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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：6 Percentile：84.97(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.
Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Takagi, Yasuhiko*; Nakamura, Tomoki*; Hiroi, Takahiro*; Matsuoka, Moe*; et al.
Nature Astronomy (Internet), 5(3), p.246 - 250, 2021/03
Times Cited Count：43 Percentile：96.93(Astronomy & Astrophysics)Here we report observations of Ryugu's subsurface material by the Near-Infrared Spectrometer (NIRS3) on the Hayabusa2 spacecraft. Reflectance spectra of excavated material exhibit a hydroxyl (OH) absorption feature that is slightly stronger and peak-shifted compared with that observed for the surface, indicating that space weathering and/or radiative heating have caused subtle spectral changes in the uppermost surface. However, the strength and shape of the OH feature still suggests that the subsurface material experienced heating above 300 
C, similar to the surface. In contrast, thermophysical modeling indicates that radiative heating does not increase the temperature above 200 C at the estimated excavation depth of 1 m, even if the semimajor axis is reduced to 0.344 au. This supports the hypothesis that primary thermal alteration occurred due to radiogenic and/or impact heating on Ryugu's parent body.
Suzuki, Tomoya; Takao, Koichiro*; Kawasaki, Takeshi*; Harada, Masayuki*; Nogami, Masanobu*; Ikeda, Yasuhisa*
Polyhedron, 96, p.102 - 106, 2015/08
Times Cited Count：5 Percentile：41.5(Chemistry, Inorganic & Nuclear)We have determined crystal structures of UO
(NO
)(
) (: 2-imidazolidone), UO(NO)(
) (: tetrahydro-2-pyrimidone) and UO(NO)(
) (: 1-methyl-2-imidazolidone) by using single crystal X-ray analysis, and examined correlations between melting points (mps) and intermolecular hydrogen bonds (HBs) of UO(NO)(CU) (CU: cyclic urea derivatives) and UO(NO)(NRP) (NRP: pyrrolidone derivative).
Shimada, Taihei; Nomura, Masahiro; Tamura, Fumihiko; Yamamoto, Masanobu; Hara, Keigo*; Hasegawa, Katsushi*; Omori, Chihiro*; Toda, Makoto*; Yoshii, Masahito*; Schnase, A.*; et al.
Proceedings of 4th International Particle Accelerator Conference (IPAC '13) (Internet), p.2750 - 2752, 2013/06
no abstracts in English
Shimada, Taihei; Suzuki, Hiromitsu; Yamamoto, Masanobu; Schnase, A.; Toda, Makoto*; Omori, Chihiro*; Hara, Keigo*; Hasegawa, Katsushi*; Nomura, Masahiro; Tamura, Fumihiko; et al.
Proceedings of 9th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1143 - 1145, 2012/08
The RF cavities of J-PARC 3 GeV synchrotron use 198 MA cores. Buckling occurred in some cores since the operation starting on the October of 2007. We have measured the inner diameters of the cores as a part of the investigation to determine the cause of the buckling when the cavities were disassembled for maintenance. We noticed that deformations of the inner shapes of the cores related to its manufacturing process and that inner diameters change over year were not measured in the most of the cores without buckled cores. Furthermore, the effective manufacturing process of cores to avoid the buckling has be established. We are going to replace old type cores with new type cores in shutdown periods in summer every year.
Nomura, Masahiro; Yamamoto, Masanobu; Schnase, A.; Shimada, Taihei; Suzuki, Hiromitsu; Tamura, Fumihiko; Hara, Keigo*; Hasegawa, Katsushi*; Omori, Chihiro*; Toda, Makoto*; et al.
Nuclear Instruments and Methods in Physics Research A, 623(3), p.903 - 909, 2010/11
Times Cited Count：9 Percentile：54.21(Instruments & Instrumentation)We have been operating ten RF cavities loaded with magnetic alloy cores in J-PARC 3 GeV RCS since September 2007. During 3 years operation, we detected three times the impedance reductions of RF cavities resulting from the buckling of MA cores. To find out the origin of the MA core buckling, we evaluated the thermal stress inside the MA cores in operation and studied the relationship between the MA core buckling and core structure. We figured out that the MA core buckling was caused by the thermal stress that was enhanced due to the impregnation with low viscosity epoxy resin.
Shimada, Taihei; Yamamoto, Masanobu; Nomura, Masahiro; Schnase, A.; Tamura, Fumihiko; Hara, Keigo*; Hasegawa, Katsushi*; Omori, Chihiro*; Toda, Makoto*; Suzuki, Hiromitsu; et al.
Proceedings of 7th Annual Meeting of Particle Accelerator Society of Japan (DVD-ROM), p.549 - 551, 2010/08
The beam pipes of the RF acceleration section in the J-PARC RCS have a large aperture (247 mm) in order to handle a high power proton beam of 1 MW with acceptable loss. When we disassemble and later reassemble the test cavity in between the high power test runs for the MA cores, it is quite hard work to take out, and reinstall the beam pipe. Therefore, instead of using an original beam pipe, risking that it becomes unusable for accelerator operation due to scratches or discharges, we developed a light weight dummy beam pipe and dedicated copper connection parts for the acceleration gaps, which are easy to take apart and to assemble. Accordingly, the copper parts, which are used to connect the acceleration gaps to the cavity tanks for the installed cavity systems were redesigned, so that the time required for assembly or disassembly is reduced. This is especially important, as the cavities in the accelerator tunnel are in a high radiation environment caused by high power RCS operation.
Schnase, A.; Tamura, Fumihiko; Koseki, Tadashi*; Tomizawa, Masahito*; Toyama, Takeshi*; Yoshii, Masahito*; Omori, Chihiro*; Nomura, Masahiro; Yamamoto, Masanobu; Toda, Makoto*; et al.
Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.1446 - 1448, 2010/05
Tamura, Fumihiko; Schnase, A.; Yoshii, Masahito*; Omori, Chihiro*; Yamamoto, Masanobu; Nomura, Masahiro; Toda, Makoto*; Suzuki, Hiromitsu; Shimada, Taihei; Hara, Keigo*; et al.
Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.1443 - 1445, 2010/05
The wide-band RF cavities in the J-PARC RCS are operated in the dual-harmonic operation, in which each single cavity is driven by a superposition of the fundamental and the second harmonic RF signals. By the dual-harmonic operation large amplitude second harmonic signals for the bunch shape manipulation are generated without extra cavities. The phase control of the second harmonic RF is a key for the bunch shape manipulation. The fundamental RF signal is controlled by the phase feedback loop to damp the dipole oscillation. The second harmonic is locked to the phase of the vector-sum phase of the fundamental RF signals. We present the system detail and the performance in the beam operation of the RCS.
Nomura, Masahiro; Schnase, A.; Shimada, Taihei; Suzuki, Hiromitsu; Tamura, Fumihiko; Yamamoto, Masanobu; Ezura, Eiji*; Omori, Chihiro*; Hara, Keigo*; Hasegawa, Katsushi*; et al.
Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.3723 - 3725, 2010/05
We have been operating the RF cavities loaded with MA cores with a high field gradient of more than 20 kV/m since October 2007. We have been measuring the RF cavity impedance at the shutdown periods, and we detected the impedance reductions of RCS RF cavities on January and June 2009. Taking out the RF cavities from the beam line and opening them, we found that many of cores showed a buckling at the inner radius. We report the detail of condition of MA cores and the relation between the impedance reduction and core condition.
Shimada, Taihei; Yamamoto, Masanobu; Nomura, Masahiro; Schnase, A.; Tamura, Fumihiko; Hara, Keigo*; Hasegawa, Katsushi*; Omori, Chihiro*; Toda, Makoto*; Yoshii, Masahito*; et al.
Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.3717 - 3719, 2010/05
Several magnetic alloy cores of the RF cavities, which are installed in the 3 GeV rapid cycling synchrotron (RCS) of J-PARC have shown buckling after about two years operation. To find the reason, why the local deformation happened, we made a test setup. There we heat up MA cores in air by 500 kHz RF and measure the thermal deformation in order to collect information about the buckling process. The results obtained by comparing the expansion of cores made by different production methods are reported.
Tamura, Fumihiko; Yamamoto, Masanobu; Yoshii, Masahito*; Omori, Chihiro*; Nomura, Masahiro; Schnase, A.; Toda, Makoto*; Suzuki, Hiromitsu; Shimada, Taihei; Hara, Keigo*; et al.
Proceedings of 6th Annual Meeting of Particle Accelerator Society of Japan (CD-ROM), p.366 - 368, 2010/03
For stable acceleration of the high intensity proton beams, increasing the bunching factor by the longitudinal painting is essentially important to reduce the space-charge tune shift. The momentum offset injection method and applying the second harmonic RF are employed for the longitudinal painting in the J-PARC RCS. We employ wide band magnetic alloy (MA) cavities to realize the dual-harmonic operation, in which each cavity is driven by the superposition of the fundamental and the second harmonic RF signals. By the dual-harmonic operation we can generate the large amplitude second harmonic RF without extra cavities for the second harmonic. We report the beam test results of the longitudinal painting.
Schnase, A.; Omori, Chihiro*; Tamura, Fumihiko; Ezura, Eiji*; Hara, Keigo*; Hasegawa, Katsushi*; Nomura, Masahiro; Shimada, Taihei; Suzuki, Hiromitsu; Takagi, Akira*; et al.
Proceedings of 6th Annual Meeting of Particle Accelerator Society of Japan (CD-ROM), p.1077 - 1079, 2010/03
Shimada, Taihei; Yamamoto, Masanobu; Suzuki, Hiromitsu; Toda, Makoto*; Hasegawa, Katsushi*; Omori, Chihiro*; Tamura, Fumihiko; Schnase, A.; Hara, Keigo*; Nomura, Masahiro; et al.
Proceedings of 6th Annual Meeting of Particle Accelerator Society of Japan (CD-ROM), p.1080 - 1082, 2010/03
Few magnetic alloys cores of the RF cavities which are installed in the 3 GeV rapid cycling synchrotron of the J-PARC have buckled after the operation of about two years. We heated cores in the air and measured thermal deformation in order to get information about the buckling process. We report the results.
Fujiwara, Kazushige*; Ito, Masanobu*; Sasanuma, Miwa*; Tanaka, Hideo*; Hirotani, Kiyoshi*; Onizawa, Kunio; Suzuki, Masahide; Amezawa, Hiroo*
Transactions of 20th International Conference on Structural Mechanics in Reactor Technology (SMiRT-20) (CD-ROM), 8 Pages, 2009/08
Concerns over aged nuclear power stations are mounting in Japan today. However, there exists only a small number of experimental studies regarding the effect of radiation exposure to concrete. We have consequently conducted an irradiation test at JMTR on concrete specimens to confirm the effect of radiation exposure on the basic material properties of concrete. Irradiation temperature was kept lower than 65C. The maximum fast neutron fluence reached 12
10
n/cm
(E
0.1 MeV), which is sufficiently exceeding total fast neutron fluence to be exposed to the concrete located at the exterior of a reactor pressure vessel in a typical BWR for 60-year operation. Compressive strength of the irradiated concrete specimens was roughly equivalent to that of concrete specimens cured for the same duration under the standard environment. By measuring chemically bound water content of irradiated specimens, no changes after irradiation were observed. It was confirmed that radiation exposure did not significantly affect the basic material properties of concrete within the range of radiation doses adopted in this study.
Schnase, A.; Tamura, Fumihiko; Yamamoto, Masanobu; Nomura, Masahiro; Hasegawa, Katsushi; Shimada, Taihei; Suzuki, Hiromitsu; Omori, Chihiro*; Yoshii, Masahito*; Ezura, Eiji*; et al.
Proceedings of 2009 Particle Accelerator Conference (PAC '09) (DVD-ROM), p.1988 - 1990, 2009/05
Tamura, Fumihiko; Yamamoto, Masanobu; Yoshii, Masahito*; Omori, Chihiro*; Nomura, Masahiro; Schnase, A.; Toda, Makoto*; Suzuki, Hiromitsu; Shimada, Taihei; Hara, Keigo*; et al.
Proceedings of 2009 Particle Accelerator Conference (PAC '09) (DVD-ROM), p.1445 - 1447, 2009/05
In the J-PARC RCS, we employ the longitudinal painting methods, the momentum offset injection method and applying the second harmonic RF voltages, to increase the bunching factor so that the space-charge tune shift is reduced. By the dual-harmonic operation with wide-band MA loaded cavities, in which each single cavity is driven by a superposition of the fundamental and the second harmonic RF signals, we can generate a large amplitude second harmonic RF voltage without extra cavities for the second harmonic RF. We present the results of the beam tests for the longitudinal painting in the J-PARC RCS. Also, we present the beam behavior at very high beam power.
Tamura, Fumihiko; Yamamoto, Masanobu; Yoshii, Masahito*; Omori, Chihiro*; Nomura, Masahiro; Schnase, A.; Toda, Makoto*; Suzuki, Hiromitsu; Shimada, Taihei; Hara, Keigo*; et al.
Physical Review Special Topics; Accelerators and Beams, 12(4), p.041001_1 - 041001_9, 2009/04
Times Cited Count：33 Percentile：85.2(Physics, Nuclear)In the rapid cycling synchrotron (RCS) of the Japan Proton Accelerator Research Complex (J-PARC), the longitudinal painting is important to alleviate the space-charge effects. It is known that the momentum offset injection and applying the second harmonic RF voltage improves the bunching factor, which is defined as the ratio of average and peak current. Our simulation studies show that the large amplitude second harmonic, 80% to the fundamental, is optimum, and the second harmonic phase sweep improves the bunching factor at the beginning of the injection period. We performed the beam tests of longitudinal painting in the J-PARC RCS. We proved that the longitudinal painting with the 80% second harmonic, the momentum offset of 
0.2% and the second harmonic phase sweep, improved bunching factors significantly.
Schnase, A.; Ezura, Eiji*; Hara, Keigo*; Hasegawa, Katsushi; Nomura, Masahiro; Omori, Chihiro*; Shimada, Taihei; Suzuki, Hiromitsu; Takagi, Akira*; Tamura, Fumihiko; et al.
Proceedings of 5th Annual Meeting of Particle Accelerator Society of Japan and 33rd Linear Accelerator Meeting in Japan (CD-ROM), p.340 - 342, 2008/00
Tamura, Fumihiko; Schnase, A.; Nomura, Masahiro; Yamamoto, Masanobu; Suzuki, Hiromitsu; Shimada, Taihei; Hasegawa, Katsushi; Yoshii, Masahito*; Omori, Chihiro*; Toda, Makoto*; et al.
Proceedings of 5th Annual Meeting of Particle Accelerator Society of Japan and 33rd Linear Accelerator Meeting in Japan (CD-ROM), p.337 - 339, 2008/00
The beam commissioning of the J-PARC RCS was started in October 2007 and acceleration of 
protons has been successfully achieved in February 2008. Also, the beam commissioning of MR began in May 2008. The RF capture of the beam and the extraction at the injection energy of 3 GeV was successfully performed. In both of the RCS and MR, MA (magnetic alloy) cavities are employed to achieve high accelerating voltages which are necessary to accelerate the high intensity proton beams. We employ full-digital LLRF control systems to realize precise and reproducible control of RF frequencies, voltages and phases. We present the status of the RF acceleration with examples of the beam signals. Also we discuss the future plans.
