IPAC2017 - List of Authors (Hotchi, H.)

Paper	Title	Page
MOPIK035	New Injection Scheme of J-PARC Rapid Cycling Synchrotron	579
	K. Yamamoto, H. Harada, H. Hotchi, J. Kamiya, P.K. Saha, T. Takayanagi, M. Yoshimoto JAEA/J-PARC, Tokai-mura, Japan N. Miki, O. Takeda Nippon Advanced Technology Co., Ltd., Tokai, Japan
	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 (MR). Present beam power of RCS 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 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 500 mm space at the injection foil .
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPIK035
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TUPVA093	Radio-Activation Caused by Secondary Particles Due to Nuclear Reactions at the Stripper Foil in the J-PARC RCS	2300
	M. Yoshimoto, H. Hotchi, S. Kato, M. Kinsho, K. Okabe, K. Yamamoto JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
	The most important issue in realizing such a MW-class high-power routine beam operation is to keep machine activations within a permissible level, that is, to preserve a better hands-on-maintenance environment. Thus, a large fraction of our effort has been concentrated on reducing and managing beam losses. However the high residual activation is appeared around the stripper foils. It is caused by not primary particles due to the beam losses but secondary particles due to nuclear reaction at the foil. This radio-activation is an intrinsically serious problem for the RCS which adopts the charge exchange multi-turn beam injection scheme with the stripper foil. In this presentation, we report a detail measurement of the residual dose around the stripper foil together with the cause estimated based on simulation studies.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA093
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WEOAA3	Realizing a High-Intensity Low-Emittance Beam in the J-PARC 3-GeV RCS	2470
	H. Hotchi, H. Harada, S. Kato, K. Okabe, P.K. Saha, Y. Shobuda, F. Tamura, N. Tani, Y. Watanabe, M. Yoshimoto JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
	The J-PARC 3-GeV rapid cycling synchrotron (RCS) has two functions; one as a proton driver to produce pulsed muons and neutrons, and the other as an injector to the following 50-GeV main ring (MR). RCS is now intensively developing a high-intensity beam test to realize a high-intensity low-emittance beam with less beam halo required from MR. This paper presents the recent experimental results, together with detailed discussions for the emittance growth and its mitigation mechanisms.
	Slides WEOAA3 [1.732 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEOAA3
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WEPIK014	Coupled Bunch Instability and Its Cure at J-PARC RCS	2946
	Y. Shobuda, H. Harada, H. Hotchi, P.K. Saha, T. Takayanagi, F. Tamura, N. Tani, T. Togashi, Y. Watanabe, K. Yamamoto, M. Yamamoto JAEA/J-PARC, Tokai-mura, Japan Y.H. Chin, Y. Irie, T. Toyama KEK, Tokai, Ibaraki, Japan
	The RCS at J-PARC is a kicker-impedance dominant machine, which violates the impedance budget from a classical viewpoint. Nevertheless, we have recently succeeded to accelerate a 1-MW equivalent beam by making maximum use of the space charge effect on the beam instabilities. In this report, we explain the manipulation to suppress the beam instability, at first. Then, we discuss some issues to suppress the beam instabilities for beams with much smaller transverse emittance, as well as the present status of our efforts to reduce the kicker impedance toward the realization of the higher beam power at the RCS.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK014
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THPAB025	Simulation Studies of Transverse Beam Instabilities and Measures Beyond 1 MW Beam Power in the 3-GeV RCS of J-PARC	3750
	P.K. Saha, H. Hotchi, Y. Shobuda JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
	The transverse impedance of the extraction kicker magnets is a significant beam instability source in the 3-GeV RCS (Rapid Cycling Synchrotron) of J-PARC (Japan Proton Accelerator Research Complex). The systematic simulation studies for beam instability by including the space charge effect has been done by using the ORBIT code. The simulation results are well reproduced in the corresponding measurements. The designed 1 MW beam power has recently been accomplished by keeping sextuple magnets off in order to stabilize the beam by utilizing the large lattice chromaticity throughout the entire acceleration period. The RCS simultaneously delivers extracted beam to the MLF (Material and Life Science Experimental Facility) and the MR (Main Ring). In order to ensure 1 MW beam power at the MLF even when RCS beam sharing to the MR is twice increased as well as when a second target station is constructed at the MLF, a beam power of 1.5 MW has to be realized in the RCS. However, the simulation shows that beyond 1 MW the beam is unstable even if no chromaticity is corrected. A reduction of the kicker impedance by at least a half is required in order to achieve 1.5 MW beam power in the RCS.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB025
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

New Injection Scheme of J-PARC Rapid Cycling Synchrotron

579

K. Yamamoto, H. Harada, H. Hotchi, J. Kamiya, P.K. Saha, T. Takayanagi, M. Yoshimoto
JAEA/J-PARC, Tokai-mura, Japan
N. Miki, O. Takeda
Nippon Advanced Technology Co., Ltd., Tokai, Japan

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 (MR). Present beam power of RCS 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 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 500 mm space at the injection foil .

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPIK035

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPVA093

Radio-Activation Caused by Secondary Particles Due to Nuclear Reactions at the Stripper Foil in the J-PARC RCS

2300

M. Yoshimoto, H. Hotchi, S. Kato, M. Kinsho, K. Okabe, K. Yamamoto
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan

The most important issue in realizing such a MW-class high-power routine beam operation is to keep machine activations within a permissible level, that is, to preserve a better hands-on-maintenance environment. Thus, a large fraction of our effort has been concentrated on reducing and managing beam losses. However the high residual activation is appeared around the stripper foils. It is caused by not primary particles due to the beam losses but secondary particles due to nuclear reaction at the foil. This radio-activation is an intrinsically serious problem for the RCS which adopts the charge exchange multi-turn beam injection scheme with the stripper foil. In this presentation, we report a detail measurement of the residual dose around the stripper foil together with the cause estimated based on simulation studies.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA093

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEOAA3

Realizing a High-Intensity Low-Emittance Beam in the J-PARC 3-GeV RCS

2470

H. Hotchi, H. Harada, S. Kato, K. Okabe, P.K. Saha, Y. Shobuda, F. Tamura, N. Tani, Y. Watanabe, M. Yoshimoto
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan

The J-PARC 3-GeV rapid cycling synchrotron (RCS) has two functions; one as a proton driver to produce pulsed muons and neutrons, and the other as an injector to the following 50-GeV main ring (MR). RCS is now intensively developing a high-intensity beam test to realize a high-intensity low-emittance beam with less beam halo required from MR. This paper presents the recent experimental results, together with detailed discussions for the emittance growth and its mitigation mechanisms.

Slides WEOAA3 [1.732 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEOAA3

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPIK014

Coupled Bunch Instability and Its Cure at J-PARC RCS

2946

Y. Shobuda, H. Harada, H. Hotchi, P.K. Saha, T. Takayanagi, F. Tamura, N. Tani, T. Togashi, Y. Watanabe, K. Yamamoto, M. Yamamoto
JAEA/J-PARC, Tokai-mura, Japan
Y.H. Chin, Y. Irie, T. Toyama
KEK, Tokai, Ibaraki, Japan

The RCS at J-PARC is a kicker-impedance dominant machine, which violates the impedance budget from a classical viewpoint. Nevertheless, we have recently succeeded to accelerate a 1-MW equivalent beam by making maximum use of the space charge effect on the beam instabilities. In this report, we explain the manipulation to suppress the beam instability, at first. Then, we discuss some issues to suppress the beam instabilities for beams with much smaller transverse emittance, as well as the present status of our efforts to reduce the kicker impedance toward the realization of the higher beam power at the RCS.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK014

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THPAB025

Simulation Studies of Transverse Beam Instabilities and Measures Beyond 1 MW Beam Power in the 3-GeV RCS of J-PARC

3750

P.K. Saha, H. Hotchi, Y. Shobuda
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan

The transverse impedance of the extraction kicker magnets is a significant beam instability source in the 3-GeV RCS (Rapid Cycling Synchrotron) of J-PARC (Japan Proton Accelerator Research Complex). The systematic simulation studies for beam instability by including the space charge effect has been done by using the ORBIT code. The simulation results are well reproduced in the corresponding measurements. The designed 1 MW beam power has recently been accomplished by keeping sextuple magnets off in order to stabilize the beam by utilizing the large lattice chromaticity throughout the entire acceleration period. The RCS simultaneously delivers extracted beam to the MLF (Material and Life Science Experimental Facility) and the MR (Main Ring). In order to ensure 1 MW beam power at the MLF even when RCS beam sharing to the MR is twice increased as well as when a second target station is constructed at the MLF, a beam power of 1.5 MW has to be realized in the RCS. However, the simulation shows that beyond 1 MW the beam is unstable even if no chromaticity is corrected. A reduction of the kicker impedance by at least a half is required in order to achieve 1.5 MW beam power in the RCS.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB025

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)