| Paper |
Title |
Page |
| TUOBB01 |
Optics Aberration at IP and Beam-beam Effects |
66 |
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- K. Ohmi, Y. Funakoshi, H. Koiso, A. Morita, Y. Ohnishi, D. Zhou
KEK, Ibaraki, Japan
- K. Hirosawa
Sokendai, Ibaraki, Japan
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Collision in SuperKEKB phase II commissioning has started in April 2018. Luminosity was lower than the geomterical value even in very low bunch current. Linear x-y coupling at IP caused by skew of QCS was conjectured as error source. x-y coupling correction using skew corrector of QCS resulted in luminosity recover of 2 times. After the QCS skew correction, luminosity is still limited at relatively low bunch current. Nonlinear x-y coupling at IP is conjectured as a source of the luminosity limitation. We discuss effects of linear and nonlinear x-y coupling at IP on the beam-beam performance.
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| DOI • |
reference for this paper
※ https://doi.org/10.18429/JACoW-eeFACT2018-TUOBB01
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| About • |
paper received ※ 25 September 2018 paper accepted ※ 19 February 2019 issue date ※ 21 April 2019 |
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| TUYBA01 |
Benchmarking of Simulations of Coherent Beam-beam Instability |
103 |
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- K. Ohmi, H. Koiso, Y. Ohnishi
KEK, Ibaraki, Japan
- D. El Khechen
CERN, Geneva, Switzerland
- K. Hirosawa
Sokendai, Ibaraki, Japan
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Coherent beam-beam nstability in head-tail mode has been predicted in collision with a large crossing angle. The instability is serious for design of future e+e− colliders based on the large crossing angle collision. It is possible to observe the instability in SuperKEKB commissioning. Horizontal beam size blow-up of both beams has been seen depending on the tune operating point. We report the measurement results of the instability in SuperKEKB phaseII commissioning.
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| DOI • |
reference for this paper
※ https://doi.org/10.18429/JACoW-eeFACT2018-TUYBA01
|
|
| About • |
paper received ※ 25 September 2018 paper accepted ※ 19 February 2019 issue date ※ 21 April 2019 |
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| WEYAA03 |
SRF System for KEKB and SuperKEKB |
256 |
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- K. Nakanishi, T. Kobayashi, M. Nishiwaki
KEK, Ibaraki, Japan
- K. Hirosawa
Sokendai, Ibaraki, Japan
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Eight superconducting accelerating cavities were operated for more than ten years at the KEKB. Commisioning operation of SuperKEKB is ongoing and those cavities are also used to accelerate the electron beam of 2.6 A. There are some issues to address the large beam current and to realize stable operation. One issue is a large HOM power of 37 kW expected to be induced in each cavity module. To cope with the HOM power issue, we have installed an additional HOM damper to the downstream of the cavity module. Another issue is degradation of Q values of the cavities during the ten years operation. Cause of the degradation was particle contamination. To clean the cavity surface, high pressure rinsing (HPR) is an effective way. Therefore we have developed a horizontal HPR. In this method, a nozzle for water jet is inserted horizontally into the cavity module without disassembly of the cavity. We applied the horizontal HPR to our degraded cavities. The RF performances of those cavities have been successfully recovered. In this report, present status of our cavity will be presented. Additionally, LLRF control issues for SuperKEKB will be introduced.
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| DOI • |
reference for this paper
※ https://doi.org/10.18429/JACoW-eeFACT2018-WEYAA03
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|
| About • |
paper received ※ 12 October 2018 paper accepted ※ 19 February 2019 issue date ※ 21 April 2019 |
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