A beam-accelerating rf cavity with an ultra-compact HOM-damping structure was developed to mitigate coupled-bunch instabilities in electron storage rings. This cavity operates in the TM020 mode, characterized by a high Q-value and a high shunt impedance. The new HOM-damping mechanism leverages the unique field distributions of the TM020 mode, allowing direct embedding of rf absorbing materials into the cavity body. This paper shows an original point of view for the innovative damping and details the insights that led to this novel structure undergone validation through rf simulations and measurements using a model cavity resonating at 508.58 MHz in the TM020 mode with a shunt impedance of 6.8 MΩ and designed to have HOM impedances of less than 0.1 MΩ longitudinally and 0.5 MΩ/m transversely.

Accelerators, from large to small, are experimental equipment that cannot function without electricity. Electricity generated at power plants is transmitted via high-voltage towers, stepped down to 6.6 kV at the nearest substation, and then stepped down to 200 V or 100 V at utility poles before reaching homes. This article provides an overview of the power receiving and distribution equipment and substations at the KEK Tsukuba Campus, as well as the renewal work for the Central Extra-High Voltage Substation and introduces the power receiving system for the high-power radio frequency power supply and electromagnet power supply used at SuperKEKB.

Taking advantage of the high penetrability of muons, we will develop the core technology for a compact system to generate high intensity muons in a humane way for the innovative development of imaging technology for non-destructive, see-through observation of the inside of infrastructure structures, containers, etc. This will realize the output objective of ‘Development of the portable system for humanly generating muons for the innovative development of imaging technology for structures and containers, and increasing the level of detector and other elemental technologies and data processing technologies for application.’

The ILC International Development Team (IDT) has compiled a list of time-consuming and important topics for the International Linear Collider (ILC) in the form of work packages: 15 work packages in the three areas of SRF, Sources, and Nanobeam. These work packages are to be addressed through international collaboration as the ILC Technology Network (ITN). In Japan, the project has been subsidized by the MEXT since 2023 as part of the development of an advanced accelerator. Internationally, two ITN meetings have been held, and ITN activities have begun in Europe and Korea. ITN is not only for the ILC, but also has various applications as a key to the development of advanced accelerators.

There is a movement towards international standardization of particle accelerator systems, mainly led by China, and Sumitomo Heavy Industries has been participating in standardization of cyclotron system. So far, the IEC standard (IEC 63175:2021) for 10–30 MeV high-intensity H⁻ cyclotrons has been completed, and IEC/TC45/WG20 is currently discussing the draft standard (IEC 63507/CD) for 200–400 MeV superconducting proton cyclotrons. The same WG20 has also begun discussion on draft standard (IEC 63589-1/CD) for electron linear accelerators for radiation processing. We report on the ongoing status of particle accelerator system standardization process at IEC/TC45/WG20.

At the 3 GeV Rapid Cycling Synchrotron (RCS) of J-PARC, we have achieved a significant beam loss mitigation to minimize the machine activation for beam operation at the designed 1 MW beam power. This was accomplished through systematic numerical simulations and beam tests during 2000 to 2022. The uncontrolled beam loss caused by foil scattering of the circulating beam during multi-turn injection period was reduced by minimizing the injection beam size and also installing a smaller size stripper foil. Subsequently, the space charge effects and the associated beam losses at 1 MW were minimized by implementing several measures, such as correcting resonances, optimizing longitudinal and transverse injection paintings as well as betatron tunes at injection. The beam loss throughout the RCS including the collimator area was 80% reduced as compared to that of 1 MW trial operation in 2020. Consequently, the residual radiation throughout the RCS was considerably reduced, obtaining a one-order-of-magnitude reduction at the collimator area for achieving a stable operation at a record high of more than 98% availability.

R&K Corporation was founded in 1977 and initially specialized in RF microwave electronic components as its main products, but has since evolved into satellite down converters, ultrasound printer drivers, medical RF amplifiers, accelerator parts, VLBI receivers, satellite receivers, PHS base station amplifiers, EMC power amplifiers, and a few hundred-KW power amplifiers for accelerators. The history of the company over the past 47 years is explained below. What was truly unique was that even though the RF propagation space used to drive the RF power changed from sound waves to radio waves to light, the transmitter and receiver themselves did not change significantly in design.

A workshop on the production of γ-ray beams and their wide use in scientific researches was held at RARiS, Tohoku University on 10–11 Sep., 2024. Nowadays γ-ray beams in the MeV to GeV energy regions are available for many fields containing photo-nuclear reaction and hadron photoproduction experiments, fundamental physics studies, radioisotope production, industrial application, and so on. In this workshop, recent achievements and new developments on accelerator-based γ-ray beam sources and various uses of them were discussed to attain further progress in common techniques and come up with the new ideas of applications. We also expressed our sincere gratitude and condolences to Prof. Haruo Ohkuma, who made great contributions to the related fields and passed away in July, 2023. This article reports an overview of the workshop.

On Saturday, October 12, 2024, a symposium entitled “Career Choices of Junior High School and Senior High School Female Students” was held by the Gender Equality Academic Association Liaison Group at Chuo University Myogadani Campus in Tokyo. Under the theme of “Career Choices of Junior High School and Senior High School Female Students,” the discussion focused on gender bias in occupational and career choices. Japan’s gender equality index is the lowest among OECD countries, partly due to the extremely low ratio of women in technical occupations. The accelerator society of Japan is no exception. In this symposium, a discussion was held on the tangible and intangible biases in career choices, the so-called unconscious bias, as the cause of the low ratio of women in technical fields. In addition to introducing the discussions at this symposium, I would like to state that, as an accelerator society, the issue of gender equality is a major challenge that may shake the existence of the field in the future.

The 2nd Accelerator Symposium “Quality of Life Supported by Technology: State-of-the-Art Advanced Medical Care by Nuclear Medicine” was held on Thursday, December 12, 2024. Theranostics (diagnostics and therapeutics) by nuclear medicine using RI has been attracting attention, including cases of cure of terminal cancer, but a stable supply of RI is essential for its realization. To achieve this, the cooperation of researchers in many fields is necessary, and many issues from upstream to downstream were discussed at the symposium. The discussions, including those with the government and private sector, provided important suggestions for considering issues in the actual dissemination of medical care, and renewed our awareness that the contribution of accelerator technology to society is not a one-way street, but an interaction with society. The following is a summary of the discussions at the symposium.