HB2016 - List of Authors (Chin, Y.H.)

Paper

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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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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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FRAM2P01

Summary WG-A

575

W. Fischer
BNL, Upton, Long Island, New York, USA
Y.H. Chin
KEK, Ibaraki, Japan
G. Franchetti
GSI, Darmstadt, Germany

Friday Summary

Slides FRAM2P01 [6.325 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)

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)

FRAM2P01	Summary WG-A	575
	W. Fischer BNL, Upton, Long Island, New York, USA Y.H. Chin KEK, Ibaraki, Japan G. Franchetti GSI, Darmstadt, Germany
	Friday Summary
	Slides FRAM2P01 [6.325 MB]
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)