IPAC2017 - List of Authors (Ishibashi, T.)

Paper	Title	Page
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
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

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

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
Export •	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)

Paper

Title

Page

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

Export •

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

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

Export •

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

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

Export •

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)