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Journal Articles

Present and new operational quantities evaluated from photon spectrum measurements at workplaces in the research reactor and accelerator facility at the JAEA

Tanimura, Yoshihiko; Yoshitomi, Hiroshi; Nishino, Sho; Tsuji, Tomoya; Fukami, Tomoyo; Shinozuka, Tomoki; Oishi, Kohei; Ishii, Masato; Takamiya, Kei; Onuki, Takaya; et al.

Radiation Measurements, 176, p.107196_1 - 107196_6, 2024/08

The ICRU has proposed to change the definitions of the operational quantities used for the area and individual monitoring for external exposure in the ICRU Report 95. As introducing the new operational quantities into the radiation monitoring may affect the dose assessment results using the present personal dosimeters, it is necessary to characterize the energy spectrum in the workplace and the energy dependency of the dosimeters to be used. In this work the photon spectra were measured using a NaI(Tl) scintillation detector or a LaBr$$_3$$(Ce) scintillation detector at the workplaces in the Japanese Research Reactor No.3 (JRR-3) and the Japan Proton Accelerator Research Complex (J-PARC) at Japan Atomic Energy Agency (JAEA). Then the present and new operational quantities were evaluated using the above mention spectra at the workplaces and compared each other.

Journal Articles

1-MW beam operation at J-PARC RCS with minimum beam loss

Saha, P. K.; Harada, Hiroyuki; Okabe, Kota; Okita, Hidefumi; Shobuda, Yoshihiro; Tamura, Fumihiko; Yamamoto, Kazami; Yoshimoto, Masahiro; Hotchi, Hideaki*

Proceedings of 68th ICFA Advanced Beam Dynamics Workshop on High Intensity and High Brightness Hadron Beams (HB2023) (Internet), p.147 - 152, 2023/10

Journal Articles

Measurement of double-differential neutron yields for iron, lead, and bismuth induced by 107-MeV protons for research and development of accelerator-driven systems

Iwamoto, Hiroki; Nakano, Keita; Meigo, Shinichiro; Satoh, Daiki; Iwamoto, Yosuke; Sugihara, Kenta*; Nishio, Katsuhisa; Ishi, Yoshihiro*; Uesugi, Tomonori*; Kuriyama, Yasutoshi*; et al.

EPJ Web of Conferences, 284, p.01023_1 - 01023_4, 2023/05

 Times Cited Count:0 Percentile:0.21(Nuclear Science & Technology)

For accurate prediction of neutronic characteristics for accelerator-driven systems (ADS) and a source term of spallation neutrons for reactor physics experiments for the ADS at Kyoto University Critical Assembly (KUCA), we have launched an experimental program to measure nuclear data on ADS using the Fixed Field Alternating Gradient (FFAG) accelerator at Kyoto University. As part of this program, the proton-induced double-differential thick-target neutron-yields (TTNYs) and cross-sections (DDXs) for iron, lead, and bismuth have been measured with the time-of-flight (TOF) method. For each measurement, the target was installed in a vacuum chamber on the beamline and bombarded with 107-MeV proton beams accelerated from the FFAG accelerator. Neutrons produced from the targets were detected with stacked, small-sized neutron detectors for several angles from the incident beam direction. The TOF spectra were obtained from the detected signals and the FFAG kicker magnet's logic signals, where gamma-ray events were eliminated by pulse shape discrimination. Finally, the TTNYs and DDXs were obtained from the TOF spectra by relativistic kinematics. The measured TTNYs and DDXs were compared with calculations by the Monte Carlo transport code PHITS with its default physics model of INCL version 4.6 combined with GEM and those with the JENDL-4.0/HE nuclear data library.

Journal Articles

Measurement of 107-MeV proton-induced double-differential thick target neutron yields for Fe, Pb, and Bi using a fixed-field alternating gradient accelerator at Kyoto University

Iwamoto, Hiroki; Nakano, Keita; Meigo, Shinichiro; Satoh, Daiki; Iwamoto, Yosuke; Sugihara, Kenta; Nishio, Katsuhisa; Ishi, Yoshihiro*; Uesugi, Tomonori*; Kuriyama, Yasutoshi*; et al.

Journal of Nuclear Science and Technology, 60(4), p.435 - 449, 2023/04

 Times Cited Count:3 Percentile:63.91(Nuclear Science & Technology)

Double-differential thick target neutron yields (TTNYs) for Fe, Pb, and Bi targets induced by 107-MeV protons were measured using the fixed-field alternating gradient accelerator at Kyoto University for research and development of accelerator-driven systems (ADSs) and fundamental ADS reactor physics research at the Kyoto University Critical Assembly (KUCA). Note that TTNYs were obtained with the time-of-flight method using a neutron detector system comprising eight neutron detectors; each detector has a small NE213 liquid organic scintillator and photomultiplier tube. The TTNYs obtained were compared with calculation results using Monte Carlo-based spallation models (i.e., INCL4.6/GEM, Bertini/GEM, JQMD/GEM, and JQMD/SMM/GEM) and the evaluated high-energy nuclear data library, i.e., JENDL-4.0/HE, implemented in the particle and heavy iontransport code system (PHITS). All models, including JENDL-4.0/HE, failed to predict high-energy peaks at a detector angle of 5$$^{circ}$$. Comparing the energy- and angle-integrated spallation neutron yields at energies of $$le$$20 MeV estimated using the measured TTNYs and the PHITS indicated that INCL4.6/GEM would be suitable for the Monte Carlo transport simulation of ADS reactor physics experiments at the KUCA.

Journal Articles

Measurement of H$$^{0}$$ particles generated by residual gas stripping in the Japan Proton Accelerator Research Complex linac

Tamura, Jun; Futatsukawa, Kenta*; Kondo, Yasuhiro; Liu, Y.*; Miyao, Tomoaki*; Morishita, Takatoshi; Nemoto, Yasuo*; Okabe, Kota; Yoshimoto, Masahiro

Nuclear Instruments and Methods in Physics Research A, 1049, p.168033_1 - 168033_7, 2023/04

 Times Cited Count:1 Percentile:63.33(Instruments & Instrumentation)

The Japan Proton Accelerator Research Complex (J-PARC) linac is a high-intensity accelerator in which beam loss is a critical issue. In the J-PARC linac, H$$^{-}$$ beams are accelerated to 191~MeV by a separated drift tube linac (SDTL) and subsequently to 400~MeV by an annular-ring coupled structure (ACS). Because there are more beam loss mechanisms in H$$^{-}$$ linacs than in proton linacs, it is imperative to investigate the beam loss circumstances for beam loss mitigation. Electron-stripping phenomena, which generate uncontrollable H$$^{0}$$ particles, are characteristic beam loss factors of H$$^{-}$$ linacs. To clarify the beam loss causes in the J-PARC linac, a new diagnostic line was installed in the beam transport between the SDTL and ACS. In this diagnostic line, H$$^{0}$$ particles were separated from the H$$^{-}$$ beam, and the intensity profiles of the H$$^{0}$$ particles were successfully measured by horizontally scanning a graphite plate in the range where H$$^{0}$$ particles were distributed. By examining the intensity variation of the H$$^{0}$$ particles with different residual pressure levels, we proved that half of the H$$^{0}$$ particles in the SDTL section are generated by the residual gas stripping in the nominal beam operation of the J-PARC linac.

Journal Articles

Recent results of beam loss mitigation and extremely low beam loss operation of J-PARC RCS

Saha, P. K.; Okabe, Kota; Nakanoya, Takamitsu; Shobuda, Yoshihiro; Harada, Hiroyuki; Tamura, Fumihiko; Okita, Hidefumi; Yoshimoto, Masahiro; Hotchi, Hideaki*

Journal of Physics; Conference Series, 2420, p.012040_1 - 012040_7, 2023/01

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

Reducing the effect of noise generated from stepper motor for H0 collimator in J-PARC RCS

Fujiyama, Hiroki*; Takahashi, Hiroki; Okabe, Kota; Ito, Yuichi*; Hatakeyama, Shuichiro; Suzuki, Takahiro*; Otsu, Satoru*; Yamakawa, Ryuto*

Proceedings of 19th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.529 - 531, 2023/01

Stepper motors are used for mechanical drive in collimators and wire scanner monitors of J-PARC accelerators. Many of these drive unit hardware have been used since the beginning of J-PARC construction, and it is necessary to take measures against aging deterioration. Therefore, we started updating the motor and control system from around 2017. However, when the stepper motor was updated to the current product in the RCS H0 collimator, a malfunction occurred. This is because the drive unit control system cannot correctly recognize the state of the LS (limit switch) due to the noise generated by the motor driver, which hinders the operation. When the noise generated from the old and new stepper motors was measured in a simple test environment for confirmation, it was found that the current product was clearly larger. As a countermeasure, when the wiring of the stepper motor, which was bundled in a single multi-core cable, was separated into separate cables for the power system and LS signal system, the noise level was reduced to about 1/10 and normal operation was restored. I was able to. In this case, we report on noise countermeasures for the RCS H0 collimator drive unit.

Journal Articles

Measurement of 107-MeV proton-induced double-differential neutron yields for iron for research and development of accelerator-driven systems

Iwamoto, Hiroki; Nakano, Keita; Meigo, Shinichiro; Satoh, Daiki; Iwamoto, Yosuke; Ishi, Yoshihiro*; Uesugi, Tomonori*; Kuriyama, Yasutoshi*; Yashima, Hiroshi*; Nishio, Katsuhisa; et al.

JAEA-Conf 2022-001, p.129 - 133, 2022/11

For accurate prediction of neutronic characteristics for accelerator-driven systems (ADS) and a source term of spallation neutrons for reactor physics experiments for the ADS at Kyoto University Critical Assembly (KUCA), we have launched an experimental program to measure nuclear data on ADS using the Fixed Field Alternating Gradient (FFAG) accelerator at Kyoto University. As part of this program, the proton-induced double-differential thick-target neutron-yields (TTNYs) and cross-sections (DDXs) for iron have been measured with the time-of-flight (TOF) method. For each measurement, the target was installed in a vacuum chamber on the beamline and bombarded with 107-MeV proton beams accelerated from the FFAG accelerator. Neutrons produced from the targets were detected with stacked, small-sized neutron detectors composed of the NE213 liquid organic scintillators and photomultiplier tubes, which were connected to a multi-channel digitizer mounted with a field-programmable gate array (FPGA), for several angles from the incident beam direction. The TOF spectra were obtained from the detected signals and the FFAG kicker magnet's logic signals, where gamma-ray events were eliminated by pulse shape discrimination applying the gate integration method to the FPGA. Finally, the TTNYs and DDXs were obtained from the TOF spectra by relativistic kinematics.

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:5 Percentile:81.82(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.

Journal Articles

Foil hits reduction by minimizing injection beam size at the foil in J-PARC RCS

Saha, P. K.; Yoshimoto, Masahiro; Okabe, Kota; Harada, Hiroyuki; Tamura, Fumihiko; Hotchi, Hideaki*

Proceedings of 12th International Particle Accelerator Conference (IPAC 21) (Internet), p.590 - 593, 2021/08

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

1.2-MW-equivalent high-intensity beam tests in J-PARC RCS

Hotchi, Hideaki; Harada, Hiroyuki; Hayashi, Naoki; Kinsho, Michikazu; Okabe, Kota; Saha, P. K.; Shobuda, Yoshihiro; Tamura, Fumihiko; Yamamoto, Kazami; Yamamoto, Masanobu; et al.

JPS Conference Proceedings (Internet), 33, p.011018_1 - 011018_6, 2021/03

no abstracts in English

Journal Articles

Phase space formation of high intensity 60 and 80 mA H$$^-$$ beam with orifice in J-PARC front-end

Shibata, Takanori*; Ikegami, Kiyoshi*; Nammo, Kesao*; Liu, Y.*; Otani, Masashi*; Naito, Fujio*; Shinto, Katsuhiro; Okoshi, Kiyonori; Okabe, Kota; Kondo, Yasuhiro; et al.

JPS Conference Proceedings (Internet), 33, p.011010_1 - 011010_6, 2021/03

Together with the intensity upgrade in J-PARC Linac Front-End, improvement of RFQ transmission ratio is an important task. This RFQ transmission ratio depends strongly upon the solenoid current settings in the low energy beam transport line (LEBT). In the present study, high beam current cases (72 mA and 88 mA H$$^-$$ beam current in LEBT) are investigated at a test-stand. Phase space distributions of the H$$^-$$ beam particles at the RFQ entrance are measured and compared with numerical results by Particle-In-Cell simulation. As a result, it has been clarified that a 15 mm $$phi$$ orifice for differential pumping of H$$_2$$ gas coming from the ion source plays a role as a collimator in these beam conditions. This leads to change the beam emittance and Twiss parameters at the RFQ entrance. Especially in the condition with the beam current up to 88 mA in LEBT, the beam collimation contributes to optimize the phase space distribution to the RFQ acceptance with relatively low solenoid current settings. As a higher solenoid current setting would be necessary to suppress the beam expansion due to high space charge effect, these results suggest that current-saving of the solenoids can be possible even in the higher beam intensity operations.

Journal Articles

High intensity beam studies for the new MEBT1 design

Okabe, Kota; Liu, Y.*; Otani, Masashi*; Moriya, Katsuhiro; Shibata, Takanori*; Chimura, Motoki*; Hirano, Koichiro; Oguri, Hidetomo; Kinsho, Michikazu

JPS Conference Proceedings (Internet), 33, p.011011_1 - 011011_6, 2021/03

To realize more stable operation of the J-PARC accelerators, we have a re-design plan of an MEBT1 (Medium Energy Beam Transport). At the J-PARC Linac, the MEBT1 has transverse and longitudinal beam matching section for the DTLs. However there are some locally activated spots in DTL area at the current beam power level. To reduce beam loss during a beam acceleration at the DTLs is a most important task for a stable user operation. The first thing we should do is investigation a connection between beam quality in the MEBT1 and parameters of the upstream hardware. In this presentation, we will report a high intensity beam study results at the MEBT1.

Journal Articles

Charge exchange method of H$$^{-}$$ beam by electron beam

Okabe, Kota

Proceedings of 17th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.446 - 448, 2020/09

One of the important research themes for further enhancement of the proton accelerator is the advancement of the charge exchange injection method. At present, the charge exchange injection method in the high-intensity proton accelerator facility currently in operation mainly uses the charge exchange foil. However, this method has a problem in that activation of the around the charge exchange injection point due to beam scattering by the foil and neutrons generated from the foil. In order to solve this problem, new charge exchange injection methods such as laser charge exchange method are being researched in accelerator facilities around the world. In this research, we focus on the charge exchange method using electron beams and proceed with the basic experiments. In this presentation, we will report the progress of the charge exchange efficiency measurement of negative hydrogen ion beam using electron beam.

Journal Articles

J-PARC 3-GeV RCS; 1-MW beam operation and beyond

Hotchi, Hideaki; Harada, Hiroyuki; Hayashi, Naoki; Kinsho, Michikazu; Okabe, Kota; Saha, P. K.; Shobuda, Yoshihiro; Tamura, Fumihiko; Yamamoto, Kazami; Yamamoto, Masanobu; et al.

Journal of Instrumentation (Internet), 15(7), p.P07022_1 - P07022_16, 2020/07

 Times Cited Count:3 Percentile:20.35(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Evaluation of 2-D transverse beam profile monitor using gas sheet at J-PARC LINAC

Kamiya, Junichiro; Okabe, Kota; Kinsho, Michikazu; Moriya, Katsuhiro; Yamada, Ippei; Ogiwara, Norio*; Hikichi, Yusuke*; Wada, K.*

Journal of Physics; Conference Series, 1350, p.012149_1 - 012149_6, 2019/12

 Times Cited Count:3 Percentile:81.79(Physics, Particles & Fields)

To obtain a getter effect to titanium vacuum duct surface, the method to remove the oxide on the surface by sputtering with ionized molecules has been developed. In the method, a sheet-shaped gas distribution with a uniform and high density is generated through a narrow slit by a small amount of gas. In this report, the gas density distribution was calculated by the Monte Carlo simulation code. As a result, it was found that a gas injection from both directions was effective to generate uniform density distribution. Furthermore, the gas injection method was applied to a non-destructive beam profile monitor, that detects ions generated by the interaction between gas molecules and beam. In this monitor, dependence of the beam profile on the injected gas amount was measured. A small amount of injected gas was found to be ideal for the beam profile measurements in the unsaturated and a high S/N ratio region.

Journal Articles

Coupling impedance of the collimator without RF-Shields at the RCS in J-PARC

Shobuda, Yoshihiro; Okabe, Kota; Kamiya, Junichiro; Moriya, Katsuhiro

Journal of Physics; Conference Series, 1350, p.012113_1 - 012113_7, 2019/12

 Times Cited Count:0 Percentile:0.06(Physics, Particles & Fields)

All holes on the chamber walls of synchrotrons should be filled with the radiofrequency (RF)-shields to suppress coupling impedances that excite beam instabilities. In a synchrotron, titanium nitride (TiN)-coated RF-shields are installed with collimators. If the holes, through which the collimator jaw enters and exits the chamber, are filled with such RF-shields, the shields may break down as the dynamic coefficient of TiN increases in vacuum. At the Rapid Cycling Synchrotron (RCS), the RF-shields are eliminated from the collimator after demonstrating that the effect due to the RF-shields is negligible on the impedance at low frequencies.

Journal Articles

Beam dynamics study for beam loss mitigation in the J-PARC RCS

Hotchi, Hideaki; Harada, Hiroyuki; Okabe, Kota; Saha, P. K.; Shobuda, Yoshihiro; Tamura, Fumihiko; Yoshimoto, Masahiro

Kasokuki, 16(2), p.109 - 118, 2019/07

no abstracts in English

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