HB2016 - List of Authors (Shobuda, Y.)

Paper

Title

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TUAM1X01

A Two Particle Model for Study of Effects of Space-Charge Force on Strong Head-Tail Instabilities.

Y.H. Chin
KEK, Ibaraki, Japan
M. Blaskiewicz
BNL, Upton, Long Island, New York, USA
A. Chao
SLAC, Menlo Park, California, USA
Y. Shobuda
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan

In this talk, I present a new two particle model for study of strong head-tail instabilities in the presence of the space-charge force. It is a simple expansion of the well-known two particle model. No chromaticity effect is included. It leads to a formula for the growth rate as a function of the two dimensionless parameters: the space-charge tune shift parameter (normalized by the synchrotron tune) and the wake field strength, Υ. The 3-dimensional contour plot of the growth rate as a function of those two dimensionless parameters reveals stopband structures. Many simulation results generally indicate that a strong head-tail instability can be damped by a weak space-charge force, but the beam becomes unstable again when the space-charge force is further increased. The new two particle model indicates a similar behavior. In weak space-charge regions, additional tune shifts by the space-charge force dissolve the mode-coupling. As the space-charge force is increased, they conversely restore the mode-coupling, but then a further increase of the space-charge force decouples the modes again. This mode coupling/decoupling behavior creates the stopbands structures.

Slides TUAM1X01 [9.082 MB]

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TUPM5X01

Injection Painting Improvements in the J-PARC RCS

299

S. Kato, K. Horino, H. Hotchi, M. Kinsho, K. Okabe, P.K. Saha, Y. Shobuda, T. Takayanagi, T. Tobita, T. Ueno
JAEA/J-PARC, Tokai-mura, Japan
H. Harada
JAEA, Ibaraki-ken, Japan

In the J-PARC 3GeV RCS, the injection painting is essential method for the reduction of the space charge force. In this method, the H⁻ beam from Linac is arranged on the large phase space area of the ring orbit during multiple turns. To implement this method, painting magnets form the time variable beam orbit. Therefore, the precise output current control of the magnet power supply is required. Because the power supply controlled by mainly feedforward signal is operated, we developed the iterative tuning method for the optimum feedforward parameter determination. As a result, we could reduce the tracking error of the current compared to before. Furthermore, to improve the accuracy of the painting area size, we applied the output readjustment additionally. Because the current monitor value of the power supply was different from the actual magnetic field due to the delay in the circuit and the leakage field, we corrected the tracking of the current based on the measured painting area size determined by the analysis of the measured COD. As a result, we achieved the precise injection painting. This talk presents these improvement results of the injection painting in the RCS.

Slides TUPM5X01 [4.122 MB]

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THAM6X01

The Path to 1 MW: Beam Loss Control in the J-PARC 3-GeV RCS

480

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

The J-PARC 3-GeV RCS started 1-MW beam test from October 2014, and successfully achieved a 1-MW beam acceleration in January 2015. The most important issues in realizing such a high power routine beam operation are control and minimization of beam loss. This talk will present the recent progress of 1-MW beam tuning, especially focusing on our approaches to beam loss issues.

Slides THAM6X01 [1.849 MB]

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THPM10X01

Stripline Beam Position Monitors With Improved Frequency Response and Their Coupling Impedances

523

Y. Shobuda
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
Y.H. Chin, K. Takata
KEK, Ibaraki, Japan
K.G. Nakamura
Kyoto University, Kyoto, Japan
T. Toyama
J-PARC, KEK & JAEA, Ibaraki-ken, Japan

In J-PARC Main Ring, transverse intra-bunch oscillations have been observed during the injection and at the onset of acceleration. Up to now, the beam instability is suppressed by the intra-bunch feedback system, where the stripline beam position monitors operate at 10⁸.8 MHz. However, there is a concern that electron cloud instabilities may appear and limit the beam current at future higher power operations. For the case, we have developed a wider-band (several GHz) beam position monitor by deforming the electrode shapes. The modification of the electrode can be done not to enhance the beam coupling impedance. For the typical electrode shapes, we show the coupling impedances as well as the frequency responses of the electrodes.

Slides THPM10X01 [5.240 MB]

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Paper	Title	Page
TUAM1X01	A Two Particle Model for Study of Effects of Space-Charge Force on Strong Head-Tail Instabilities.
	Y.H. Chin KEK, Ibaraki, Japan M. Blaskiewicz BNL, Upton, Long Island, New York, USA A. Chao SLAC, Menlo Park, California, USA Y. Shobuda JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
	In this talk, I present a new two particle model for study of strong head-tail instabilities in the presence of the space-charge force. It is a simple expansion of the well-known two particle model. No chromaticity effect is included. It leads to a formula for the growth rate as a function of the two dimensionless parameters: the space-charge tune shift parameter (normalized by the synchrotron tune) and the wake field strength, Υ. The 3-dimensional contour plot of the growth rate as a function of those two dimensionless parameters reveals stopband structures. Many simulation results generally indicate that a strong head-tail instability can be damped by a weak space-charge force, but the beam becomes unstable again when the space-charge force is further increased. The new two particle model indicates a similar behavior. In weak space-charge regions, additional tune shifts by the space-charge force dissolve the mode-coupling. As the space-charge force is increased, they conversely restore the mode-coupling, but then a further increase of the space-charge force decouples the modes again. This mode coupling/decoupling behavior creates the stopbands structures.
	Slides TUAM1X01 [9.082 MB]
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPM5X01	Injection Painting Improvements in the J-PARC RCS	299
	S. Kato, K. Horino, H. Hotchi, M. Kinsho, K. Okabe, P.K. Saha, Y. Shobuda, T. Takayanagi, T. Tobita, T. Ueno JAEA/J-PARC, Tokai-mura, Japan H. Harada JAEA, Ibaraki-ken, Japan
	In the J-PARC 3GeV RCS, the injection painting is essential method for the reduction of the space charge force. In this method, the H⁻ beam from Linac is arranged on the large phase space area of the ring orbit during multiple turns. To implement this method, painting magnets form the time variable beam orbit. Therefore, the precise output current control of the magnet power supply is required. Because the power supply controlled by mainly feedforward signal is operated, we developed the iterative tuning method for the optimum feedforward parameter determination. As a result, we could reduce the tracking error of the current compared to before. Furthermore, to improve the accuracy of the painting area size, we applied the output readjustment additionally. Because the current monitor value of the power supply was different from the actual magnetic field due to the delay in the circuit and the leakage field, we corrected the tracking of the current based on the measured painting area size determined by the analysis of the measured COD. As a result, we achieved the precise injection painting. This talk presents these improvement results of the injection painting in the RCS.
	Slides TUPM5X01 [4.122 MB]
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THAM6X01	The Path to 1 MW: Beam Loss Control in the J-PARC 3-GeV RCS	480
	H. Hotchi, H. Harada, S. Kato, M. Kinsho, K. Okabe, P.K. Saha, Y. Shobuda, F. Tamura, N. Tani, Y. Watanabe, K. Yamamoto, M. Yamamoto, M. Yoshimoto JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
	The J-PARC 3-GeV RCS started 1-MW beam test from October 2014, and successfully achieved a 1-MW beam acceleration in January 2015. The most important issues in realizing such a high power routine beam operation are control and minimization of beam loss. This talk will present the recent progress of 1-MW beam tuning, especially focusing on our approaches to beam loss issues.
	Slides THAM6X01 [1.849 MB]
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPM10X01	Stripline Beam Position Monitors With Improved Frequency Response and Their Coupling Impedances	523
	Y. Shobuda JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan Y.H. Chin, K. Takata KEK, Ibaraki, Japan K.G. Nakamura Kyoto University, Kyoto, Japan T. Toyama J-PARC, KEK & JAEA, Ibaraki-ken, Japan
	In J-PARC Main Ring, transverse intra-bunch oscillations have been observed during the injection and at the onset of acceleration. Up to now, the beam instability is suppressed by the intra-bunch feedback system, where the stripline beam position monitors operate at 10⁸.8 MHz. However, there is a concern that electron cloud instabilities may appear and limit the beam current at future higher power operations. For the case, we have developed a wider-band (several GHz) beam position monitor by deforming the electrode shapes. The modification of the electrode can be done not to enhance the beam coupling impedance. For the typical electrode shapes, we show the coupling impedances as well as the frequency responses of the electrodes.
	Slides THPM10X01 [5.240 MB]
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)