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Journal Articles

Abnormally enhanced diamagnetism in Al-Zn-Mg alloys

Nishimura, Katsuhiko*; Matsuda, Kenji*; Lee, S.*; Nunomura, Norio*; Shimano, Tomoki*; Bendo, A.*; Watanabe, Katsumi*; Tsuchiya, Taiki*; Namiki, Takahiro*; Toda, Hiroyuki*; et al.

Journal of Alloys and Compounds, 774, p.405 - 409, 2019/02

 Percentile:100(Chemistry, Physical)

Journal Articles

Recent progress of J-PARC RCS beam commissioning; Efforts for realizing a high-intensity low-emittance beam

Hotchi, Hideaki; Harada, Hiroyuki; Kato, Shinichi; Okabe, Kota; Saha, P. K.; Shobuda, Yoshihiro; Tamura, Fumihiko; Tani, Norio; Watanabe, Yasuhiro; Yoshimoto, Masahiro

Proceedings of 14th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.95 - 99, 2017/12

no abstracts in English

Journal Articles

Achievement of a low-loss 1-MW beam operation in the 3-GeV rapid cycling synchrotron of the Japan Proton Accelerator Research Complex

Hotchi, Hideaki; Harada, Hiroyuki; Hayashi, Naoki; Kato, Shinichi; Kinsho, Michikazu; Okabe, Kota; Saha, P. K.; Shobuda, Yoshihiro; Tamura, Fumihiko; Tani, Norio; et al.

Physical Review Accelerators and Beams (Internet), 20(6), p.060402_1 - 060402_25, 2017/06

The 3-GeV rapid cycling synchrotron (RCS) of the Japan Proton Accelerator Research Complex (J-PARC) is the world's highest class of high-power pulsed proton driver, aiming for an output beam power of 1 MW. The most important issues in realizing such a high-power beam operation are to control and minimize beam loss for maintaining machine activations within permissible levels. In RCS, numerical simulation was successfully utilized along with experimental approaches to isolate the mechanism of beam loss and find its solution. By iteratively performing actual beam experiments and numerical simulations, and also by several hardware improvements, we have recently established a 1-MW beam operation with very low fractional beam loss of a couple of 10$$^{-3}$$. In this paper, our recent efforts toward realizing such a low-loss high-intensity beam acceleration are presented.

Journal Articles

Realizing a high-intensity low-emittance beam in the J-PARC 3-GeV RCS

Hotchi, Hideaki; Harada, Hiroyuki; Kato, Shinichi; Okabe, Kota; Saha, P. K.; Shobuda, Yoshihiro; Tamura, Fumihiko; Tani, Norio; Watanabe, Yasuhiro; Yoshimoto, Masahiro

Proceedings of 8th International Particle Accelerator Conference (IPAC '17) (Internet), p.2470 - 2473, 2017/06

For this past year, RCS beam tuning was focused on realizing a high-intensity low-emittance beam required from the downstream facility. The extraction beam emittance including its tail part was successfully decreased by optimizing transverse injection painting, and tune and chromaticity manipulations, where bipolar sextupole field patterns were newly introduced to simultaneously achieve emittance growth mitigation at the early stage of acceleration and beam instability suppression after the middle stage of acceleration. This paper presents the recent experimental results, together with detailed discussions for the emittance growth and its mitigation mechanisms.

Journal Articles

Theoretical elucidation of space charge effects on the coupled-bunch instability at the 3 GeV Rapid Cycling Synchrotron at the Japan Proton Accelerator Research Complex

Shobuda, Yoshihiro; Chin, Y. H.*; Saha, P. K.; Hotchi, Hideaki; Harada, Hiroyuki; Irie, Yoshiro*; Tamura, Fumihiko; Tani, Norio; Toyama, Takeshi*; Watanabe, Yasuhiro; et al.

Progress of Theoretical and Experimental Physics (Internet), 2017(1), p.013G01_1 - 013G01_39, 2017/01

AA2016-0375.pdf:3.07MB

 Times Cited Count:5 Percentile:26.6(Physics, Multidisciplinary)

The Rapid Cycling Synchrotron (RCS), whose beam energy ranges from 400 MeV to 3 GeV and which is located in the Japan Proton Accelerator Research Complex, is a kicker-impedance dominant machine, which violates the impedance budget from a classical viewpoint. Contrary to conventional understanding, we have succeeded to accelerate a 1-MW equivalent beam. The machine has some interesting features: for instance, the beam tends to be unstable for the smaller transverse beam size, the beam is stabilized by increasing the peak current ${it etc}$. Space charge effects play an important role in the beam instability at the RCS. In this study, a new theory has been developed to calculate the beam growth rate with the head-tail and coupled-bunch modes ($$m,mu$$) while taking space charge effects into account. The theory sufficiently explains the distinctive features of the beam instabilities at the RCS.

Journal Articles

Conceptual design of main magnets for the J-PARC RCS energy upgrade

Tani, Norio; Watanabe, Yasuhiro; Hotchi, Hideaki; Harada, Hiroyuki; Yamamoto, Masanobu; Kinsho, Michikazu; Igarashi, Susumu*; Sato, Yoichi*; Shirakata, Masashi*; Koseki, Tadashi*

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.708 - 711, 2016/11

At the J-PARC Main Ring (MR), there have been various investigation carried out at the moment aiming at the beam operation of MW order. As one of the investigations, a study of the Rapid-Cycling Synchrotron (RCS) magnets was implemented. Increase of the extraction energy of RCS was needed to reduce beam loss, as beam loss in the MR injection region was large under influence of Space Charge effect at the injection beam of 3GeV. Therefore conceptual design of the extraction energy upgrade using dipole and quadrupole magnets of RCS was performed. In this paper, we will report the contents of the study in extraction energy upgrade of RCS magnets and problems which became clear as a result.

Journal Articles

Beam loss caused by edge focusing of injection bump magnets and its mitigation in the 3-GeV rapid cycling synchrotron of the Japan Proton Accelerator Research Complex

Hotchi, Hideaki; Tani, Norio; Watanabe, Yasuhiro; Harada, Hiroyuki; Kato, Shinichi; Okabe, Kota; Saha, P. K.; Tamura, Fumihiko; Yoshimoto, Masahiro

Physical Review Accelerators and Beams (Internet), 19(1), p.010401_1 - 010401_11, 2016/01

AA2015-0742.pdf:2.84MB

 Times Cited Count:6 Percentile:31.2(Physics, Nuclear)

In the J-PARC 3-GeV RCS, transverse injection painting is utilized not only to suppress space-charge induced beam loss but also to mitigate foil scattering beam loss during charge-exchange injection. The space-charge induced beam loss is well minimized by the combination of modest transverse painting and full longitudinal painting. But, for sufficiently mitigating the foil scattering beam loss, the transverse painting area has to be further expanded. However, such a wide-ranging transverse painting had not been realized until recently due to beta function beating caused by edge focusing of pulsed injection bump magnets. This beta function beating additionally excites random betatron resonances, causing significant extra beam loss when expanding the transverse painting area. To solve this issue, we newly installed pulse-type quadrupole correctors to compensate the beta function beating. This paper presents recent experimental results on this correction scheme, while discussing the beam loss and its mitigation mechanisms.

Journal Articles

Numerical study for beam loss occurring for wide-ranging transverse injection painting and its mitigation scenario in the J-PARC 3-GeV RCS

Hotchi, Hideaki; Tani, Norio; Watanabe, Yasuhiro

Nuclear Instruments and Methods in Physics Research A, 778, p.102 - 114, 2015/04

 Times Cited Count:5 Percentile:34.97(Instruments & Instrumentation)

In the J-PARC 3-GeV Rapid Cycling Synchrotron (RCS), transverse injection painting is utilized to mitigate the space charge induced beam loss. But now the available range of transverse painting is limited to small area due to beta function beating caused by the edge focus of injection bump magnets. This beta function beating additionally excites random betatron resonances through a distortion of the lattice super-periodicity, leading to a deterioration of the betatron motion stability and its resultant decline of the flexibility of transverse painting. For the beta function beating, the correction scheme with pulse-type quadrupole correctors was proposed. The numerical simulation confirmed that this correction scheme effectively mitigates the random betatron resonances by recovering the lattice super-periodicity.

Journal Articles

Review of five investigation committees' reports on the Fukushima Dai-ichi Nuclear Power Plant severe accident; Focusing on accident progression and causes

Watanabe, Norio; Yonomoto, Taisuke; Tamaki, Hitoshi; Nakamura, Takehiko; Maruyama, Yu

Journal of Nuclear Science and Technology, 52(1), p.41 - 56, 2015/01

 Times Cited Count:5 Percentile:34.97(Nuclear Science & Technology)

On March 11, 2011, the Tohoku District-off the Pacific Ocean Earthquake and the subsequent tsunami resulted in the severe core damage at TEPCO's Fukushima Dai-ichi Nuclear Power Plant Units 1-3, involving hydrogen explosions at Units 1, 3, and 4 and the large release of radioactive materials to the environment. Four independent committees were established by the Japanese government, the Diet of Japan, the Rebuild Japan Initiative Foundation, and TEPCO to investigate the accident and published their respective reports. Also, the Nuclear and Industrial Safety Agency carried out an analysis of accident causes to obtain the lessons learned from the accident and made its report public. This article reviews the reports and clarifies the differences in their positions, from the technological point of view, focusing on the accident progression and causes. Moreover, the undiscussed issues are identified to provide insights useful for the near-term regulatory activities including accident investigation by the Nuclear Regulation Authority.

JAEA Reports

Seismically-induced reactor coolant leakage as an allegedly-possible cause of accident at unit 1 of Fukushima Dai-ichi Nuclear Power Station

Kukita, Yutaka; Watanabe, Norio

JAEA-Technology 2014-036, 38 Pages, 2014/11

JAEA-Technology-2014-036.pdf:26.08MB

NAIIC emphasized the possibility of seismically-induced reactor coolant leakage and implied its causal connection to the accident, in particular at the Fukushima Daiichi Unit 1. This view of NAIIC has been addressed by the Accident Investigation Committee established by the Cabinet decision, NISA, and the Secretariat of NRA. Based on seismic response analyses, plant records and simulations, their reports uniformly note that seismically-induced leakage is unlikely to be a causal factor for the core damage though the possibility of insignificantly small leakage cannot be ruled out completely. Also refuted are some of the arguments made by NAIIC as grounds for suspecting safety-significant leakage. The present report re-examines the leak detection capability through the review of plant instruments and post-accident simulations, and adds some arguments in order to resolve the issue raised by NAIIC without technical ambiguity as far as possible. As well, the plant design uniqueness of Unit 1, the history of facility changes, the operating procedures and the actual operations are looked into to raise issues for further investigation.

JAEA Reports

Study on precursors to accident at Fukushima Daiichi Nuclear Power Station

Watanabe, Norio

JAEA-Review 2014-031, 18 Pages, 2014/08

JAEA-Review-2014-031.pdf:4.92MB

It has been recognized an important means to learn lessons from operating experience and to feed them back to the design, construction, operation and management of facilities. A lot of events involved similar occurrences which have been experienced in the past. These are referred to as precursors. In the present study, identified and discussed are the precursors to the accident at Fukushima Daiichi Nuclear Power Plant to obtain the generic lessons which should have been learned. As precursors to the Fukushima accident, six events are identified: massive internal flooding and loss of safety systems; prolonged station blackout involving loss of control room and loss of residual heat removal; external flooding involving loss of safety systems and multi units site issue; loss of offsite power with one of two emergency diesel generators inoperable; tsunami-induced flooding; common-mode loss of instrument power. Furthermore, the most notable near-miss to the Fukushima accident is discussed.

Journal Articles

Progress of injection energy upgrade project for J-PARC RCS

Hayashi, Naoki; Harada, Hiroyuki; Horino, Koki; Hotchi, Hideaki; Kamiya, Junichiro; Kinsho, Michikazu; Saha, P. K.; Shobuda, Yoshihiro; Takayanagi, Tomohiro; Tani, Norio; et al.

Proceedings of 4th International Particle Accelerator Conference (IPAC '13) (Internet), p.3833 - 3835, 2014/07

no abstracts in English

Journal Articles

Development of control system for J-PARC RCS main magnet power supplies

Watanabe, Yasuhiro; Tani, Norio; Inoue, Keigo*

Proceedings of 10th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.628 - 631, 2014/06

no abstracts in English

Journal Articles

Design consideration of beam duct for quadrupole correctors in J-PARC RCS

Kamiya, Junichiro; Kinsho, Michikazu; Hayashi, Naoki; Hotchi, Hideaki; Ogiwara, Norio; Tani, Norio; Watanabe, Yasuhiro

Journal of the Vacuum Society of Japan, 57(4), p.131 - 135, 2014/04

In J-PARC 3GeV synchrotron (RCS), new quadrupole magnets (quadrupole correctors) are planned to be installed in order to correct the edge focusing effect and tune. In this report, we describe a deliberation flow about the design of the beam ducts, which are installed in the quadrupole corrector. The effects of eddy current were examined in the case of the titanium duct. The calculated results showed that the temperature rise was too much (up to over 350$$^{circ}$$C) and the magnetic field in the beam duct is largely distorted. Therefore we decided to employ alumina ceramics beam ducts. The stress and displacement, which are caused by the atmospheric pressure, were estimated by simulating the realistic equipments in the beam line. It was found that there was no large stress and displacement by installing the alumina ceramics duct.

Journal Articles

Review of five investigation committees' reports on the Fukushima Dai-ichi Nuclear Power Plant severe accident; Focusing on accident progression and causes

Watanabe, Norio; Yonomoto, Taisuke; Tamaki, Hitoshi; Nakamura, Takehiko; Maruyama, Yu

Nippon Genshiryoku Gakkai Wabun Rombunshi, 12(2), p.113 - 127, 2013/06

On March 11, 2011, the Tohoku District - off the Pacific Ocean Earthquake and the subsequent tsunami resulted in the severe core damage at the TEPCO's Fukushima Dai-ichi Nuclear Power Station Units 1-3, involving hydrogen explosions at Units 1, 3, and 4 and the large release of radioactive materials to the environment. The four independent committees were established by the Government, the Diet of Japan and the Rebuild Japan Initiative Foundation as well as TEPCO to investigate the accident and published their respective reports. Also, the Nuclear and Industrial Safety Agency carried out the analysis of accident causes to obtain the lessons learned from the accident and made its report public. This article reviews the reports and clarifies the differences in their positions, from the technological point of view, focusing on the accident progression and causes. As well, the undiscussed issues are identified to provide insights useful for the near-term regulatory activities including accident investigation by the Nuclear Regulation Authority.

Journal Articles

Development of a feedback control system for resonant power supplies in the J-PARC 3-GeV synchrotron

Watanabe, Yasuhiro; Tani, Norio

Proceedings of 4th International Particle Accelerator Conference (IPAC '13) (Internet), p.672 - 674, 2013/06

no abstracts in English

Journal Articles

Operation maintenance of the thyratron for the power supply of the extraction kicker magnet in the J-PARC 3GeV RCS

Togashi, Tomohito; Watanabe, Masao; Suganuma, Kazuaki; Takayanagi, Tomohiro; Ueno, Tomoaki; Tani, Norio; Watanabe, Yasuhiro; Kinsho, Michikazu

Proceedings of 9th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.471 - 473, 2012/08

The 3-GeV RCS (Rapid Cycling Synchrotron) of J-PARC (Japan Proton Accelerator Research Complex) uses 8 pulse kicker magnets for the beam extraction at a repetition rate of 25 Hz. Each kicker power supply has 2 thyratrons and thus they are 16 in total. An average life time of thyratrons even more than the J-PARC annual operation time of 5000 hours and a stable operation with a downtime of less than only 0.5% has already been achieved. The present maintenance procedures and statistics for the long term operation with thyratrons are reported in this paper.

Journal Articles

High precision tracking control for rapid cycling magnets

Watanabe, Yasuhiro; Tani, Norio; Adachi, Toshikazu*; Someya, Hirohiko*; Irie, Yoshiro*

Proceedings of 9th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.538 - 540, 2012/08

Rapid cycling magnets are excited using a resonant circuit and the current waveform is a DC-biased sinusoidal pattern. However, non-linear characteristic of the magnet produces harmonic components in the magnetic field. The harmonic components are different for each type of magnet depending upon the degree of saturation, and it causes a tracking error. This paper proposes harmonic current control in the resonant circuit to reduce harmonic components in the magnetic field.

Journal Articles

Design of a high-precision and wide dynamic range pulsed magnet power supply

Watanabe, Yasuhiro; Tani, Norio; Inoue, Keigo*

Proceedings of 9th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.531 - 533, 2012/08

In order to compensate a quadrupole component caused by edge filed in bump magnets, pulsed quadrupole magnets will be installed in the J-PARC RCS. The pulsed quadrupole-magnet power supply is required large voltage and low current ripple. This paper proposes a high-precision and wide dynamic range pulsed power supply.

Journal Articles

A Simple method for estimating the structure temperatures and the cesium revaporization inside the reactor pressure vessel, 1; Basic concepts and model descriptions for the Fukushima Daiichi Nuclear Power Plant

Liu, Q.; Ishikawa, Jun; Maruyama, Yu; Watanabe, Norio

Journal of Nuclear Science and Technology, 49(5), p.479 - 485, 2012/05

 Times Cited Count:2 Percentile:74.11(Nuclear Science & Technology)

This paper presents a simple approach for estimating the temperature of the structures in the reactor pressure vessel (RPV) and the release rates of fission products (FPs) at the time of several months after the core melt accident at the Fukushima Daiichi Nuclear Power Plant. In this paper, basic concepts are firstly presented and then, a heat balance model is proposed to estimate the temperature of the uncovered reactor core and the upper structures in the RPV with the measured temperatures of the RPV outer wall. In addition, models for estimating the revaporization rate of cesium hydroxide (CsOH) inside the RPV and the leak rate of CsOH to the primary containment vessel are also presented. This approach is anticipated to be applicable to the Fukushima Daiichi #1, #2 and #3 Units.

129 (Records 1-20 displayed on this page)