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Journal Articles

In-situ measurement of radiation driven back-conversion from para to ortho liquid hydrogen state in cold moderators at J-PARC

Teshigawara, Makoto; Lee, Y.*; Tatsumoto, Hideki*; Hartl, M.*; Aso, Tomokazu; Iverson, E. B.*; Ariyoshi, Gen; Ikeda, Yujiro*; Hasegawa, Takumi*

Nuclear Instruments and Methods in Physics Research B, 557, p.165534_1 - 165534_10, 2024/12

 Times Cited Count:0

At Japanese Spallation Neutron Source in J-PARC, the para-hydrogen fraction was measured by using Raman spectroscopy in-situ for an integrated beam power of 9.4 MW$$cdot$$h at 1 MW operation, to evaluate the functionality of the ferric oxyhydroxide catalyst. This result showed that full functionality of the catalyst was retained up to the 1 MW operation. We attempted to study the effect of neutron scattering driven para to ortho-hydrogen back-conversion rate in the absence of the catalyst effect with a bypass line without catalyst. The measured increase of ortho-hydrogen fraction was 0.44% for an integrated beam power of 2.4 MW$$cdot$$h at 500 kW operation, however, which was considered to be due to not only to neutron collisions in cold moderators but also to the high ortho-hydrogen fraction of initially static liquid hydrogen in the bypass line and passive exudation of quasi-static hydrogen in the catalyst vessel to the main loop.

Journal Articles

Application of machine learning to spattering phenomena in laser cutting

Kusumoto, Toshiyuki*; Saruta, Koichi; Naoe, Takashi; Teshigawara, Makoto; Futakawa, Masatoshi; Hasegawa, Kazuo*; Tsuboi, Akihiko

Jikken Rikigaku, 23(4), p.310 - 315, 2023/12

Reducing spatter, i.e., melt droplets flown out of the melt pool, is one of the critical issues when laser cutting is employed as a machining tool for radioactive wastes because the ejected droplets can lead to radioactive contamination with potential human exposure. The spattering phenomena are complicated processes that involve multiple physical phenomena, causing difficulty in the determination of laser parameters to minimize the amount of spatter. Here we observe the spatter ejected from 316L stainless steel plates using a high-speed camera and apply a machine learning technique to these captured images on the basis of three distinctive behaviors appeared at specific time intervals of the process of spattering phenomena: (I) a vapor, (II) a liquid film and breakup into droplets, and (III) a liquid capillary. The numerical model established through the machine learning technique predicts the spattering phenomena with an accuracy of 89% and can be used to determine the laser power and beam diameter that reduce the spatter eruption during laser irradiation.

Journal Articles

Experiment and numerical simulation of pulsation flow in single channel for Li-7 enrichment technology development by MCCCE method

Horiguchi, Naoki; Yoshida, Hiroyuki; Kitatsuji, Yoshihiro; Hasegawa, Makoto*; Kishimoto, Tadafumi*

Proceedings of 30th International Conference on Nuclear Engineering (ICONE30) (Internet), 7 Pages, 2023/05

From the viewpoint of energy security in Japan and reduction of the environmental load, continuous operation of light water reactors is essential. Since a pH adjuster with enriched Li-7 ions is required for water quality control on PWR, the development of Li-7 enrichment technology is one of the key issues. The multi-channel counter-current electrophoresis (MCCCE) method has been developed as the technology with a low environmental load. To put this method into practical use, it is necessary to understand Li-7 ion behavior in the channel flow and optimize the experimental condition to separate Li-7 and its isotope. In this paper, to understand Li-7 ion behavior in a single channel of the experimental apparatus, a numerical simulation method based on a computational fluid dynamics (CFD) code with a particle tracking method, TPFIT-LPT, was developed. In the method, the motion of multiple ions under the electric field was simulated as a particle with an added velocity by the electric field. The difference in the isotopes was represented by changing of the magnitude of the added velocity. We also considered that although it is impossible to measure the behavior of each ion, it is important to measure the flow velocity of the bulk fluid for the validation of the numerical simulation. We developed a lab-scale experimental apparatus in which the single channel of the actual apparatus was simplified to measure the flow velocity by Particle Image Velocimetry (PIV). We set a pulsation flow condition on the lab-scale experiment, which is one of difficult conditions for the numerical simulation, and measured the velocity. As the result, we confirmed that the pulsation flow was reproduced. We set the measured data as the inlet boundary condition of the numerical simulation and conducted it. As the numerical result, we confirmed the ions affected by the electric field moved upstream with pulsation. We also confirmed the effect of the electric field on the motion of the isotope.

Journal Articles

Measurement of displacement cross section for proton in the kinetic energy range from 0.4 GeV to 3 GeV

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.

Journal Articles

Measurement of displacement cross-sections of copper and iron for proton with kinetic energies in the range 0.4 - 3 GeV

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:12 Percentile:76.86(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.

Journal Articles

Measurement of displacement cross section of structural materials utilized in the proton accelerator facilities with the kinematic energy above 400 MeV

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:0.00(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.

Journal Articles

Measurement of displacement cross section of structural materials utilized in the proton accelerator facilities with the kinematic energy above 400 MeV

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

Journal Articles

Recovery of helium refrigerator performance for cryogenic hydrogen system at J-PARC MLF

Aso, Tomokazu; Teshigawara, Makoto; Hasegawa, Shoichi; Muto, Hideki; Aoyagi, Katsuhiro; Nomura, Kazutaka; Takada, Hiroshi

Journal of Physics; Conference Series, 1021(1), p.012085_1 - 012085_4, 2018/06

BB2016-1899.pdf:0.54MB

 Times Cited Count:0 Percentile:0.00(Nuclear Science & Technology)

Journal Articles

Measurement of displacement cross-section for structural materials in High-Power Proton Accelerator Facility

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

JAEA Reports

Investigation and measures of abnormal events of helium refrigerator for cryogenic hydrogen system at J-PARC

Aso, Tomokazu; Teshigawara, Makoto; Hasegawa, Shoichi; Aoyagi, Katsuhiro*; Muto, Hideki*; Nomura, Kazutaka*; Takada, Hiroshi; Ikeda, Yujiro

JAEA-Technology 2017-021, 75 Pages, 2017/08

JAEA-Technology-2017-021.pdf:33.03MB

Liquid hydrogen is employed as a cold neutron moderator material at the spallation neutron source of Materials and Life science experimental Facility of Japan Proton Accelerator Research Complex (J-PARC). From January 2015, it became observable that the differential pressure between heat exchangers and an 80 K adsorber (ADS) in a helium refrigerator system increased with operating time. In November 2015, the differential pressure rise became more significant, leading to degrade the refrigerating performance in cooling liquid hydrogen. In order to investigate the cause of the abnormal differential pressure rise between the heat exchangers and the ADS, we carried out visual inspection inside the heat exchangers and analyzed the impurities contained in the helium gas. Unfortunately, we could not identify the impurities causing the performance degradation, but observed a trace of oil in the inlet piping of the heat exchanger. Based on investigations of the abnormal events occurred in the refrigerators with similar refrigerating capacity at other facilities, we took measures that cleaning the heat exchangers with Freon and replacing the ADS with new one. As a result, the differential pressure rise phenomenon was removed to recover the performance. We have detected oil from the Freon used for cleaning the heat exchangers and at a felt supporting charcoal packed in the ADS. In particular, oil was accumulated in membranous form onto the felt at the entrance side in the ADS. The amount of oil contained in the helium gas was about 10 ppb or so, less than the design value, in the helium refrigerator. However, the oil accumulated onto the felt in the ADS through long operating period may cause abnormal differential pressure rise, leading to the performance degradation of the helium refrigerator. Further study is needed to specify the cause more clearly.

Journal Articles

Development of stress intensity factors for cracks with large aspect ratios in pipes and plates

Li, Y.; Hasegawa, Kunio*; Udagawa, Makoto

Journal of Pressure Vessel Technology, 139(2), p.021202_1 - 021202_13, 2017/04

 Times Cited Count:3 Percentile:16.80(Engineering, Mechanical)

Journal Articles

Vacuum tube operation analysis under multi-harmonic driving and heavy beam loading effect in J-PARC RCS

Yamamoto, Masanobu; Nomura, Masahiro; Shimada, Taihei; Tamura, Fumihiko; Hara, Keigo*; Hasegawa, Katsushi*; Omori, Chihiro*; Toda, Makoto*; Yoshii, Masahito*; Schnase, A.*

Nuclear Instruments and Methods in Physics Research A, 835, p.119 - 135, 2016/11

 Times Cited Count:7 Percentile:47.31(Instruments & Instrumentation)

A magnetic alloy loaded cavity is used to generate multi-harmonic rf voltage in J-PARC RCS. However, a vacuum tube operation analysis under the multi-harmonic driving is very complicated because many variables should be solved with a self consistency. At the conventional operation analysis, a hand work by tracing the constant current curve of the tube was performed, or an appropriate single harmonic wave form was assumed. We have developed a numerical analysis code which calculates the vacuum tube operation automatically and it realizes the multi-harmonic vacuum tube operation analysis. The code is verified at the high power beam acceleration test and we confirm the calculation results are consistent with the measurement ones. We can calculate the vacuum tube operation precisely by using the code, and it will contribute to improving the quality of the beam in the high intensity proton synchrotron.

Journal Articles

Disposal project for LLW and VLLW generated from research facilities in Japan; A Feasibility study for the near surface disposal of VLLW that includes uranium

Sakai, Akihiro; Hasegawa, Makoto; Sakamoto, Yoshiaki; Nakatani, Takayoshi

Proceedings of International Conference on the Safety of Radioactive Waste Management (Internet), p.98_1 - 98_4, 2016/11

The radioactivity of uranium-bearing waste contaminated by refined uranium increases with the production of its progeny on a long-term timescale. Therefore, the long-term safety concept of the near surface disposal of uranium-bearing waste is very important. The Japan Atomic Energy Agency (JAEA) examines disposal safety by controlling the average uranium radioactivity concentration in each section of disposal facility and performing safety assessment for very conservative assumptions.

Journal Articles

Simulation of beam behavior caused by odd harmonics of beam loading in J-PARC RCS

Yamamoto, Masanobu; Nomura, Masahiro; Shimada, Taihei; Tamura, Fumihiko; Hara, Keigo*; Hasegawa, Katsushi*; Omori, Chihiro*; Toda, Makoto*; Yoshii, Masahito*

Proceedings of 7th International Particle Accelerator Conference (IPAC '16) (Internet), p.3443 - 3445, 2016/06

The J-PARC RCS accelerates 2 bunches at the harmonic number 2. The major Fourier component of the beam current is even harmonics. However, the odd harmonics grow under some conditions even though they are very small amplitude at the beginning. Particle tracking simulation suggests that the displacement and the deformation of the bunch are caused by the odd harmonics, it is synchronized with the potential distortion, and it results in the beam instability. We describe the particle tracking simulation results for the odd harmonic beam loading effect in the RCS.

Journal Articles

Mechanisms of increasing of the magnetic alloy core shunt impedance by applying a transverse magnetic field during annealing

Nomura, Masahiro; Shimada, Taihei; Tamura, Fumihiko; Yamamoto, Masanobu; Hara, Keigo*; Hasegawa, Katsushi*; Omori, Chihiro*; Toda, Makoto*; Yoshii, Masahito*

Nuclear Instruments and Methods in Physics Research A, 797, p.196 - 200, 2015/10

 Times Cited Count:1 Percentile:9.26(Instruments & Instrumentation)

In the J-PARC synchrotrons, Magnetic Alloy (MA) cores loaded RF cavities are employed to achieve a high field gradient. We are successful to increase the shunt impedance of the MA cores for the Main Ring synchrotron RF cavities by applying a transverse magnetic field during annealing. The shunt impedances of the cores with transverse field annealing are around 50% higher than the cores without one. By applying the transverse magnetic field during annealing, the magnetization processes occur by mainly magnetization rotations, and consequently the core loss is reduced and the relative complex permeability shows an excellent frequency behavior. The MA core shunt impedance is increased by those improvements of the magnetic properties.

Journal Articles

Summary of discussion on AESJ special committee; Study of ensuring safety for near-surface disposal of uranium-bearing waste

Iguchi, Tetsuo*; Hasegawa, Makoto; Takahashi, Kuniaki; Enokido, Yuji*

Dekomisshoningu Giho, (52), p.12 - 19, 2015/09

no abstracts in English

Journal Articles

Simulation of phase modulation for longitudinal emittance blow-up in J-PARC MR

Yamamoto, Masanobu; Ezura, Eiji*; Hara, Keigo*; Hasegawa, Katsushi*; Nomura, Masahiro; Omori, Chihiro*; Schnase, A.*; Shimada, Taihei; Takagi, Akira*; Takata, Koji*; et al.

JPS Conference Proceedings (Internet), 8, p.012015_1 - 012015_6, 2015/09

The J-PARC MR provides a coasting proton beam for nuclear physics experiments by slow extraction. The longitudinal emittance should be enlarged until the MR flat top to mitigate the microwave instability. We have investigated a Phase Modulation (PM) method by using a High Frequency Cavity (HFC) to increase the emittance. We have performed extensive simulation studies to find the appropriate parameters of the PM through the particle tracking simulation. We found that the effective HFC frequency has linear dependence with the PM frequency, where the emittance is smoothly enlarged. Furthermore, we found that the required HFC voltage is inverse proportional to the square root of the duration time of the PM. These PM properties will be used for the design of the HFC. We describe the particle tracking simulation results of controlled emittance blow-up by the PM.

Journal Articles

High intensity single bunch operation with heavy periodic transient beam loading in wide band RF cavities

Tamura, Fumihiko; Hotchi, Hideaki; Schnase, A.*; Yoshii, Masahito*; Yamamoto, Masanobu; Omori, Chihiro*; Nomura, Masahiro; Toda, Makoto*; Shimada, Taihei; Hasegawa, Katsushi*; et al.

Physical Review Special Topics; Accelerators and Beams, 18(9), p.091004_1 - 091004_8, 2015/09

 Times Cited Count:4 Percentile:29.82(Physics, Nuclear)

The RCS in the J-PARC was originally designed to accelerate two high intensity bunches, while some of neutron experiments in the MLF and a muon experiment using MR beams require a single bunch operation mode. The beam intensity in the single bunch operation has been limited by longitudinal beam losses due to the rf bucket distortions by the wake voltage of the odd harmonics in the wide band MA cavities. We installed an additional rf feedforward system to compensate the wake voltages of the odd harmonics (h=1,3,5). The longitudinal beam losses during the single bunch acceleration disappeared with feedforward for the odd harmonics. We also confirmed that the beam quality in the single bunch acceleration are similar to that of the normal operation with two bunches. Thus, high intensity single bunch acceleration at the intensity of 2.3$$times$$10$$^{13}$$ protons per bunch has been achieved in the J-PARC RCS.

Journal Articles

Development of high power baluns using MA cores, 2

Tamura, Fumihiko; Shimada, Taihei; Yoshii, Masahito*; Omori, Chihiro*; Yamamoto, Masanobu; Nomura, Masahiro; Toda, Makoto*; Hasegawa, Katsushi*; Hara, Keigo*

Proceedings of 12th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.639 - 642, 2015/09

In the J-PARC RCS, magnetic alloy (MA) loaded rf cavities are employed to achieve a high accelerating voltage and to realize the dual harmonic operation, where a single cavity is driven by the fundamental accelerating rf and the second harmonic. The cavity is driven by a class-AB push-pull tetrode amplifier. R&D for a high power balun to mitigate the unbalanced output voltages of two tubes is undergoing. The balun is a rf transformer, which consists of a MA core and high voltage cables. In application to the RCS rf system, the maximum rf voltage is very high in the order of 15kV and suppression of corona dischages is a key. We presentthe techniques to suppress corona discharges. Also, the R&D status of cooling of the MA core and cables.

Journal Articles

Study of shunt impedance of the FT3L magnetic alloy core

Nomura, Masahiro; Yamamoto, Masanobu; Shimada, Taihei; Tamura, Fumihiko; Omori, Chihiro*; Toda, Makoto*; Hasegawa, Katsushi*; Hara, Keigo*; Yoshii, Masahito*

Proceedings of 12th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1096 - 1110, 2015/09

We are successful in increasing the shunt impedance of the MA cores by applying a transverse magnetic field during annealing. In this paper, we discuss the effects of transverse field annealing on the MA core shunt impedance by comparing two kinds of MA cores, those are the FT3M core that is annealed without any magnetic fields and the FT3L core that is annealed with a transverse magnetic field. We also discuss the shunt impedance of the MA core when the magnetization processes are governed by ideal magnetization rotations. To understand the ribbon thickness and the permeability dependences of the shunt impedance intuitively, we represent the shunt impedance as the resistance of the closed rectangular loop through which the eddy current flows.

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