IPAC2018 - List of Authors (Hirosawa, K.)

Paper	Title	Page
THPAF089	Mode Coupling Theory in Collisions With a Large Crossing Angle	3197
	N. Kuroo UTTAC, Tsukuba, Ibaraki, Japan K. Hirosawa, K. Ohmi, D. Zhou KEK, Ibaraki, Japan K. Oide, F. Zimmermann CERN, Geneva, Switzerland
	We discuss a novel coherent beam-beam instability in collisions with a large crossing angle. The instability appears in the correlated head-tail motion of the two colliding beams. Cross wake force is introduced to represent the head-tail correlation between colliding beams. The cross wake force is localized at the collision point. Mode coupling theory based on the cross wake force is developed. Collision scheme with a large crossing angle is being very popular in design of electron positron collider. In SuperKEKB project, a collision with a large crossing angle is performed to boost the luminosity ~ 10³⁶ cm^-2s⁻¹. Future circular collider, FCC is also designed with a large crossing angle. Strong-strong simulations have shown a strong coherent head-tail instability, which can limit the performance of proposed future colliders. The mode coupling theory using the cross wake force explains the instability. The instability may affect all colliders designs based on the crab waist scheme.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF089
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WEPAL001	LLRF Control and Master Oscillator System for Damping Ring at SuperKEKB	2137
	T. Kobayashi, K. Akai, A. Kabe, K. Nakanishi, M. Nishiwaki, J.-I. Odagiri KEK, Ibaraki, Japan H. Deguchi, K. Hayashi, J. Mizuno Mitsubishi Electric TOKKI Systems, Amagasaki, Hyogo, Japan K. Hirosawa Sokendai, Ibaraki, Japan
	For SuperKEKB, new low level RF (LLRF) control systems has ben developed and they worked successfully in the first beam commissioning (Phase-1) of SuperKEKB, which was accomplished in 2016. Damping ring (DR) was newly constructed for positron beam injection, in order to make significantly emittance smaller for SuperKEKB. The beam commissioning of DR will be conducted in JFY2017 for the Phase-2 commissioning. Phase-2 is scheduled in the last quater of JFY2017. DR has an RF station, and two cavities (or three cavities in future) are driven by a klystron. New LLRF control system for DR (DR-LLRF) was also developed and installed. RF frequency of DR operation is common with the main storage rings (MR) of SuperKEKB. The good performance of DR-LLRF was demonstrated in test operation, and RF conditioning of the pair of two cavities was successfully completed in June 2017. This paper reports the detail of the performance results of DR-LLRF controls, and also the other some relevant issues in LLRF controls for DR, including the master oscillator system (synchronization with the injection linac), are introduced.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL001
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THPAK099	The Influence of Higher Order Multipoles of IR Magnets on Luminosity for SuperKEKB	3463
SUSPF061	use link to see paper's listing under its alternate paper code
	K. Hirosawa, T. Okada Sokendai, Ibaraki, Japan N. Kuroo UTTAC, Tsukuba, Ibaraki, Japan K. Ohmi, N. Ohuchi, D. Zhou KEK, Ibaraki, Japan
	SuperKEKB is an electron-positron circular collider upgraded from KEKB. To reach higher luminosity, values of beta are extremely small at Interaction Point. Although magnets in interaction region have a very strong focusing effect, they make a large disturbance to beams. Higher order multipoles and their skew components of magnetic fields of IR magnets are located at a very high beta section with pi/2 phase difference from IP. These multipoles can give critical effect to beam dynamics at interaction point and reduce luminosity on SuperKEKB design. In this study, we calculated beam dynamics for effect of skew components for multipole magnet, and estimated the influence on luminosity by them.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK099
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Mode Coupling Theory in Collisions With a Large Crossing Angle

3197

N. Kuroo
UTTAC, Tsukuba, Ibaraki, Japan
K. Hirosawa, K. Ohmi, D. Zhou
KEK, Ibaraki, Japan
K. Oide, F. Zimmermann
CERN, Geneva, Switzerland

We discuss a novel coherent beam-beam instability in collisions with a large crossing angle. The instability appears in the correlated head-tail motion of the two colliding beams. Cross wake force is introduced to represent the head-tail correlation between colliding beams. The cross wake force is localized at the collision point. Mode coupling theory based on the cross wake force is developed. Collision scheme with a large crossing angle is being very popular in design of electron positron collider. In SuperKEKB project, a collision with a large crossing angle is performed to boost the luminosity ~ 10³⁶ cm^-2s⁻¹. Future circular collider, FCC is also designed with a large crossing angle. Strong-strong simulations have shown a strong coherent head-tail instability, which can limit the performance of proposed future colliders. The mode coupling theory using the cross wake force explains the instability. The instability may affect all colliders designs based on the crab waist scheme.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF089

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

WEPAL001

LLRF Control and Master Oscillator System for Damping Ring at SuperKEKB

2137

T. Kobayashi, K. Akai, A. Kabe, K. Nakanishi, M. Nishiwaki, J.-I. Odagiri
KEK, Ibaraki, Japan
H. Deguchi, K. Hayashi, J. Mizuno
Mitsubishi Electric TOKKI Systems, Amagasaki, Hyogo, Japan
K. Hirosawa
Sokendai, Ibaraki, Japan

For SuperKEKB, new low level RF (LLRF) control systems has ben developed and they worked successfully in the first beam commissioning (Phase-1) of SuperKEKB, which was accomplished in 2016. Damping ring (DR) was newly constructed for positron beam injection, in order to make significantly emittance smaller for SuperKEKB. The beam commissioning of DR will be conducted in JFY2017 for the Phase-2 commissioning. Phase-2 is scheduled in the last quater of JFY2017. DR has an RF station, and two cavities (or three cavities in future) are driven by a klystron. New LLRF control system for DR (DR-LLRF) was also developed and installed. RF frequency of DR operation is common with the main storage rings (MR) of SuperKEKB. The good performance of DR-LLRF was demonstrated in test operation, and RF conditioning of the pair of two cavities was successfully completed in June 2017. This paper reports the detail of the performance results of DR-LLRF controls, and also the other some relevant issues in LLRF controls for DR, including the master oscillator system (synchronization with the injection linac), are introduced.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL001

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

THPAK099

The Influence of Higher Order Multipoles of IR Magnets on Luminosity for SuperKEKB

3463

SUSPF061

use link to see paper's listing under its alternate paper code

K. Hirosawa, T. Okada
Sokendai, Ibaraki, Japan
N. Kuroo
UTTAC, Tsukuba, Ibaraki, Japan
K. Ohmi, N. Ohuchi, D. Zhou
KEK, Ibaraki, Japan

SuperKEKB is an electron-positron circular collider upgraded from KEKB. To reach higher luminosity, values of beta are extremely small at Interaction Point. Although magnets in interaction region have a very strong focusing effect, they make a large disturbance to beams. Higher order multipoles and their skew components of magnetic fields of IR magnets are located at a very high beta section with pi/2 phase difference from IP. These multipoles can give critical effect to beam dynamics at interaction point and reduce luminosity on SuperKEKB design. In this study, we calculated beam dynamics for effect of skew components for multipole magnet, and estimated the influence on luminosity by them.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK099

Export •

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