IPAC2017 - List of Authors (Zhou, D.)

Paper	Title	Page
MOPIK076	Optimization of Dynamic Aperture with Constraints on Linear Chromaticity	705
	H. Sugimoto, H. Koiso, A. Morita, Y. Ohnishi, K. Oide, D. Zhou KEK, Ibaraki, Japan
	This paper presents numerical technique to optimize dynamic aperture with constraints on linear chromaticity of optical functions. By solving a set of linear equations at each iteration step of dynamic aperture optimization, the linear chromaticity is kept unchanged. The variable range of tuning knobs is taken into account in order to make the technique applicable to practical use. Numerical simulations assuming the SuperKEKB design lattice are performed, and it is demonstrated that the dynamic aperture obtained with the presented scheme is almost comparable to that without constraints. Luminosity simulations assuming weak-strong model show that the constraints lead to improvements of luminosity performance.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPIK076
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THPAB021	Wake Field and Head-Tail Instability in Beam-Beam Collision with a Large Crossing Angle	3738
	K. Ohmi, D. Zhou KEK, Ibaraki, Japan N. Kuroo UTTAC, Tsukuba, Ibaraki, Japan K. Oide, F. Zimmermann CERN, Geneva, Switzerland
	Head-tail type of coherent beam-beam instability has been seen in a strong-strong beam-beam simulation for collision with a large Piwinski angle σ_zθ/σ_x>>1, where θ is a half crossing angle. Beta x* is key parameter for the instability. The instability is not serious for SuperKEKB, but can be seen in phase II commissioning stage. It has a large impact for design of FCC-ee. We introduce wake field due to the beam-beam collision. The wake field gives turn-by-turn correlation of head-tail mode. Head-tail instability caused by the wake field explains that seen in the strong-strong beam-beam simulation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB021
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THPVA002	Numerical Investigation of Beam Halo From Beam Gas Scattering in KEK-ATF	4410
	R.J. Yang, P. Bambade LAL, Orsay, France K. Kubo, T. Okugi, N. Terunuma, D. Zhou KEK, Ibaraki, Japan
	To demonstrate the final focus schemes of the Future Linear Collider (FLC), the Accelerator Test Facility 2 (ATF2) at KEK is devoted to focus the beam to a RMS size of a few tens of nanometers (nm) vertically and to provide stability at the nm level at the virtual Interaction Point (IP). However, the loss of halo particles upstream will introduce background to the diagnostic instrument measuring the ultra-small beam, using a laser interferometer monitor. To help the realization of the above goals and beam operation, understanding and mitigation of beam halo are crucial. In this paper, we present the systematical simulation of beam halo formation from beam gas Coulomb scattering (BGS) in the ATF damping ring. The behavior of beam halo with various machine parameters is also discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA002
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THPVA012	Transverse Impedance Measurement in SuperKEKB	4442
	N. Kuroo UTTAC, Tsukuba, Ibaraki, Japan T. Ishibashi, T. Mimashi, K. Ohmi, Y. Ohnishi, K. Shibata, Y. Suetsugu, S. Terui, M. Tobiyama, D. Zhou KEK, Ibaraki, Japan
	In KEK(Japan), SuperKEKB project is progressing toward upgrade. This project aims improvement luminosity (8×10³⁵ cm^-2s- 1) which is 40 times of the performance of the KEKB accelerator. In Phase 1 of this project, a performance test as storage ring was carried out. Understanding of ring Impedance/wake is an important subject in phase I. Measurement of Head Tail Damping using Turn by Turn monitor was performed to evaluate impedance/wake. Betatron motion is excited by kicker and its damping is measured for several parameters sets of bunch current and chromaticity in both HER and LER. The wake field was calculated from the decrement of betatron amplitude. We present the wake field which is cross-checked with tune shift based on the current dependence.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA012
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Paper

Title

Page

Optimization of Dynamic Aperture with Constraints on Linear Chromaticity

705

H. Sugimoto, H. Koiso, A. Morita, Y. Ohnishi, K. Oide, D. Zhou
KEK, Ibaraki, Japan

This paper presents numerical technique to optimize dynamic aperture with constraints on linear chromaticity of optical functions. By solving a set of linear equations at each iteration step of dynamic aperture optimization, the linear chromaticity is kept unchanged. The variable range of tuning knobs is taken into account in order to make the technique applicable to practical use. Numerical simulations assuming the SuperKEKB design lattice are performed, and it is demonstrated that the dynamic aperture obtained with the presented scheme is almost comparable to that without constraints. Luminosity simulations assuming weak-strong model show that the constraints lead to improvements of luminosity performance.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPIK076

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THPAB021

Wake Field and Head-Tail Instability in Beam-Beam Collision with a Large Crossing Angle

3738

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

Head-tail type of coherent beam-beam instability has been seen in a strong-strong beam-beam simulation for collision with a large Piwinski angle σ_zθ/σ_x>>1, where θ is a half crossing angle. Beta x* is key parameter for the instability. The instability is not serious for SuperKEKB, but can be seen in phase II commissioning stage. It has a large impact for design of FCC-ee. We introduce wake field due to the beam-beam collision. The wake field gives turn-by-turn correlation of head-tail mode. Head-tail instability caused by the wake field explains that seen in the strong-strong beam-beam simulation.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB021

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THPVA002

Numerical Investigation of Beam Halo From Beam Gas Scattering in KEK-ATF

4410

R.J. Yang, P. Bambade
LAL, Orsay, France
K. Kubo, T. Okugi, N. Terunuma, D. Zhou
KEK, Ibaraki, Japan

To demonstrate the final focus schemes of the Future Linear Collider (FLC), the Accelerator Test Facility 2 (ATF2) at KEK is devoted to focus the beam to a RMS size of a few tens of nanometers (nm) vertically and to provide stability at the nm level at the virtual Interaction Point (IP). However, the loss of halo particles upstream will introduce background to the diagnostic instrument measuring the ultra-small beam, using a laser interferometer monitor. To help the realization of the above goals and beam operation, understanding and mitigation of beam halo are crucial. In this paper, we present the systematical simulation of beam halo formation from beam gas Coulomb scattering (BGS) in the ATF damping ring. The behavior of beam halo with various machine parameters is also discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA002

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

THPVA012

Transverse Impedance Measurement in SuperKEKB

4442

N. Kuroo
UTTAC, Tsukuba, Ibaraki, Japan
T. Ishibashi, T. Mimashi, K. Ohmi, Y. Ohnishi, K. Shibata, Y. Suetsugu, S. Terui, M. Tobiyama, D. Zhou
KEK, Ibaraki, Japan

In KEK(Japan), SuperKEKB project is progressing toward upgrade. This project aims improvement luminosity (8×10³⁵ cm^-2s- 1) which is 40 times of the performance of the KEKB accelerator. In Phase 1 of this project, a performance test as storage ring was carried out. Understanding of ring Impedance/wake is an important subject in phase I. Measurement of Head Tail Damping using Turn by Turn monitor was performed to evaluate impedance/wake. Betatron motion is excited by kicker and its damping is measured for several parameters sets of bunch current and chromaticity in both HER and LER. The wake field was calculated from the decrement of betatron amplitude. We present the wake field which is cross-checked with tune shift based on the current dependence.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA012

Export •

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