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Journal Articles

Consideration of high intensity single bunch acceleration in J-PARC RCS

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.

Journal Articles

Japanese Evaluated Nuclear Data Library version 5; JENDL-5

Iwamoto, Osamu; Iwamoto, Nobuyuki; Kunieda, Satoshi; Minato, Futoshi; Nakayama, Shinsuke; Abe, Yutaka*; Tsubakihara, Kosuke*; Okumura, Shin*; Ishizuka, Chikako*; Yoshida, Tadashi*; et al.

Journal of Nuclear Science and Technology, 60(1), p.1 - 60, 2023/01

 Times Cited Count:17 Percentile:99.99(Nuclear Science & Technology)

Journal Articles

Results of 1-MW operation in J-PARC 3 GeV rapid cycling synchrotron, 2

Yamamoto, Kazami; Yamamoto, Masanobu; Yamazaki, Yoshio; Nomura, Masahiro; Suganuma, Kazuaki; Fujirai, Kosuke; Kamiya, Junichiro; Nakanoya, Takamitsu; Hatakeyama, Shuichiro; Yoshimoto, Masahiro; et al.

Proceedings of 19th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.277 - 281, 2023/01

The J-PARC 3GeV Rapid Cycling Synchrotron (RCS) is aiming to provide the proton beam of very high power for neutron experiments and the main ring synchrotron. We have continued the beam commissioning and the output power from RCS have been increasing. In recent years, we have been trying continuous supply of 1-MW high-intensity beam, which is the design value, to a neutron target. We tried to operate continuously for over 40 hours in June 2020. However, some trouble occurred and the operation was frequently suspended. In June 2021, we tried again 1-MW operation but it was suspended due to deterioration of the cooling water performance. Last summer shutdown period, we recovered performance of the cooling water system and retried in this June. In the final case, the outside temperature became extremely high. We could not keep 1-MW power, whereas 600 kW beam was delivered in stable.

Journal Articles

Achievement of low beam loss at high-intensity operation of J-PARC 3 GeV RCS

Saha, P. K.; Okabe, Kota; Nakanoya, Takamitsu; Yoshimoto, Masahiro; Shobuda, Yoshihiro; Harada, Hiroyuki; Tamura, Fumihiko; Okita, Hidefumi; Hatakeyama, Shuichiro; Moriya, Katsuhiro; et al.

Proceedings of 19th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1 - 5, 2023/01

Journal Articles

Structure and properties of amorphous magnesium carbonate, a key material for geological storage of carbon dioxide

Kyono, Atsushi*; Yamamoto, Genichiro*; Yoneda, Yasuhiro; Okada, Satoru*

Isotope News, (783), p.23 - 27, 2022/10

Mineral traps are attracting attention as an underground storage method for carbon dioxide. Carbon dioxide laden groundwater reacts with basalt to form magnesite. The formed magnesium carbonate phase varies in many ways, but we tried to clarify the structure because all of them pass through amorphous magnesium carbonate. Pair distribution function using high-energy X-ray diffraction revealed that amorphous magnesium carbonate has a structure similar to that of hydromagnesite. It can be said that it is a safe sequestration method as a carbon dioxide storage technology.

Journal Articles

Structural analysis of high-energy implanted Ni atoms into Si(100) by X-ray absorption fine structure spectroscopy

Entani, Shiro*; Sato, Shinichiro*; Honda, Mitsunori; Suzuki, Chihiro*; Taguchi, Tomitsugu*; Yamamoto, Shunya*; Oshima, Takeshi*

Radiation Physics and Chemistry, 199, p.110369_1 - 110369_7, 2022/10

 Times Cited Count:1 Percentile:35.78(Chemistry, Physical)

Ni silicide synthesis by Ni ion beam irradiation into Si attracts attention due to its advantages including the ability of formation of local structures, the controllability of ion beams, the formability of silicide without heat treatment and the high reproducibility of the resulting specimen. In this work, we investigate the local atomic structure of Si implanted with 3.0 MeV Ni$$^{+}$$ ions. Analysis of Ni K-edge fluorescent-yield extended X-ray absorption fine structure reveals that Ni atoms have mixed structure of metallic-like face-centered cubic Ni and NiSi$$_{2}$$ phases at the initial stage of the irradiation and the formation of NiSi$$_{2}$$ promotes significantly with the ion fluence above 10 $$^{15}$$ ions cm$$^{-2}$$. With consideration of the agreement between the ion fluence threshold for the structural transition and the critical Si-amorphization fluence, it is concluded that the amorphization of Si plays an important role in the synthesis of the NiSi$$_{2}$$ phase in Ni$$^{+}$$-irradiated Si.

Journal Articles

Design and actual performance of J-PARC 3 GeV rapid cycling synchrotron for high-intensity operation

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:3 Percentile:82.38(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.

JAEA Reports

Report of the design examination and the installation work for the radiation shield at the beam injection area in the 3 GeV synchrotron

Nakanoya, Takamitsu; Kamiya, Junichiro; Yoshimoto, Masahiro; Takayanagi, Tomohiro; Tani, Norio; Kotoku, Hirofumi*; Horino, Koki*; Yanagibashi, Toru*; Takeda, Osamu*; Yamamoto, Kazami

JAEA-Technology 2021-019, 105 Pages, 2021/11

JAEA-Technology-2021-019.pdf:10.25MB

Since a user operation startup, the 3 GeV synchrotron accelerator (Rapid-Cycling Synchrotron: RCS) gradually reinforced the beam power. As a result, the surface dose rate of the apparatus located at the beam injection area of the RCS, such as the magnet, vacuum chambers, beam monitors, etc., increases year by year. The beam injection area has many apparatuses which required manual maintenance, so reducing worker's dose is a serious issue. To solve this problem, we have organized a task force for the installation of the shield. The task force has aimed to optimize the structure of the radiation shield, construct the installation procedure with due consideration of the worker's dose suppression. As the examination result of the shield design, we have decided to adopt removal shielding that could be installed quickly and easily when needed. We carried out shield installation work during the 2020 summer maintenance period. The renewal work required to install the shielding has been carried out in a under high-dose environment. For this reason, reducing the dose of workers was an important issue. So, we carefully prepared the work plan and work procedure in advance. During the work period, we implemented various dose reduction measures and managed individual dose carefully. As a result, the dose of all workers could be kept below the predetermined management value. We had installed removal shielding at the beam injection area in the 2020 summer maintenance period. We confirmed that this shield can contribute to the reduction of the dose during work near the beam injection area. It was a large-scale work to occupy the beam injection area during almost of the summer maintenance period. However, it is considered very meaningful for dose suppression in future maintenance works.

Journal Articles

Comparison of sodium fast reactor core assembly seismic evaluation using the Japanese and French simulation tools

Yamamoto, Tomohiko; Matsubara, Shinichiro*; Harada, Hidenori*; Saunier, P.*; Martin, L.*; Gentet, D.*; Dirat, J.-F.*; Collignon, C.*

Nuclear Engineering and Design, 383, p.111406_1 - 111406_14, 2021/11

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

Japan-France collaboration on ASTRID (Advanced Sodium Technological Reactor for Industrial Demonstration) project is launched in 2014. In this project, Japan-France evaluates core assemblies with interferences on seismic event. The object of this study is to verify the seismic evaluation method on core assemblies between Japan and France by comparing the results. The analysis of this benchmark calculation shows a satisfactory agreement between the Japanese and French tools and the figures show a good behavior of the core in horizontal direction under French seismic condition.

Journal Articles

Neutron measurement in the accelerator tunnel of J-PARC Rapid Cycling Synchrotron

Yamamoto, Kazami; Hatakeyama, Shuichiro; Otsu, Satoru*; Matsumoto, Tetsuro*; Yoshimoto, Masahiro

Proceedings of 18th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.494 - 498, 2021/10

J-PARC 3 GeV Rapid Cycling Synchrotron (RCS) provides more than 700 kW proton beam to the neutron target. In order to investigate the influence of the radiation, we intend to evaluate the radiations such as the neutron and gamma-rays, which are generated due to the proton beam loss. If the amount of beam loss is excessive, it becomes difficult to identify the individual neutron and gamma ray. Therefore, we investigated the signal rate of the extraction point of RCS. Preliminary result indicated that we can enough distinguish the neutron and gamma-ray by the liquid scintillator.

Journal Articles

Radiation shielding installation for beam injection section of 3GeV synchrotron

Nakanoya, Takamitsu; Kamiya, Junichiro; Yoshimoto, Masahiro; Takayanagi, Tomohiro; Tani, Norio; Kotoku, Hirofumi*; Horino, Koki*; Yanagibashi, Toru*; Takeda, Osamu*; Yamamoto, Kazami

Proceedings of 18th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.238 - 242, 2021/10

Since a user operation startup, the 3GeV synchrotron accelerator (Rapid-Cycling Synchrotron: RCS) gradually reinforced the beam power. As a result, the surface dose rate of the apparatus located at the beam injection area of the RCS increases year by year. The beam injection area has many apparatuses which required manual maintenance, so reducing worker's dose is a serious issue. To solve this problem, we have decided to adopt removal shielding that could be installed quickly and easily when needed. We carried out shield installation work during the 2020 summer maintenance period. The installation work of the shield has been carried out in a under high-dose environment. For this reason, reducing the dose of workers was an important issue. So, we carefully prepared the work plan and work procedure in advance. During the work period, we implemented various dose reduction measures and managed individual dose carefully. As a result, the dose of all workers could be kept below the predetermined management value. We had installed removal shielding at the beam injection area in the 2020 summer maintenance period. We confirmed that this shield can contribute to the reduction of the dose during work near the beam injection area.

Journal Articles

Improved vacuum system for high-power proton beam operation of the rapid cycling synchrotron

Kamiya, Junichiro; Kotoku, Hirofumi*; Kurosawa, Shunta*; Takano, Kazuhiro; Yanagibashi, Toru*; Yamamoto, Kazami; Wada, Kaoru

Physical Review Accelerators and Beams (Internet), 24(8), p.083201_1 - 083201_23, 2021/08

 Times Cited Count:0 Percentile:0.02(Physics, Nuclear)

Through the operation of the vacuum system in J-PARC, it becomes evident that the high-power beam has more powerful effects on the vacuum system than expected. Those effects are the malfunction of vacuum equipment and the large pressure rise. The former is the failure of the turbomolecular pump (TMP) controller. The TMP itself is also damaged by a bearing crush due to a touch-down. We have developed a TMP controller that can connect with long cables of more than 200 m lengths to install the controller in a control room where there is no radiation influence. The TMP with high-strength bearing has been also developed. The latter is an extreme pressure rise with increasing the beam power. It is indicated that the pressure rise mechanism is a result of ion-stimulated gas desorption. It is finally confirmed that the dynamic pressure during the high-power beam is effectually suppressed by additionally installing the NEG pumps.

Journal Articles

Dependence of charge-exchange efficiency on cooling water temperature of a beam transport line

Yamamoto, Kazami; Hatakeyama, Shuichiro; Saha, P. K.; Moriya, Katsuhiro; Okabe, Kota; Yoshimoto, Masahiro; Nakanoya, Takamitsu; Fujirai, Kosuke; Yamazaki, Yoshio; Suganuma, Kazuaki

EPJ Techniques and Instrumentation (Internet), 8(1), p.9_1 - 9_9, 2021/07

The 3 GeV Rapid Cycling Synchrotron at the Japan Proton Accelerator Research Complex supplies a high-intensity proton beam for neutron experiments. Various parameters are monitored to achieve a stable operation, and it was found that the oscillations of the charge-exchange efficiency and cooling water temperature were synchronized. We evaluated the orbit fluctuations at the injection point using a beam current of the injection dump, which is proportional to the number of particles that miss the foil and fail in the charge exchange, and profile of the injection beam. The total width of the fluctuations was approximately 0.072 mm. This value is negligible from the user operation viewpoint as our existing beam position monitors cannot detect such a small signal deviation. This displacement corresponds to a 1.63$$times$$10$$^{-5}$$ variation in the dipole magnetic field. Conversely, the magnetic field variation in the L3BT dipole magnet, which was estimated by the temperature change directly, is 4.08$$times$$10$$^{-5}$$. This result suggested that the change in the cooling water temperature is one of the major causes of the efficiency fluctuation.

Journal Articles

Observation of longitudinal magnetic fluctuations at a first-order ferromagnetic quantum phase transition in UGe$$_2$$

Noma, Yuichiro*; Kotegawa, Hisashi*; Kubo, Tetsuro*; To, Hideki*; Harima, Hisatomo*; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika*; Ito, Kohei*; Nakamura, Ai*; et al.

Journal of the Physical Society of Japan, 90(7), p.073707_1 - 073707_5, 2021/07

 Times Cited Count:0 Percentile:0(Physics, Multidisciplinary)

Journal Articles

Crystal structure of nesquehonite, MgCO$$_{3}$$ $$cdot$$ 3H(D)$$_{2}$$O by neutron diffraction and effect of pH on structural formulas of nesquehonite

Yamamoto, Genichiro*; Kyono, Atsushi*; Abe, Jun*; Sano, Asami; Hattori, Takanori

Journal of Mineralogical and Petrological Sciences, 116(2), p.96 - 103, 2021/04

 Times Cited Count:3 Percentile:34.11(Mineralogy)

Neutron diffraction, Raman spectroscopy, and thermal analysis were performed to investigate the composition, structure, and formation conditions of the magnesium carbonate hydrate nesquehonite. The time-of-flight neutron diffraction revealed the crystal structure of the monoclinic space group $$P$$2$$_{1}/n$$ with lattice parameters of $$a$$=7.72100(12)$AA, $b$$=5.37518(7)$AA, $c$$=12.1430(3)$AA, $beta$$=90.165(4)$$^circ$$, in which two deuterium atoms are coordinated to the O1, O2, and O6 atoms to form water molecules. The three water molecules in the structure suggests the structural formula of the nesquehonite should be MgCO$$_{3}$$ $$cdot$$ 3H$$_{2}$$O rather than Mg(HCO$$_{3}$$)(OH) $$cdot $$2H$$_{2}$$O.

Journal Articles

Recent status & improvements of the RCS vacuum system

Kamiya, Junichiro; Kotoku, Hirofumi; Hikichi, Yusuke*; Takahashi, Hiroki; Yamamoto, Kazami; Kinsho, Michikazu; Wada, Kaoru*

JPS Conference Proceedings (Internet), 33, p.011023_1 - 011023_6, 2021/03

The vacuum system is the key for the stable high power beam operation in J-PARC 3 GeV rapid cycling synchrotron (RCS), because the gas molecules in the beam line make the beam loss due to the scattering. The more than 10 years operation of the RCS vacuum system showed that the ultra-high vacuum (UHV) has been stably maintained by the several developments. The challenges for lower beam line pressure will exist in a future operation with higher beam power. For such challenge, a TMP with a rotor of titanium alloy, which have much higher mechanical strength than aluminum allow for the normal rotter, has been developed. Overcoming the difficulties of the machining performance of the titanium alloy rotor was successfully manufactured. We will report the summary of the 10 years operation of the RCS vacuum system and the incoming developments towards the XHV.

Journal Articles

Thermally altered subsurface material of asteroid (162173) Ryugu

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:30 Percentile:97.01(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 $$^{circ}$$C, similar to the surface. In contrast, thermophysical modeling indicates that radiative heating does not increase the temperature above 200 $$^{circ}$$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.

Journal Articles

High voltage dependence measurement of beam loss monitor in J-PARC RCS

Hatakeyama, Shuichiro; Yoshimoto, Masahiro; Yamamoto, Kazami

Proceedings of 17th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.475 - 477, 2020/09

J-PARC accelerators consist of linear accelerator (LINAC), 3GeV synchrotron (RCS) and main ring synchrotron (MR). RCS is an important facility delivering the beam to Materials and Life Science Experimental Facility (MLF) and MR. In RCS 87 proportional counter type beam loss monitors (PBLM) are installed and it is protecting the equipments on the beam line from the radioactivation by alerting the machine protection system (MPS) when the integrated value of the beam loss in an accelerating cycle gets over the limit. In this presentation, -1000V to -2000V high voltage are adapted to PBLMs and output was measured. In result, some PBLMs where the beam loss is large enough, there are saturations around -1400V to -2000V about the peak value of beam loss but no saturation about integral value of beam loss. Also it is considered the new HV system which solves some issues of the on-going HV system.

Journal Articles

Results of 1-MW operation in J-PARC 3 GeV rapid cycling synchrotron

Yamamoto, Kazami; Yamamoto, Masanobu; Yamazaki, Yoshio; Nomura, Masahiro; Suganuma, Kazuaki; Fujirai, Kosuke; Kamiya, Junichiro; Hatakeyama, Shuichiro; Hotchi, Hideaki; Yoshimoto, Masahiro; et al.

Proceedings of 17th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.209 - 213, 2020/09

The J-PARC 3GeV Rapid Cycling Synchrotron (RCS) is aiming to provide the proton beam of very high power for neutron experiments and the main ring synchrotron. We have continued the beam commissioning and the output power from RCS have been increasing. In recent years, just before the summer shutdown period, we have been trying continuous supply of 1-MW high-intensity beam, which is the design value, to a neutron target. First trial was 1-hour continuous operation in July 2018, and second trial was 10-hours continuous in July 2019. In both cases, we achieved almost stable operation. Furthermore, in June 2020, we tried to operate continuously for over 40 hours. But in this case, some trouble occurred and the operation was frequently suspended. Through these continuous operation trials, we have identified issues for stable operation of 1 MW. In this presentation, we will report the results of 1-MW continuous operation and issues obtained from these results.

Journal Articles

First measurement and online monitoring of the stripper foil thinning and pinhole formation to achieve a longer foil lifetime in high-intensity accelerators

Saha, P. K.; Yoshimoto, Masahiro; Hatakeyama, Shuichiro; Hotchi, Hideaki; Harada, Hiroyuki; Tamura, Fumihiko; Yamamoto, Kazami; Yamazaki, Yoshio; Kinsho, Michikazu; Irie, Yoshiro*

Physical Review Accelerators and Beams (Internet), 23(8), p.082801_1 - 082801_13, 2020/08

AA2020-0279.pdf:1.92MB

 Times Cited Count:4 Percentile:46.72(Physics, Nuclear)

320 (Records 1-20 displayed on this page)