Achievement of low beam loss at high-intensity operation of J-PARC 3 GeV RCS

Saha, P. K.; Okabe, Kota; Nakanoya, Takamitsu; Yoshimoto, Masahiro; Shobuda, Yoshihiro; Harada, Hiroyuki; Tamura, Fumihiko; Okita, Hidefumi; Hatakeyama, Shuichiro; Moriya, Katsuhiro; et al.

Proceedings of 19th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1 - 5, 2023/01

https://www.pasj.jp/web_publish/pasj2022/proceedings/PDF/TUOP/TUOPA03.pdf

Report of summer holiday practical training 2020; Feasibility study on nuclear battery using HTTR core; Feasibility study for nuclear design, 3

Ishitsuka, Etsuo; Mitsui, Wataru*; Yamamoto, Yudai*; Nakagawa, Kyoichi*; Ho, H. Q.; Ishii, Toshiaki; Hamamoto, Shimpei; Nagasumi, Satoru; Takamatsu, Kuniyoshi; Kenzhina, I.*; et al.

JAEA-Technology 2021-016, 16 Pages, 2021/09

JAEA-Technology-2021-016.pdf:1.8MB

As a summer holiday practical training 2020, the feasibility study for nuclear design of a nuclear battery using HTTR core was carried out, and the downsizing of reactor core were studied by the MVP-BURN. As a result, it is clear that a 1.6 m radius reactor core, containing 54 (183 layers) fuel blocks with 20% enrichment of U, and BeO neutron reflector, could operate continuously for 30 years with thermal power of 5 MW. Number of fuel blocks of this compact core is 36% of the HTTR core. As a next step, the further downsizing of core by changing materials of the fuel block will be studied.

Flexible chopper gate pulse generation for the J-PARC RCS

Tamura, Fumihiko; Yamamoto, Masanobu; Yoshii, Masahito*; Sugiyama, Yasuyuki*; Hotchi, Hideaki; Saha, P. K.; Yoshimoto, Masahiro; Harada, Hiroyuki

JPS Conference Proceedings (Internet), 33, p.011021_1 - 011021_6, 2021/03

https://doi.org/10.7566/JPSCP.33.011021

Chopped beam injection is employed in the J-PARC RCS to avoid the longitudinal beam losses. A fast beam chopper is installed in the MEBT section of the linac. The chopper is driven by the gate pulses sent from the LLRF control system of the RCS. The delay from the zero crossing of the RCS rf and the width are set so that the beam pulse is injected into the proper phase position of the rf bucket. A unique feature of the J-PARC chopper gate pulse generation is thinning of the pulses. The thinning is useful to control the beam intensity without changing much the condition of the longitudinal painting. Also, the beam macro pulse can be trimmed down to a single intermediate pulse by setting the parameters. In this poster, we present the overview of the generation of the chopper gate pulse in the LLRF control system and various beam commissioning results utilizing the flexibility of it. Also, we discuss the upgrade of the chopper gate pulse generation.

First measurement and online monitoring of the stripper foil thinning and pinhole formation to achieve a longer foil lifetime in high-intensity accelerators

Saha, P. K.; Yoshimoto, Masahiro; Hatakeyama, Shuichiro; Hotchi, Hideaki; Harada, Hiroyuki; Tamura, Fumihiko; Yamamoto, Kazami; Yamazaki, Yoshio; Kinsho, Michikazu; Irie, Yoshiro*

Physical Review Accelerators and Beams (Internet), 23(8), p.082801_1 - 082801_13, 2020/08

AA2020-0279.pdf:1.92MB

https://doi.org/10.1103/PhysRevAccelBeams.23.082801

The -electron state of the heavy fermion superconductor NpPdAl and the isostructural family

Metoki, Naoto; Aczel, A. A.*; Aoki, Dai*; Chi, S.*; Fernandez-Baca, J. A.*; Griveau, J.-C.*; Hagihara, Masato*; Hong, T.*; Haga, Yoshinori; Ikeuchi, Kazuhiko*; et al.

JPS Conference Proceedings (Internet), 30, p.011123_1 - 011123_6, 2020/03

https://doi.org/10.7566/JPSCP.30.011123

Rare earths (4) and actinides (5) provide variety of interesting states realized with competing interactions between the increasing number of electrons. Since crystal field splitting of many-body electron system is smaller than the bandwidth, (1) high resolution experiments are needed, (2) essentially no clear spectrum with well defined peaks is expected in itinerant Ce and U compounds, and (3) Np and Pu is strictly regulated. Therefore, systematic research on magnetic excitations by neutron scattering experiments of localized compounds and rare earth iso-structural reference is useful. We describe the electron states of heavy electron compounds NpPdAl and actinide and rare earth based iso-structural family.

Recent progress of the J-PARC RCS beam commissioning and operation; Efforts to realize a higher beam power beyond 1 MW

Hotchi, Hideaki; Harada, Hiroyuki; Hayashi, Naoki; Kinsho, Michikazu; Okabe, Kota; Saha, P. K.; Shobuda, Yoshihiro; Tamura, Fumihiko; Yamamoto, Kazami; Yamamoto, Masanobu; et al.

Proceedings of 16th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.574 - 578, 2019/07

https://www.pasj.jp/web_publish/pasj2019/proceedings/index.html

no abstracts in English

Measurement and analysis of in-vessel component activation and gamma dose rate distribution in Joyo, 2

Yamamoto, Takahiro; Ito, Chikara; Maeda, Shigetaka; Ito, Hideaki; Sekine, Takashi

JAEA-Technology 2017-036, 41 Pages, 2018/02

JAEA-Technology-2017-036.pdf:7.86MB

In the experimental fast reactor Joyo, the damaged upper core structure (UCS) was retrieved into the cask in May 2014 The dose rate on UCS surface was quite high due to the activation for over 30 years operation. In order to attain the optimum safety design, manufacture and operation of equipment for UCS replacement, the method to evaluate UCS surface dose rate was developed on the basis of C/E obtained by the in-vessel dose rate measurement in Joyo. In order to verify the evaluation method, the axial gamma-ray distribution measurement on the surface of the cask, which contained UCS, was conducted using a plastic scintillating optical fiber (PSF) detector. This paper describes the comparison results between calculation and measurement as follows. (1) The measured axial gamma-ray distribution on the cask surface had a peak on proper location with considering the cask shielding structure and agree well with the calculated distribution. (2) The C/E of axial gamma-ray distribution on the cask surface was ranged from 1.1 to 1.7. It was confirmed that the calculation for UCS replacement equipment design had a margin conservatively. Then, the results showed that the developed evaluation method for UCS replacement equipment design was sufficiently reliable.

New injection system design of the J-PARC rapid cycling synchrotron

Yamamoto, Kazami; Kamiya, Junichiro; Saha, P. K.; Takayanagi, Tomohiro; Yoshimoto, Masahiro; Hotchi, Hideaki; Harada, Hiroyuki; Takeda, Osamu*; Miki, Nobuharu*

Proceedings of 14th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.374 - 378, 2017/12

The 3-GeV Rapid Cycling Synchrotron (RCS) of Japan Proton Accelerator Research Complex (J-PARC) aims to deliver 1-MW proton beam to the neutron target and Main Ring synchrotron. Present beam power of the Rapid Cycling Synchrotron is up to 500-kW and the higher radiation doses were concentrated in the injection area. These activations were caused by the interaction between the foil and the beam. To reduce the worker dose near the injection point, we have studied a new design of the injection scheme to secure enough space for radiation shielding and bellows. In the new system, two of four injection pulse bump magnets are replaced and we are able to ensure the additional space around the injection foil chamber. So far, new injection system seems not impossible. However, preliminary study result indicated that temperature of the duct and shielding metals would be slightly higher. The eddy current due to the shift bump magnet field generates heat. Thus we have to study details of above effect.

Coupled bunch instability and its cure at J-PARC RCS

Shobuda, Yoshihiro; Saha, P. K.; Hotchi, Hideaki; Harada, Hiroyuki; Takayanagi, Tomohiro; Tamura, Fumihiko; Tani, Norio; Togashi, Tomohito; Toyama, Takeshi*; Watanabe, Yasuhiro; et al.

Proceedings of 8th International Particle Accelerator Conference (IPAC '17) (Internet), p.2946 - 2949, 2017/05

https://doi.org/10.18429/JACoW-IPAC2017-WEPIK014

no abstracts in English

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

https://doi.org/10.1093/ptep/ptw169

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 . 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 () while taking space charge effects into account. The theory sufficiently explains the distinctive features of the beam instabilities at the RCS.