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Journal Articles

RF design of the prototype spoke cavity for the JAEA-ADS linac

Tamura, Jun; Kondo, Yasuhiro; Yee-Rendon, B.; Meigo, Shinichiro; Maekawa, Fujio; Hasegawa, Kazuo; Kako, Eiji*; Umemori, Kensei*; Sakai, Hiroshi*; Konomi, Taro*

JPS Conference Proceedings (Internet), 33, p.011049_1 - 011049_6, 2021/03

Journal Articles

Comprehensive analysis and evaluation of Fukushima Daiichi Nuclear Power Station Unit 2

Yamashita, Takuya; Sato, Ikken; Honda, Takeshi*; Nozaki, Kenichiro*; Suzuki, Hiroyuki*; Pellegrini, M.*; Sakai, Takeshi*; Mizokami, Shinya*

Nuclear Technology, 206(10), p.1517 - 1537, 2020/10

 Times Cited Count:9 Percentile:91.73(Nuclear Science & Technology)

Journal Articles

How different is the core of $$^{25}$$F from $$^{24}$$O$$_{g.s.}$$ ?

Tang, T. L.*; Uesaka, Tomohiro*; Kawase, Shoichiro; Beaumel, D.*; Dozono, Masanori*; Fujii, Toshihiko*; Fukuda, Naoki*; Fukunaga, Taku*; Galindo-Uribarri, A.*; Hwang, S. H.*; et al.

Physical Review Letters, 124(21), p.212502_1 - 212502_6, 2020/05

 Times Cited Count:11 Percentile:78.03(Physics, Multidisciplinary)

The structure of a neutron-rich $$^{25}$$F nucleus is investigated by a quasifree ($$p,2p$$) knockout reaction. The sum of spectroscopic factors of $$pi 0d_{5/2}$$ orbital is found to be 1.0 $$pm$$ 0.3. The result shows that the $$^{24}$$O core of $$^{25}$$F nucleus significantly differs from a free $$^{24}$$O nucleus, and the core consists of $$sim$$35% $$^{24}$$O$$_{rm g.s.}$$, and $$sim$$65% excited $$^{24}$$O. The result shows that the $$^{24}$$O core of $$^{25}$$F nucleus significantly differs from a free $$^{24}$$O nucleus. The result may infer that the addition of the $$0d_{5/2}$$ proton considerably changes the neutron structure in $$^{25}$$F from that in $$^{24}$$O, which could be a possible mechanism responsible for the oxygen dripline anomaly.

Journal Articles

Measurement of the angular distribution of $$gamma$$-rays after neutron capture by $$^{139}$$La for a T-violation search

Okudaira, Takuya; Shimizu, Hirohiko*; Kitaguchi, Masaaki*; Hirota, Katsuya*; Haddock, C. C.*; Ito, Ikuya*; Yamamoto, Tomoki*; Endo, Shunsuke*; Ishizaki, Kohei*; Sato, Takumi*; et al.

EPJ Web of Conferences, 219, p.09001_1 - 09001_6, 2019/12

Parity violating effects enhanced by up to 10$$^6$$ times have been observed in several neutron induced compound nuclei. There is a theoretical prediction that time reversal (T) violating effects can also be enhanced in these nuclei implying that T-violation can be searched for by making very sensitive measurements. However, the enhancement factor has not yet been measured in all nuclei. The angular distribution of the (n,$$gamma$$) reaction was measured with $$^{139}$$La by using a germanium detector assembly at J-PARC, and the enhancement factor was obtained. From the result, the measurement time to achieve the most sensitive T-violation search was estimated as 1.4 days, and a 40% polarized $$^{139}$$La target and a 70% polarized $$^3$$He spin filter whose thickness is 70 atm$$cdot$$cm are needed. Therefore high quality $$^3$$He spin filter is developed in JAEA. The measurement result of the (n,$$gamma$$) reaction at J-PARC and the development status of the $$^3$$He spin filter will be presented.

Journal Articles

Electromagnetic design of the prototype spoke cavity for the JAEA-ADS linac

Tamura, Jun; Kondo, Yasuhiro; Yee-Rendon, B.; Meigo, Shinichiro; Maekawa, Fujio; Hasegawa, Kazuo; Kako, Eiji*; Umemori, Kensei*; Sakai, Hiroshi*; Konomi, Taro*

Proceedings of 19th International Conference on RF Superconductivity (SRF 2019) (Internet), p.399 - 402, 2019/11

Journal Articles

Study on gas entrainment from unstable drifting vortexes on liquid surface

Hirakawa, Moe*; Kikuchi, Yuichiro*; Sakai, Takaaki*; Tanaka, Masaaki; Ohshima, Hiroyuki

Proceedings of 26th International Conference on Nuclear Engineering (ICONE-26) (Internet), 8 Pages, 2018/07

Gas entrainment (GE) from cover gas is one of key issue for Sodium-cooled fast reactors to prevent unexpected effects to core reactivity. By using a computational fluid dynamics (CFD) code, analyses have been conducted to estimate the drifting vortexes on water experiments which were generated as wake vortexes behind a plate obstacle in the circulating water channel. In this paper, the results of comparison between experiments and analyses were discussed and the gas core lengths from the surface vortexes were evaluated by using the evaluation tool named StreamViewer developed by Japan Atomic Energy Agency.

Journal Articles

Progress of the general control system for the Materials and Life Science Experimental Facility in J-PARC

Sakai, Kenji; Oi, Motoki; Watanabe, Akihiko; Kai, Tetsuya; Kato, Yuko; Meigo, Shinichiro; Takada, Hiroshi

JAEA-Conf 2015-002, p.593 - 598, 2016/02

For safe and stable beam operation, a MLF general control system (GCS) consists of several subsystems such as an integral control, interlock, server, network, and timing distribution systems. Since the first beam injection in 2008, the GCS has operated stably without any serious troubles in comparison with upgrade of target devices for ramping up beam power and increment of user apparatuses year by year. In recent years, however, it has been improved significantly in view of sustainable long-term operation and maintenance. The monitor and operation system of the GCS has been upgraded by changing its framework software to improve potential flexibility in its maintenance. Its interlock system was also modified in accordance with the re-examination of the risk management system of J-PARC. This paper reports recent progress of the MLF-GCS.

Journal Articles

Operational experience of CW SRF injector and main linac cryomodules at the Compact ERL

Sakai, Hiroshi*; Enami, Kazuhiro*; Furuya, Takaaki*; Kako, Eiji*; Kondo, Yoshinari*; Michizono, Shinichiro*; Miura, Takako*; Qiu, F.*; Sato, Masato*; Shinoe, Kenji*; et al.

Proceedings of 56th ICFA Advanced Beam Dynamics Workshop on Energy Recovery Linacs (ERL 2015) (Internet), p.63 - 66, 2015/12

no abstracts in English

Journal Articles

Upgrade of monitoring and operation systems for the MLF-GCS base on EPICS and CSS

Oi, Motoki; Sakai, Kenji; Watanabe, Akihiko; Akutsu, Atsushi; Meigo, Shinichiro; Takada, Hiroshi

JPS Conference Proceedings (Internet), 8, p.036007_1 - 036007_5, 2015/09

This paper reports on upgrading of the monitor and operation (MO) system for a general control system (GCS) of the Materials and Life science experimental Facility (MLF) at J-PARC. The MLF-GCS consists of programmable logic controllers (PLCs), operator interfaces (OPIs) for integral control and interlock systems, shared servers, and so on. It is controlling various components of the pulsed spallation neutron source such as a mercury target and hydrogen moderators. The MO system is used for monitoring, alarm notification and remote control from the MLF control room. The GCS has been working well as expected, but current MO system which consists of the OPIs and data servers based on iFix has some problems in view of sustainable maintenance because of its poor flexibility of supported OS and software version compatibility. To overcome the problems, we upgraded the MO system to be operated using the framework of EPICS, the OPI of Control System Studio (CSS) and the server software of Postgre SQL. This improves versatility of the MO system, enabling to run on various platforms such as Windows, Linux and Mac OS. At first, we made a prototype MO system, which processed 100 points of data and 5 operation screens and verified that the MO system functions correctly. Then we made full spec MO system which processes the data point of 7000 and operation screens of 130. It was operated in parallel with the current system to evaluate its performance with real data such as data transmission speed from PLCs, control functions from OPI, storage capability of servers and long-term reliability. As results, the new MO system achieved the communication speed of 2 Hz and its operability compatible to the current system. Now, we are operating and debugging it in comparison with the current system during the operating period as a preparation for the system replacement at the end of 2014.

Journal Articles

The Operation status of the superconducting cavity for CERL main linac; Toward the deep understanding inside the superconducting cavity with high current beam

Numata, Naoto*; Asakawa, Tomoyuki*; Sakai, Hiroshi*; Umemori, Kensei*; Furuya, Takaaki*; Shinoe, Kenji*; Enami, Kazuhiro*; Egi, Masato*; Sakanaka, Shogo*; Michizono, Shinichiro*; et al.

Proceedings of 12th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.566 - 570, 2015/09

no abstracts in English

Journal Articles

Photoelectron diffraction from laser-aligned molecules with X-ray free-electron laser pulses

Nakajima, Kyo*; Teramoto, Takahiro*; Akagi, Hiroshi; Fujikawa, Takashi*; Majima, Takuya*; Minemoto, Shinichiro*; Ogawa, Kanade*; Sakai, Hirofumi*; Togashi, Tadashi*; Tono, Kensuke*; et al.

Scientific Reports (Internet), 5, p.14065_1 - 14065_11, 2015/09

 Times Cited Count:34 Percentile:84.61(Multidisciplinary Sciences)

We report on the measurement of deep inner-shell 2p X-ray photoelectron diffraction (XPD) patterns from laser-aligned I$$_{2}$$ molecules using X-ray free-electron laser (XFEL) pulses. The XPD patterns of the I$$_{2}$$ molecules, aligned parallel to the polarization vector of the XFEL, were well matched with our theoretical calculations. Further, we propose a criterion for applying our molecular-structure-determination methodology to the experimental XPD data. In turn, we have demonstrated that this approach is a significant step toward the time-resolved imaging of molecular structures.

Journal Articles

On-site background measurements for the J-PARC E56 experiment; A Search for the sterile neutrino at J-PARC MLF

Ajimura, Shuhei*; Bezerra, T. J. C.*; Chauveau, E.*; Enomoto, T.*; Furuta, Hisataka*; Harada, Masahide; Hasegawa, Shoichi; Hiraiwa, T.*; Igarashi, Yoichi*; Iwai, Eito*; et al.

Progress of Theoretical and Experimental Physics (Internet), 2015(6), p.063C01_1 - 063C01_19, 2015/06

 Times Cited Count:4 Percentile:38.04(Physics, Multidisciplinary)

The J-PARC E56 experiment aims to search for sterile neutrinos at the J-PARC Materials and Life Science Experimental Facility (MLF). In order to examine the feasibility of the experiment, we measured the background rates of different detector candidate sites, which are located at the third floor of the MLF, using a detector consisting of plastic scintillators with a fiducial mass of 500 kg. The gammas and neutrons induced by the beam as well as the backgrounds from the cosmic rays were measured, and the results are described in this article.

JAEA Reports

Report on decontamination pilot projects to establish guidelines for environmental remediation of residential areas contaminated with radioactive materials discharged from the Fukushima Daiichi Nuclear Power Station Accident

Kihara, Shinji; Amazawa, Hiroya; Sakai, Akihiro; Nakata, Hisakazu; Kugo, Teruhiko; Matsuda, Norihiro; Oizumi, Akito; Sasamoto, Hiroshi; Mitsui, Seiichiro; Miyahara, Kaname

JAEA-Research 2013-033, 320 Pages, 2014/07


JAEA performed decontamination experiments at two test sites that combined a range of buildings and different types of land use, located in Date and Minami Soma municipalities as field pilot projects in order to accumulate knowledge and data for full-scale decontamination activities performed by local governments. In the pilot projects, we established its plan using practical decontamination methods that can be easily implemented, according to decontamination targets (e.g., forests, agricultural land, residential house and roads) at each site. As a result of the decontamination, the average air dose rates were reduced to approximately one half of the values before decontamination.

Journal Articles

Mechanical vibration search of compact ERL main linac superconducting cavities in cryomodule

Sato, Masato*; Enami, Kazuhiro*; Furuya, Takaaki*; Michizono, Shinichiro*; Miura, Takako*; Qiu, F.*; Sakai, Hiroshi*; Shinoe, Kenji*; Umemori, Kensei*; Sawamura, Masaru; et al.

Proceedings of 5th International Particle Accelerator Conference (IPAC '14) (Internet), p.2531 - 2533, 2014/07

For the main linac of ERL, high loaded Q (QL) operation is desirable to reduce the input generator power. In such operation mode, the suppression of the micophonics is important to stabilize RF amplitude and phase. One of reasons which causes microphonics is mechanical vibration, which changes the cavity frequency. The vibrations of the cavities, the cryomodule and the floor were investigated and compared with the microphnics data taken during cERL operation.

Journal Articles

Performance evaluation of ERL main linac tuner

Enami, Kazuhiro*; Furuya, Takaaki*; Sakai, Hiroshi*; Sato, Masato*; Shinoe, Kenji*; Umemori, Kensei*; Michizono, Shinichiro*; Miura, Takako*; Qiu, F.*; Arakawa, Dai*; et al.

Proceedings of 5th International Particle Accelerator Conference (IPAC '14) (Internet), p.2534 - 2536, 2014/07

We evaluated a slidejack tuner adopted as compact ERL Main Linac tuner. The tuner compensates the frequency by extending a cavity. Tuning is driven by two system, piezo and slidejack system. Slide-jack mechanism with long stroke drives coarsely piezo adjust precisely and fast. We tested performance of the tuners on operation.

Journal Articles

Operation status of compact ERL main linac cryomodule

Umemori, Kensei*; Enami, Kazuhiro*; Furuya, Takaaki*; Michizono, Shinichiro*; Miura, Takako*; Qiu, F.*; Sakai, Hiroshi*; Sato, Masato*; Shinoe, Kenji*; Sawamura, Masaru; et al.

Proceedings of 5th International Particle Accelerator Conference (IPAC '14) (Internet), p.2537 - 2539, 2014/07

We developed ERL main linac cryomodule for Compact ERL (cERL) project, which was constructed in KEK. The module includes two 9-cell L-band superconducting cavities. After construction of cERL recirculation loop, beam operation was started. First electron beam successfully passed the main linac cavities. After adjusting beam optics, energy recovery operation was achieved. Main linac cavity was enough stable for ERL beam operation, however, field emission was a problem for long term operation.

Journal Articles

Operation status of interlock system of Materials and Life Science Experimental Facility (MLF) in J-PARC

Sakai, Kenji; Kai, Tetsuya; Oi, Motoki; Watanabe, Akihiko; Nakatani, Takeshi; Higemoto, Wataru; Meigo, Shinichiro; Sakamoto, Shinichi; Takada, Hiroshi; Futakawa, Masatoshi

Progress in Nuclear Science and Technology (Internet), 4, p.264 - 267, 2014/04

no abstracts in English

Journal Articles

Magnetoresistance effects in current-perpendicular-to-plane structures based on Fe$$_{3}$$Si/FeSi$$_{2}$$ artificial lattices

Sakai, Kenichiro*; Noda, Yuta*; Takeda, Kaoru*; Takeda, Masayasu; Yoshitake, Tsuyoshi*

Physica Status Solidi (C), 10(12), p.1862 - 1865, 2013/12

 Times Cited Count:0 Percentile:0.01

JAEA Reports

Upgrade of general control system employed for Materials and Life Science Experimental Facility of J-PARC

Watanabe, Akihiko; Sakai, Kenji; Oi, Motoki; Meigo, Shinichiro; Takada, Hiroshi

JAEA-Technology 2013-028, 21 Pages, 2013/11


The General Control System (GCS) of the MLF of J-PARC has a problem that it costs very much in the maintenance because of its poor flexibility on OS, etc. For resolving the problem, we have re-examined framework and application softwares for the MLF-GCS, in considering functions that PLCs in many local control panels are controlled by the plural exclusive PCs, and operating data over 7000 are acquired, stored and distributed with suitable data format by shared servers. Furthermore, we have made a prototype of an upgraded GCS and evaluated its concrete performances with true data such as communication speed between the PLCs and PCs, control functions from operating windows, storage capability of data server, and long-term stability of the system. In conclusion, we decided to adopt following softwares for the upgraded GCS: EPICS as framework software, Takebishi OPC server as data input/output module, CSS as user interface window and PostgreSQL for the data storage server.

Journal Articles

Development of MLF-inhibit system for J-PARC

Ishiyama, Tatsuya; Ito, Yuichi; Kikuzawa, Nobuhiro; Suzuki, Takahiro; Oi, Motoki; Meigo, Shinichiro; Sakai, Kenji; Kato, Yuko

Proceedings of 9th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.714 - 716, 2013/08

no abstracts in English

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