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Kikuchi, Tatsuya*; Nakajima, Kenji; Kawamura, Seiko; Inamura, Yasuhiro; Nakamura, Mitsutaka; Wakai, Daisuke*; Aoyama, Kazuhiro*; Iwahashi, Takaaki*; Kambara, Wataru*
Physica B; Condensed Matter, 564, p.45 - 53, 2019/07
Times Cited Count：1 Percentile：4.22(Physics, Condensed Matter)Details of the background, that is, unwanted signals accumulated by the data acquisition system of neutron instruments, observed by the cold-neutron chopper spectrometer AMATERAS installed at the Materials and Life Science Experimental Facility at J-PARC are reported. In the design phase of AMATERAS, we carefully considered the achievement of high signal-to-noise ratio, and possible countermeasures were implemented. Actually, recent scientific outputs from AMATERAS indicates that the spectrometer is one of excellent neutron instruments with low background. In spite of that, in nine years of AMATERAS operation, we have encountered unwanted signals due to various reasons, including gamma-rays emitted at materials on or near the beam line including the sample itself, scattered neutrons from the beam line devices, air scattering, electronic noise in data acquisition system, cosmic rays, T0 burst, and other unknown sources. In this report, we discuss the background observed by AMATERAS, especially in the conditions of without samples, comprehensively. The possible sources of these signals and the countermeasures considered against the above sources are discussed, which may be helpful to those who are engaged in other existing or planned neutron-scattering instruments.
Kawamura, Seiko; Takahashi, Ryuta*; Ishikado, Motoyuki*; Yamauchi, Yasuhiro*; Nakamura, Masatoshi*; Ouchi, Keiichi*; Kira, Hiroshi*; Kambara, Wataru*; Aoyama, Kazuhiro*; Sakaguchi, Yoshifumi*; et al.
Journal of Neutron Research, 21(1-2), p.17 - 22, 2019/05
The Cryogenics and Magnets group in the Sample Environment team is responsible for operation of cryostats and magnets for user's experiments at the MLF in J-PARC. We have introduced a top-loading 
He cryostat, a bottom-loading 
He cryostat, a dilution refrigerator insert and a superconducting magnet. The frequency of use of them dramatically becomes higher in these two years, as the beam power and the number of proposal increase. To respond such situation, we have made efforts to enhance performance of these equipment as follows. The He cryostat originally involves an operation software for automatic initial cooling down to the base temperature and automatic re-charge of He. Recently we made an additional program for automatic temperature control with only the sorb heater. Last year, a new outer vacuum chamber of the magnet with an oscillating radial collimator (ORC) was fabricated. The data quality was drastically improved by introducing this ORC so that the magnet can be used even for the inelastic neutron scattering experiments.
Kajimoto, Ryoichi; Ishikado, Motoyuki*; Kira, Hiroshi*; Kaneko, Koji; Nakamura, Mitsutaka; Kamazawa, Kazuya*; Inamura, Yasuhiro; Ikeuchi, Kazuhiko*; Iida, Kazuki*; Murai, Naoki; et al.
Physica B; Condensed Matter, 556, p.26 - 30, 2019/03
Times Cited Count：2 Percentile：9.38(Physics, Condensed Matter)Nakamura, Mitsutaka; Kambara, Wataru*; Iida, Kazuki*; Kajimoto, Ryoichi; Kamazawa, Kazuya*; Ikeuchi, Kazuhiko*; Ishikado, Motoyuki*; Aoyama, Kazuhiro*
Physica B; Condensed Matter, 551, p.480 - 483, 2018/12
Times Cited Count：6 Percentile：28.27(Physics, Condensed Matter)Recently there has been an increasing need for inelastic neutron scattering experiments under some special environments such as magnetic fields, pressure and high temperatures. In order to obtain high quality data, the unnecessary scattering caused by sample environmental apparatus should be suppressed as much as possible. We have developed an oscillating radial collimator with a view to satisfying users' needs, which is specialized for the Fermi chopper spectrometer 4SEASONS at J-PARC.4SEASONS provides relatively high incident energies, and thus we chose hydrogen free metal sheets as the collimator blades. The control system of this oscillating radial collimator enables us to flexibly tune the oscillating pattern, such as the oscillating speed and oscillating angle. In this presentation, we report the performances and remaining issues of the newly developed oscillating radial collimator for 4SEASONS.
Nakajima, Kenji; Kawamura, Seiko; Kikuchi, Tatsuya*; Kofu, Maiko; Kawakita, Yukinobu; Inamura, Yasuhiro; Kambara, Wataru*; Aoyama, Kazuhiro*; Wakai, Daisuke*; Harada, Masahide; et al.
Journal of Physics; Conference Series, 1021(1), p.012031_1 - 012031_5, 2018/06
Times Cited Count：6 Percentile：93.40(Nuclear Science & Technology)Kajimoto, Ryoichi; Nakamura, Mitsutaka; Inamura, Yasuhiro; Kamazawa, Kazuya*; Ikeuchi, Kazuhiko*; Iida, Kazuki*; Ishikado, Motoyuki*; Nakajima, Kenji; Kawamura, Seiko; Nakatani, Takeshi; et al.
JAEA-Conf 2015-002, p.319 - 329, 2016/02
Nakamura, Mitsutaka; Kawakita, Yukinobu; Kambara, Wataru; Aoyama, Kazuhiro; Kajimoto, Ryoichi; Nakajima, Kenji; Kawamura, Seiko; Ikeuchi, Kazuhiko*; Kikuchi, Tatsuya; Inamura, Yasuhiro; et al.
JPS Conference Proceedings (Internet), 8, p.036011_1 - 036011_6, 2015/09
The needs for inelastic neutron scattering experiments under the special sample environment such as strong magnetic field and high temperature are recently increasing. However, the unwanted scatterings originating from these devices affect the detection of weak inelastic signals. In order to overcome this problem we have developed an oscillating radial collimator specialized for the chopper spectrometer at Materials and Life Science Experimental Facility (MLF) in J-PARC. In this study, we will report the performances of newly-developed oscillating radial collimators both for 4SEASONS and AMATERAS.
Cs in seabed sediment off the Fukushima coast; Implications from numerical simulationsMisumi, Kazuhiro*; Tsumune, Daisuke*; Tsubono, Takaki*; Tateda, Yutaka*; Aoyama, Michio*; Kobayashi, Takuya; Hirose, Katsumi*
Journal of Environmental Radioactivity, 136, p.218 - 228, 2014/10
Times Cited Count：24 Percentile：55.43(Environmental Sciences)Major controls on spatiotemporal variations of Cs activity in seabed sediments derived from the Fukushima Dai-ichi Nuclear Power Plant accident during the first year after the accident were investigated by using numerical simulations. The model successfully reproduced major features of the observed spatiotemporal variations of Cs activity in sediments. The spatial pattern of Cs in sediments, which mainly reflected the history of Cs activity in the bottom water overlying the sediment and the sediment particle size distribution, became established during the first several months after the accident. Taking Cs activities in sediments in the coastal area and in the vicinity of the power plant into account, increased the simulated total inventory of Cs in sediments off the Fukushima coast to a value on the order of 10
Bq.
Ito, Chikara; Ito, Hideaki; Ishida, Koichi; Hatoori, Kazuhiro; Oyama, Kazuhiro; Sukegawa, Kazuya*; Murakami, Takanori; Kaito, Yasuaki; Nishino, Kazunari; Aoyama, Takafumi; et al.
JNC TN9410 2005-003, 165 Pages, 2005/03
JNC-TN9410-2005-003.pdf:12.66MB
At experimental fast reactor JOYO, appraisal of detection efficiency of behavior and FFD and FFDL of the fission product which is discharged inside the furnace as one of safety research of the country, is carried out. In MK-II core, the slit in the gas plenum part of the test sub-assembly, the test which irradiates this(1985 April, FFDL in-pile test(I)), providing the slit in the fuel column part of the test sub-assembly, the test which it irradiates(1992 November, FFDL in-pile test(II)) were carried out.MK-III reactor core replacement was completed and started in 2004. That the behavior in the system of FP with the reactor core replacement and so on changes in the MK-III reactor core and to have an influence on the sensitivity and the replying of FFD and FFDL are thought of. Therefore, behavior of FP in the fuel failure in the MK-III reactor core, the performance of FFD and FFDL must be confirmed beforehand. Moreover, to prepare for the fuel failure and the RTCB test which is doing a future plan, and to confirm a plant operation procedure in the fuel failure in MK-III reactor core operation and to attempt for the correspondency to improve are important.Therefore, in the period from 2004 November 11th to November 29th, it carried out the FFDL in-pile(III). It did a series of plant operation to stop a nuclear reactor after loading a reactor core center with the fuel element for the test which provided an artificial slit for the fuel cladding in the MK-III reactor core and irradiating it and detecting fuel damaging and to take out fuel. And it confirmed the operation procedure of the fast reactor in the fuel failure.Also, the improvement items such as the improvement of the operation and the procedure and the remodeling and the service of the facilities could be picked up. In the future, it attempts these compatible, and it prepares for the MK-III reactor core operation and it incorporates a final examination result by the improvement of the safety of FBR.
Maeda, Yukimoto; Aoyama, Takafumi; Yoshida, Akihiro; Sekine, Takashi; Ariyoshi, Masahiko; Ito, Chikara; Nemoto, Masaaki; Murakami, Takanori; Isozaki, Kazunori; Hoshiba, Hideaki; et al.
JNC TN9410 2003-011, 197 Pages, 2004/03
JNC-TN9410-2003-011.pdf:10.26MB
MK-III performance tests began in June 2003 to fully characterize the upgraded core and heat transfer system. Then, the last pre-use inspection was finished in November 2003.This report summarize the result of each performance test.
Oyama, Kazuhiro; Aoyama, Takafumi
JNC TN9200 2003-005, 175 Pages, 2004/03
JNC-TN9200-2003-005.pdf:17.64MB
On 2004 February 26th it hosted the conference which does a communication about the current status and the technical development,etc of JOYO , CEFR and MONJU.Through the meeting, a discussion was done for the information exchange meeting and the mutual sending of the technical expert as the cooperation of the future. We were possible to confirm about the field to be interested in CEFR.
Kambara, Wataru; Aoyama, Kazuhiro; Yamauchi, Yasuhiro; Iwahashi, Takaaki; Ono, Shino; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Shibata, Kaoru; Nakajima, Kenji; Kawamura, Seiko; et al.
no journal, ,
Nakajima, Kenji; Kawamura, Seiko; Kikuchi, Tatsuya; Inamura, Yasuhiro; Kawakita, Yukinobu; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Soyama, Kazuhiko; Arai, Masatoshi; Aoyama, Kazuhiro; et al.
no journal, ,
no abstracts in English
Nakamura, Mitsutaka; Kajimoto, Ryoichi; Inamura, Yasuhiro; Aoyama, Kazuhiro; Kambara, Wataru*; Kawakami, Kazuhiro; Kubo, Naoya; Kamazawa, Kazuya*; Ikeuchi, Kazuhiko*; Iida, Kazuki*; et al.
no journal, ,
We have developed a newly designed Fermi chopper for MLF/BL01 4SEASONS, and has been open for users since March 2015. It was found that the gain factor achieved in the low-energy region is more than 10, thus, we succeeded to greatly improve the measurement efficiency of 4SEASONS. In this presentation we will show the details of both specification and design for a newly-developed Fermi chopper.
Kajimoto, Ryoichi; Nakamura, Mitsutaka; Inamura, Yasuhiro; Nakajima, Kenji; Kawamura, Seiko; Nakatani, Takeshi; Kambara, Wataru*; Kubo, Naoya; Aoyama, Kazuhiro; Kawakami, Kazuhiro; et al.
no journal, ,
no abstracts in English
Nakamura, Mitsutaka; Kajimoto, Ryoichi; Inamura, Yasuhiro; Aoyama, Kazuhiro; Kambara, Wataru*; Kawakami, Kazuhiro; Kubo, Naoya; Kamazawa, Kazuya*; Ikeuchi, Kazuhiko*; Iida, Kazuki*; et al.
no journal, ,
The chopper spectrometer 4SEASONS at J-PARC MLF had used a Fermi chopper borrowed from the SNS facility until 2014. A new Fermi chopper which reviewed the design of the slit package has recently started operation. As a result, we have succeeded in achieving the intensity gain up of to several tens of times in the low-energy region. In this presentation we will report the details of spec and design of a new Fermi chopper.
Nakajima, Kenji; Kawamura, Seiko; Kikuchi, Tatsuya; Kawakita, Yukinobu; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Aoyama, Kazuhiro; Kambara, Wataru*; Yamauchi, Yasuhiro; Kubo, Naoya
no journal, ,
AMATERAS is a cold-neutron multi disk-chopper spectrometer at Materials and Life Science Experimental Facility (MLF) in J-PARC. The spectrometer has had the first neutron beam in May 2009 and had the first user in December 2009. The user program on AMATERAS is running successfully for 5 years. In this presentation, we will present the current status of AMATERAS together with ideas of future upgrade plans.
Nakamura, Mitsutaka; Kambara, Wataru*; Kajimoto, Ryoichi; Ikeuchi, Kazuhiko*; Iida, Kazuki*; Kamazawa, Kazuya*; Ishikado, Motoyuki*; Inamura, Yasuhiro; Aoyama, Kazuhiro
no journal, ,
The needs for inelastic neutron scattering experiments under a special sample environment are recently increasing. However, the unwanted scatterings originating from these devices affect the detection of weak inelastic signals. In order to overcome this problem we have developed an oscillating radial collimator (ORC) specialized for the Fermi chopper spectrometer 4SEASONS on the BL01 beamline at MLF in J-PARC. The developed ORC is equipped with the control system which guarantee the homogeneity of scattering signal. In this presentation, we report the performances and remaining issues of newly-developed ORC for 4SEASONS.
Nakajima, Kenji; Kawamura, Seiko; Kofu, Maiko; Kikuchi, Tatsuya*; Inamura, Yasuhiro; Aoyama, Kazuhiro*; Wakai, Daisuke*
no journal, ,
no abstracts in English
Tanabe, Kazuhiro*; Yanagihara, Satoshi*; Iguchi, Yukihiro; Takiya, Hiroaki; Narikawa, Isao*; Kobashi, Hiroaki*; Aoyama, Yoshiharu*; Iida, Keiichi*; Yanagida, Akihiro*; Murayama, Kazunari*; et al.
no journal, ,
In order to make safer and more rational efforts possible for a decommissioning project that is about to begin in full swing, we organized our experience, achievements and knowledge, including maintenance and dismantling work in the plant, and evaluated basic issues for decommissioning.
