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Hashidate, Ryuta; Kondo, Yuki; Yada, Hiroki; Takaya, Shigeru; Enuma, Yasuhiro
Hozengaku, 25(2), p.59 - 67, 2026/07
To construct a maintenance schedule, it is necessary to clarify maintenance preconditions that constrain the operational states of systems and components in the plant. In this study, a new method for extracting maintenance preconditions using graph structures that represent relationship among systems and components was proposed. Then, this proposed method was integrated into the automatic maintenance scheduling program developed by authors. A plant maintenance schedule can be created more efficiently by using this integrated program. Furthermore, plant configuration design issues that caused prolonged maintenance terms can be investigated by using graph structure. This approach was applied to a simplified plant model to demonstrate the effectiveness of the proposed method.
Yee-Rendon, B.; Kondo, Yasuhiro; Tamura, Jun; Meigo, Shinichiro; Maekawa, Fujio
JPS Conference Proceedings (Internet), 45, p.011174_1 - 011174_10, 2026/06
A 30 MW continuous wave proton linac is devised by the Japan Atomic Energy Agency (JAEA) for the use of Accelerator Driven Subcritical System (ADS) technology. The efficiency of the accelerator is crucial for the realization of ADS in terms of minor actinides management. Therefore, it is necessary to assess the overall efficiency of the different components to ensure the accelerator's feasibility. This study estimated the power required to operate RF cavities, considering effects such as beam loading and microphonics. Additionally, the contribution of cryogenics was considered by calculating the heat load generated by the cryomodules, as well as the power consumption of auxiliary systems such as magnets. In this analysis, we will present the efficiency estimations of the JAEA-ADS linac, as well as the methodology used to obtain the results.
Yee-Rendon, B.; Kondo, Yasuhiro; Tamura, Jun; Meigo, Shinichiro; Maekawa, Fujio
JPS Conference Proceedings (Internet), 45, p.011173_1 - 011173_7, 2026/06
The Japan Atomic Energy Agency (JAEA) is carrying out research and development on an Accelerator Driven Subcritical System (ADS) for nuclear transmutation. The JAEA-ADS consists of a CW superconducting proton linac of 30 MW coupling with a subcritical core reactor. The linac will accelerate a 20-mA proton beam to a final energy of 1.5 GeV, starting with a Normal Conducting section up to 2.5 MeV, and followed by a Superconducting part. More than 300 LLRF systems will control longitudinal parameters of the RF structures that compose the linac. In addition to ensuring stability on RF settings for efficient linac performance, the JAEA-ADS LLRF system will also enable fault-tolerance compensations to increase the availability of the linac, which is a major challenge for ADS operation. In this work, we will discuss the necessity of the ADS LLRF and present a proposed model that satisfies these demands.
Yamaguchi, Yuji; Kondo, Yasuhiro; Meigo, Shinichiro; Oguri, Hidetomo; Oi, Motoki; Saha, P. K.; Shinozaki, Shinichi; Takayanagi, Tomohiro; Yamamoto, Kazami
JPS Conference Proceedings (Internet), 45, p.011162_1 - 011162_7, 2026/06
A high-power 3-GeV proton beam from a rapid cycling synchrotron (RCS) is transported to a neutron production target at Materials and Life Science Experimental Facility (MLF) by a 3-GeV RCS to Neutron facility Beam Transport (3NBT) line in J-PARC. Recently, the design beam power of 1 MW has been achieved. By this achievement, a future plan of MLF second target station (TS2) is motivated for enhancing brightness of the secondary beams and requires a new beam transport line for the 3-GeV proton beam. The design study of the new transport line has been started based on the previous work and is being performed regarding the optics and shielding of the beamline incorporating latest beam commissioning results. In this presentation, we report a brief concept of the new transport line and current status of the design study.
Tamura, Jun; Kondo, Yasuhiro; Yee-Rendon, B.; Meigo, Shinichiro; Maekawa, Fujio; Kako, Eiji*; Umemori, Kensei*; Sakai, Hiroshi*; Domae, Takeshi*
JPS Conference Proceedings (Internet), 45, p.011171_1 - 011171_7, 2026/06
Yee-Rendon, B.; Kondo, Yasuhiro; Tamura, Jun; Meigo, Shinichiro; Maekawa, Fujio; Pla
ais, A.*; Bouly, F.*
Proceedings of 22nd International Conference on RF Superconductivity (SRF2025) (Internet), p.316 - 320, 2026/04
High-intensity accelerators, particularly Accelerator-Driven Systems (ADS), require high availability and reliability for proper operation. For superconducting linear accelerators, the ability to continue operating even when one of the RF cavities fails is key to achieving the required availability, known as cavity compensation. Beam dynamics studies of the JAEA-ADS linear accelerator have demonstrated the possibility of operating with multiple RF cavities disabled with acceptable beam quality. Several other superconducting linear accelerator laboratories have adopted similar methods and developed their procedures. Among these efforts, the LightWin tool has proven to be an effective tool for automatically and systematically identifying compensation settings for each cavity failure in any linear accelerator. This software has been successfully utilized on the MINERVA linac, as well as on the high-energy part of the JAEA-ADS linac. It has currently been tested and improved to ease SPIRAL2 operation. This work presents an analysis of cavity compensation in the JAEA-ADS superconducting linear accelerator using the LightWin tool and compares the results with previous studies.
Yee-Rendon, B.; Kondo, Yasuhiro; Tamura, Jun; Meigo, Shinichiro; Maekawa, Fujio; Miyamoto, Ryoichi*; Milas, N.*; Eshraqi, M.*
Proceedings of 22nd International Conference on RF Superconductivity (SRF2025) (Internet), p.58 - 62, 2026/04
The European Spallation Source (ESS) superconducting proton linac is currently undergoing commissioning. During the initial operation phase, the final beam energy will be about 800 MeV, reaching a 2 MW power. High reliability and availability are crucial for the success of the ESS science programs and thus operations will be maintained even with failures of main linac components such as cavities and quadrupoles, as long as ~50 percent of the intended power can be achieved. To this end, we developed beam optics strategies to address failures in the cavities of the superconducting linac. Due to the constraints in the RF cavity amplitudes, we implemented a modified version of standard cavity compensation techniques. The results indicated that this strategy enables beam recovery that meets the beam quality specifications, thereby enhancing the availability of the ESS linac.
Tamura, Jun; Kondo, Yasuhiro; Yee-Rendon, B.; Meigo, Shinichiro; Maekawa, Fujio; Kako, Eiji*; Umemori, Kensei*; Sakai, Hiroshi*; Domae, Takeshi*
Proceedings of 22nd International Conference on RF Superconductivity (SRF2025) (Internet), p.691 - 694, 2026/04
Japan Atomic Energy Agency (JAEA) has been proposing an accelerator-driven nuclear transmutation system (ADS) as a future nuclear system to efficiently reduce high-level radioactive waste generated in nuclear power plants. As the first step toward the full-scale CW proton linac for the JAEA-ADS, we are currently prototyping a low-beta (around 0.2) single-spoke cavity. Since there is no experience in manufacturing superconducting spoke cavities in Japan, prototyping and performance evaluation of the cavity are essential to ensure the feasibility of the JAEA-ADS. The actual cavity fabrication started in 2020, and the cavity assembly by electron beam welding was finally completed in fiscal year 2024. In this assembly, the target resonance frequency of 324 MHz was achieved by trimming the ends of the cavity parts several times before the final welding. In the final welding, smooth weld beads were obtained by combining circular-correction and end-thinning for the cavity parts to be welded. The fabrication of the prototype spoke cavity is presented.
Kondo, Yasuhiro; Chimura, Motoki; Cicek, E.*; Fukui, Yuji*; Futatsukawa, Kenta*; Fuwa, Yasuhiro; Goto, Rikuto*; Hirano, Koichiro; Ishikawa, Masaki*; Ito, Takashi; et al.
Proceedings of 22nd Annual Meeting of Particle Accelerator Society of Japan (Internet), p.124 - 129, 2026/03
Various upgrade plans of the J-PARC linac are underway, and repetition-rate doubling project is one of the most important part. Currently, the linac supplies a 400~MeV H
ion beam to the 3~GeV synchrotron (RCS) at a repetition rate of 25~Hz. However, to deliver the beam to both RCS and proton-beam irradiation facility under planning, it is necessary to raise the repetition rate from 25~Hz to 50~Hz. Prior to construction of the beamline to the irradiation facility, we conducted a verification of the 50~Hz operation of all the linac apparatus simultaneously within the current operational limits in May 2025. And also, the verification of the 50~Hz operation of the particle counter system, which is one of the most important safety device of the J-PARC accelerator, was conducted. As a result, any significant problems were not found out, and it is now ready for the upcoming 50~Hz-beam acceleration demonstration. This paper describes this details of the demonstration of the 50~Hz operation, without beam acceleration, of the J-PARC linac.
Yamaguchi, Yuji; Kondo, Yasuhiro; Meigo, Shinichiro; Takayanagi, Tomohiro; Fujimori, Hiroshi*; Shinozaki, Shinichi
Proceedings of 22nd Annual Meeting of Particle Accelerator Society of Japan (Internet), p.655 - 660, 2026/03
Preliminary designs of new bending magnets have been considered for the second target station (TS2) of Materials and Life Science Experimental Facility (MLF), J-PARC. To give a design approach for the bending magnets, several examples of bending magnets, such as a pulse bending magnet and a septum magnet were reviewed. The reviewed magnet specifications compared with requirements for the new bending magnets indicate that the new pulse bending magnet requires a new design idea, while the new septum magnet can be designed based on the previous design of an extraction septum magnet for the 3-GeV synchrotron in J-PARC. The new design idea for the pulse bending magnet and the septum magnet design idea based on the previous one are presented.
Kondo, Ayaka*; Iijima, Toru*; Sumi, Kazumichi*; Takeuchi, Yusuke*; Cicek, E.*; Ego, Hiroyasu*; Otani, Masashi*; Nakazawa, Yuga*; Futatsukawa, Kenta*; Mibe, Tsutomu*; et al.
Proceedings of 22nd Annual Meeting of Particle Accelerator Society of Japan (Internet), p.18 - 22, 2026/03
The muon anomalous magnetic moment (
) and electric dipole moment (EDM) are sensitive to new physics beyond the Standard Model. At J-PARC, precision measurements using a novel low-emittance muon beam generated via cooling and acceleration are planned. The muon linac consists of four types of RF cavities for different 
ranges. For the medium-velocity range (=0.3-0.7), a prototype bridge coupler, which electromagnetically connects DAW tanks while allowing space for quadrupole magnets, was designed and fabricated. Low-power tests yielded a Q value of 4500 (50% of the design) and 10% field flatness. This paper reports on the design and test results.
Yee-Rendon, B.; Kondo, Yasuhiro; Tamura, Jun; Meigo, Shinichiro; Maekawa, Fujio
Proceedings of 22nd Annual Meeting of Particle Accelerator Society of Japan (Internet), p.130 - 134, 2026/03
Accelerator-Driven Systems (ADS) represent an efficient solution to the challenge of nuclear waste disposal. Therefore, the Japan Atomic Energy Agency (JAEA) is designing a 30-MW proton linac as a key element of its proposal for the use of ADS technology. A key feature of ADS accelerators is their extremely high availability and reliability that is required to avoid thermal stress on reactor structures. To this end, JAEA-ADS adopted a combined strategy of hot standby in the front part of the linac and standby element compensation as a fast and efficient way to reduce the downtime due to an element failure. The JAEA-ADS injector is mainly composed of a normal conducting section and ends with the first section of superconducting cavities (Half Wave Resonator). This paper presents the details of the optics design of the JAEA-ADS injector and the results of beam dynamics simulations.
ion beam at J-PARC frontendShibata, Takanori*; Nammo, Kesao*; Shinto, Katsuhiro; Okoshi, Kiyonori; Kawai, Isao*; Kitamura, Ryo; Morishita, Takatoshi; Kondo, Yasuhiro; Sato, Yoichi*
Proceedings of 16th International Particle Accelerator Conference (IPAC25) (Internet), p.514 - 516, 2025/11
no abstracts in English
Takayanagi, Tomohiro; Fuwa, Yasuhiro; Otani, Masashi*; Shimomura, Koichiro*; Mibe, Tsutomu*; Kondo, Yasuhiro; Futatsukawa, Kenta*; Cicek, E.*; Nakazawa, Yuga*; Tokuchi, Akira*; et al.
Proceedings of 16th International Particle Accelerator Conference (IPAC25) (Internet), p.1884 - 1886, 2025/11
We have been developing a compact pulse power supply with high output and high frequency specifications: output voltage of 75 kV, current of 40 A, main pulse width of 50 us, and repetition frequency of 25 Hz for short pulse waveforms. This power supply is used to drive klystron for muon linac, which requires high stability and reliability. It uses a next-generation power semiconductor SiC-MOSFET with excellent characteristics of ultra-high withstand voltage of 13 kV and low loss, which was realized through the technological development of wide band gap semiconductor devices. Combining this SiC-MOSFET with the Marx circuit that generates ultra-high voltage pulses will realize a more compact pulse power supply with lower losses than conventional ones. In addition, future ap-plications in portable accelerators are also possible. In this presentation, the circuit design of the Marx power supply will be reported.
Otani, Masashi*; Ego, Hiroyasu*; Kondo, Yasuhiro
Proceedings of 16th International Particle Accelerator Conference (IPAC25) (Internet), p.1534 - 1537, 2025/11
The muon linac has been developed at J-PARC to accelerate muons from thermal energy (25 meV) to 212 MeV using electrostatic extraction and four different types of radio-frequency cavities: RFQ, IH-DTL, DAW-CCL, and disk-loaded structures. Although some of the technologies employed were relatively novel, most proof-of-principle demonstrations have been successfully completed through prototype testing and actual production. Based on these experiences, it has become possible to propose a shorter or more efficient schematic design derived from the current design. In this poster, the new schematic design will be presented.
Liu, Y.*; Otani, Masashi*; Miyao, Tomoaki*; Nakazawa, Yuga*; Shibata, Takanori*; Nammo, Kesao*; Fang, Z.*; Futatsukawa, Kenta*; Fukui, Yuji*; Mizobata, Satoshi*; et al.
Proceedings of 16th International Particle Accelerator Conference (IPAC25) (Internet), p.855 - 857, 2025/11
Nakazawa, Yuga*; Cicek, E.*; Ishida, Katsuhiko*; Futatsukawa, Kenta*; Shimomura, Koichiro*; Otani, Masashi*; Kimura, Masato*; Kamioka, Shusei*; Yamazaki, Takayuki*; Mibe, Tsutomu*; et al.
Proceedings of 16th International Particle Accelerator Conference (IPAC25) (Internet), p.1163 - 1166, 2025/11
At the Japan Proton Accelerator Research Complex (J-PARC), low-emittance muon beams with a linear accelerator (linac) are proposed as a new approach to precisely measure the anomalous magnetic moment and electric dipole moment of the muon. Low-emittance muon beams can also be employed as new probes for non-destructive imaging techniques to see through structures. In the low-velocity section of the muon linac, a radio-frequency quadrupole linac (RFQ) and an interdigital H-mode drift tube linac (IH-DTL) are used to accelerate muons to = v/c = 0.08 and 0.28, respectively, at an operating frequency of 324 MHz. To reduce construction costs, the IH-DTL employs the alternating phase focusing (APF) method, which uses the transverse focusing force derived from the RF electric field. Because the APF method limits the transverse and longitudinal acceptances simultaneously, careful beam diagnostics and commissioning are essential to suppress the emittance growth derived from beam mismatches. As a result of the beam simulation, by conducting appropriate beam matching, the normalized rms emittance of 0.3 
-mm-mrad and the transmission to the downstream detector of 97% was obtained. In this paper, the results of the tracking simulation and the development status of the diagnostic and transport beamlines in the low-velocity section are described.
Kondo, Ayaka*; Iijima, Toru*; Sumi, Kazumichi*; Takeuchi, Yusuke*; Cicek, E.*; Ego, Hiroyasu*; Otani, Masashi*; Nakazawa, Yuga*; Futatsukawa, Kenta*; Mibe, Tsutomu*; et al.
Journal of Physics; Conference Series, 3094(1), p.012025_1 - 012025_6, 2025/09
A muon linear accelerator is under development at J-PARC for precise measurement of the muon anomalous magnetic moment (g-2) and electric dipole moment (EDM). Adisk-and-washer (DAW) structure is employed to accelerate muons from 30% of the speed of light (kinetic energy 4 MeV) to 70% (40 MeV) at 1296 MHz. The muon DAWconsists of tanks accelerating the muons and bridge couplers that couple the tanks and focus the beam using an internal quadrupole doublet. A bridge-coupler prototype is currently being fabricated and will be tested. This paper presents the design and performance evaluation of the bridge coupler prototype.
Yamaguchi, Yuji; Kondo, Yasuhiro; Meigo, Shinichiro; Shinozaki, Shinichi; Takayanagi, Tomohiro; Fujimori, Hiroshi*; Kawamura, Naritoshi*
Journal of Physics; Conference Series, 3094(1), p.012023_1 - 012023_5, 2025/09
The 3-GeV proton beam from the rapid cycling synchrotron (RCS) of J-PARC is transported to the spallation neutron source at Materials and Life Science Experimental Facility (MLF) by a 3-GeV RCS to Neutron facility Beam Transport (3NBT) line. Recently, the first design idea of a new proton beam transport line has been proposed for a future target station of the MLF (TS2). In the present study, proton beam transport is simulated near the TS2 target where a bending magnet and a solenoid are located for muon beam transport. The purposes are to clarify the magnetic field effects on the proton beam by the magnets and to present a method to correct each effect. Orbit deviation by the bending magnet and vertical size expansion due to profile rotation by the solenoid can be corrected by installing additional bending magnets and a solenoid with reversal magnetic field, respectively. The correction method is expected to be effective and also needs to be studied further for detail design.
Kawai, Keito*; Nemoto, Yoshiyuki; Fujimura, Yuki; Kondo, Keietsu; Abe, Yosuke; Mohamad, A. B.; Pham, V. H.; Ishikawa, Norito; Ishijima, Yasuhiro; Ioka, Ikuo; et al.
Nihon Genshiryoku Gakkai Wabun Rombunshi (Internet), 24(3), p.82 - 98, 2025/08
An accident tolerant fuel (ATF) cladding, which is more resistant to accidents than the conventional Zircaloy cladding, is under development. One of these claddings is a chromium (Cr)-coated cladding with an outer surface coated with Cr, which is expected to improve the resistance to high-temperature steam oxidation. In this study, electrochemical plating was applied to coat a Cr layer on the cladding outer surface, and its properties under accidental conditions were evaluated. In a loss-of-coolant accident (LOCA), the cladding will burst and both the outer and inner surfaces of the cladding will be oxidized. Thus, as-received Zircaloy-4 and Cr-coated claddings were tested for oxidation in high-temperature steam to investigate differences in oxidation behavior, hydrogen absorption behavior, and mechanical properties after oxidation. Oxidation tests were conducted using a thermobalance. The amount of oxidation of coated samples decreased by half compared with that of uncoated samples, indicating that the coating was effective in inhibiting oxidation. However, the hydrogen absorption of coated samples was found to be higher than that of uncoated samples. In this paper, we discuss the mechanism behind this difference in hydrogen absorption and its effect on mechanical properties.
