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Tamura, Fumihiko; Okita, Hidefumi; Hotchi, Hideaki*; Saha, P. K.; Meigo, Shinichiro; Yoshii, Masahito*; Omori, Chihiro*; Yamamoto, Masanobu; Seiya, Kiyomi*; Sugiyama, Yasuyuki*; et al.
Proceedings of 20th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.64 - 68, 2023/11
The J-PARC 3GeV synchrotron (RCS) provides high intensity proton beams to the Materials and Life Science Experimental Facility (MLF) and the Main Ring (MR). The harmonic number (h) of the RCS is 2 and the RCS normally accelerates two bunches. For some experiments at the MLF, a single bunch is preferred. In this case, one of the rf bucket is filled with protons and the other is empty. Therefore the beam intensity is halved. If the RCS can accelerate with h=1, the intensity per bunch can be doubled, enabling to provide single bunch beams to the MLF with the maximum intensity. This possibly increases the MR beam power by injecting high intensity single bunches eight times. In this presentation, we report mainly on the consideration of h=1 acceleration in the RCS by longitudinal simulations.
Yamamoto, Kazami; Kinsho, Michikazu; Hayashi, Naoki; Saha, P. K.; Tamura, Fumihiko; Yamamoto, Masanobu; Tani, Norio; Takayanagi, Tomohiro; Kamiya, Junichiro; Shobuda, Yoshihiro; et al.
Journal of Nuclear Science and Technology, 59(9), p.1174 - 1205, 2022/09
Times Cited Count：5 Percentile：87.42(Nuclear Science & Technology)In the Japan Proton Accelerator Research Complex, the purpose of the 3 GeV rapid cycling synchrotron (RCS) is to accelerate a 1 MW, high-intensity proton beam. To achieve beam operation at a repetition rate of 25 Hz at high intensities, the RCS was elaborately designed. After starting the RCS operation, we carefully verified the validity of its design and made certain improvements to establish a reliable operation at higher power as possible. Consequently, we demonstrated beam operation at a high power, namely, 1 MW. We then summarized the design, actual performance, and improvements of the RCS to achieve a 1 MW beam.
Tamura, Jun; Kondo, Yasuhiro; Yee-Rendon, B.; Meigo, Shinichiro; Maekawa, Fujio; Hasegawa, Kazuo; Kako, Eiji*; Umemori, Kensei*; Sakai, Hiroshi*; Konomi, Taro*
JPS Conference Proceedings (Internet), 33, p.011049_1 - 011049_6, 2021/03
Meigo, Shinichiro; Matsuda, Hiroki; Iwamoto, Yosuke; Yoshida, Makoto*; Hasegawa, Shoichi; Maekawa, Fujio; Iwamoto, Hiroki; Nakamoto, Tatsushi*; Ishida, Taku*; Makimura, Shunsuke*
JPS Conference Proceedings (Internet), 33, p.011050_1 - 011050_6, 2021/03
R&D of the beam window is crucial in the ADS, which serves as a partition between the accelerator and the target region. Although the displacement per atom (DPA) is used to evaluate the damage on the window, experimental data on the displacement cross section is scarce in the energy region above 20 MeV. We started to measure the displacement cross section for the protons in the energy region between 0.4 to 3 GeV. The displacement cross section can be derived by resistivity change divided by the proton flux and the resistivity change per Frankel pair on cryo-cooled sample to maintain damage. Experiments were conducted at the 3 GeV proton synchrotron at the J-PARC Center, and aluminum and copper was used as samples. As a result of comparison between the present experiment and the calculation of the NRT model, which is widely used for calculation of the displacement cross section, it was found that the calculation of the NRT model overestimated the experiment by about 3 times.
Yee-Rendon, B.; Tamura, Jun; Kondo, Yasuhiro; Hasegawa, Kazuo; Maekawa, Fujio; Meigo, Shinichiro; Oguri, Hidetomo
JPS Conference Proceedings (Internet), 33, p.011043_1 - 011043_5, 2021/03
The Japan Atomic Energy Agency (JAEA) has been working in the research and development of an Accelerator Driven Subcritical System (ADS) for the transmutation of nuclear waste. The ADS proposed by JAEA consists of a CW proton linac of 30 MW coupling with a subcritical core reactor. The accelerator will be operated with a beam current of 20 mA. Normal conducting Radio-Frequency Cavities (NRFC) and Superconducting Radio-Frequency Cavities (SRFC) will be used to achieve final energy of 1.5 GeV, and the SRFC will be employed for the main part of the acceleration: from 2 MeV to 1.5 GeV. In the first stage of the accelerator development, the focus was the design and optimization of the SRFC models and the beam optics. For the SRFC sections, the acceleration will be done by using Half Wave Resonators (HWR), Single Spokes (SS), and Elliptical cavities (Ellip) operating with a frequency of 162, 324, and 648 MHz, respectively. The beam optics were optimized satisfying the equipartitioning condition to control the emittance growth, which helped to reduce the beam halos and the beam loss.
Matsuda, Hiroki; Meigo, Shinichiro; Iwamoto, Yosuke; Yoshida, Makoto*; Hasegawa, Shoichi; Maekawa, Fujio; Iwamoto, Hiroki; Nakamoto, Tatsushi*; Ishida, Taku*; Makimura, Shunsuke*
Journal of Nuclear Science and Technology, 57(10), p.1141 - 1151, 2020/10
Times Cited Count：11 Percentile：75.12(Nuclear Science & Technology)To estimate the structural damages of materials in accelerator facilities, displacement per atom (dpa) is widely employed as a damage index, calculated based on the displacement cross-section obtained using a calculation model. Although dpa is applied as standard, the experimental data of the displacement cross-section for a proton in the energy region above 20 MeV are scarce. Among the calculation models, difference of about factor 8 exist, so that the experimental data of the cross-section are crucial to validate the model. To obtain the displacement cross-section, we conducted experiments at J-PARC. The displacement cross-section of copper and iron was successfully obtained for a proton projectile with the kinetic energies, 0.4 - 3 GeV. The results were compared with those obtained using the widely utilized Norgertt-Robinson-Torrens (NRT) model and the athermal-recombination-corrected (arc) model based on molecular dynamics. It was found that the NRT model overestimates the present displacement cross-section by 3.5 times. The calculation results obtained using with the arc model based on the Nordlund parameter show remarkable agreement with the experimental data. It can be concluded that the arc model must be employed for the dpa calculation for the damage estimation of copper and iron.
Meigo, Shinichiro; Matsuda, Hiroki; Iwamoto, Yosuke; Yoshida, Makoto*; Hasegawa, Shoichi; Maekawa, Fujio; Iwamoto, Hiroki; Nakamoto, Tatsushi*; Ishida, Taku*; Makimura, Shunsuke*
EPJ Web of Conferences, 239, p.06006_1 - 06006_4, 2020/09
Times Cited Count：0 Percentile：0.1(Nuclear Science & Technology)R&D of the beam window is crucial in the ADS, which serves as a partition between the accelerator and the target region. Although the displacement per atom (DPA) is used to evaluate the damage on the window, experimental data on the displacement cross section is scarce in the energy region above 20 MeV. We started to measure the displacement cross section for the protons in the energy region between 0.4 to 3 GeV. The displacement cross section can be derived by resistivity change divided by the proton flux and the resistivity change per Frankel pair on cryo-cooled sample to maintain damage. Experiments were conducted at the 3 GeV proton synchrotron at the J-PARC Center, and copper was used as samples. As a result of comparison between the present experiment and the calculation of the NRT model, which is widely used for calculation of the displacement cross section, it was found that the calculation of the NRT model overestimated the experiment by about 3 times.
Meigo, Shinichiro; Matsuda, Hiroki; Iwamoto, Yosuke; Yoshida, Makoto*; Hasegawa, Shoichi; Maekawa, Fujio; Iwamoto, Hiroki; Nakamoto, Tatsushi*; Ishida, Taku*; Makimura, Shunsuke*
JPS Conference Proceedings (Internet), 28, p.061004_1 - 061004_6, 2020/02
no abstracts in English
Tamura, Jun; Kondo, Yasuhiro; Yee-Rendon, B.; Meigo, Shinichiro; Maekawa, Fujio; Hasegawa, Kazuo; Kako, Eiji*; Umemori, Kensei*; Sakai, Hiroshi*; Konomi, Taro*
Proceedings of 19th International Conference on RF Superconductivity (SRF 2019) (Internet), p.399 - 402, 2019/11
Yee-Rendon, B.; Tamura, Jun; Kondo, Yasuhiro; Hasegawa, Kazuo; Maekawa, Fujio; Meigo, Shinichiro; Oguri, Hidetomo
Proceedings of 16th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.107 - 111, 2019/07
Meigo, Shinichiro; Matsuda, Hiroki; Iwamoto, Yosuke; Iwamoto, Hiroki; Hasegawa, Shoichi; Maekawa, Fujio; Yoshida, Makoto*; Ishida, Taku*; Makimura, Shunsuke*; Nakamoto, Tatsushi*
Proceedings of 9th International Particle Accelerator Conference (IPAC '18) (Internet), p.499 - 501, 2018/06
no abstracts in English
Harada, Hiroyuki; Saha, P. K.; Tamura, Fumihiko; Meigo, Shinichiro; Hotchi, Hideaki; Hayashi, Naoki; Kinsho, Michikazu; Hasegawa, Kazuo
Progress of Theoretical and Experimental Physics (Internet), 2017(9), p.093G01_1 - 093G01_16, 2017/09
Times Cited Count：3 Percentile：28.88(Physics, Multidisciplinary)The 3 GeV rapid cycling synchrotron (RCS) of the J-PARC is a high intensity proton accelerator of 1 MW. The accelerated proton beams in the RCS are extracted by eight pulsed kicker magnets and are delivered to a materials and life science experimental facility and main ring synchrotron. However, the fields of the magnets experience ringing that displaces the position of the extracted beam. This is a major issue from the viewpoint of target integrity and large beam loss. The ringing was directly measured as the displacement of the extracted beams by using a shorter pulsed beam and scanning the entire trigger timing of the kickers. We managed to cancel out the ringing by optimizing trigger timing and achieved the beam extraction with high accuracy. We developed automatic correction system of the timing and now have a higher stability. In this paper, we report our procedure and experimental results for ringing compensation.
Ajimura, Shuhei*; Bezerra, T. J. C.*; Chauveau, E.*; Enomoto, T.*; Furuta, Hisataka*; Harada, Masahide; Hasegawa, Shoichi; Hiraiwa, T.*; Igarashi, Yoichi*; Iwai, Eito*; et al.
Progress of Theoretical and Experimental Physics (Internet), 2015(6), p.063C01_1 - 063C01_19, 2015/06
Times Cited Count：6 Percentile：45.13(Physics, Multidisciplinary)The J-PARC E56 experiment aims to search for sterile neutrinos at the J-PARC Materials and Life Science Experimental Facility (MLF). In order to examine the feasibility of the experiment, we measured the background rates of different detector candidate sites, which are located at the third floor of the MLF, using a detector consisting of plastic scintillators with a fiducial mass of 500 kg. The gammas and neutrons induced by the beam as well as the backgrounds from the cosmic rays were measured, and the results are described in this article.
Sakai, Kenji; Sakamoto, Shinichi; Kinoshita, Hidetaka; Seki, Masakazu; Haga, Katsuhiro; Kogawa, Hiroyuki; Wakui, Takashi; Naoe, Takashi; Kasugai, Yoshimi; Tatsumoto, Hideki; et al.
JAEA-Technology 2011-039, 121 Pages, 2012/03
JAEA-Technology-2011-039.pdf:10.87MB
This report investigates the behavior, damage and restoration of a neutron source station of the MLF at the Great East Japan Earthquake and verified the safety design for emergency accidents in the neutron source station. In the MLF, after an occurrence of the Earthquake, strong quakes were detected at the instruments, the external power supply was lost, all of the circulators shut down automatically, and the hydrogen gas was released. The leakages of mercury, hydrogen and radio-activation gases did not occur. While, the quakes made gaps between the shield blocks and ruptured external pipe lines by subsidence around the building. But significant damages to the components were not found though the pressure drop of compressed air lines influenced on a target trolley lock system and so on. These results substantiated the validity of the safety design for emergency accidents in the source station, and suggested several points of improvement.
Sakai, Kenji; Futakawa, Masatoshi; Takada, Hiroshi; Sakamoto, Shinichi; Maekawa, Fujio; Kinoshita, Hidetaka; Seki, Masakazu; Haga, Katsuhiro; Kogawa, Hiroyuki; Wakui, Takashi; et al.
Proceedings of 20th Meeting of the International Collaboration on Advanced Neutron Sources (ICANS-20) (USB Flash Drive), 6 Pages, 2012/03
This report investigates behaviors and damages of each component in a neutron target station of the MLF at the J-PARC at the time of the Great East Japan Earthquake (GEJE). At the date of the GEJE, in the MLF, strong quakes were detected at several instruments, an external power supply were lost, all of the circulation systems were shut down automatically, and a hydrogen gas was released as planned. Leakage of activation liquids and gases did not occur. While, the quakes made gaps between shield blocks and ruptured external pipe lines for air and water by subsidence. But significant damages on the components of the target station were not found though a loss of compressed air supply affected lock systems with air cylinders and pneumatic operation values. These results substantiated a validity of safety design on the target station for emergency accidents.
Kobayashi, Takayuki; Isayama, Akihiko; Hasegawa, Koichi; Suzuki, Sadaaki; Hiranai, Shinichi; Sato, Fumiaki; Wada, Kenji; Yokokura, Kenji; Shimono, Mitsugu; Sawahata, Masayuki; et al.
Fusion Engineering and Design, 86(6-8), p.763 - 767, 2011/10
Times Cited Count：6 Percentile：44.16(Nuclear Science & Technology)Progress of antenna development of the Electron Cyclotron Range of Frequency system for JT-60 SA is presented. Capability of pulse length of 100 s, which requires active cooling for mirrors, and flexibility of beam injection angles in both poloidal and toroidal directions are required for the antenna with high reliability. Mechanical and structural design works of the launcher (antenna and its support with steering structure) based on a linear motion antenna concept are in progress. The key component is a long-stroke bellows which enables to alter poloidal injection angle and a bellows which enables to alter toroidal injection angle. Using a newly fabricated mock-up of the steering structure, it was confirmed that the antenna was mechanically realized for poloidal and toroidal injection angle ranges of -10 to +45
and -15 to +15, respectively. Those angles are consistent with angles required in JT-60SA. The results of thermal and structural analyses are also presented.
Kobayashi, Takayuki; Isayama, Akihiko; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Sawahata, Masayuki; Suzuki, Sadaaki; Terakado, Masayuki; Hiranai, Shinichi; Sato, Fumiaki; et al.
Nuclear Fusion, 51(10), p.103037_1 - 103037_10, 2011/10
Times Cited Count：19 Percentile：62.29(Physics, Fluids & Plasmas)A new gyrotron operation technique to increase oscillation efficiency was developed on the JT 60 ECRF system. The electron pitch factor was optimized by controlling anode voltage within 0.1 s after the start of the operation. By applying this technique, the gyrotron output power of 1.5 MW for 4 s was recorded, for the first time. The reduced collector heat load at 1.5 MW operations was reduced by 20% and it will be acceptable for longer pulse operation. A new gyrotron with an improved mode converter was developed in order to demonstrate reduction of the stray radiation which had limited the pulse length. The stray radiation was reduced to 1/3 of that of the original gyrotron. A conditioning operation of the improved gyrotron is proceeding up to 31 s at 1 MW. These progresses significantly contribute to enhancing the high power and long pulse capability of the ECRF system toward JT 60SA.
Hiranai, Shinichi; Suzuki, Sadaaki; Sato, Fumiaki; Kobayashi, Takayuki; Hasegawa, Koichi; Yokokura, Kenji; Moriyama, Shinichi
JAEA-Technology 2010-031, 24 Pages, 2010/09
JAEA-Technology-2010-031.pdf:1.71MB
The JT-60U electron cyclotron heating (ECH) system injects a millimeter wave at 110 GHz into the JT-60U plasma, and heats the plasma or drives a current locally to enhance the confinement performance of the JT-60U plasma. The ECH system of high power gyrotrons, transmission lines and antenna that launch millimeter wave beams toward the plasma. On the long pulse injection, one of the most important purposes is to prevent arcing in the transmission lines and to transmit millimeter wave beams efficiently. This report describes the problems occurred in a long pulse injection test (0.5 MW, 30 s), e.g., increase in released gas, temperature rise of the transmission line and an arcing at the vacuum window during the conditioning process. It also describes measures for the problems, e.g., improvements in vacuum pumping system, cooling system, and arc detector and introduction of the new dummy road system.
Kobayashi, Takayuki; Isayama, Akihiko; Fasel, D.*; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Sawahata, Masayuki; Suzuki, Sadaaki; Terakado, Masayuki; Hiranai, Shinichi; et al.
Journal of Plasma and Fusion Research SERIES, Vol.9, p.363 - 368, 2010/08
Improvements are required for expanding the pulse length of the JT-60 ECRF system (5s) for JT-60SA (100s). Newly developed power supplies will be fabricated and installed by EU. The conditioning operation of an improved gyrotron equipping a newly designed mode convertor has been started. The mode convertor will reduce heat flux on the internal components and therefore expected to enable long pulse operation at 1 MW. Pre-programmed and/or feedback control of the heater current and anode voltage, which was successfully demonstrated in JT-60U, will be key techniques because the beam current decreases during a shot. The evacuated transmission lines have a capability of 1 MW per line. Since maintenance of the components in the vacuum vessel is difficult, a linear motion antenna concept was proposed to reduce risks of water leakage and fault of the driving mechanism in the vacuum vessel. The detailed design and the low power test of a mock-up antenna have been started.
Kobayashi, Takayuki; Terakado, Masayuki; Sato, Fumiaki; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Sawahata, Masayuki; Suzuki, Sadaaki; Hiranai, Shinichi; Igarashi, Koichi; et al.
Plasma and Fusion Research (Internet), 4, p.037_1 - 037_10, 2009/08
Electron cyclotron (EC) heating and current drive (CD) are key tools to control fusion plasma especially for effective electron heating and for suppression of neoclassical tearing mode (NTM). Recently, developments of a high power gyrotron and a power modulation technique have been successfully achieved on JT-60U ECRF system in order to enhance the system performance. Stable gyrotron oscillation with oscillation power of 1.5 MW for 1 s was demonstrated in 2007, for the first time. Then temperature rise of cavity and collector has been investigated. It has been shown that the longer pulse operation with 1.5 MW by an improved 110 GHz gyrotron is possible. In addition, modulated ECCD in synchronized with NTM rotation has been performed with the oscillation power of 0.8 MW and the frequency around 5 kHz. The synchronizing system has worked very well and it has played an essential role in NTM suppression experiments on JT-60U.
