■Press Release
(1) Unusual Muon Behavior in Ice Revealed - Quantum Behavior Holds the Key to a 50-Year-Old Mystery - (July 10)
It has been known for about 50 years, since the beginning of muon research, that the spin state of muons differs between water and ice. However, the mechanism behind this change has remained unknown.
The research group precisely measured changes over time in the spin of implanted positive muons in a magnetic field of 20 gauss, using the ARTEMIS spectrometer in the S1 area of the Muon Facility at the Materials and Life Science Experimental Facility (MLF) of J-PARC.
The results showed that in liquid water, a regular waveform-like signal, similar to the wobbling motion of the muon spin, continued for a long time. In ice, however, the signal weakened quickly, and the period of the wave shifted slightly.
To explain this phenomenon, the research group developed a model in which the muon spin in a MuOH molecule interacts quantum mechanically with surrounding water molecules.
(Mu is a bound state of a positive muon and an electron and corresponds to a hydrogen atom.) The model was confirmed to reproduce the experimental data, revealing that quantum effects appear in muons in ice.
For more details (in Japanese only), please visit the J-PARC website.
https://j-parc.jp/c/press-release/2026/07/10001847.html

(2) Elucidating the Origin of Barrier Function in Antithrombogenic Polymers - Analysis of Intermediate Water Motions Using Neutron Scattering - (July 21)
Treatment using extracorporeal membrane oxygenation (ECMO) has become an indispensable medical technology for sustaining the lives of patients not only with coronavirus infection but also with severe respiratory diseases. The surface of the artificial circuit through which blood flows is coated with a polymer material designed to resist blood clot formation; however, since long-term use remains challenging, there is a demand for the development of new materials with superior antithrombogenic properties. Previous research suggested that a specially structured form of water (intermediate water), formed through interaction with the polymer, acts as a barrier layer that suppresses thrombus formation.
However, the mechanism by which this barrier layer forms had not been elucidated.
The research group conducted neutron scattering experiments using the dynamics analyzer BL02, DNA at J-PARC MLF, investigating the motional states of antithrombogenic polymers and the water adsorbed on their surfaces in order to clarify the mechanism underlying their antithrombogenic properties. As a result, the group demonstrated for the first time that intermediate water exists on the polymer surface, with its motion 10 to 100 times slower than that of bulk water. This achievement is expected to serve as a guideline for designing new materials that can more effectively control intermediate water, thereby supporting the development of next-generation medical devices that combine both safety and performance.
For more details (in Japanese only), please visit the J-PARC website.
https://j-parc.jp/c/press-release/2026/07/21001850.html

■J-PARC Hello Science "Intermediate Water Cherenkov Detector - A Neutrino Detector That Floats and Moves Up and Down Like a Ship" (July 31)
Dr. AKUTSU Ryosuke of the Particle and Nuclear Physics Division introduced the current status of the construction of the "Intermediate Water Cherenkov Detector," a neutrino experimental facility being built as part of the Hyper-Kamiokande project.
The Hyper-Kamiokande project aims to begin operation in FY2028. It will observe neutrino oscillations with greater precision and seek a definitive test of CP violation. The Intermediate Water Cherenkov Detector, which is currently under construction, is an important part of the project. It will be installed about 1 km from the neutrino production target at J-PARC. The detector will float in a water-filled shaft and move up and down as the water level changes. By changing the position of the detector, neutrinos can be observed under different energy conditions before oscillation. This will allow accurate measurement of neutrino interaction events that will be detected as signals at Hyper-Kamiokande.
Participants asked many questions about collaboration with research projects overseas. A member of the Intermediate Water Cherenkov Detector construction team also shared their hope of "building a more precise experimental facility while understanding the research being conducted."

■Tokai Village Enjoy Summer School 2026 (July 24 and 30, August 5 and 20, Tokai Village Museum)
With the cooperation of local communities, organizations, and businesses in Tokai Village, the "Tokai Village Enjoy Summer School," a hands-on event for elementary school students, was held.
J-PARC held four science experiment workshops as part of "J-PARC Hello Science: Summer Vacation Science Experiment Classes." The classes included "Make Accessories with Hadrons," "Tilted but Won't Fall! The Mystery of Spinning Tops," "Think About What Is Inside by Looking at Differences in Rocks - Minerals Are Interesting," and "What Are Air and a Vacuum?"
Many of the children who participated said in the questionnaire that they had fun. This experience is expected to inspire the children to make new discoveries and learn more about science.

■Hands-on Workshop Held at Children's Kasumigaseki Tour Day (July 29-30, Ministry of Education, Culture, Sports, Science and Technology)
Children's Kasumigaseki Tour Day was held during the summer vacation, with the Ministry of Education, Culture, Sports, Science and Technology and other government ministries and agencies working together to offer various activities and exhibitions. At the JAEA booth, children took part in a hands-on workshop with the theme "Let's Make a Box That Makes Invisible Colors Visible! A Rainbow of Colors Floating in Pitch-Black Darkness."
First, the children made a cube-shaped box by putting together four black craft boards and covering the front and back with polarizing filters. They then placed a transparent origami crane inside the box. When they looked inside, an origami crane in rainbow colors appeared to float in the pitch-black darkness.
The children turned the box around and tilted their heads, gazing at the faintly colored crane with curiosity.

■Muographic Investigation of Ancient Burial Mounds in Tokai (July 26, Tokai Village Museum)
The third activity of FY2026 was held. In the first part, Dr. FUJII gave an update on the two detectors. After reviewing the previously reported observation results from "Detector for History and Future No. 1," he explained the status of "Detector for History and Future No. 2," which was newly installed last November. Although the detector experienced flooding caused by a typhoon in June and problems due to high temperatures in July, the necessary measures have already been taken, and smooth observations are expected.
In the second part, seven scientists participating in the project gave short talks on the theme, "What were they like as children, and how did they become scientists?" After listening to the talks, the children asked questions of their own, including, "What should I do if I study physics at university?" and "Why are there so few female scientists?" A girl sitting in the front row asked the latter question. A female scientist who participated in the event answered that although there are still fewer female scientists, their number has increased compared with the past, and there is no difference between women and men when it comes to study.
The children listened with curiosity as the scientists shared stories about their childhoods and their journeys to becoming scientists. They seemed to relate the scientists' experiences to their own lives.

■J-PARC Sanpo-michi 73: - The MR Above and Below Ground After Nearly 20 Years -
At J-PARC, the paths taken by protons in all three accelerators are located more than ten meters underground. Above the tunnel of the largest accelerator, the MR, soil was piled up to form a 1.6-km-long ridge around the accelerator ring. However, trees have grown thickly in the area, making it difficult to see the entire ridge from above ground.
During the construction of the MR, the ground was first dug up to build the tunnel. After construction was completed, the soil was put back, and trees were planted except in areas with buildings, such as the handling building, power supply building, and machinery building. This was done to restore the greenery around the facility. The MR facility was completed in January 2007, so nearly 20 years have now passed since its completion.
Inside the 1.6-km-long tunnel, the curved sections are lit by evenly spaced lights. The reflections of the lights create gentle arcs on the walls and floor. Various magnets that guide the proton beam are neatly arranged inside the tunnel. At first glance, the scene may look the same as it did before. However, equipment has been replaced and improved over the years, and the power of the proton beam has increased greatly since the facility was first completed. Like the area above ground, the accelerator underground has continued to change and improve over the years.

■Award
2026 Japan Radioisotope Association Encouragement Award
Dr. OKUDAIRA Takuya, Assistant Professor at the Graduate School of Science, Nagoya University, and Visiting Researcher at the Fundamental Technology Development Section, Materials and Life Science Division, J-PARC Center, has received the 2026 Japan Radioisotope Association Encouragement Award.
Dr. OKUDAIRA has been conducting spin-polarized neutron experiments using a neutron polarization device, a ³He spin filter, and successfully developed a high-performance ³He spin filter at J-PARC. The device has been put into practical use at various neutron beamlines at J-PARC. In particular, he applied polarized epithermal neutron beams to fundamental research on time-reversal symmetry violation in neutron absorption reactions by atomic nuclei. Experiments at J-PARC MLF BL04 "ANNRI" revealed that the gamma rays emitted after atomic nuclei absorb polarized epithermal neutrons exhibit an angular distribution. In addition, at BL22 "RADEN," he successfully measured the spin dependence of the cross section between polarized nuclei and polarized epithermal neutrons by polarizing a ¹³⁹La nuclear target using a superconducting magnet and a dilution refrigerator.
By comparing these results with nuclear theory models, he demonstrated that time-reversal symmetry violation can be extremely strongly enhanced in the neutron absorption reaction of ¹³⁹La.
The award ceremony was held on July 10 at the National Museum of Emerging Science and Innovation (Miraikan).

■Press Release
(1) - Establishing an Important Foundation for the Development of Novel Magnetic Memory - (June 19)
Atoms in materials have tiny magnetic properties called magnetic moments, which can be thought of as tiny magnets. In helical magnets, the direction of neighboring magnetic moments gradually rotates, forming a helical magnetic structure throughout the material.
The way the helix twists, known as chirality (right-handed or left-handed), has been suggested to be controllable using electric currents and magnetic fields. However, there had been no clear experimental evidence that this chirality could actually be controlled.
This achievement is expected to provide an important foundation for the development of next-generation magnetic memory using helical magnetic materials.
For more details (in Japanese only), please visit the J-PARC website.
https://j-parc.jp/c/press-release/2026/06/19001833.html

(2) Establishing a New Design Guideline for Topological Magnetic Materials
- Discovery of a Homologous Series of Square-Lattice Materials with Dirac Electrons - (July 2)
Topological quantum materials have electronic states protected by topology, in addition to quantum properties such as magnetism and superconductivity. Because these electronic states are highly stable against external disturbances, topological quantum materials are expected to be used in next-generation spintronics and quantum computing. However, unlike layered oxides such as high-temperature superconductors, there has been no established guideline for controlling the properties of these materials by changing the number of layers.
The research group has, for the first time, realized a homologous series of square-lattice magnetic materials with topological electronic states, in which the number of layers can be controlled. Neutron scattering experiments using the JRR-3 research reactor and BL18 "SENJU" at the J-PARC MLF, together with theoretical calculations and high-magnetic-field measurements, showed that both the magnetic properties and topological electronic states can be controlled by changing the number of layers.
This achievement is expected to accelerate the development of new materials for next-generation quantum technologies and lead to the discovery of new quantum phenomena and innovative quantum functions.
For more details (in Japanese only), please visit the J-PARC website.
https://j-parc.jp/c/press-release/2026/06/19001833.html

■11 Junior and Senior High School Students Conduct Beam Experiments J-PARC Muon Facility (June 20-21)
With support from Accel Kitchen, 11 junior and senior high school students conducted muon beam experiments in the Muon D1 area of the MLF. This was the second time that junior and senior high school students had conducted beam experiments at J-PARC, following last year's program. The program was expanded this year, with more participants and an increased number of research topics than last year.
Accel Kitchen has provided junior and senior high school students with simple radiation detectors and supported more than 300 students in conducting radiation and cosmic-ray observations at home. For this program, the organization invited proposals for muon beam experiments, and five projects involving 11 students were selected for experiments at J-PARC. The students will now analyze the data they obtained and plan to present their findings at academic conferences and in research papers.
For more details (in Japanese only), please visit the J-PARC website.
https://j-parc.jp/c/press-release/2026/07/03001838.html

■FY2026 Neutron Industrial Application Report Meeting Held (July 16-17, AKIHABARA Convention Hall and Online)
The meeting focuses on introducing cutting-edge measurement technologies and research results using neutrons and muons to meet the needs of industry, and on matching these technologies with what people in industry want to see. The number of participants has gradually increased each year, and this year, 284 people attended the meeting in person and 149 joined online.
As special lectures, on July 16, Mr. SHIMAZU Takashi, President and Chief Research Officer (CRO) of Toyota Central R&D Labs., Inc., gave a lecture titled "Manufacturing Supported by Quantum Beams - 60 Years of Industrial Applications in the Toyota Group."
On July 17, Dr. ORIMO Shin-ichi, Director of the Advanced Institute for Materials Science and Professor at the Institute for Materials Research, Tohoku University, gave a lecture titled "Future Prospects for Hydrogen Science and Technology - From Materials Development to the Use of AI."
The meeting also included general presentations and poster sessions, with active discussions among the participants.

■GSA Science Seminar (July 18-19, Hida City, Gifu Prefecture)
GSA (Geospace Adventure) is an event that offers participants the opportunity to explore the former Kamioka Mine and visit research facilities such as Super-Kamiokande.
Approximately 800 visitors entered the actual mine tunnels, where they stood above the huge water tank of Super-Kamiokande at the deepest point of the tunnel and learned about the neutrinos detected there and their relationship with J-PARC.
On July 18, a seminar commemorating the 30th GSA event was held under the title "Telling the Story of Science - What Is Being Studied in One of the World's Largest Underground Experiments?" The speakers were Dr. KOBAYASHI Takashi, Director of the J-PARC Center Dr. ICHIKAWA Atsuko, Professor at Tohoku University and recipient of the Saruhashi Prize, and Naoki Prize-winning author IYOHARA Shin. The seminar was moderated by science writer Mr. ARAFUNE Yoshitaka. The speakers discussed the appeal and fascination of science, as well as the personal side of researchers.
On July 18 and 19, Dr. KOBAYASHI also gave a lecture titled "The World's Most Powerful Proton Accelerator - Exploring the Origins of the Universe and Matter at J-PARC."

■J-PARC Hello Science "Particle Production Target: Extreme Design Technology" (June 26)

At the seminar, Mr. SUNAGAWA Hikaru of the Materials and Life Science Division introduced the "production target," which is used to produce muons, one of the elementary particles, and supports cutting-edge research at J-PARC.
The target receives the high-intensity proton beam from J-PARC, which has one of the highest beam intensities in the world, and is designed to produce large amounts of muons stably. Various ideas and advanced technologies are used in the target, from selecting suitable materials and installing components to cooling and the rotation mechanism.
Graphite, which has high heat resistance and resistance to thermal shock, is used as the target material. The target is also shaped like a donut and rotated to prevent the high-intensity beam from continuously hitting the same spot, reducing heat concentration and damage.
The lecture also covered the challenges faced during the development of the current production target and the technical approaches used to overcome them. Participants asked a series of questions about material selection and maintenance, showing their strong interest in the production target.

■Outreach
(1) KIPP Nakameguro - Children's Program at Nakameguro Elementary School - (July 4)
A workshop titled "The World's Smallest? Make a Mysterious Spinning Top and Explore the World of Elementary Particles" was held at the Nakameguro Elementary School Children's Program for 13 students from first to sixth grade. The workshop was led by Dr. OTANI Masashi of the Accelerator Section, who introduced the world of elementary particles using spinning tops.
First, the children learned about J-PARC and elementary particles. They then spun gyroscopes and made their own spinning tops. By changing the center of gravity of their handmade tops, they observed changes in the direction of precession and learned that the motion of precession is similar to the spin property of elementary particles.

(2) Yunago Elementary School, Hitachi City (July 7)
Mr. ITABA Tatsunori of the Particle and Nuclear Physics Division delivered a lecture titled "What Is the Universe Made Of? - Light." The lecture was held at the request of the Hitachi Civic Center as a parent-child learning session for third-grade students at Yunago Elementary School. A total of 30 students and their parents participated.
The participants had fun learning about waves, quantum phenomena, and light together through questions such as, "What properties do waves have?" and "What colors does light have?" During quizzes about waves and light, the children actively shared their ideas, and there were moments when they expressed surprise as they confirmed the answers through experiments.
At the end of the session, the children also made kaleidoscopes using the properties of light, enjoying the craft activity while experiencing the wonders of light.

(3) National Institute of Technology, Kagawa College, Takamatsu Campus (July 8)
Dr. OTANI Masashi of the Accelerator Division gave a special lecture titled "How Accelerators Work to Explore the Microscopic World" at the Kagawa National Institute of Technology.
In the lecture, he introduced the basic principles of accelerators and examples of their applications, including medical applications. He also discussed the use of muons and the latest developments in accelerator technology and elementary particle research.
During the Q&A session, students asked a wide range of questions, from technical questions such as "How does J-PARC achieve one of the world's highest beam powers?" to career-related questions such as "What kind of work do graduates of technical colleges do at KEK?"

■Muographic Investigation of Ancient Burial Mounds in Tokai: "Mock Excavation" Experience (June 28, Tokai Village Museum)
On June 28, although there were concerns that two typhoons might hit the area, the typhoons passed through without major disruption, allowing the second activity to take place. Following a previous session on the basics of archaeological excavation given by Prof. TANAKA of Ibaraki University, the children took part in a "mock" excavation experience this time.
The 11 children were divided into five groups and began their excavation using "archaeological excavation experience kits." The kits were prepared by graduate students from Ibaraki University, who worked until the night before the event. Based on five types of archaeological sites from the Middle and Late Jomon periods, the Yayoi period, the Kofun period, and the Nara and Heian periods, each kit consisted of three layers: a grass-covered surface layer, cultivated soil, and a black soil layer containing artifacts. The panels were designed to fit together like a puzzle. The children carefully "excavated" the soil panels layer by layer using small spoons as miniature shovels, taking care not to move the artifacts.
Afterward, Prof. TANAKA taught the children how to carry out surveying using a method called "yarikata," a type of construction surveying technique. The children then carefully recorded the positions of pottery and other artifacts they had uncovered on graph paper.
Using strings stretched over the model as a guide, they recorded the positions on the graph paper at half scale. They struggled with measuring the distances with a ruler, dividing them in half, and transferring them to the graph paper, but the experience gave them an opportunity to learn both the importance and the difficulty of keeping accurate records.

■J-PARC Sanpo-michi 72: - The Deuteration Laboratory "D-Lab" in the Heat of Summer -
When people think of J-PARC experimental facilities, they may imagine huge accelerators and large experimental facilities. However, J-PARC also has smaller, specialized laboratories that cannot be found anywhere else. One of them is the D-Lab (Deuteration Laboratory), located in the J-PARC Research Building.
Although the room may look like a laboratory at a university or pharmaceutical company, it is where biological samples are prepared for neutron experiments. Unlike X-rays, neutrons are particularly useful for detecting light elements. This makes it possible to distinguish between hydrogen and deuterium in a sample. By replacing hydrogen with deuterium in specific parts of a sample, researchers can study its structure and properties in greater detail.
At the D-Lab, genetically modified microorganisms are grown in heavy water to produce deuterated biological samples. After going through various processes, the resulting high-purity, high-quality deuterated samples are brought to neutron beamlines such as "TAIKAN," "DNA,""SENJU," and "iBIX," where they are exposed to high-intensity neutron beams.
The temperature inside the D-Lab is kept at around 20℃ throughout the year to ensure proper sample purification and maintain the performance of the equipment. When you enter the D-Lab from outside, it feels almost like stepping into a limestone cave. While we cannot share the cool air with you directly, we hope that the photo showing the colorful reagents lined up in the laboratory will help you feel a little cooler.

     J-PARC Project Newsletter

                                No.103, July 2026
Japan Proton Accelerator Research Complex under joint operation by the
High Energy Accelerator Research Organization (KEK) and the Japan Atomic
Energy Agency (JAEA)
http://j-parc.jp/index-e.html
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HEADLINES AND CONTENTS

1. [Overview]
- RECOVERY FROM THE 50 GEV SUBSTATION FIRE AND RESUMPTION OF USER OPERATION
- STEADY PROGRESS TOWARD HIGHER BEAM POWER

2. [Accelerator Division]
- OPERATION STATUS OF THE ACCELERATORS
- DR. ADACHI KYOSUKE RECEIVED THE YOUNG PRESENTATION AWARD

3. [Particle and Nuclear Physics Division]
- FACILITY UPGRADES TOWARD THE WORLD'S HIGHEST-INTENSITY NEUTRINO BEAM AND PROGRESS IN IWCD CONSTRUCTION
- STATUS OF THE JSNS2 / JSNS2-II (SEARCH FOR STERILE NEUTRINOS AT J-PARC MLF, E56 / E82)
- SUCCESSFUL MEASUREMENT OF PHI MESONS PRODUCED ON NUCLEAR TARGETS
- STATUS OF THE COMET EXPERIMENT
- STATUS OF THE MUON g-2/ELECTRIC DIPOLE MOMENT (EDM) (E34)

4. [Materials and Life Science Division]
- NEUTRON SOURCE; CONTINUATION OF BEAM OPERATION AND PLANNING OF MAINTENANCE DURING THE LONG SUMMER SHUTDOWN
- NEUTRON INSTRUMENT AND SCIENCE; STUDENTS JOIN MLF RESEARCH PROGRAMS
- MUON SCIENCE FACILITY (MUSE); ACCEL KITCHEN HOSTS 2ND ANNUAL HIGH SCHOOL MUON BEAM EXPERIMENTS

 5. [Quantum Beam Technology Division]
- INTRODUCTION OF THE QUANTUM BEAM TECHNOLOGY DIVISION

 6. [Safety Division]
- J-PARC SAFETY DAY 2026

 7. [Outreach Activities]

 8. [Editorial Note]
PAST ISSUES ARE AVAILABLE FROM THE LINK BELOW.
http://j-parc.jp/c/en/topics/project-newsletter/index.html

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1. [Overview] by KOBAYASHI Takashi
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RECOVERY FROM THE 50 GEV SUBSTATION FIRE AND RESUMPTION OF USER OPERATION
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A fire that occurred in the 50 GeV substation on April 7 forced the suspension of user operations across J-PARC. Following a thorough investigation of the cause, inspections of related equipment, and implementation of preventive measures, MLF user operation resumed on June 1. However, just before the scheduled restart of the Main Ring, an unexpected failure of a high-voltage disconnecting switch was discovered in a receiving panel. Because replacement of the damaged component required a long lead time, MR user operation could not resume before the summer shutdown. We sincerely apologize to all users and collaborators whose research activities were delayed or canceled by these unforeseen events. We fully recognize the significant impact on the user community and are making every effort to strengthen the reliability of our facilities.

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STEADY PROGRESS TOWARD HIGHER BEAM POWER
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Despite these operational challenges, important technical progress was achieved. Stable MLF user operation resumed successfully after recovery, and Slow Extraction (SX) user operation reached the 100 kW level. J-PARC will continue to improve the reliability of accelerator operation while pursuing higher beam power to support world-leading science.

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2. [Accelerator Division] by YAMAMOTO Kazami
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OPERATION STATUS OF THE ACCELERATORS
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User operations were temporarily suspended during the final week of March due to scheduled maintenance work and accelerator beam tuning. Operations at MLF and HD subsequently resumed sequentially on April 1. However, this was interrupted when a fire broke out in a high-voltage switchboard inside the J-PARC 50 GeV substation at approximately 7:00 a.m. on April 7. Consequently, user operations were halted for approximately two months to allow time for investigating the cause of the fire and implementing preventative measures.
Investigations conducted at the accelerator facility determined that cable degradation was the primary cause of the incident. Following necessary repairs, MLF user operation resumed on June 1. MR operation was initially scheduled to restart for HD users on June 2; however, immediately prior to this restart, a malfunction was discovered in one of the high-voltage disconnecting switches. Since repairing the faulty component required more than a month, the MR operation for the first half of 2026 was canceled.

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DR. ADACHI KYOSUKE RECEIVED THE YOUNG PRESENTATION AWARD
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We are pleased to announce that Dr. ADACHI Kyosuke, a postdoctoral researcher in Accelerator Section II, received the Young Presentation Award from the Beam Physics Research Society/Young Researchers' Association for his presentation entitled "Optimization Study of Longitudinal Bunch Flattening in the J-PARC RCS."
In this study, he investigated a method for flattening the longitudinal beam bunch profile by applying a second-harmonic RF during the final stage of acceleration. This technique successfully reduced beam loss and is expected to make a significant contribution toward achieving even higher-intensity beam operation at J-PARC.
https://j-parc.jp/c/en/topics/2026/04/15001807.html

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3. [Particle and Nuclear Physics Division]
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FACILITY UPGRADES TOWARD THE WORLD'S HIGHEST-INTENSITY NEUTRINO BEAM AND PROGRESS IN IWCD CONSTRUCTION (by ISHIDA Taku)
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The J-PARC Neutrino Experimental Facility successfully achieved stable high-power beam operation at 900 kW from January to March 2026. Optimization efforts in the Main Ring (MR) accelerator, including a shorter repetition cycle and reduced beam losses, enabled efficient and reliable neutrino beam production. In February 2026, a beam extraction test corresponding to 1 MW beam power was also successfully carried out, marking an important milestone toward future beam power upgrades. These achievements represent a key step toward the Hyper-Kamiokande experiment, scheduled to begin operation in FY2028, and demonstrate the technical readiness required for long-term MW-class beam operation.
The Neutrino Experimental Facility is currently undergoing upgrades to support operation at 1.3 MW beam power. During the summer shutdown period of 2026, a new 1.3 MW production target will be installed, together with upgrades to the target helium cooling system, secondary beamline cooling-water system, and remote-maintenance capabilities for the final focusing horn section. Upon completion of these improvements, the neutrino beamline will be capable of accepting 1.3 MW-class proton beams, representing a major step forward in preparation for the high-intensity beam operation required by Hyper-Kamiokande.
The Intermediate Water Cherenkov Detector (IWCD), currently under construction as the intermediate detector of the Hyper-Kamiokande project, is designed to measure the neutrino beam at different off-axis positions by moving vertically within a 48-meter-deep shaft. Full-scale shaft excavation began at the Tokai construction site in April 2026, and construction of the third caisson segment is currently underway. Construction activities are progressing toward completion in 2028 while continuously monitoring environmental impacts on the surrounding area.

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STATUS OF THE JSNS2 / JSNS2-II (SEARCH FOR STERILE NEUTRINOS AT J-PARC MLF, E56 / E82) (by MARUYAMA Takasumi)
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The JSNS2 (E56) / JSNS2-II (E82) collaboration investigates the anomaly reported by the LSND experiment, namely the observed excess of electron antineutrinos, through a direct measurement at the J-PARC Materials and Life Science Experimental Facility (MLF).
Data taking with both the near detector, located on the third floor of the MLF, and the far detector, installed outside the MLF building, for the current physics run has been completed. As of 14 June 2026, new physics data corresponding to 1.137×10²² Proton-On-Target (POT) have been accumulated with the near detector. This corresponds to approximately 23% of the total data accumulated between 2021 and 2024.
In parallel with the ongoing data-taking efforts, we have analyzed the data collected in 2022 and 2024. The results will be shown at the Neutrino 2026 conference held in June 2026.
The new far detector is currently in the commissioning phase. Effective passive shielding against neutron backgrounds is required and is being investigated through various measurements. Based on these studies, the number of neutrons originating from one of the MLF neutron beamlines has been reduced by approximately a factor of three. Further background reduction studies are ongoing.

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SUCCESSFUL MEASUREMENT OF PHI MESONS PRODUCED ON NUCLEAR TARGETS (by NAKASUGA Satomi, OZAWA Kyoichiro)
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Hadrons, including protons and neutrons, are composed of quarks, yet their observed masses are about two orders of magnitude larger than the masses of bare quarks. This discrepancy is thought to arise from the spontaneous breaking of approximate symmetry in the strong interaction. To explore how hadron masses are generated, the E16 experiment at the J-PARC Hadron Experimental Facility studies hadrons in a high-density environment using nuclear targets.
The experiment focuses on phi mesons, which are well suited for investigating in-medium mass modifications. By embedding the production process in atomic nuclei, the E16 experiment examines how the properties of hadrons change under dense conditions. To directly probe phi mesons inside nuclei, their decay into electron-positron pairs is measured, since these particles do not interact strongly with the surrounding nuclear medium and can carry clean information.
However, detecting these electrons is highly challenging. They must be distinguished from a large background of pi mesons, which are roughly 100 times more abundant. Moreover, the electron-positron decay channel is extremely rare, occurring in only about one out of every 10,000 phi meson decays. These constraints require a high-intensity proton beam and advanced detection techniques, capabilities that are currently realized at J-PARC.
After more than a decade of detector development and several years of commissioning, the E16 experiment has successfully observed phi meson decays into electron-positron pairs.
This marks the first measurement of this kind using nuclear targets in this energy range.
During commissioning in June 2024, the phi meson mass was reconstructed and its production yield evaluated. The results were published in Progress of Theoretical and Experimental Physics (S. Nakasuga et al., Prog. Theor. Exp. Phys. 2026, 043D03) and highlighted in a press release.
This achievement represents the first physics result obtained with the newly constructed high-momentum proton beamline, establishing an important step forward in expanding research capabilities at the J-PARC Hadron Experimental Facility.

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STATUS OF THE COMET EXPERIMENT (by MIHARA Satoshi)
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The COMET experiment aims to search for the lepton-flavor-violating muon reaction, mu-e conversion, with a sensitivity better than 10-14 in Phase I.
The COMET collaboration has been making steady progress toward the commissioning of the Detector Solenoid (DS). Preparations for the magnetic field mapping are now nearly complete. The required measurement instruments have been calibrated, and the field mapping campaign is ready to begin as soon as the magnet is available for operation.
Assembly work has also started for the installation of the Central Drift Chamber (CDC), the experiment's central tracking detector, inside the DS. The CDC is first mounted in the support structure known as the Cradle. After the Cylindrical Trigger Hodoscopes (CTHs) are installed at both ends of the Cradle, the entire assembly will be inserted into the DS. The collaboration is currently carrying out the final adjustments in preparation for the installation.

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STATUS OF THE MUON g-2/ELECTRIC DIPOLE MOMENT (EDM) (E34) (by MIBE Tsutomu)
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The E34 collaboration aims for precision measurements of the muon anomalous magnetic moment and its electric dipole moment. In June, the collaboration collected data on characterizing ultra-slow muon generation and acceleration to 0.3 MeV at H2 area with the laser system for muonium ionization using a Lyman-α laser, Ultra-slow muon diagnosis beam line, and Radio Frequency Quadrupole cavity. These results and other updates were discussed in the collaboration meeting at J-PARC on June 24-26.

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4. [Materials and Life Science Division]
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NEUTRON SOURCE; CONTINUATION OF BEAM OPERATION AND PLANNING OF MAINTENANCE DURING THE LONG SUMMER SHUTDOWN (by HARADA Masahide)
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Beam operation of FY2026 at the MLF resumed on April 1 with the beam power of 780 kW, following a one-week break at the end of March, and continued stably until the fire incident at the J-PARC 50 GeV substation on April 7. After confirming the safety of both the MLF and the accelerators, the beam operation resumed on June 1 with a reduced power of 680 kW due to malfunction of the power supply unit of the proton beam transport line, which recovered to 780 kW on June 10. The beam operation will end on June 23 for the long summer shutdown.
During the long summer shutdown, we plan to carry out essential maintenance activities to ensure safe and stable beam operation. These include the used target vessel transport from the MLF to the RAM building, cutting of the used proton beam window, replacing air filters at hot cells, replacing the motor and power cable of the mercury pump and mercury target trolley, and other related tasks.
After all the maintenance work is completed, the beam operation will resume around October 22.
Awards:
Dr. WAKAI Eiichi, a Research Fellow at the J-PARC Center, received the 8th Achievement Award of the Materials Science and Technology Division, Atomic Energy Society of Japan.
He led research activities as the first JAEA contact person for the J-PARC RaDIATE collaboration.
https://www.j-parc.jp/c/en/topics/2026/05/19001830.html

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NEUTRON INSTRUMENT AND SCIENCE; STUDENTS JOIN MLF RESEARCH PROGRAMS (by SANO Asami)
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2026B Proposal Call and Review Status:
MLF resumed normal operation at the beginning of June and continued the remaining scheduled experiments for the 2026A cycle. The 2026A proposals that could not be carried out due to facility-related circumstances are scheduled to be carried over to the next cycle.
For the 2026B proposal call, MLF received 326 general proposals for neutron experiments.
The number of domestic proposals increased by 9% compared with the previous proposal call and accounted for 54% of all submissions. All proposals are currently under review.

Students in MLF Research Programs:
This fiscal year, MLF welcomed students as long-term research fellows. JAEA has accepted three students as interns, while KEK has accepted one student as a special joint-use researcher. All have already begun their research activities at MLF.

Awards:
A paper co-authored by Dr. HARJO Stefanus received the 16th Materia Award from the Journal of the Japan Institute of Metals and Materials. In addition, Dr. KAJIMOTO Ryoichi and Dr. NAKAMURA Mitsutaka received the Editors' Suggestion designation and were featured in Physical Review Letters for their collaborative research conducted at BL01 of MLF.

Scientific Achievements (Press Release):
BL11 on May 13 "Hydrogen in the Earth core inferred from neutron imaging and diffraction"
https://doi.org/10.1038/s41598-026-49969-z

BL18 on April 30 "Enhanced elastocaloric cooling beyond Clausius-Clapeyron limits"
https://doi.org/10.1038/s41467-026-72172-7

BL21 on April 7 "Bulk Amorphous Alumina: The Density-Driven Interplay of Pentahedral Pyramids and Octahedra for High Dielectric Permittivity"
https://doi.org/10.1021/jacs.5c22344

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MUON SCIENCE FACILITY (MUSE); ACCEL KITCHEN HOSTS 2ND ANNUAL HIGH SCHOOL MUON BEAM EXPERIMENTS (by STRASSER Patrick)
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The operation resumed at the beginning of April but was soon after suspended due to a fire that broke out in a high-voltage switchboard inside the J-PARC 50 GeV substation on April 7. After safety checks were performed and corrective measures taken, the user's program in MLF resumed on June 1 and was conducted smoothly until the end of the cycle. The general-use proposals scheduled during the suspension period will be conducted this autumn onwards when the operation resumes after the long summer shutdown. We are currently preparing for the summer maintenance work to resume beam operations in the fall.
Building on the success of last year's event, high school students supported by Accel Kitchen LLC returned to the D-line on June 20-21 to conduct real-world Muon Beam Experiments. Accel Kitchen (Kasoku Kitchen in Japanese) is an innovative Japanese educational organization and social enterprise that allows junior high and high school students to conduct real-world research in particle physics, cosmic rays, and radiation science. The project originally started as hands-on physics workshops at Tohoku University. It has since expanded into a nationwide network that connects students with bleeding-edge scientific research. In short, Accel Kitchen bridges the gap between high school classrooms and world-class particle physics labs. This year's program featured five experiments proposed by a team of 12 high school students, who were supported by four university students. The experiments were carried out as Instrumental Development Use in the D1 area. On the first day, the students toured the beamline and prepared their setups, followed by the active execution of their experiments on the second day.
The Muon Section entered the new fiscal year on April 1 with a shift in leadership. Dr. STRASSER Patrick has been appointed as the new Muon Section Leader, taking over from Dr. KAWAMURA Naritoshi, with Dr. TAKESHITA Soshi stepping in as Sub-Leader.

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5. [Quantum Beam Technology Division] by SHINOZAKI Shinichi
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INTRODUCTION OF THE QUANTUM BEAM TECHNOLOGY DIVISION
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The Quantum Beam Technology Division was established on April 1, 2026, as a core organization supporting the stable supply of quantum beams across the accelerator, MLF, hadron, and neutrino experimental facilities at J‑PARC. The Division takes an integrated and cross-disciplinary approach to technological development, covering everything from accelerators and targets to beamlines, with the aim of realizing highly reliable and stable beam delivery. Looking ahead, we will further promote the use of machine learning and artificial intelligence for equipment condition monitoring, anomaly prediction, and optimization of operational parameters, thereby advancing the sophistication of facility operations. In addition, we will work to enhance beam intensity and pursue system upgrades and improvements, contributing to the further advancement and diversification of user research. Building on a foundation of safe and stable operation, we will continue to support J‑PARC's research activities through the ongoing evolution of quantum beam infrastructure.

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6. [Safety Division] by BESSHO Kotaro
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J-PARC SAFETY DAY 2026
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The J-PARC Center annually holds "J-PARC Safety Day" around May 23-the date of the radioactive material leak incident in 2013. For FY2026, the event was held on May 22, with 379 staff members participating through a hybrid format.
The morning session, titled "Safety Information Exchange Meeting," featured reports from various facilities and sections detailing initiatives related to radiation safety. Topics covered included cooling water system issues, beam loss reduction strategies, improvements to workwear in controlled areas, and the management of radiation-induced degradation of LED lighting, leading to lively discussions among participants.
In the afternoon, the "Workshop for Fostering Safety Culture" took place. The session began with the J-PARC Safety Awards Ceremony, where the Hadron Section received the Award for Most Safety Best Practices, and three staff members were honored with the Safety Contribution Award.
Following the awards, Professor Tetsuya Takemi from the Disaster Prevention Research Institute at Kyoto University delivered an invited talk titled "The Mechanisms Behind Extreme Weather Events Such as Heavy Rain and Tornadoes, and How to Prepare for Them." He provided a detailed explanation of the mechanisms behind torrential rains, tornadoes, typhoons, and lightning, noting their characteristics in recent years.
Furthermore, he emphasized that since disaster risks are constantly changing due to factors like climate change and urban development, disaster preparedness measures must be continuously updated.
The day concluded with the screening of the documentary video, "The Radioactive Material Leak Incident at J-PARC: Toward the Resumption of the Hadron Experiment Facility." All participants reflected on their memories of the incident, reaffirming their commitment to ensuring that these critical lessons are never forgotten.

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7. [Outreach Activities]
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★ The 15th Koshien of Science National Competition in Tsukuba (March 20-23)
https://www.j-parc.jp/c/en/topics/2026/05/28001818.html

★ KEK Exhibited at Nico Nico Chokaigi 2026 (April 25-26)
https://www.j-parc.jp/c/en/topics/2026/07/02001837.html

★ Outreach Lecture at National Institute of Technology, Akita College (May 8)
https://www.j-parc.jp/c/en/topics/2026/05/26001817.html

★ Outreach Lecture at Kanrin Japanese School, Aoba Ward, Yokohama City (May 27)
https://www.j-parc.jp/c/en/topics/2026/05/26001817.html

★ Outreach Lecture at Bakery Sasaki-tei, Kitashiobara Village, Yama District, Fukushima Prefecture (May 30)
https://www.j-parc.jp/c/en/topics/2026/05/26001817.html

★ Muographic Investigation of Ancient Burial Mounds in Tokai (May 31)
https://www.j-parc.jp/c/en/topics/2026/08/03001861.html

★ Outreach Lecture at Narusawa Elementary School, Hitachi City (June 2)
https://www.j-parc.jp/c/en/topics/2026/07/22001852.html

★ Outreach Lecture at Hakuoh University Ashikaga Junior High School, Tochigi Prefecture (June 6)
https://www.j-parc.jp/c/en/topics/2026/07/22001852.html

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8. [Editorial Note]
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  Past issues are available from the link below.
  http://j-parc.jp/c/en/topics/project-newsletter/index.html

┏----…----…----…----…----…----…----…----…----…----…----…----…☆
┃ Editorial Board:
┃ OGURI Hidetomo (Chair) : oguri.hidetomo[at]jaea.go.jp
┃ SHOBUDA Yoshihiro: yoshihiro.shobuda[at]j-parc.jp
┃ OZAWA Kyoichiro: ozawa[at]post.kek.jp
┃ MARUSAWA Machiko: machiko[at]post.kek.jp
┃ Bruce YEE-RENDON: byee[at]post.j-parc.jp
┃ OGAWA China (Secretary) : ogawa.china[at]jaea.go.jp
┃ * Please replace "(at)" with "@" when you enter an email address.
★----…----…----…----…End of Letter…----…----…----…----…----

■Award
The 16th Materia Japan Award for Science and Technology
A paper co-authored by Dr. HARJO Stefanus of the Materials and Life Science Division (first author: Prof. YAMASAKI Michiaki, Kumamoto University) received the 16th Materia Japan Award for Science and Technology.
This award is presented to outstanding papers published in Materia, the bulletin of the Japan Institute of Metals and Materials, that have made significant academic or scientific and technological contributions to the advancement of metals and related materials.
The award-winning paper, "Design of Wrought Light Metals with Both High Strength and High Ductility through Functional Multimodal Control," was published in the January 2024 issue of Materia. The paper elucidates the mechanisms responsible for the exceptional combination of high strength and high ductility in wrought magnesium alloys, based on an understanding of nanoscale dynamic behavior.

■Press Release
Possible Presence of Large Amounts of Hydrogen in Earth's Outer Core
- First Direct Determination of Hydrogen Content in Liquid Iron by In-Situ Observation - (May 13)
The Earth's core, which is composed mainly of iron, is known to have a lower density than pure iron under the high-pressure and high-temperature conditions found there. This lower density is thought to be caused by the presence of light elements mixed within the core, with hydrogen considered a leading candidate. This is because hydrogen is the most abundant element in the universe and dissolves easily into iron under high-pressure conditions.
However, there had been no way to observe hydrogen in liquid iron under such extreme conditions, so the amount of the hydrogen that could be dissolved has remained unknown.
In this study, researchers observed hydrogen-bearing liquid iron (FeHx) under conditions of 1,127℃ and 34,000 atmospheres via neutron imaging at the high-pressure neutron diffractometer PLANET at the Materials and Life Science Experimental Facility (MLF) of J-PARC, and succeed in directly determining the hydrogen content in liquid iron for the first time in the world.
The results revealed that liquid iron can dissolve hydrogen at a concentration of 0.17 wt%. This suggests that outer core can contain 70 to 85 times the amount of hydrogen (H) currently present in oceans, and that the dissolution of hydrogen could account for more than half of the density deficit of the Earth's outer core.
This study provides the constraint on hydrogen content of the Earth's outer core through direct measurement for the first time. The findings have implications for a wide range of fields, including our understanding of hydrogen circulation inside the Earth and the core formation processes of other planets. Moving forward, we are interested in determining the hydrogen content under higher pressures and in investigating differences in solubility when hydrogen coexists with other light elements.
For more details, click here (J-PARC website)
https://j-parc.jp/c/press-release/2026/05/13001802.html

■J-PARC Safety Day (May 22)
On May 23, 2013, a radioactive material leak incident occurred at the Hadron Experimental Facility at J-PARC, causing significant concern and inconvenience to local residents and many others. Every year around this date, J-PARC holds J-PARC Safety Day as an opportunity to reflect on the importance of safety.
The event was held for the 13th time this year in a hybrid format, with 379 participants. During the morning session, as the Safety Information Exchange Meeting, each section introduced initiatives and case studies related to radiation safety. In the afternoon the Workshop for Fostering Safety Culture, the J-PARC Safety Awards were presented. The Hadron Section received the Award for the Most Safety Best Practices, while three J-PARC staff members were honored with the Safety Contribution Award for their long-standing commitment to safety at J-PARC. This was followed by a lecture titled "Mechanisms Behind Extreme Weather Events Such as Heavy Rainfall and Tornadoes, and How to Prepare for Them," presented by Prof. TAKEMI Tetsuya of the Disaster Prevention Research Institute, Kyoto University. He explained the mechanisms and recent characteristics of extreme weather events—including heavy rainfall, tornadoes, typhoons, and lightning—from both global and local perspectives. He also emphasized that disaster risks continue to change as land use evolves through urban redevelopment and other factors, highlighting the importance of continuously reviewing and updating disaster preparedness rather than assuming that past experience guarantees future safety. The event concluded with a screening of a documentary on the J-PARC Radioactive Material Leak Incident, reaffirming the participants' commitment to preserving the lessons learned from the accident.
J-PARC will continue to hold this event annually and remain committed to placing the highest priority on safety in all research activities to ensure that such an accident never occurs again.

■J-PARC Hello Science
Beams and the Theory of Relativity (May 29)

The content of Hello Science is presented in a four-panel comic.
In the May session of Hello Science, Dr. SAWADA Shinya of the Particle and Nuclear Physics Division explained how Einstein's theory of relativity is indispensable to research at J-PARC.
At J-PARC, researchers use proton beams accelerated to nearly the speed of light, as well as the secondary particle beams they produce, to investigate the fundamental structure of atomic nuclei and matter. The theory of relativity plays a particularly important role in experiments involving unstable secondary particles with finite lifetimes.
During the session, participants used the calculator app on their smartphones or scientific calculators to calculate how the theory of relativity is applied in experiments at J-PARC.
Concepts that often seem difficult to understand became much more accessible as the calculations produced concrete numerical results on their screens, helping participants gain a deeper understanding of both the theory of relativity and J-PARC research.
Previous Hello Science videos are also available on the J-PARC YouTube channel!
https://youtube.com/playlist?list=PLoJacoLqZ0cXiowgQmKybiPLv9rkPTa0h&si=s9-44k_eLdrLOdMR

■J-PARC Outreach Lecture
(1) Kanrin Japanese School, Aoba Ward, Yokohama City (May 27)
Dr. KOMATSUBARA Takeshi from the J-PARC Center delivered a science experiment workshop at Kanrin Japanese School on the theme of a cloud chamber.
Second-year students participated in the workshop and built cloud chambers in groups. The students were fascinated as they carefully observed the fleeting tracks left by invisible particles.
Each time a white track appeared in the cloud chamber, excited voices could be heard in the classroom. The workshop not only helped the students deepen their understanding of the research conducted at J-PARC, but also provided a valuable opportunity to broaden their learning. Many students were seen actively communicating in Japanese while working together in groups.

(2) Narusawa Elementary School, Hitachi City (June 2)
Dr. KAMIYA Junichiro of the Accelerators Division delivered a lecture and experimental workshop titled "Let's Explore the Invisible World of Vacuum" at Narusawa Elementary School in Hitachi City.
Twenty-six fourth-grade students learned what happens to objects such as marshmallows and balloons in a vacuum through a series of experiments. The students watched with great interest as the marshmallows and balloons expanded when placed in a vacuum.
They also took part in various experiments, including the Magdeburg hemispheres experiment and an experiment demonstrating what happens to a feather and a coin when they fall inside a transparent vacuum tube.
Finally, through a vacuum cannon experiment, Dr. KAMIYA explained that vacuum plays an important role in accelerating particles at J-PARC.

(3) Hakuoh University Ashikaga Junior High School, Tochigi Prefecture (June 6)
Dr. OTANI Masashi of the Accelerators Division delivered a lecture titled “How Accelerators Reveal the Microscopic World: Muon Acceleration Technology for Probing from Particle Phenomena to Massive Structures” at Hakuoh University Ashikaga Junior High School.
In the lecture, Dr. OTANI explained the principles of particle accelerators and their applications, including medical uses. He also introduced the properties of muons, methods of muon acceleration, and recent technological developments and research in particle physics using muon acceleration technology.
In addition, he presented an ongoing human resource development program for accelerator engineers through the construction of compact accelerators in collaboration with the National Institute of Technology (KOSEN).
According to the post-lecture questionnaire, students showed a strong interest in accelerator technology. Some commented that they would like to learn more about methods for controlling high voltages in multi-stage acceleration systems.

■Muographic Investigation of Ancient Burial Mounds in Tokai: Artifact Handling and Excavation Workshop (Tokai Village Museum, May 31)
The first activity of FY2026 was held on May 31. This project is now in its fourth year, and excavation of the surrounding moat will begin this year. In preparation for the excavation, museum curators Mr. NAKAIZUMI and Ms. HAYASHI gave a lecture on how to handle excavated artifacts, followed by an excavation workshop by Prof. TANAKA of Ibaraki University.
First, Mr. NAKAIZUMI and Ms. HAYASHI explained how to handle excavated artifacts. Ms. HAYASHI intentionally handled a replica pottery piece incorrectly by using one hand and wearing a wristwatch. The children were asked to find what was wrong and think about what should not be done during an actual excavation.
Next, participants observed real Jomon pottery and haniwa. After looking at the differences in their shapes and colors, they carefully touched the artifacts. They then practiced lifting them out of the box and placing them gently on the table. Everyone handled the artifacts carefully while remembering what they had learned.
In the second half of the program, Prof. TANAKA of Ibaraki University gave a talk titled "Archaeological Excavation Means Unearthing Everyone's Treasure." Participants learned about the importance of archaeological excavation and discussed what should be kept in mind during excavation work. The event ended with everyone chanting, "Muon ni Kofun!"

■J-PARC Sanpo-michi 71: - J-PARC Director Gives an Outreach Lecture at a Refreshing Highland Resort -
Urabandai in Fukushima Prefecture is one of Japan's leading resort areas, surrounded by volcanoes, forests, and lakes. J-PARC Director General Kobayashi, an enthusiastic sports lover, has visited the area dozens of times for skiing and hiking and has many friends in the local community. At their request, he gave an outreach lecture on May 30 at Sasakitei, a local bakery and cafe.
J-PARC frequently offers outreach lectures at schools, science museums, and similar venues, but this was the first time such an event had been held at a highland resort. Although there were initial concerns about attendance, the venue was filled to capacity on the day of the event.
The lecture took place in the spacious rear section of a log cabin-style building with a high ceiling. When the large windows were opened, a refreshing breeze flowed through the fresh green trees. In this warm and relaxed atmosphere, participants settled into their seats and listened with great interest to talks about the mysteries of the universe, the unique features of J-PARC, and its latest research achievements.
Located at an elevation of about 800 meters and far from any large cities, Urabandai offers excellent conditions for stargazing. Following the lecture, participants suggested holding a future event that would combine stargazing through telescopes with presentations on cutting-edge research, including neutrinos, to explore the mysteries of the universe. They also expressed interest in making these outreach lectures a regular series.

◆◇◆KPIP Nakameguro - Children's Program at Nakameguro Elementary School - (Saturday, July 4, 2026) ◆◇◆

A workshop titled "The World's Smallest? Make a Mysterious Spinning Top and Explore the World of Elementary Particles" was held at the Nakameguro Elementary School Children's Program for 13 students from first to sixth grade. The workshop was led by Dr. OTANI Masashi of the Accelerator Section, who introduced the world of elementary particles using spinning tops.
First, the children learned about J-PARC and elementary particles. They then spun gyroscopes and made their own spinning tops. By changing the center of gravity of their handmade tops, they observed changes in the direction of precession and learned that the motion of precession is similar to the spin property of elementary particles.

◆◇◆Yunago Elementary School, Hitachi City (Tuesday, July 7, 2026) ◆◇◆

Mr. ITABA Tatsunori of the Particle and Nuclear Physics Division delivered a lecture titled "What Is the Universe Made Of? - Light." The lecture was held at the request of the Hitachi Civic Center as a parent-child learning session for third-grade students at Yunago Elementary School. A total of 30 students and their parents participated.
The participants had fun learning about waves, quantum phenomena, and light together through questions such as, "What properties do waves have?" and "What colors does light have?" During quizzes about waves and light, the children actively shared their ideas, and there were moments when they expressed surprise as they confirmed the answers through experiments.
At the end of the session, the children also made kaleidoscopes using the properties of light, enjoying the craft activity while experiencing the wonders of light.

◆◇◆National Institute of Technology, Kagawa College, Takamatsu Campus (Wednesday, July 8, 2026) ◆◇◆

Dr. OTANI Masashi of the Accelerator Division gave a special lecture titled "How Accelerators Work to Explore the Microscopic World" at the Kagawa National Institute of Technology.
In the lecture, he introduced the basic principles of accelerators and examples of their applications, including medical applications. He also discussed the use of muons and the latest developments in accelerator technology and elementary particle research.
During the Q&A session, students asked a wide range of questions, from technical questions such as "How does J-PARC achieve one of the world's highest beam powers?" to career-related questions such as "What kind of work do graduates of technical colleges do at KEK?"

■Award
The 8th Achievement Award of the Materials Science and Technology Division, Atomic Energy Society of Japan
Dr. WAKAI Eiichi, a Research Fellow at the J-PARC Center, received the 8th Achievement Award of the Materials Science and Technology Division, Atomic Energy Society of Japan.
This award is presented to researchers who have made outstanding contributions and achievements in the field of nuclear materials science.
Dr. WAKAI led research activities as the first JAEA contact person for the J-PARC RaDIATE collaboration.

■Press Release
(1) Transparent Bulk Amorphous Alumina Produced under High Pressure
- An Ultra-Dense Structure Composed of Five- and Six-Coordinated Aluminum and a Dielectric Constant Exceeding That of Crystalline Sapphire - (April 7)
Aluminum oxide (alumina) is widely used in industry because of its durability and chemical stability. Amorphous alumina, in which atoms are arranged irregularly, is used as a coating material for products such as cooking utensils. However, alumina has long been known as an oxide that is difficult to produce in the form of bulk glass.
In this study, researchers successfully produced transparent bulk alumina glass by applying high pressure to an alumina film at room temperature. The resulting material showed high thermal conductivity and hardness. Its dielectric constant was approximately 11.3, exceeding that of sapphire, a crystalline form of alumina, which has a dielectric constant of about 10.
Structural analysis using neutron diffraction at the High-Intensity Total Diffractometer NOVA of the Materials and Life Science Experimental Facility (MLF) at J-PARC revealed that distorted five-coordinated aluminum polyhedra (AlO5) were the dominant structural units. The study also found that high pressure produced dense six-coordinated octahedra (AlO6), a structure not normally observed in amorphous materials.
This study demonstrates a new approach to controlling material structures under high pressure to achieve enhanced properties. The method combines structural calculations and advanced structural analysis techniques, opening new possibilities for materials discovery and development. Further accumulation of knowledge using this approach is expected to lead to the discovery and development of innovative materials.
For more details (in Japanese only), please visit the J-PARC website.
https://j-parc.jp/c/press-release/2026/04/07001776.html

(2) World's First Direct Observation of Muonic Molecules Driving Muon-Catalyzed Fusion - High-Resolution X-ray Spectroscopy Confirms Theoretical Model Experimentally - (April 16)
Nuclear fusion, currently under development for practical applications, requires the control of plasma under extremely high-temperature and high-density conditions. In contrast, muon-catalyzed fusion (μCF) is a phenomenon that can occur at room temperature without the need for plasma. In μCF, a negatively charged muon replaces an electron and binds with hydrogen isotopes such as deuterium to form a "muonic molecule." This brings the hydrogen nuclei extremely close together, allowing nuclear fusion to occur. After the reaction, the muon can be reused repeatedly as a catalyst until it decays naturally, with an average lifetime of about two millionths of a second.
However, the formation process of muonic molecules, which is key to understanding μCF, has remained unclear for many years because theoretical predictions did not agree with experimental results.
In this study, the joint research group introduced a superconducting transition-edge sensor (TES) microcalorimeter, which provides more than ten times higher energy resolution than conventional silicon detectors. Using this detector, the researchers successfully observed weak X-rays emitted from the resonant states of muonic molecules, which had been difficult to detect directly. The observed results agreed with theoretical predictions that take these resonant states into account, resolving the long-standing discrepancy between theory and experiment. The findings are expected to contribute to a deeper understanding of μCF and support future efforts to improve its efficiency.
For more details (in Japanese only), please visit the J-PARC website.
https://j-parc.jp/c/press-release/2026/04/16001781.html

(3) Development of a Next-Generation Solid-State Refrigerant Operating over a Wide Temperature Range
- Discovery of an Elastocaloric Effect Beyond Conventional Theoretical Scaling - (April 30)
Conventional cooling technologies used in air conditioners and refrigerators rely on the expansion and compression of refrigerant gases. As a result, they face challenges such as high energy consumption and greenhouse gas emissions. In recent years, next-generation cooling technologies based on solid materials have attracted increasing attention.
In this study, the research group conducted compression tests on a Ti-Al-Cr superelastic alloy developed in 2025. The alloy exhibited superelastic behavior over an extremely wide temperature range from -196℃ to +187℃, returning almost to its original shape after the applied force was removed.
Using SENJU, the Special Environment Single-Crystal Neutron Diffractometer at the Materials and Life Science Experimental Facility (MLF) of J-PARC, the researchers directly observed changes in the crystal structure of the alloy under applied stress.
They also confirmed that the material exhibited an endothermic reaction (cooling effect) when the applied force was removed over a wide temperature range from -171℃ to +129℃. In particular, a remarkable temperature drop of approximately 10℃ was observed near room temperature, demonstrating its potential as a practical cooling material.
The thermal and elastic properties revealed in this study were observed over a much wider temperature range than predicted by conventional theories, providing a new design concept for elastocaloric materials. The material is also expected to have a wide range of applications, including thermal control systems for space technologies and other fields requiring temperature management over broad temperature ranges.

■J-PARC Hello Science
Power Electronics for Accelerator Magnet Systems (April 21)
Dr. MORITA Yuichi from the Accelerator Division introduced efforts to improve the beam function of the Main Ring (MR), the largest accelerator at J-PARC.
In January 2026, the beam power of the MR reached 900 kW, far surpassing its original target of 750 kW. This increase in beam power was supported by newly developed magnet power supplies. To achieve a higher repetition rate by shortening the beam cycle and increasing the acceleration frequency, the entire system was reviewed and upgraded, including the development of a new capacitor bank and the reconfiguration of existing power supplies. Rather than outsourcing the work entirely to manufacturers, J-PARC staff played a central role in these developments. By directly participating in the development and improvement of the equipment, researchers and engineers have been able to perform adjustments and maintenance more flexibly and efficiently. These efforts have contributed not only to improved performance but also to cost reduction.
Currently, further upgrades are underway in preparation for the Hyper-Kamiokande project, which is scheduled to begin operation in FY2028. Efforts are being made to shorten the beam cycle from 1.28 seconds to 1.16 seconds and ultimately increase the beam power to 1.3 MW. These improvements are expected to lead to new scientific achievements.

■J-PARC Outreach Lecture
National Institute of Technology, Akita College (May 8)
Dr. OTANI Masashi of the Accelerator Division delivered a lecture titled "How Accelerators Reveal the Microscopic World: Muon Acceleration Technology for Probing from Particle Phenomena to Massive Structures" at the National Institute of Technology, Akita College.
During the lecture, Dr. OTANI explained the principles of particle accelerators and their applications, including medical uses. He also presented recent technological developments and research involving muons, his area of expertise, as well as particle physics research using muon acceleration technology.
In addition, he introduced an ongoing human resource development program for accelerator engineers through the construction of compact accelerators in collaboration with National Institute of Technology colleges, mainly the National Institute of Technology, Oyama College.
In a questionnaire conducted after the lecture, students shared comments on the research topics, such as "I thought the research using muons to investigate dark matter sounded interesting." Others also expressed interest in actually building accelerators, saying, "I would like to learn more about the accelerators being developed at National Institute of Technology colleges," and "I would like to know more about how to make electromagnets because I want to try building one myself."

■KEK Exhibits at Nico Nico Chokaigi 2026 (April 25-26)
KEK exhibited a booth titled "Super KEK" at Nico Nico Chokaigi 2026, held at Makuhari Messe in Chiba Prefecture. Nico Nico Chokaigi is a unique festival that brings together online and real-world communities and is centered around users of Nico Nico, one of Japan's largest video-sharing services operated by DWANGO Co., Ltd. This year's event attracted 138,228 visitors.
For its fourth participation in the event, KEK adopted "Nobel Prizes" as the theme of its exhibit. Highlights included an official replica of the Nobel Prize medal awarded to Prof. KOBAYASHI Makoto, KEK Distinguished Professor Emeritus, who received the Nobel Prize in Physics in 2008, as well as a timeline introducing Nobel Prize-winning research directly or indirectly connected to KEK. The booth also featured the Silicon Vertex Detector (SVD), which contributed to Nobel Prize-winning research in physics. Researchers at the booth explained accelerators and particle detectors to visitors.
In addition, a talk session was held featuring KEK Director General Dr. ASAI and members of the N High School Group Research Department. They discussed cutting-edge research being conducted at KEK and various approaches to scientific research activities.
The booth also featured an SNS campaign, a lottery linked to a Nobel Prize-themed quiz, and the distribution of special fans created in collaboration with Ibaraki Prefecture. The event provided an excellent opportunity for visitors to learn more about KEK and J-PARC.

■Announcement
Announcement of the "J-PARC and Nuclear Science Research Institute Open House 2026"
J-PARC and the Nuclear Science Research Institute will jointly host the "J-PARC and Nuclear Science Research Institute Open House 2026" on Sunday, September 13, from 9:30 a.m. to 4:00 p.m., under the theme of "See, Hear, and Experience Cutting-Edge Science!" Visitors will have the opportunity to tour accelerator and experimental facilities that are not normally accessible to the public.
A variety of activities will also be joined, including science cafes, hands-on science workshops, and food trucks, making the event enjoyable for both children and adults.
Admission is free and no reservation is required.* We look forward to welcoming you!
*Reservations will be required for some facilities.

■J-PARC Sanpo-michi 70: - J-PARC Shrouded in Sea Fog -
The photograph shows the MLF building as seen from the J-PARC Research Center building on May 8, when the fresh greenery of spring had become increasingly vibrant.
Although the building is only a few dozen meters away, it is almost completely hidden by dense sea fog. The day was unusually cool for May, and walking through the fog created a sense of calm tension.
Sea fog frequently occurs along the coast of Ibaraki from spring to early summer. Warm air is rapidly cooled when it comes into contact with the cold sea surface, causing excess moisture in the air to condense into fog. While sea fog creates beautiful and mysterious scenery, it can also disrupt transportation, including ship navigation, and may even cause agricultural damage due to reduced sunlight.
Sea fog contains a large amount of salt. The fog can penetrate buildings and accelerate corrosion of facilities and piping. For this reason, careful inspections for rust are carried out daily, and any problems found must be addressed promptly. The safe and stable operation of J-PARC, located close to the coast, is supported by these steady maintenance efforts.

◆◇◆Narusawa Elementary School, Hitachi City (Tuesday, June 2, 2026) ◆◇◆

Dr. KAMIYA Junichiro of the Accelerators Division delivered a lecture and experimental workshop titled "Let's Explore the Invisible World of Vacuum" at Narusawa Elementary School in Hitachi City.
Twenty-six fourth-grade students learned what happens to objects such as marshmallows and balloons in a vacuum through a series of experiments. The students watched with great interest as the marshmallows and balloons expanded when placed in a vacuum.
They also took part in various experiments, including the Magdeburg hemispheres experiment and an experiment demonstrating what happens to a feather and a coin when they fall inside a transparent vacuum tube.
Finally, through a vacuum cannon experiment, Dr. KAMIYA explained that vacuum plays an important role in accelerating particles at J-PARC.

◆◇◆Hakuoh University Ashikaga Junior High School, Tochigi Prefecture (Saturday, June 6, 2026) ◆◇◆

Dr. OTANI Masashi of the Accelerators Division delivered a lecture titled "How Accelerators Reveal the Microscopic World: Muon Acceleration Technology for Probing from Particle Phenomena to Massive Structures" at Hakuoh University Ashikaga Junior High School.
In the lecture, Dr. OTANI explained the principles of particle accelerators and their applications, including medical uses. He also introduced the properties of muons, methods of muon acceleration, and recent technological developments and research in particle physics using muon acceleration technology.
In addition, he presented an ongoing human resource development program for accelerator engineers through the construction of compact accelerators in collaboration with the National Institute of Technology (KOSEN).
According to the post-lecture questionnaire, students showed a strong interest in accelerator technology. Some commented that they would like to learn more about methods for controlling high voltages in multi-stage acceleration systems.

■Fire from a High-voltage Switchboard inside the J-PARC 50 GeV Substation
At approximately 7:00 a.m. on Tuesday April 7, a fire broke out from a high-voltage switchyard inside the J-PARC 50 GeV Substation. The fire was extinguished by the public fire department at around 7:47 a.m. There were no injuries or impact on the surrounding environment. The cause of this fire is currently under investigation.
We sincerely apologize for the inconvenience and trouble this incident may cause. We will make every effort to prevent a recurrence.

Takashi Kobayashi, Director of the J-PARC Center

For more information, please visit the J-PARC website.
https://j-parc.jp/c/en/information/2026/04/07001779.html

■Construction Site Tour of the Hyper-Kamiokande Intermediate Water Cherenkov Detector (IWCD) (April 2)
KEK held a press tour of the construction site for the Intermediate Water Cherenkov Detector (IWCD), a neutrino detector newly developed for experiments related to the Hyper-Kamiokande project.
For more details (in Japanese only), please visit the J-PARC website.
https://www.kek.jp/ja/topics/202604221400

■Award
Beam Physics Young Presentation Award 2025
Dr. ADACHI Kyosuke, a postdoctoral researcher of Accelerator Section II, received the Young Presentation Award 2025 at the 2025 Beam Physics Workshop and Young Researchers' Meeting for his presentation entitled "Optimization study of bunch lengthening with second harmonic RF voltage in J-PARC RCS." This award is presented to outstanding young researchers and students in the field of beam physics in order to encourage their research activities and support their independence and development as researchers and professionals.
Dr. ADACHI investigated a method for flattening the beam bunch shape by applying a radio-frequency voltage with twice the fundamental frequency during the final stage of acceleration in the accelerator. This approach successfully reduced beam loss and is expected to contribute significantly to realizing even higher-intensity beams at J-PARC.

■Press Release
(1) Corrosion-Resistant Structural Material with Self-Healing Ability in Flowing Lead-Bismuth Eutectic - A Step toward Realizing Accelerator-Driven Systems that Convert Nuclear Waste into Energy - (March 3)
Toward the realization of carbon neutrality by 2050, Accelerator-Driven Systems (ADS), which can provide zero-carbon electricity while effectively using high-level radioactive waste as an energy source, are attracting attention. However, ADS uses liquid lead-bismuth eutectic (LBE) as both a target material and a coolant, and LBE is corrosive to structural materials. Therefore, improving the reliability of structural materials under high-temperature and high-flow conditions is important for the practical use of ADS.
In this study, in collaboration with Institute of Science Tokyo, corrosion tests of FeCrAl alloy, one of the candidate structural materials for ADS, were carried out using the large non-isothermal high-temperature liquid metal flow loop "OLLOCHI" installed at JAEA.
The corrosion tests were conducted in flowing LBE for up to 4000 hours. As a result, it was confirmed that a multilayer oxide film formed on the surface of the FeCrAl alloy effectively suppressed corrosion during a 2000-hour test in flowing LBE at 723 K (450℃).
Furthermore, the study found that this multilayer oxide film has a self-healing function.
Even when part of the film was artificially damaged, it was spontaneously re-formed after an additional 2000-hour immersion in flowing LBE.
These results are expected to greatly improve the reliability of structural materials for the practical use of ADS, which aims to reduce the volume and toxicity of radioactive waste while supplying zero-carbon electricity at the same time. In the future, long-term functional evaluation tests considering the structure and function of in-reactor equipment will be conducted to establish material design guidelines and reliability-based lifetime prediction models under actual operating conditions.
For more details (in Japanese only), please visit the J-PARC website.
https://j-parc.jp/c/press-release/2026/03/03001762.html

(2) Balancing Both Coercivity and Magnetization - Toward Next-Generation Energy-Efficient Magnetic Memory with up to Tenfold Higher Coercivity - (March 18)
As power consumption continues to increase, next-generation magnetic memory with low standby power consumption is attracting attention. However, there has long been a trade-off relationship between coercivity, which is related to information stability, and magnetization, which is related to signal strength.
This study introduced a "nano-gradient design," in which the concentration of additive materials is continuously changed on the nanometer scale along the thickness direction of the film. As a result, the coercivity was improved by up to about ten times while maintaining high magnetization at room temperature. To clarify the mechanism of this performance enhancement, complementary analyses combining polarized neutron reflectometry using SHARAKU at the Materials and Life Science Experimental Facility (MLF) of J-PARC and synchrotron radiation analysis at NanoTerasu in Miyagi Prefecture were carried out.
This study demonstrates that properties previously considered difficult to achieve simultaneously can be improved together by utilizing magnetization enhancement inside the material. Such material design is expected to contribute to the development of next-generation magnetic memory with nearly zero standby power consumption and ultra-high-performance magnetic sensors.
For more details (in Japanese only), please visit the J-PARC website.
https://j-parc.jp/c/press-release/2026/03/18001766.html

(3) Successful Observation of Φ Mesons at J-PARC - A New Measurement Approaching the Origin of Mass in Matter - (March 23)
All matter is made of elementary particles called quarks. However, even if we add up the masses of all the quarks in our body, they cannot account for the total mass of the human body. This is because most of the mass of matter is thought to originate not from the particles themselves, but from the strong interaction between them. Theories concerning the "origin of mass" predict that the mass of the Φ meson, which consists of a quark and an antiquark, changes in high-density environments such as inside atomic nuclei. To study this effect, it is necessary to measure the decay of the Φ meson into an electron-positron pair, because the electron and positron can carry information out of the nucleus. However, this decay is very rare, occurring only once in several thousand events, which makes the measurement extremely challenging.
In this study, the research group directed one of the world's highest-intensity proton beams onto carbon and copper targets and precisely measured the emitted electron-positron pairs using the E16 spectrometer at the J-PARC Hadron Experimental Facility. As a result, the group succeeded for the first time in reconstructing Φ mesons using electron-positron pairs in the 30 GeV incident-energy region. Furthermore, the production yield of Φ mesons was found to be nearly proportional to the nuclear mass number. This result indicates that the mesons are not strongly absorbed inside nuclei.
This method enables information to pass through the "walls" of the nucleus and be carried outside. The establishment of this method is expected to contribute to future studies on the origin of mass.
For more details (in Japanese only), please visit the J-PARC website.
https://j-parc.jp/c/press-release/2026/03/23001769.html

■J-PARC Hello Science
Handling Technologies for Lead-Bismuth Eutectic toward the Realization of Accelerator-Driven Systems (March 19)
Dr. OBAYASHI Hironari of the Transmutation Division* introduced handling technologies for lead-bismuth eutectic (LBE), which is indispensable for the Accelerator-Driven System (ADS).
Spent nuclear fuel from nuclear power plants contains long-lived radionuclides that continue to emit radiation over long periods of time. ADS has attracted attention as a technology capable of converting these radionuclides into more stable and shorter-lived ones. In ADS, LBE plays an important role both as a coolant for removing generated heat and as a target material for producing neutrons. On the other hand, LBE presents several technical challenges because it easily corrodes metals, has strong surface tension, and exhibits flow characteristics different from those of ordinary liquids such as water.
At J-PARC, research toward the realization of ADS is being conducted while improving the understanding of the properties of LBE and addressing these technical challenges.
Participants asked many questions regarding LBE flow measurement technologies, corrosion control techniques, and areas in which Japanese technologies are superior compared with those overseas, reflecting the high level of interest in this field.
*Currently the Quantum Beam Technology Division.

■The 15^th Science Koshien National Tournament (March 20-23, Tsukuba International Congress Center and Tsukuba Capio)
The "Science Koshien" National Tournament, a nationwide science competition for high school students, where science-loving students from across Japan gather to compete and showcase their talents, was held at the Tsukuba International Congress Center and Tsukuba Capio. Approximately 400 high school students participated in the event.
With the aim of allowing students to enjoy and engage with science and technology in Ibaraki Prefecture, the Ibaraki Prefectural Government invited organizations to set up exhibition booths. On the afternoon of March 22, the third day of the competition, a total of 17 organizations, including the J-PARC Center, took part in the exhibition.
At the J-PARC Center booth, Dr. MUTO Ryotaro and Dr. CHIMURA Motoki presented exhibits, including a model of the accelerator, and provided explanations. High school students who visited the booth listened with great interest.

■J-PARC Sanpo-michi 69: - The Meaning of 36.4 Degrees -
36.4 degrees--what does this number bring to mind? For many people, it may be the average human body temperature.
The J-PARC neutrino experimental facility is located at latitude 36.4° north and longitude 140.6° east. Meanwhile, both the Super-Kamiokande detector and the newly constructed Hyper-Kamiokande detector are located at latitude 36.4° north and longitude 137.3° east. Although located about 295 kilometers apart, both detectors share the same latitude.
Neutrinos produced at J-PARC travel almost directly westward toward the enormous water tanks in Kamioka.
The line of latitude at 36.4° north crosses a remarkable range of landscapes across Japan. It stretches from the alluvial plains of Ibaraki Prefecture, passes through the Fossa Magna that divides the Japanese archipelago, and reaches the Hida region of Gifu Prefecture, home to some of Japan's oldest rocks. Along this line are diverse geographical features, including the Tone River, which has the largest drainage basin in Japan, the Shinano River, the country's longest river, Mount Asama, one of Japan's most active volcanoes, and the Hida Mountains, among the steepest mountain ranges in the country. As a result, the climate also changes dramatically along the same latitude--from the intensely hot northern Kanto Plain to the snow-covered Northern Alps and the heavy snowfall regions of Hida.
A new facility, the Intermediate Water Cherenkov Detector (IWCD), has now joined this unique 36.4° north latitude line. Located about one kilometer from J-PARC, IWCD is designed to precisely measure the properties of neutrinos immediately after they are produced. These measurements will improve the accuracy of neutrino oscillation observations at Hyper-Kamiokande.
Neutrinos are extremely small particles that rarely interact with matter. Yet humanity, with an average body temperature of around 36.4 degrees, is trying to understand the origins of the universe by studying the behavior of these mysterious particles. Research toward that goal is now accelerating.

◆◇◆National Institute of Technology, Akita College (Friday, May 8, 2026) ◆◇◆

Dr. OTANI Masashi of the Accelerator Division delivered a lecture titled "How Accelerators Reveal the Microscopic World: Muon Acceleration Technology for Probing from Particle Phenomena to Massive Structures" at the National Institute of Technology, Akita College.
During the lecture, Dr. OTANI explained the principles of particle accelerators and their applications, including medical uses. He also presented recent technological developments and research involving muons, his area of expertise, as well as particle physics research using muon acceleration technology.
In addition, he introduced an ongoing human resource development program for accelerator engineers through the construction of compact accelerators in collaboration with National Institute of Technology colleges, mainly the National Institute of Technology, Oyama College.
In a questionnaire conducted after the lecture, students shared comments on the research topics, such as "I thought the research using muons to investigate dark matter sounded interesting." Others also expressed interest in actually building accelerators, saying, "I would like to learn more about the accelerators being developed at National Institute of Technology colleges," and "I would like to know more about how to make electromagnets because I want to try building one myself."

◆◇◆Kanrin Japanese School, Aoba Ward, Yokohama City (Wednesday, May 27, 2026) ◆◇◆

Dr. KOMATSUBARA Takeshi from the J-PARC Center delivered a science experiment workshop at Kanrin Japanese School on the theme of a cloud chamber.
Second-year students participated in the workshop and built cloud chambers in groups. The students were fascinated as they carefully observed the fleeting tracks left by invisible particles.
Each time a white track appeared in the cloud chamber, excited voices could be heard in the classroom. The workshop not only helped the students deepen their understanding of the research conducted at J-PARC, but also provided a valuable opportunity to broaden their learning. Many students were seen actively communicating in Japanese while working together in groups.

◆◇◆Bakery Sasaki-tei, Kitashiobara Village, Yama District, Fukushima Prefecture (Saturday, May 30, 2026) ◆◇◆

Dr. KOBAYASHI Takashi, Director of the J-PARC Center, delivered an outreach lecture at Bakery Sasaki-tei in Urabandai, Fukushima Prefecture. In a warm and friendly atmosphere, Dr. KOBAYASHI provided an overview of J-PARC and its unique features, and introduced the mysteries of the universe.

     J-PARC Project Newsletter

                                No.102, April 2026
Japan Proton Accelerator Research Complex under joint operation by the
High Energy Accelerator Research Organization (KEK) and the Japan Atomic
Energy Agency (JAEA)
http://j-parc.jp/index-e.html
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HEADLINES AND CONTENTS

1. [Overview]
- STABLE OPERATION FROM LAST OCTOBER TO MARCH
- MR SUCCEEDED IN A 1 MW DEMONSTRATION OF FAST EXTRACTION FOR NEUTRINO BEAM, A BIG MILESTONE TOWARD HYPER-KAMIOKANDE EXPERIMENT
- TWO PROJECTS FROM J-PARC APPROVED UNDER THE SPACE STRATEGY FUND
- INTERNATIONAL ADVISORY COMMITTEE WAS HELD
❋ J-PARC has suspended operations since April 7 due to a fire that occurred at the 50 GeV substation. Further details will be provided in the next issue.

2. [Accelerator Division]
- OPERATION STATUS OF THE ACCELERATORS
- ACCELERATOR TECHNICAL ADVISORY COMMITTEE (A-TAC) MEETING WAS HELD
- THE RCS BEAM COMMISSIONING GROUP, REPRESENTED BY DR. PRANAB KUMAR SAHA, HAS WON THE SUWA PRIZE

3. [Particle and Nuclear Physics Division]
- PROGRAM ADVISORY COMMITTEE MEETING
- ACHIEVEMENT OF STABLE 900 kW HIGH-POWER OPERATION AT THE NEUTRINO EXPERIMENTAL FACILITY AND THE INTERNATIONAL ADVISORY COMMITTEE MEETING TOWARD THE HYPER-KAMIOKANDE PROJECT
- STATUS OF THE JSNS2 / JSNS2-II (SEARCH FOR STERILE NEUTRINOS AT J-PARC MLF, E56 / E82)
- MAJOR HONORS FOR KEK/J-PARC RESEARCH: SUWA PRIZE FOR TWO PIONEER LEADERS OF RARE K DECAY EXPERIMENTS AND AWARD-WINNING RESULTS FROM THE J-PARC E40 EXPERIMENT
- STATUS OF THE COMET EXPERIMENT
- STATUS OF THE MUON g-2/ELECTRIC DIPOLE MOMENT (EDM) (E34)

4. [Materials and Life Science Division]
- NEUTRON SOURCE, CONTINUATION OF STABLE BEAM OPERATION
- MLF ADVANCES TOWARD 2026A WITH NEW PROPOSAL CALL, ADVISORY REVIEWS, AND A SERIES OF KEY MEETINGS
- DR. SHINOHARA TAKENAO OF THE NEUTRON SCIENCE SECTION AND COLLEAGUES RECEIVE THE KOSHIBA AWRAD
- SYMPOSIUM AND WORKSHOP
- MUON SCIENCE FACILITY (MUSE), MAC WAS HELD

 5. [Nuclear Transmutation Division]
- THE TECHNICAL ADVISORY COMMITTEE (T-TAC) MEETING WAS HELD

 6. [Safety Division]
- 10TH SYMPOSIUM ON SAFETY IN ACCELERATOR FACILITIES

 7. [Outreach Activities]

 8. [Editorial Note]
PAST ISSUES ARE AVAILABLE FROM THE LINK BELOW.
http://j-parc.jp/c/en/topics/project-newsletter/index.html

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1. [Overview] by KOBAYASHI Takashi
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STABLE OPERATION FROM LAST OCTOBER TO MARCH
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J-PARC has maintained stable user operations from October through March for both accelerators and experimental facilities following the summer maintenance period. All major facilities delivered beams reliably, supporting a wide range of scientific programs. This steady performance reflects continued improvements in operational efficiency and coordination across the complex.

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MR SUCCEEDED IN A 1 MW DEMONSTRATION OF FAST EXTRACTION FOR NEUTRINO BEAM, A BIG MILESTONE TOWARD HYPER-KAMIOKANDE EXPERIMENT
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The Main Ring (MR) successfully demonstrated 1 MW beam power with fast extraction for the neutrino beamline. This achievement represents a significant milestone toward the realization of the Hyper-Kamiokande experiment. It confirms both the technical readiness and the stability required for future high-power neutrino operations.

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TWO PROJECTS FROM J-PARC APPROVED UNDER THE SPACE STRATEGY FUND
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Two proposals from J-PARC have been selected under Japan's Space Strategy Fund program. One project will establish a proton irradiation facility by branching the beam from the LINAC, while the other will construct a new proton beamline and irradiation facility in the hall of the Hadron Experimental Facility. Both projects aim to provide test environments for radiation-induced soft errors in semiconductors and electronic systems, supporting space and advanced technology applications.

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INTERNATIONAL ADVISORY COMMITTEE WAS HELD
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The International Advisory Committee (IAC) meeting was held this year in a fully remote format, similar to the arrangement adopted during the COVID-19 period. External experts reviewed J-PARC's recent progress and future plans, providing valuable feedback on scientific priorities, facility upgrades, and long-term strategy. Their recommendations will contribute to shaping the next phase of J-PARC development.

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2. [Accelerator Division] by YAMAMOTO Kazami
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OPERATION STATUS OF THE ACCELERATORS
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After the New Year's holiday, beam commissioning resumed on January 9 as part of Run #93, which began in October. The user program for the Materials and Life Science experimental Facility (MLF) restarted on January 15, followed by the Neutrino Facility (NU) on January 22nd. The user program for the Materials and Life Science experimental Facility (MLF) restarted on January 15th, followed by the Neutrino Facility (NU) on January 22.The beam power was approximately 700 kW for the MLF and 900 kW for the NU. User operations at both facilities proceeded smoothly and are scheduled to continue until March 25. After the completion of the user run, maintenance work will be carried out on the accelerators. In addition, MR successfully demonstrated a 1 MW beam acceleration for NU.

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ACCELERATOR TECHNICAL ADVISORY COMMITTEE (A-TAC) MEETING WAS HELD
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The 25th A TAC meeting (https://j-parc.jp/c/en/forum-and-committee/a-tac-e.html) was held from February 12 to 14 in a hybrid format, with most members participating on-site. (Seven of the nine committee members attended in person.) The main topics of discussion were the accelerator status and the responses to previous recommendations. The committee also noted J PARC's steady progress, including high power MR operation, while emphasizing the need to strengthen engineering resources and enhance cross divisional collaboration to support future reliability and upgrades.

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THE RCS BEAM COMMISSIONING GROUP, REPRESENTED BY DR. PRANAB KUMAR SAHA, HAS WON THE SUWA PRIZE
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The RCS Beam Commissioning Group, represented by Dr. SAHA Pranab Kumar, has been awarded the Suwa Prize by the Foundation for High Energy Accelerator Science (FAS). The award recognizes the group's significant contributions to the stable operation of the J-PARC RCS. Through rigorous beam simulations and systematic experiments, the group successfully minimized beam emittance and beam losses during the 1 MW operation of the MLF, thereby significantly increasing the beam power in the Main Ring. These achievements were published in Physical Review Accelerators and Beams (selected as an Editors' Suggestion) and have garnered international recognition.
https://www.j-parc.jp/c/en/topics/2026/03/11001783.html

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3. [Particle and Nuclear Physics Division]
…-------------------------------------------------------------------------------------------------★

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PROGRAM ADVISORY COMMITTEE MEETING (by NAKADAIRA Takeshi)
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The 41st Program Advisory Committee (PAC) meeting was held on January 21-23, 2026. Updates were provided on the status of J-PARC accelerator operations following the summer maintenance in 2025, prospects for Main Ring (MR) beam power improvements, and the status of experiments along with plans for operations leading up to summer 2026. A summary of experimental proposals for the coming years was also presented.

This time, one proposal was submitted.
Details can be found at the following link:
https://kds.kek.jp/event/58237/

The PAC report will be available on the following webpage:
https://j-parc.jp/researcher/Hadron/en/PAC_for_NuclPart_e.html

The next PAC meeting is scheduled to be held in July 2026.

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ACHIEVEMENT OF STABLE 900 kW HIGH-POWER OPERATION AT THE NEUTRINO EXPERIMENTAL FACILITY AND THE INTERNATIONAL ADVISORY COMMITTEE MEETING TOWARD THE HYPER-KAMIOKANDE PROJECT (by ISHIDA Taku)
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The Neutrino Experimental Facility had been operating at 750 kW until December 2025. In January 2026, the repetition cycle was shortened from 1.36 s to 1.28 s, enabling higher repetition-rate operation. As a result, acceleration of 2.4 × 10¹⁴ protons per pulse--representing a world record for a synchrotron--enabled operation at 900 kW, which is the upper limit acceptable for the current target system. From late November 2025 to March 2026, the beamline achieved an operational availability of 85%, providing highly stable data acquisition. This achievement represents an important step toward long-term stable operation at the MW-class level and contributes to strengthening the foundation for the realization of the Hyper-Kamiokande project, scheduled to start in JFY2028.
Upgrades to the beamline system required for 1.3 MW operation--including improvements to remote maintenance in the final focusing magnet section, the target and its cooling system, and the secondary beamline cooling water system--are scheduled for summer 2026.
To discuss the validity of these upgrade plans and technical challenges toward MW-class beam operation, such as optimization of replacement cycles for the target and beam window, an International Advisory Committee meeting was held on February 16-17, 2026. During the meeting, valuable comments were provided by committee members with extensive experience in the operation of high-power target facilities worldwide.

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STATUS OF THE JSNS2 / JSNS2-II (SEARCH FOR STERILE NEUTRINOS AT J-PARC MLF, E56 / E82) (by MARUYAMA Takasumi)
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The JSNS2 (E56) / JSNS2-II (E82) collaboration investigates the anomaly reported by the LSND experiment, namely the observed excess of electron antineutrinos, through a direct measurement at the J-PARC Materials and Life Science Experimental Facility (MLF).
Data taking with both the near detector, located on the third floor of the MLF, and the far detector, installed outside the MLF building, has been ongoing since November 2025. As of 12 March 2026, new physics data corresponding to 9.088×10²¹ Proton-On-Target (POT) have been accumulated for the near detector. This already corresponds to approximately 19% of the total data accumulated between 2021 and 2024. The current run is scheduled to continue until June 2026.
In parallel with the ongoing data-taking efforts, we have also presented and published the first results of our studies based on data collected in 2022 (http://arxiv.org/abs/2602.06274). The new far detector is currently in the commissioning phase. Analysis of the beam commissioning data indicates that the rate of beam-induced neutrons is higher than expected. To mitigate this issue, effective passive shielding is being investigated through various measurements.

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MAJOR HONORS FOR KEK/J-PARC RESEARCH: SUWA PRIZE FOR TWO PIONEER LEADERS OF RARE K DECAY EXPERIMENTS AND AWARD-WINNING RESULTS FROM THE J-PARC E40 EXPERIMENT (by NOMURA Tadashi and TAKAHASHI Hitoshi)
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Researchers and experiments at KEK and J-PARC have recently received significant recognition from the scientific community for their contributions to particle and nuclear physics. Two pioneer leaders of rare kaon decay experiments were awarded the 2025 Suwa Prize, honoring their long-standing leadership and groundbreaking work in the field. In addition, the J-PARC E40 experiment was honored with the 31st Outstanding Paper Award from the Physical Society of Japan, recognizing the impact of its published results. Together, these achievements highlight the continued global influence of KEK and J-PARC in advancing our understanding of fundamental particles and interactions.
The KOTO experiment at the Hadron Experimental Facility is the world-leading experiment dedicated to searching for the CP-violating rare kaon decay, where a long-lived neutral kaon decays to a neutral pion and a neutrino-antineutrino pair. Although the decay mode is attractive because the theoretical uncertainty of the branching ratio is small, and thus it can be a good probe to study physics beyond the Standard Model, realization of the experiment had been thought to be extremely difficult. However, two pioneer leaders and their experimental teams have successfully realized it.
The first dedicated experiment to search for the KL→π0νν decay was conducted at KEK 12 GeV proton synchrotron by KEK E391a group in the early 2000s, led by Professor Takao Inagaki (KEK). He brought unique ideas for the experiment, such as a thin neutral beam, a hermetic veto system that ensures no extra particle other than two photons from π0 decay, and a differential pumping scheme that enables a clean vacuum at a level of 1e-5 Pa separated by a thin film from a low vacuum region (～0.1 Pa) for the detectors.
Its successor is the KOTO experiment, led by Professor Taku Yamanaka (University of Osaka), utilizing the high intensity proton beam at J-PARC. He has been a world leader of kaon physics through the KTeV experiment at Fermi National Laboratory in the U.S. and introduced the high-resolution electromagnetic calorimeter based on ~2700 undoped CsI crystals used in KTeV to KOTO. Under his leadership, KOTO achieved the world-best sensitivity of the search, which corresponds to more than an order of magnitude improvement of the world record.
In recognition of the establishment of an innovative experimental method to study the KL→π0νν decay and long-term contributions to the new physics search, professors emeritus T. Inagaki and T. Yamanaka received Suwa Prize of the year 2025 (by Foundation for High Energy Accelerator Science). The awards ceremony was held on February 27, 2026.
KOTO continues accumulating data for several years toward another order of magnitude improvement, seeking a signature of new physics.
A paper published by the J-PARC E40 experiment has received the 31st Outstanding Paper Award of the Physical Society of Japan.
The E40 experiment was conducted at the K1.8 beamline of the Hadron Experimental Facility with the aim of performing high-statistic measurements of hyperon-nucleon scattering.
The award-winning paper reports the measurement results for the differential cross section of elastic scattering between Sigma+ hyperons and protons with a statistical precision 100 times greater than that of previous experiments.
Through phase analysis, it derived the magnitude of the repulsive force between the two particles for the first time in the world, representing a highly significant achievement in elucidating the origin of the repulsive core of the nuclear force.
See the paper: T. Nanamura et al, "Measurement of differential cross sections for Sigma+p elastic scattering in the momentum range 0.44-0.80 GeV/c," Prog. Theor. Exp. Phys. 2022, 093D01. https://doi.org/10.1093/ptep/ptac101

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STATUS OF THE COMET EXPERIMENT (by FUKAO Yoshinori)
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Construction of the COMET experiment, which aims to search for muon-to-electron conversion with a Phase-I sensitivity of 10^-14 or better, is underway.
Installation of the detector solenoid magnet (DS) and the bridge solenoid (BS) was successfully completed last December, thanks to the great efforts of the J-PARC cryogenic section. With their completion, all superconducting magnets for COMET Phase-I are now present in the experimental hall. The DS and BS, as well as the muon transport solenoid (MTS), have been cooled down as expected, and their commissioning to reach the designed operating current is in progress. This series of activities will be followed by a campaign of magnetic field measurements inside the DS, which is one of the important milestones toward the physics measurements. Detector assembly and operation tests are also being continuously carried out at J-PARC in preparation for installation into the DS later this year.
The 48th collaboration meeting was held at Yokohama National University (YNU) in March. The experimental status and technical issues were presented and discussed in order to accomplish the construction in an optimized configuration. An impressive discussion on theoretical aspects was also held since one of the theory groups in the COMET collaboration is affiliated with YNU.

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STATUS OF THE MUON g-2/ELECTRIC DIPOLE MOMENT (EDM) (E34) (by MIBE Tsutomu)
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The E34 collaboration aims for precision measurements of the muon anomalous magnetic moment and its electric dipole moment.
The collaboration carried out the commissioning of the surface muon beam in the MLF H line. Silicon strip detectors, which will be used as positron tracking detectors, were installed in the muonium hyperfine structure measurement experiment (MuSEUM), and data acquisition of positrons from muon decay was performed for its evaluation. In November, tests and performance evaluations of the Ultra-slow muon Diagnostic Line (UDL) were carried out in the S2 area, confirming its basic performance. In December, the system was moved to the H2 area. In parallel, the group prepared the laser system for muonium ionization using a Lyman-α laser. By the end of December, the collaboration had successfully generated, ionized, and extracted muonium in the H2 area. Since then, the muon source has been reconfigured so that it can be connected to the RF accelerating cavity. In parallel, preparations for the operation of the RFQ accelerating cavities are underway. In the future, we plan to test the ultra-cold muon source and to demonstrate RF acceleration up to an energy of 0.3 MeV in the 2026A period. A research group from INFN (Italy) and Osaka Metropolitan University has newly joined the collaboration.

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4. [Materials and Life Science Division]
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NEUTRON SOURCE, CONTINUATION OF STABLE BEAM OPERATION (by HARADA Masahide)
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Beam operation at the MLF resumed at 780 kW on October 30, 2025. The beam power was adjusted to 710 kW on November 27 due to a change in the MR accelerator mode. Although issues occurred in the cooling water system and the cryogenic system of the neutron source during the beam operation, they were resolved through several measures. As of the end of March 2026, the beam operation has continued, following a brief shutdown over the New Year holiday period. The neutron source has maintained excellent operational stability, achieving a facility availability of over 92%.
Finally, from January 26 to 29, 2026, a joint workshop on neutron sources was held at J-PARC with the Spallation Neutron Source (SNS) group of Oak Ridge National Laboratory (ORNL). In-depth discussions were conducted on operational status, technical issues, research and development activities, and future research collaboration related to the neutron source.

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MLF ADVANCES TOWARD 2026A WITH NEW PROPOSAL CALL, ADVISORY REVIEWS, AND A SERIES OF KEY MEETINGS (by NAKAMURA Mitsutaka)
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The call for neutron general proposals for the 2026A cycle has opened. The general proposal category covers short-term experimental assignments, including one year proposals. A total of 324 applications were submitted for neutron experiments alone, which is almost the same as the average in recent cycles. In the 2025B term, the MLF call was open only to domestic users, as the available beam time was quite limited. Proposals originating from overseas accounted for 54% of the total, which was roughly the same proportion as in 2025A. All programs were reviewed at the MLF Advisory Board on March 10.

Report on Meetings and Other Events:
• Neutron Advisory Committee (NAC), February 16-18
https://kds.kek.jp/event/58692/

Reports were presented on the development status of neutron beamlines, detectors, and sample environments, as well as on industrial applications. Committee members provided advice on data utilization and on the roadmap for future progress.

Recent press release from Neutron Science at MLF:
BL15 and BL18 on Feb. 27 "Multiscale Insights into Sodium Storage in Hard Carbon from Operando Small- and Wide-Angle Neutron Scattering Measurements"
https://doi.org/10.1038/s41586-025-09633-4
BL21 on Feb. 17 "Superprotonic Conduction in Donor Co-Doped Perovskites"
https://doi.org/10.1002/anie.202521773
BL21 and S1 on Jan. 19 "Frustrated random-singlet state with ice-type structural fluctuation in spinel titanates"
https://doi.org/10.1073/pnas.2517926123

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DR. SHINOHARA TAKENAO OF THE NEUTRON SCIENCE SECTION AND COLLEAGUES RECEIVE THE KOSHIBA AWRAD (by NAKAMURA Mitsutaka)
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Dr. SHINOHARA Takenao (J-PARC MLF) and Dr. KATO Satoru and colleagues (Toyota Central R&D Labs., Inc.) received the FY2025 Koshiba Award for "Establishment of multiphase transport visualization methods using energy-selective neutron imaging". They developed an advanced neutron imaging technique to distinguish and visualize water and ice inside operating fuel cells at sub-zero temperatures at BL22 RADEN.
https://www.j-parc.jp/c/en/topics/2026/03/11001784.html

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SYMPOSIUM AND WORKSHOP
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• FY2025 Quantum Beam Science Festa (QBSF) and 17th MLF Symposium, March 12-13 in Mito
At the MLF Symposium held on March 13, facility reports, presentations on recent achievements, and the general meeting of the J-PARC MLF Users Society took place.
• 2nd MLF Roadmap Workshop, March 14 in Mito
Group discussions were conducted across a wide range of scientific and technical fields.

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MUON SCIENCE FACILITY (MUSE), MAC WAS HELD（by KAWAMURA Naritoshi)
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Beam operation is proceeding smoothly following the scheduled shutdown over the New Year's holiday period.
In the Muon Science Proposal Review Committee (MSPRC) meeting, 46 proposals submitted for the 2026A period, including 5 KEK IMSS S2-type proposals, were reviewed, resulting in 38 approved and 8 reserved.
The Muon Advisory Committee (MAC) meeting was held from January 26 to 27, chaired by Prof. Klaus Kirch of the Paul Scherrer Institute (PSI): https://kds.kek.jp/event/57889/.
The facility staff reported the progress in the target system and each beamline. In addition, during the session on prospects for the MLF, discussions were held regarding the MLF-double project, which aims to maximize the results of the current first target station and the second target station (MLF-TS2) project. After two days of thorough discussion, the committee provided us with valuable recommendations. Based on these recommendations, we will strive to ensure stable operations next fiscal year and advance the plans.
Dr. UMEGAKI Izumi received the 2026 Fumiko Yonezawa Memorial Award of the Physical Society of Japan for her work on "Application of muon beam to Li-ion battery research":
https://www.jps.or.jp/english/meetings-and-awards/awards/yonezawa/yonezawa7-2026e.html.

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5. [Nuclear Transmutation Division] by MAEKAWA Fujio
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THE TECHNICAL ADVISORY COMMITTEE (T-TAC) MEETING WAS HELD
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The 11th TEF (Transmutation Experimental Facility) Technical Advisory Committee (T-TAC) meeting was held at the J-PARC Research Building on February 2-3, 2026. Three foreign and two Japanese committee members gathered to review the current progress of planning the Proton Beam Irradiation Facility, an advanced concept of TEF, and related research and development (R&D) studies. At the meeting, after an overview of J-PARC, division staff introduced their activities in two sessions: the facility design update session and the R&D activities session. On the second day, the meeting concluded with a summary talk by the chair, followed by a site tour.
On February 24, 2026, we received the final T-TAC report, which included 27 observations, 28 comments, and a general conclusion. T-TAC provided positive statements such as, "In its current form, the project demonstrates the capacity to deliver tangible impact in the short term while preserving the flexibility required to accommodate longer-term developments."
https://j-parc.jp/c/en/forum-and-committee/t-tac-e.html

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6. [Safety Division] by BESSHO Kotaro, KASUGAI Yoshimi
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10TH SYMPOSIUM ON SAFETY IN ACCELERATOR FACILITIES
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The 10th Symposium on Safety in Accelerator Facilities was held on January 29 at the Tokai-mura Industry and Information Plaza (iVil) with 71 participants in a face-to-face format. The topics of the workshop were the current status and challenges in online education for radiation safety and heatstroke prevention measures at accelerator facilities. Seven accelerator facilities introduced their circumstances and approaches to address these issues. In addition, 14 posters highlighting various safety initiatives were displayed, and the coffee break provided an opportunity for information exchange and networking. It is expected that the information shared will be effectively utilized to improve safety at each facility.

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7. [Outreach Activities]
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★ Outreach Lecture at the National Institute of Technology, Ibaraki College (December 24)
https://www.j-parc.jp/c/en/topics/2026/02/27001761.html

★ Outreach Lecture at Yokoshibahikari Town Community Center, Sambu District, Chiba Prefecture (January 17)
https://www.j-parc.jp/c/en/topics/2026/02/03001732.html

★ Outreach Lecture at Muramatsu Elementary School, Tokai Village (January 27)
https://www.j-parc.jp/c/en/topics/2026/02/03001732.html

★ Outreach Lecture at Nagi Junior High School, Nagi Town, Okayama Prefecture (February 6)
https://www.j-parc.jp/c/en/topics/2026/02/10001733.html

★ Kojima Children's Science Park (February 21)
https://www.j-parc.jp/c/en/topics/2026/04/27001796.html

★ Outreach Lecture at Ishigami Elementary School (February 26)
https://www.j-parc.jp/c/en/topics/2026/04/17001785.html

★ Sakurie Science Festival (March 14)
https://www.j-parc.jp/c/en/topics/2026/04/27001796.html

★ Muographic Investigation of Ancient Burial Mounds in Tokai: Summary of Activities in 2025 (March 15)
https://www.j-parc.jp/c/en/topics/2026/04/27001796.html

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8. [Editorial Note]
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  Past issues are available from the link below.
  http://j-parc.jp/c/en/topics/project-newsletter/index.html

┏----…----…----…----…----…----…----…----…----…----…----…----…☆
┃ Editorial Board:
┃ OGURI Hidetomo (Chair) : oguri.hidetomo[at]jaea.go.jp
┃ SHOBUDA Yoshihiro: yoshihiro.shobuda[at]j-parc.jp
┃ OZAWA Kyoichiro: ozawa[at]post.kek.jp
┃ MARUSAWA Machiko: machiko[at]post.kek.jp
┃ Bruce YEE-RENDON: byee[at]post.j-parc.jp
┃ OGAWA China (Secretary) : ogawa.china[at]jaea.go.jp
┃ * Please replace "(at)" with "@" when you enter an email address.
★----…----…----…----…End of Letter…----…----…----…----…----

■Award
Awarded the 15th High Energy Accelerator Science Research Encouragement Awards: Koshiba Award and Suwa Award (February 27)
Researchers including Dr. SHINOHARA Takenao from the Neutron Science Section were awarded the Koshiba Award, and researchers including Dr. SAHA Pranab Kumar from the Accelerator Division were awarded the Suwa Award.
For more details, please visit the J-PARC website.
(1) Koshiba Award https://www.j-parc.jp/c/en/topics/2026/03/11001784.html
(2) Suwa Awrad https://www.j-parc.jp/c/en/topics/2026/03/11001783.html

■Press Release
(1) Significant Improvement in Proton Conductivity at Intermediate Temperatures by Co-doping with Two Elements - Achieving both higher conductivity than existing materials and high chemical stability - (February 17)
In a hydrogen energy society, which is key to a carbon-neutral future, protonic ceramic fuel cells (PCFCs) and protonic ceramic electrolysis cells (PCECs), which operate at intermediate temperatures of 220-400℃, are attracting attention as next-generation technologies. These devices can efficiently convert hydrogen into electricity. However, it has been difficult to find materials with both high proton conductivity and good chemical stability at these temperatures.
In this study, a new material design called "donor co-doping" was applied to an oxygen-deficient perovskite oxide, BaScO_2.5. By adding two donor elements, molybdenum (Mo) and tungsten (W), a new ceramic material, BaSc_0.8Mo_0.1W_0.1O_2.8, was discovered. This material exhibits world-leading proton conductivity at intermediate temperatures, along with high chemical stability. Neutron diffraction analysis using the high-intensity total scattering instrument "NOVA" at the Materials and Life Science Experimental Facility (MLF), together with first-principles molecular dynamics calculations, revealed that this material has a high proton diffusion coefficient. In addition, donor co-doping does not cause an increase in the activation energy (proton trapping), which is a problem in conventional acceptor co-doping, and it can maintain a low activation energy.
The proton-conducting material discovered in this study is expected to contribute to distributed energy systems that integrate hydrogen production, storage, and utilization. It is also suitable for long-term operation under practical conditions. In the future, PCFCs and PCECs using this material as an electrolyte will be developed and evaluated, with the aim of achieving lower operating temperatures and higher performance.
For more details (in Japanese only), please visit the J-PARC website.
https://j-parc.jp/c/press-release/2026/02/17001747.html

(2) First Direct Observation of the Charging Mechanism in Next-Generation Sodium-Ion Batteries - Revealing the mystery of hard carbon through multi-scale observation using neutron scattering - (February 27)
Sodium-ion batteries (NIBs), which are low-cost and sustainable alternatives to lithium-ion batteries, are attracting attention. For their wider use, it has been important to understand how sodium is stored in hard carbon, a material used for the negative electrode--specifically, where it accumulates and in what order.
In this study, the neutron small- and wide-angle scattering instrument "TAIKAN" at the MLF was used to observe how sodium moves inside the battery during charging. The behavior was observed simultaneously across multiple scales, from the mesoscale (less than about one-thousandth of a millimeter) to the atomic scale (about one ten-millionth of a millimeter). The results showed that sodium is stored in three steps: adsorption on the surface, insertion between layers, and filling nanoscale pores. In addition, theoretical calculations supported that the structural changes in the carbon layers observed in the experiment are reasonable.
This study clearly revealed the sodium storage process in hard carbon through multi-scale observations. These findings provide useful guidelines for designing sodium-ion batteries and are expected to accelerate the development of low-cost and sustainable energy storage systems that do not rely on lithium, as well as long-life and highly reliable next-generation batteries.
For more details (in Japanese only), please visit the J-PARC website.
https://j-parc.jp/c/press-release/2026/02/27001759.html

■International Advisory Committee (IAC 2026) Held Online (March 9, 10, and 17 at J-PARC)
The IAC was established under the "Fundamental Collaboration Agreement Regarding the Management of High-Intensity Proton Accelerator Facilities" and serves as a committee in which domestic and international experts deliberate on important matters concerning the operation, user access, and facility development of J-PARC. The committee, consisting of 16 members (12 from abroad and 4 from Japan), which is led by the Chair (Science & Technology Facilities Council, UK), submitted recommendations regarding J-PARC's management, operations, and R&D activities for fiscal year 2025. While J-PARC possesses technical superiority, structural challenges such as financial constraints, human resource issues, and aging infrastructure have become apparent, raising questions about the facility's sustainability.
The J-PARC Center takes these recommendations seriously and will work to improve its future management, operations, and business activities.

■Quantum Beam Science Festa 2025 Held (March 11-13, Mito City Civic Center)
The 17th MLF Symposium and the 43rd PF Symposium, known as the Quantum Beam Science Festa (QBSF), provide a place for researchers to connect across different probes, including synchrotron radiation, neutrons, muons, and positrons, at the Photon Factory (PF) of KEK and the MLF of J-PARC. The event is held alternately in Tsukuba and Mito each year, and 607 participants registered this year.
At QBSF, the PF Symposium was held on the first day, followed by keynote lectures, poster presentations, and parallel sessions on the second day, and the MLF Symposium on the third day. A total of 227 posters were presented, including 63 entries for the Student Encouragement Award. Three MLF users received awards, and the award ceremony was held during a reception attended by more than 150 participants.
At the MLF Symposium, research results from MLF were mainly presented. In addition, future plans were discussed at the 2nd Roadmap Workshop, a satellite event held on the following day.

■J-PARC Hello Science
Next-Generation Radiography Using Neutrons (February 27)
Dr. TSUCHIKAWA Yusuke of the Materials and Life Science Division introduced "neutron imaging," a technique used to observe the inside of objects using neutrons. One of the major features of neutron imaging is its capability to perform non-destructive measurements, which is difficult to achieve with X-rays. For example, it allows us to observe the movement of water inside metal containers. It can also reveal what elements are inside an object, in what state, and how much is contained. By taking many images while rotating the sample little by little, it is possible to reconstruct the internal structure in three dimensions.
At the MLF of J-PARC, pulsed neutrons are generated every 0.04 seconds. By measuring the arrival time of neutrons that have passed through the sample at a two-dimensional detector, it is possible to analyze the energy spectrum of neutrons at each pixel with very high accuracy. The results obtained at MLF are used in many fields, such as decommissioning research through investigations of reactor structures, non-destructive elemental analysis of cultural properties, and research on battery materials and new functional materials.

■Sakurie Science Festival (March 14, Hitachi Civic Center Science Museum)
At the science festival, the J-PARC Center held workshops on hadron accessories and cloud chambers, and demonstrations and hands-on activities of a superconducting coaster. The hadron accessory workshop was very popular, and queue tickets for each session were quickly taken. In the cloud chamber workshop, all participants were able to observe the tracks of radiation.
During the superconducting coaster demonstration, many children listened carefully to explanations about extremely low temperatures and superconductivity. At the hands-on booth, many people from children to adults enjoyed running the coaster and trying simple experiments to learn about the properties of superconductors.
They also experienced unique experiments using liquid nitrogen, such as making a light bulb glow brighter by cooling a wire, and changing the color of an orange LED to green when cooled with liquid nitrogen, which was unveiled for the first time at this event.

■J-PARC Outreach Lecture
(1) Kojima Children's Science Park, Tochigi Prefecture (February 21)
Superconducting coaster workshops have previously been held at various locations. Following one such event, Kojima Children's Science Park asked us to hold an experiment class for elementary and junior high school students at the Kurashi Lounge. This museum was renewed in October last year. It has many hands-on exhibits, and it is a popular place with about 4,000 to 5,000 visitors on weekends.
Dr. SASAKI Kenichi from the Cryogenics Section was the instructor. He held two classes, one in the morning and one in the afternoon. The class included quizzes such as "What happens when we cool a balloon or a rubber ball with liquid nitrogen?" Participants experienced a superconducting coaster and closely observed that a magnet ring rolls down more slowly when it passes next to a cooled copper plate.

(2) Ishigami Elementary School (Thursday, February 26, 2026)
The MLF Outreach Group "Protons" delivered a special outreach class for approximately 30 fourth-grade students. This class was conducted as a joint program with the Tokai Village Museum.
The lesson focused on the theme, "The first step in research is careful observation," and included two activities: "Let's Observe Daphnia, the Masters of Swimming!" and "Dissecting Dried Sardines."
In fourth-grade science, students study the structure of the human body in the unit "Our Body and Movement." In this class, students observed the movements of Daphnia using microscopes and examined the anatomical features of dried sardines using magnifying glasses. Through these hands-on activities, they learned about "life" by exploring the structure of living organisms. Many students actively asked questions, making the class highly engaging and meaningful.
This outreach lecture was supported in part by the KEK Mirai Fund program, "Sowing the Seeds of Science for the Next Generation from J-PARC."
For more details (in Japanese only), please visit the J-PARC website.
https://www2.kek.jp/kff/

■Muographic Investigation of Ancient Burial Mounds in Tokai: Summary of Activities in 2025 (Tokai Village Museum, March 15)
The final activity of FY2025 was held with 19 participants on March 15. First, Dr. FUJII from J-PARC gave a lecture titled "Can you find the Nobel Prize peak?" Participants looked at data from the 2012 LHC experiment, where the Higgs boson was discovered, and worked in groups to identify which peak corresponded to the Higgs boson. Through this activity, they learned that "peaks have meaning."
After that, Mr. KUZUBA from Ibaraki University reported on the analysis of data from the first detector measurement device installed at the Detector for History and Future No. 2 on October 13, 2024. Participants also worked in groups to examine the data and discussed possible locations of cavities (stone chambers). As a result of the analysis, three possible cavity areas were identified at this stage.
While measurements with the first detector continue, the second detector was installed on November 16, 2025, and the data has been steadily collected. The second detector device observes from a direction almost perpendicular to the first one, so analyzing this data may help identify the exact locations of the cavities.
The Muographic Investigation of Ancient Burial Mounds in Tokai will continue its activities next year. Updates will be shared as further analysis results of the burial mound have become available.

■J-PARC Sanpo-michi 68: 15 Years of Recovery and Progress
Visitors who come to J-PARC for the first time often say that it looks like a huge factory. In fact, the facilities are built with extremely high precision. The position of beamline components is controlled within 0.1 mm. For example, to keep the 330 m-long linac tunnel straight, its center must be about 2 mm lower than both ends, assuming they are at the same elevation. This is because the Earth is round, and a completely level structure would not be straight.
During the Great East Japan Earthquake 15 years ago, Tokai Village was hit by strong shaking (seismic intensity 6−), and J-PARC was seriously damaged. In the linac tunnel, more than 10 cm of groundwater collected, reaching about 100 tons in total. Inside the tunnel, there was no power, and the water was strongly alkaline (pH 11). It was treated with sulfuric acid and then removed in very humid conditions. Another major challenge was restoring the beam path. Due to the strong shaking, the tunnel was deformed, and in some places the linac subsided by up to 43 mm compared to before the earthquake. Such large deformation made it difficult to realign the magnets and restore a straight beamline. Instead, a new beam path with a slight bend was introduced to follow the deformation of the floor. As a result, the linac successfully resumed beam operation on December 9, eight months after the earthquake.
Even today, the proton beam path in the linac remains slightly V-shaped. However, the beam power at MLF has increased from 200 kW before the earthquake to 1,000 kW today.