Oi, Motoki; Teshigawara, Makoto; Harada, Masahide; Ikeda, Yujiro
Journal of Nuclear Science and Technology, 56(7), p.573 - 579, 2019/07
In pulsed neutron sources, a neutron absorber called decoupler is attached to the moderator to sharpen the neutron pulses for achieving good neutron energy resolutions. Cadmium and boron carbide (BC) are widely used as the decoupler materials. However, it is difficult to use BC in MW-class spallation neutron sources owing to high burn-up, which decreases cut-off energy and increase of helium gas swelling. To solve these issues, we introduce the concept of pre-decoupler to reduce neutron absorption in the BC decoupler, which is sandwiched by appropriate neutron absorption materials. Then, we study impacts of the pre-decouplers on BC decoupler in terms of burn-up by performing simplified model calculations. It is shown that neutron absorption in BC is reduced by 60% by using a Cd pre-decoupler without neutron intensity penalty. Moreover, helium gas swelling in BC is restrained to be one-third of the value when not using the pre-decoupler.
Teshigawara, Makoto; Tsuchikawa, Yusuke*; Ichikawa, Go*; Takata, Shinichi; Mishima, Kenji*; Harada, Masahide; Oi, Motoki; Kawamura, Yukihiko*; Kai, Tetsuya; Kawamura, Seiko; et al.
Nuclear Instruments and Methods in Physics Research A, 929, p.113 - 120, 2019/06
A nano-diamond is an attractive neutron reflection material below cold neutron energy. The total neutron cross section of a nano-diamond was derived from a neutron transmission measurement over the neutron energy range of 0.2 meV to 100 meV because total neutron cross section data were not available. The total cross section of a nano-diamond with particle size of approximately 5 nm increased with a decrease in neutron energy to 0.2 meV. It was approximately two orders of magnitude larger than that of graphite at 0.2 meV. The contribution of inelastic scattering to the total cross section was to be shown negligible small at neutron energies of 1.2, 1.5, 1.9, 2.6, and 5.9 meV in the inelastic neutron scattering measurement. Moreover, small-angle neutron scattering measurements of the nano-diamond showed a large scattering cross section in the forward direction for low neutron energies.
Ikeda, Yujiro; Shimizu, Hirohiko*
Reza Kenkyu, 46(11), p.641 - 646, 2018/11
In viewing significant progresses in technical achievement toward a high-intensity neutron source driven by a high-power laser came up with the high power laser development, we have reviewed the currently most advanced moderator system and neutron optics, which are the key elements for the neutron beam applications. Regarding the moderators, concepts adopted in J-PARC pulsed neutron source, which is one of most advanced system, were described to give a baseline design. Also a new direction of moderator concept is shown, which could be a high brightness candidate for the high-intensity laser driven system. On the neutron optics, the most fundamental consideration is primarily reviewed along with recent progress in new devises for enrichment of neutron-beam characteristics.
Arikawa, Yasunobu*; Ikeda, Yujiro; Shimizu, Hirohiko*; Hanayama, Ryohei*; Kondo, Yasuharu*; Kurosawa, Shunsuke*
Reza Kenkyu, 46(11), p.634 - 640, 2018/11
Compact neutron sources have been used as various diagnostics such as a neutron diffraction, neutron resonant analysis, and neutron radiography. The developments of the neutron detectors are essential for all of these applications, while the techniques are strongly dependent on the neutron energy and the aim of the measurement. This paper reviews neutron detection techniques pertinent to promote compact neutron source uses. Along with general neutron detection systems with conventional counters for slow neutrons, we have highlighted detectors for high energy neutrons with high time resolution and high sensitivity which could be applied in a laser-driven compact neutron source.
Harada, Masahide; Teshigawara, Makoto; Oi, Motoki; Klinkby, E.*; Zanini, L.*; Batkov, K.*; Oikawa, Kenichi; Toh, Yosuke; Kimura, Atsushi; Ikeda, Yujiro
Nuclear Instruments and Methods in Physics Research A, 903, p.38 - 45, 2018/09
Teshigawara, Makoto; Ikeda, Yujiro; Oi, Motoki; Harada, Masahide; Takada, Hiroshi; Kakishiro, Masanori*; Noguchi, Gaku*; Shimada, Tsubasa*; Seita, Kyoichi*; Murashima, Daisuke*; et al.
Nuclear Materials and Energy (Internet), 14, p.14 - 21, 2018/01
We developed an Au-In-Cd (AuIC) decoupler material to reduce induced radioactivity instead of Ag-In-Cd one, which has a cut off energy of 1eV. In order to implement it into an actual moderator-reflector assembly, a number of critical engineering issues need to be resolved with regard to large-sized bonding between AuIC and A5083 alloys by the hot isostatic pressing process. We investigated this process in terms of the surface conditions, sizes, and heat capacities of large AuIC alloys. We also show a successful implementation of an AuIC decoupler into a reflector assembly, resulting in a remarkable reduction of radioactivity by AuIC compared to AIC without sacrificing neutronic performance.
Aso, Tomokazu; Teshigawara, Makoto; Hasegawa, Shoichi; Aoyagi, Katsuhiro*; Muto, Hideki*; Nomura, Kazutaka*; Takada, Hiroshi; Ikeda, Yujiro
JAEA-Technology 2017-021, 75 Pages, 2017/08
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.
Hamon, 21(3), p.152 - 155, 2011/08
Maekawa, Fujio; Harada, Masahide; Oikawa, Kenichi; Teshigawara, Makoto; Kai, Tetsuya; Meigo, Shinichiro; Oi, Motoki; Sakamoto, Shinichi; Takada, Hiroshi; Futakawa, Masatoshi; et al.
Nuclear Instruments and Methods in Physics Research A, 620(2-3), p.159 - 165, 2010/08
The J-PARC 1-MW pulsed spallation neutron source JSNS was successfully launched on 30th of May 2008. To demonstrate the unique features of the moderator design and the neutronic performance of JSNS the neutron spectral intensity, absolute neutron flux, and time structure of the neutron pulse shapes etc have been measured using several neutron instruments since then. The measured energy spectra clearly revealed the feature of the para-hydrogen, as expected when designing the moderator. The measured neutron flux below 0.4 eV agreed with the corresponding design value within 20%, thus suggesting that the JSNS design calculations to have been reliable. World-class high-resolution diffraction data could be recorded due to the suitability of design of the moderators and the instruments. Another world-class high-intensity neutron flux was also capable of being demonstrated due to the unique design of the large cylindrical coupled moderator.
Maekawa, Fujio; Oikawa, Kenichi; Harada, Masahide; Kai, Tetsuya; Meigo, Shinichiro; Kasugai, Yoshimi; Oi, Motoki; Sakai, Kenji; Teshigawara, Makoto; Hasegawa, Shoichi; et al.
Nuclear Instruments and Methods in Physics Research A, 600(1), p.335 - 337, 2009/02
A neutron beam line (BL10) of JSNS, NOBORU, has been constructed in the Materials and Life Science Experimental Facility (MLF) at J-PARC. A primal mission of NOBORU is to study neutronic performance of JSNS. We will measure the memorable first neutron pulse of JSNS at the Day-one by using NOBORU, and then measure neutron pulse shape, spectrum, intensity distribution, etc. for facility diagnostics. Since NOBORU also has an aspect as a test port, it welcomes trial uses to develop innovative instruments. Trial experiments to demonstrate several innovative instruments at NOBORU are under planning.
Harada, Masahide; Meigo, Shinichiro; Ito, Manabu; Dantsuji, Eiji; Takagiwa, Katsunori; Takada, Hiroshi; Maekawa, Fujio; Futakawa, Masatoshi; Nakamura, Mitsutaka; Miyake, Yasuhiro*; et al.
Nuclear Instruments and Methods in Physics Research A, 600(1), p.87 - 90, 2009/02
In MLF of J-PARC, since weights of a building and shields are considerably heavy as 130,000 tons and 80,000 tons, respectively, large settlement of the MLF building is expected. The 3NBT line with 300 m in length is similar. To achieve a precise alignment under the large settlement, we conducted periodical survey measurements at the MLF building and 3NBT. At the completion of construction of the MLF building in December 2005, the settlement was about 40 mm. By extrapolating this result with weights to be added in the future for neutron beam line shields, we predicted that the MLF building settled in about 68mm at the completion of all neutron instrument construction. We decided that the muon target should be installed 5 mm higher than the neutron target with expecting future uneven settlement of the MLF building. The validation in the end of 2007 indicated that the measured level difference came up to the expected value.
Oikawa, Kenichi; Takada, Hiroshi; Maekawa, Fujio; Harada, Masahide; Futakawa, Masatoshi; Ikeda, Yujiro
Nuclear Instruments and Methods in Physics Research A, 600, p.84 - 86, 2009/02
Neutron beam shutter system of JSNS at J-PARC has been designed under a particular precondition that every shutter should be controlled and maintained independently. This is very important from viewpoints of usability and interlock system of JSNS. The biggest challenge we faced was that to meet a single shutter design on asymmetric and narrow angular intervals of JSNS beam-lines; 6.7 in minimum and 12.7 in maximum. To realize this precondition, a compact ball screw jack system sustaining a shutter gate with two shafts was designed. Rotating motion during open/close stroke is absorbed by a couple of oilless bearings (OILES corp.) fitted in every shaft guide. The assembly is driven by an electric servomotor.
Oyama, Yukio; Ikeda, Yujiro; Arai, Masatoshi; Morii, Yukio
Nippon Genshiryoku Gakkai-Shi, 51(1), p.14 - 19, 2009/01
The beam commissioning of the J-PARC facilities of which the construction was started in 2001 is now progressed toward completion at the end of JFY2008. Of the J-PARC facilities, especially the pulsed neutron source with the world highest performance is able to open a new era of neutron application research. In this article, the outline of J-PARC, the pulsed neutron source which will start the user operation on December 2008, and their neutron instruments which is under construction are introduced. The neutron research is one of the important applications of quantum beam technology and expected to expand to broad research area such as bio-science, materials science, industrial use, etc. by start of J-PARC utilization. The latest achievement of neutron research mostly conducted at the JRR-3 research reactor in operation and future prospect are overviewed.
Futakawa, Masatoshi; Kogawa, Hiroyuki; Hasegawa, Shoichi; Naoe, Takashi; Ida, Masato; Haga, Katsuhiro; Wakui, Takashi; Tanaka, Nobuatsu*; Matsumoto, Yoichiro*; Ikeda, Yujiro
Journal of Nuclear Science and Technology, 45(10), p.1041 - 1048, 2008/10
The life time of mercury target will be reduced by the cavitation damage induced by pressure waves. Micro-bubble injection into mercury is one of prospective technologies to mitigate the pressure waves. We have carried out damage tests using mercury loop with an impact generator to evaluate the bubbling effect on the pressure response and cavitation damage. The impulsive pressure was hardly changed but the damage was reduced remarkably by the micro-bubble injection. Numerical simulation was performed to investigate the bubbling effects. It was understandable that micro bubbles suppressed cavitation inception.
Futakawa, Masatoshi; Kogawa, Hiroyuki; Hasegawa, Shoichi; Ikeda, Yujiro; Riemer, B.*; Wendel, M.*; Haines, J.*; Bauer, G.*; Naoe, Takashi; Okita, Kohei*; et al.
Journal of Nuclear Materials, 377(1), p.182 - 188, 2008/06
no abstracts in English
Oikawa, Kenichi; Maekawa, Fujio; Harada, Masahide; Kai, Tetsuya; Meigo, Shinichiro; Kasugai, Yoshimi; Oi, Motoki; Sakai, Kenji; Teshigawara, Makoto; Hasegawa, Shoichi; et al.
Nuclear Instruments and Methods in Physics Research A, 589(2), p.310 - 317, 2008/05
NOBORU, NeutrOn Beam-line for Observation and Research Use, has been constructed in the Materials and Life Science Facility (MLF) of J-PARC. NOBORU is designed to "Observe" a 1 MW Japan Spallation Neutron Source (JSNS), i.e., to study the neutronic performance of JSNS. NOBORU also will be used for "Research" activities, i.e., as a test port for R&D activities and trial users who have new ideas. In this paper, the design and application of NOBORU are described, and its expected performance is investigated by Monte Carlo simulations.
Nippon Kessho Gakkai-Shi, 50(1), p.2 - 6, 2008/02
Hamon, 18(1), p.27 - 31, 2008/01
As the J-PARC user operation is scheduled to start within one year, a system for the user program has been thoroughly discussed in the J-PARC team in terms of access policy, program review, beam-time fee, treatment of output, intellectual property protection policy, etc. This paper reports the general concept of the J-PARC user program system.
Harada, Masahide; Watanabe, Noboru*; Teshigawara, Makoto; Kai, Tetsuya; Kato, Takashi; Ikeda, Yujiro
Nuclear Instruments and Methods in Physics Research A, 574(3), p.407 - 419, 2007/05
Neutronic performance of a poisoned hydrogen moderator was studied in details. Using a simple rectangular-shape moderator-model, its basic characteristics were studied as a function of the poison position. We, for the first time, turned up that the pulse width was rather decreasing with increasing the moderator thickness of the back part from the poison. This is due to the fact that source neutron pulses entering through the back part of poison are narrow while those from the target and the reflector through the decoupler and liner are broad. Next, we studied the pulse deterioration in regard to a finite beam-extraction-angle by using a canteen shape and a concave shape. It turns out that the pulse deterioration is large in both cases even at a small extraction angle. The concave-shape moderator indicates a finite improvement compared to the canteen shape one. Finally, merits and demerits of two poison materials, Cd and Gd, were discussed considering the burn-up issue of poison.