IPAC2017 - List of Authors (Saha, P.K.)

Paper	Title	Page
MOPAB070	Beam Position Measurement During Multi-Turn Painting Injection at the J-PARC RCS	277
	N. Hayashi, A. Miura, P.K. Saha, M. Yoshimoto JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
	Multi-turn painting injection scheme is important for high intensity proton accelerators. At the J-PARC RCS, a transverse painting scheme was adapted by adding vertical painting magnets to the beam transport line before the injection point, with horizontal painting being performed by a set of dedicated pulse magnets in the ring. To establish a transverse painting condition, it is usual to base on the pulse magnet current pattern. However, it is more desirable to directly measure the beam orbit time variation for evaluation. A linac beam was chopped to match the ring RF bucket. We thought that it would be difficult to measure the position for each pulse; however, the average position could be extracted by introducing a particular device. For the beam injected into the ring, because the linac RF frequency component was diminished due to debunching quickly, one could determine its position in the beginning of the injection period. However, due to rebunching effect the position determination becomes difficult. This problem needs to be resolved.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB070
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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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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
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Paper

Title

Page

Beam Position Measurement During Multi-Turn Painting Injection at the J-PARC RCS

277

N. Hayashi, A. Miura, P.K. Saha, M. Yoshimoto
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan

Multi-turn painting injection scheme is important for high intensity proton accelerators. At the J-PARC RCS, a transverse painting scheme was adapted by adding vertical painting magnets to the beam transport line before the injection point, with horizontal painting being performed by a set of dedicated pulse magnets in the ring. To establish a transverse painting condition, it is usual to base on the pulse magnet current pattern. However, it is more desirable to directly measure the beam orbit time variation for evaluation. A linac beam was chopped to match the ring RF bucket. We thought that it would be difficult to measure the position for each pulse; however, the average position could be extracted by introducing a particular device. For the beam injected into the ring, because the linac RF frequency component was diminished due to debunching quickly, one could determine its position in the beginning of the injection period. However, due to rebunching effect the position determination becomes difficult. This problem needs to be resolved.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB070

Export •

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

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

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

Export •

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

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)