initiative.
A Q&A session was held before and after the lecture, during which students asked questions not only about heavy-ion cancer therapy featured in the lecture but also about other medical applications and what research life is like at KEK( High Energy Accelerator Research Organization) and J-PARC.
These exchanges revealed that many students were inspired to consider future careers in accelerator-related fields, indicating that the lecture served as strong motivation for their career planning.
■Koka Gakuen Junior and Senior High School (May 7)
Approximately 900 female students, ranging from the first year of junior high school to the third year of high school, attended a lecture presented by Director KOBAYASHI Takashi and Dr. SHIBAZAKI-FUNYU Chie from the Technology Development Section. Dr. SHIBAZAKI, an alumna of Koka Gakuen who attended the school from kindergarten through high school and later taught science there for seven years after graduating from university. Her talk began with fond memories of her time as a student, followed by insights from her experience as a science teacher and the inspiration that led her to pursue a research career. She concluded by introducing her current work on determining protein structures using neutron crystallography. Following her presentation, Director Kobayashi provided an overview of J-PARC and introduced cutting-edge research related to the universe and life sciences.
After the lecture, the students asked a variety of questions and shared creative ideas that reflected their curiosity about science. These included, “Do aliens exist?,” “If we were to artificially create a Big Bang, where would be the best place to do it?,” and “What if we wove long molecules to create spider silk like in Spider-Man?”
Interestingly, in a survey asking which topic interested them the most, the top response was “Women’s careers and life paths,” reflecting the unique perspective of an all-girls school. Notably, while over 90% of the students had never heard of J-PARC before the lecture, more than 80% responded that they became interested in it afterward – a clear sign that the lecture made a strong impact.
■Suwa Elementary School in Hitachi City (May 13)
The class, titled "Let’s Explore the Invisible Vacuum," was conducted for 80 fifth and sixth-grade students at Suwa Elementary School, operated by the City of Hitachi. It was organized as part of a science program by the Hitachi Civic Center, with Ms. MOROHASHI Yuko from the J-PARC Center Accelerator Division serving as the instructor.
Using well-known items such as balloons, hot water, and marshmallows, the vacuum experiments captivated the students, who cheered with excitement each time a visible change occurred.
Students and teachers shared their impressions, saying things like:
“The vacuum cannon was so powerful, it surprised me!”
“It was fascinating to see the water drawn into the cup—it was mysterious and fun.”
“It was a great experience to witness phenomena I had only seen in textbooks.”
■Open University of Japan – Library Lecture Series (May 17)
As the first lecture in JFY2025 of the "Library Lecture Series" hosted by the Ibaraki Learning Center of the Open University of Japan, Director KOBAYASHI Takashi delivered an engaging lecture titled “Exploring the Origins of the Universe and Matter with J-PARC, the World’s Most Powerful Accelerator at Ibaraki” at the Ibaraki Prefectural Library. He explained the research conducted at J-PARC in an accessible and easy-to-understand manner. More than 50 participants attended the event, listening attentively and taking notes throughout the lecture.
After the lecture, participants asked questions such as, “How can we distinguish between neutrinos and antineutrinos? “ and "How are neutrinos from space differentiated from those coming from J-PARC when detected in Kamioka?" Pointing to the materials projected on the large screen, Director KOBAYASHI responded, "Antineutrinos have the opposite spin orientation," and added, "Since the emission time of neutrinos from J-PARC is precisely measured, we can also determine their arrival time in Kamioka.
■Muographic Investigation of Ancient Burial Mounds in Tokai
- The second muon detector completed (April 27)
Since November of last year, 31 elementary, junior high, and high school students have been working under the guidance of researchers and graduate students to build a second muon detector. On April 27, the long-awaited second muon detector was finally completed.
On that day, 18 participants gathered at the Tokai Village Museum. Following instructions by Dr. FUJII Yoshiaki from J-PARC, they completed the cabling and installed the ceiling panels. A test run was then conducted, and the detector successfully observed cosmic-ray muons falling on the Tokai Village Museum.
The students involved in the project voted on the name “Detector for History and the Future Unit 2.” This second unit will be installed at Funatsuka Tumulus Group No. 2. Together with the first one, the team will continue to see through ancient burial mounds using muography.
■KEK Exhibits at Niconico Chokaigi 2025 (April 26–27)
KEK participated in Niconico Chokaigi 2025 at the Makuhari Messe International Exhibition Hall under the banner of “Cho KEK,”—“Cho” means super -- marking its third consecutive year of exhibition at the event.
Niconico Chokaigi, hosted by Dwango Co., Ltd., is one of Japan’s largest cultural festivals, blending online and in-person experiences. It centers around the users of the video-sharing platform "Niconico." This year, the event welcomed 132,657 attendees.
The theme of this year’s Cho KEK booth was “Accelerators.” The booth featured hands-on exhibits, including a section where visitors could peer inside actual accelerator components that had been used in research. Interactive activities such as the “Vacuum Challenge” game and a riddle event provided attendees with an engaging opportunity to experience and learn about the cutting-edge research conducted at KEK and J-PARC.
In addition, the “Cho KEK Live Broadcast” featured nine talk shows over two days, with researchers and engineers sharing their work via live streaming. As part of this program, Dr. UMEGAKI Izumi from the Materials and Life Science Division gave a talk titled: “Cutting Open a Battery with an Ultra-Rare Quantum Beam! – The Muon Beam Edition –” Meanwhile, Dr. MORI Kazuhiro presented: “Cutting Open a Battery with an Ultra-Rare Quantum Beam! – The Neutron Beam Edition –” These talks introduced cutting-edge research at J-PARC using different quantum beams—muons and neutrons—to visualize the internal state of batteries. The relatable topic of batteries drew great interest, and many questions were received from both on-site visitors and online viewers.
Furthermore, a volunteer team of KEK researchers and engineers participated in the “Cho Niconico Mini 4WD 2025” corporate competition—and won first place. Other outreach efforts included a social media campaign and a stage appearance at the Ibaraki Prefecture booth, where local ambassadors known as the “Ibaraki Wakadanna” took on the Vacuum Challenge, helping promote awareness of KEK and J-PARC.
■J-PARC Sanpomichi 58
"PARK" and "PARC"
The facilities of J-PARC are spread out across a vast site, and commuting between them often relies on cars. As a result, parking lots—referred to simply as “Parking”—are provided around the buildings, taking on various shapes depending on the layout and constraints of the site. For instance, the lot on the seaward side of the Research Building is arranged in a single row, while the one near the Materials and Life Science Experimental Facility (MLF) radiates outward.
The linear parking lot brings to mind the facility’s linear accelerator. Among the three proton accelerators, only the upstream one—the linac—is straight. To rapidly accelerate a continuous stream of protons, it consists almost entirely of accelerating cavities. Since the acceleration process requires a straight path, the entire structure is built in a linear form.
In contrast, the radial parking lot evokes the image of the neutron beamlines. At the MLF, maximizing the number of neutron experiments is a key objective. To achieve this, a mercury target that generates neutrons is placed near the center of the building. The neutrons travel along beamlines that radiate outward to experimental stations where samples are placed. This radial layout allows for the installation of up to 23 beamlines across two experimental halls.
In daytime aerial photographs, the crisp white lines of the parking lots shine distinctly. These designs likely reflect efforts to use space efficiently while ensuring smooth vehicle movement. Seen from above, they reveal a striking geometric beauty. Likewise, the linac, neutron beamlines, and other components—engineered to deliver maximum performance within limited space—embody a kind of functional elegance that rivals the visual appeal of the parking lots themselves.
