IPAC2017 - List of Authors (Suetsugu, Y.)

Paper	Title	Page
WEPIK007	Optics Design and Observation for the Beam Abort System in SuperKEKB HER	2922
	N. Iida, K. Egawa, Y. Enomoto, Y. Funakoshi, M. Kikuchi, T. Mimashi, Y. Ohnishi, K. Oide, Y. Suetsugu KEK, Ibaraki, Japan
	In the first commissioning of SuperKEKB, which is 'Phase 1', the new abort system is tested in the High Energy Ring (HER). There is a risk that aborted beams with low emittance and high current may destroy the window for extraction from beam pipe. In order to enlarge the aborted beam at the window, quadrupole field is applied only for the aborted beam. In the Low Energy Ring (LER), quadrupole pulsed magnets will be installed to enlarge the aborted beam, and in the HER, a pair of identical sextupole magnets is installed between the abort kickers and the extraction window. These sextrupole magnets are connected by I or 'I transformation to cancel the geometrical nonlinearity for the stored beam in the ring. This paper will report the optics design for the abort system of the HER as well as the observation of the aborted beam.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK007
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WEPIK008	Problems in SuperKEKB Vacuum System During the Phase-1 Commissioning and Their Mitigation Measures	2925
	Y. Suetsugu, H. Hisamatsu, T. Ishibashi, K. Kanazawa, K. Shibata, M. Shirai, S. Terui KEK, Ibaraki, Japan
	The first (Phase-1) commissioning of the SuperKEKB, an energy-asymmetric electron-positron collider in KEK, Japan, started in February and ended in June, 2016. The vacuum system of the main ring worked well through the commissioning period as a whole, but experienced several problems, such as the electron cloud effect (ECE) in the positron ring, the pressure bursts accompanying beam losses due to dust particles in the beam pipe, an air leak at a connection flange due to the direct hitting of synchrotron radiation (SR), and so on. Towards the next (Phase-2) commissioning, countermeasures to these problems are taken during the shutdown period. For example, permanent magnets generating axial magnetic fields are attached to beam pipes at drift spaces for the suppression of the ECE. Knockers, which can artificially drop dust particles attached to the top surface in beam pipes by continuous impacts, are prepared to the beam pipes at which the pressure bursts had been frequently observed. Bellows chambers with masks are installed to protect the leaked flange from SR. The problems and their mitigation measures will be summarized in the presentation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK008
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WEPIK009	Collimators for SuperKEKB Main Ring	2929
	T. Ishibashi, Y. Suetsugu, S. Terui KEK, Ibaraki, Japan
	SuperKEKB, which is an upgrade project of KEKB, is an electron-positron collider with extremely high luminosity. Collimators (movable masks) for SuperKEKB have been designed to fit an antechamber scheme of the vacuum system and will be operated to improve backgrounds in the particle detector named Belle II. We are developing two types of collimators; a horizontal and vertical collimator. The collimator has a pair of horizontally or vertically opposed movable jaws with RF fingers. Each jaw travels independently through 5-25 mm horizontally or 2-12 mm vertically in a distance between the beam axis and the tip of the jaw. SuperKEKB will operate with high currents of short bunch lengths, therefore it is important to estimate and decrease the impedance of the collimators. Two horizontal collimators were already installed in the positron ring and operated during Phase-1 commissioning for approximately 5 months, from February to June 2016. In this presentation, the latest design, and the results in the Phase-1 commissioning are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK009
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WEPIK012	Performance of SuperKEKB High Energy Ring Beam Abort System	2939
	T. Mimashi, Y. Enomoto, N. Iida, M. Kikuchi, K. Kodama, T. Mori, Y. Suetsugu KEK, Ibaraki, Japan K. Abe Hitachi Power Semiconductor Device, Ltd., Hitachishi, Ibaraki, Japan K. Kise, A. Tokuchi Pulsed Power Japan Laboratory Ltd., Kusatsu-shi Shiga, Japan
	New Beam abort system was installed at the Super-KEKB High Energy Ring. It was designed to enlarge the horizontal beam size at the beam extraction window to protect the extraction window, and it also makes the beam abort gap shorter. It consists of four horizontal kicker magnets, one vertical kicker to sweep the beam position in vertical direction, sextupole magnet to enlarge the horizontal beam size, one lambertson magnet, Ti extraction window and beam dump. Four horizontal kicker magnets and one vertical kicker magnet connects to the one power supply. The ceramic chambers cooled by the water are inserted in each kicker coils. The Abort system had been used during SuperKEKB phase 1 operation. This paper describes the performance of the abort system.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK012
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WEPIK075	Electron Cloud Instability in SuperKEKB Phase I Commissioning	3104
	K. Ohmi, J.W. Flanagan, H. Fukuma, H. Ikeda, E. Mulyani, K. Shibata, Y. Suetsugu, M. Tobiyama KEK, Ibaraki, Japan
	Beam size blow-up due to electron cloud has been observed in Phase I commissioning of SuperKEKB. Vacuum chambers in LER (low energy positron ring) were cured by antechamber and TiN coating for electron cloud. Some parts, bellows, were not cured by the coating. In the early stage of Phase I commissioning, beam size blow up has been observed above a threshold current. The blow up was suppressed by weak permanent magnets generating longitudinal field, which cover the bellows. Electron cloud current have been monitored during the commissioning. The thresholds for the electron cloud induced fast head-tail instability have been simulated in the operating beam conditions. Coupled bunch instability caused by electron cloud has been measured in the operating beam conditions and installation of the permanent magnets. The measurement and simulation results are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK075
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WEPVA058	Development of HOM Absorber for SuperKEKB	3394
	S. Terui, T. Ishibashi, Y. Suetsugu, Y. Takeuchi, K. Watanabe KEK, Ibaraki, Japan H. Ishizaki, A. Kimura, T. Sawhata Metal Technology Co. Ltd., Ibaraki, Japan
	Higher-order modes (HOM) absorbers are necessary components for recent high-power accelerators in order to prevent beam instabilities (e.g. HOM- Beam Break Up instabilities) or the overheating of vacuum components. Several kinds of absorber materials, such as SiC, ferrite and Kanthal, have been investigated and applied in accelerators. Among these materials, ferrite has been found to be superior to others because of its higher HOM absorbing efficiency. However, because of its low tensile strength and small thermal expansion rate, it cannot be easily bonded to other metals thus limiting its use as a HOM absorber. We reported the success of the fabrication of ferrite-copper-blocks using the spark plasma sintering (SPS)-technique last year. This year we report testing with a high-power RF source and measuring gas desorption rate after baking and secondary electron yield.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA058
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THPAB022	Ion Instability in SuperKEKB Phase I Commissioning	3741
	K. Ohmi, H. Fukuma, Y. Suetsugu, M. Tobiyama KEK, Ibaraki, Japan
	Ion instability has been observed in SuperKEKB phase I commissioning. Unstable modes, their growth rates, tune shift were measured. Frequency of the unstable modes is slower than theoretical prediction and the growth rate is also slower. We discuss possible model to explain the measurements.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB022
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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

Optics Design and Observation for the Beam Abort System in SuperKEKB HER

2922

N. Iida, K. Egawa, Y. Enomoto, Y. Funakoshi, M. Kikuchi, T. Mimashi, Y. Ohnishi, K. Oide, Y. Suetsugu
KEK, Ibaraki, Japan

In the first commissioning of SuperKEKB, which is 'Phase 1', the new abort system is tested in the High Energy Ring (HER). There is a risk that aborted beams with low emittance and high current may destroy the window for extraction from beam pipe. In order to enlarge the aborted beam at the window, quadrupole field is applied only for the aborted beam. In the Low Energy Ring (LER), quadrupole pulsed magnets will be installed to enlarge the aborted beam, and in the HER, a pair of identical sextupole magnets is installed between the abort kickers and the extraction window. These sextrupole magnets are connected by I or 'I transformation to cancel the geometrical nonlinearity for the stored beam in the ring. This paper will report the optics design for the abort system of the HER as well as the observation of the aborted beam.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK007

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

WEPIK008

Problems in SuperKEKB Vacuum System During the Phase-1 Commissioning and Their Mitigation Measures

2925

Y. Suetsugu, H. Hisamatsu, T. Ishibashi, K. Kanazawa, K. Shibata, M. Shirai, S. Terui
KEK, Ibaraki, Japan

The first (Phase-1) commissioning of the SuperKEKB, an energy-asymmetric electron-positron collider in KEK, Japan, started in February and ended in June, 2016. The vacuum system of the main ring worked well through the commissioning period as a whole, but experienced several problems, such as the electron cloud effect (ECE) in the positron ring, the pressure bursts accompanying beam losses due to dust particles in the beam pipe, an air leak at a connection flange due to the direct hitting of synchrotron radiation (SR), and so on. Towards the next (Phase-2) commissioning, countermeasures to these problems are taken during the shutdown period. For example, permanent magnets generating axial magnetic fields are attached to beam pipes at drift spaces for the suppression of the ECE. Knockers, which can artificially drop dust particles attached to the top surface in beam pipes by continuous impacts, are prepared to the beam pipes at which the pressure bursts had been frequently observed. Bellows chambers with masks are installed to protect the leaked flange from SR. The problems and their mitigation measures will be summarized in the presentation.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK008

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WEPIK009

Collimators for SuperKEKB Main Ring

2929

T. Ishibashi, Y. Suetsugu, S. Terui
KEK, Ibaraki, Japan

SuperKEKB, which is an upgrade project of KEKB, is an electron-positron collider with extremely high luminosity. Collimators (movable masks) for SuperKEKB have been designed to fit an antechamber scheme of the vacuum system and will be operated to improve backgrounds in the particle detector named Belle II. We are developing two types of collimators; a horizontal and vertical collimator. The collimator has a pair of horizontally or vertically opposed movable jaws with RF fingers. Each jaw travels independently through 5-25 mm horizontally or 2-12 mm vertically in a distance between the beam axis and the tip of the jaw. SuperKEKB will operate with high currents of short bunch lengths, therefore it is important to estimate and decrease the impedance of the collimators. Two horizontal collimators were already installed in the positron ring and operated during Phase-1 commissioning for approximately 5 months, from February to June 2016. In this presentation, the latest design, and the results in the Phase-1 commissioning are presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK009

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WEPIK012

Performance of SuperKEKB High Energy Ring Beam Abort System

2939

T. Mimashi, Y. Enomoto, N. Iida, M. Kikuchi, K. Kodama, T. Mori, Y. Suetsugu
KEK, Ibaraki, Japan
K. Abe
Hitachi Power Semiconductor Device, Ltd., Hitachishi, Ibaraki, Japan
K. Kise, A. Tokuchi
Pulsed Power Japan Laboratory Ltd., Kusatsu-shi Shiga, Japan

New Beam abort system was installed at the Super-KEKB High Energy Ring. It was designed to enlarge the horizontal beam size at the beam extraction window to protect the extraction window, and it also makes the beam abort gap shorter. It consists of four horizontal kicker magnets, one vertical kicker to sweep the beam position in vertical direction, sextupole magnet to enlarge the horizontal beam size, one lambertson magnet, Ti extraction window and beam dump. Four horizontal kicker magnets and one vertical kicker magnet connects to the one power supply. The ceramic chambers cooled by the water are inserted in each kicker coils. The Abort system had been used during SuperKEKB phase 1 operation. This paper describes the performance of the abort system.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK012

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

WEPIK075

Electron Cloud Instability in SuperKEKB Phase I Commissioning

3104

K. Ohmi, J.W. Flanagan, H. Fukuma, H. Ikeda, E. Mulyani, K. Shibata, Y. Suetsugu, M. Tobiyama
KEK, Ibaraki, Japan

Beam size blow-up due to electron cloud has been observed in Phase I commissioning of SuperKEKB. Vacuum chambers in LER (low energy positron ring) were cured by antechamber and TiN coating for electron cloud. Some parts, bellows, were not cured by the coating. In the early stage of Phase I commissioning, beam size blow up has been observed above a threshold current. The blow up was suppressed by weak permanent magnets generating longitudinal field, which cover the bellows. Electron cloud current have been monitored during the commissioning. The thresholds for the electron cloud induced fast head-tail instability have been simulated in the operating beam conditions. Coupled bunch instability caused by electron cloud has been measured in the operating beam conditions and installation of the permanent magnets. The measurement and simulation results are presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK075

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WEPVA058

Development of HOM Absorber for SuperKEKB

3394

S. Terui, T. Ishibashi, Y. Suetsugu, Y. Takeuchi, K. Watanabe
KEK, Ibaraki, Japan
H. Ishizaki, A. Kimura, T. Sawhata
Metal Technology Co. Ltd., Ibaraki, Japan

Higher-order modes (HOM) absorbers are necessary components for recent high-power accelerators in order to prevent beam instabilities (e.g. HOM- Beam Break Up instabilities) or the overheating of vacuum components. Several kinds of absorber materials, such as SiC, ferrite and Kanthal, have been investigated and applied in accelerators. Among these materials, ferrite has been found to be superior to others because of its higher HOM absorbing efficiency. However, because of its low tensile strength and small thermal expansion rate, it cannot be easily bonded to other metals thus limiting its use as a HOM absorber. We reported the success of the fabrication of ferrite-copper-blocks using the spark plasma sintering (SPS)-technique last year. This year we report testing with a high-power RF source and measuring gas desorption rate after baking and secondary electron yield.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA058

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THPAB022

Ion Instability in SuperKEKB Phase I Commissioning

3741

K. Ohmi, H. Fukuma, Y. Suetsugu, M. Tobiyama
KEK, Ibaraki, Japan

Ion instability has been observed in SuperKEKB phase I commissioning. Unstable modes, their growth rates, tune shift were measured. Frequency of the unstable modes is slower than theoretical prediction and the growth rate is also slower. We discuss possible model to explain the measurements.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB022

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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

Export •

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