IPAC2017 - List of Authors (Nakanishi, K.)

Paper	Title	Page
TUPAB006	Achievement of Stable Pulsed Operation at 31 MV/m in the STF-2 Cryomodule for the ILC	1308
	Y. Yamamoto, T. Dohmae, M. Egi, K. Hara, T. Honma, E. Kako, Y. Kojima, T. Konomi, N. Kota, T. Kubo, T. Matsumoto, T. Miura, H. Nakai, K. Nakanishi, G.-T. Park, T. Saeki, H. Shimizu, T. Shishido, T. Takenaka, K. Umemori KEK, Ibaraki, Japan
	In the Superconducting RF Test Facility (STF) in KEK, the cooldown test for the STF-2 cryomodule with 12 cavities has been done totally three times since 2014. In 2016, the 3rd cooldown test for the STF-2 cryomodule including the capture cryomodule with 2 cavities, which was used for Quantum Beam Project in 2012, was successfully done. The main purpose is the vector-sum operation with 8 cavities at average accelerating gradient of 31 MV/m as the ILC specification, and the others are the measurement for Lorenz Force Detuning (LFD) and unloaded Q value, and Low Level RF (LLRF) study, etc. During 8 cavities operation, piezo actuators were used for the compensation of LFD, and the feed-forward and vector-sum control system by LLRF worked perfectly for keeping the lowest forward power and the stable flat-top of accelerating gradient. In this paper, the result for the STF-2 cryomodule in the 3rd cooldown test will be presented in detail.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB006
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THPAB114	Operation of LLRF Control Systems in SuperKEKB Phase-1 Commissioning	3986
	T. Kobayashi, K. Akai, K. Ebihara, A. Kabe, K. Nakanishi, M. Nishiwaki, J.-I. Odagiri, S.I. Yoshimoto KEK, Ibaraki, Japan K. Hirosawa Sokendai, Ibaraki, Japan
	First beam commissioning of SuperKEKB (Phase-1), which had started in February 2016 and continued until the end of June, has been successfully accomplished. Target beam current for Phase-1 needed for sufficient vacuum scrubbing was achieved in both 7-GeV electron and 4-GeV positron rings. This presentation summarize the operation results related to low level RF (LLRF) control issues during the Phase-1 commissioning, including the system tuning, the coupled bunch instability and the bunch gap transient effect. RF system of SuperKEKB consists of about thirty klystron stations in both rings. Newly developed LLRF control system, which is composed of recent digital technique, is applied to the nine stations among the thirty for Phase-1. The RF reference signal distribution system has been also upgraded for SuperKEKB. These new systems worked well without serious problem and they contributed to smooth progress of the commissioning. The old existing systems, which had been used in the KEKB operation, were still reused for the most stations, and they also worked as soundly as performed in the KEKB operation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB114
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THPAB115	Development of a Longitudinal Feedback System for Coupled Bunch Instabilities Caused by the Accelerating Mode at Superkekb	3989
	K. Hirosawa, K. Akai, E. Ezura, T. Kobayashi, K. Nakanishi, M. Nishiwaki, S.I. Yoshimoto KEK, Ibaraki, Japan
	SuperKEKB is an asymmetric energy electron-positron circular collider. Phase-I commissioning was operated from February to June in 2016. The purpose of this accelerator is to aim at the higher luminosity than KEKB, so a larger beam current is made for it. In the future plan, beam currents in the electron and positron rings will be increased to 2.6A and 3.6A, respectively. As we consider beam dynamics in the storage ring, higher mode instability associated with the accelerating mode will be caused by a large beam current. Especially the target instability of this study is called μ=-2 mode Coupled Bunch Instability. To suppress it, we developed new feedback components for longitudinal coupled bunch instability. We have same mechanism feedback components for KEKB, but it supports only μ=-1 mode instability. Since a large current makes μ=-1 mode instability big, there is a possibility that suppression is difficult only by using KEKB components. In order to deal with this problem, new components we developed support μ=-1, -2, and -3 mode instabilities, and we improved the performance and usability as compared to existing components. We schedule studies using a beam at Phase-II.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB115
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Paper

Title

Page

Achievement of Stable Pulsed Operation at 31 MV/m in the STF-2 Cryomodule for the ILC

1308

Y. Yamamoto, T. Dohmae, M. Egi, K. Hara, T. Honma, E. Kako, Y. Kojima, T. Konomi, N. Kota, T. Kubo, T. Matsumoto, T. Miura, H. Nakai, K. Nakanishi, G.-T. Park, T. Saeki, H. Shimizu, T. Shishido, T. Takenaka, K. Umemori
KEK, Ibaraki, Japan

In the Superconducting RF Test Facility (STF) in KEK, the cooldown test for the STF-2 cryomodule with 12 cavities has been done totally three times since 2014. In 2016, the 3rd cooldown test for the STF-2 cryomodule including the capture cryomodule with 2 cavities, which was used for Quantum Beam Project in 2012, was successfully done. The main purpose is the vector-sum operation with 8 cavities at average accelerating gradient of 31 MV/m as the ILC specification, and the others are the measurement for Lorenz Force Detuning (LFD) and unloaded Q value, and Low Level RF (LLRF) study, etc. During 8 cavities operation, piezo actuators were used for the compensation of LFD, and the feed-forward and vector-sum control system by LLRF worked perfectly for keeping the lowest forward power and the stable flat-top of accelerating gradient. In this paper, the result for the STF-2 cryomodule in the 3rd cooldown test will be presented in detail.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB006

Export •

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

THPAB114

Operation of LLRF Control Systems in SuperKEKB Phase-1 Commissioning

3986

T. Kobayashi, K. Akai, K. Ebihara, A. Kabe, K. Nakanishi, M. Nishiwaki, J.-I. Odagiri, S.I. Yoshimoto
KEK, Ibaraki, Japan
K. Hirosawa
Sokendai, Ibaraki, Japan

First beam commissioning of SuperKEKB (Phase-1), which had started in February 2016 and continued until the end of June, has been successfully accomplished. Target beam current for Phase-1 needed for sufficient vacuum scrubbing was achieved in both 7-GeV electron and 4-GeV positron rings. This presentation summarize the operation results related to low level RF (LLRF) control issues during the Phase-1 commissioning, including the system tuning, the coupled bunch instability and the bunch gap transient effect. RF system of SuperKEKB consists of about thirty klystron stations in both rings. Newly developed LLRF control system, which is composed of recent digital technique, is applied to the nine stations among the thirty for Phase-1. The RF reference signal distribution system has been also upgraded for SuperKEKB. These new systems worked well without serious problem and they contributed to smooth progress of the commissioning. The old existing systems, which had been used in the KEKB operation, were still reused for the most stations, and they also worked as soundly as performed in the KEKB operation.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB114

Export •

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

THPAB115

Development of a Longitudinal Feedback System for Coupled Bunch Instabilities Caused by the Accelerating Mode at Superkekb

3989

K. Hirosawa, K. Akai, E. Ezura, T. Kobayashi, K. Nakanishi, M. Nishiwaki, S.I. Yoshimoto
KEK, Ibaraki, Japan

SuperKEKB is an asymmetric energy electron-positron circular collider. Phase-I commissioning was operated from February to June in 2016. The purpose of this accelerator is to aim at the higher luminosity than KEKB, so a larger beam current is made for it. In the future plan, beam currents in the electron and positron rings will be increased to 2.6A and 3.6A, respectively. As we consider beam dynamics in the storage ring, higher mode instability associated with the accelerating mode will be caused by a large beam current. Especially the target instability of this study is called μ=-2 mode Coupled Bunch Instability. To suppress it, we developed new feedback components for longitudinal coupled bunch instability. We have same mechanism feedback components for KEKB, but it supports only μ=-1 mode instability. Since a large current makes μ=-1 mode instability big, there is a possibility that suppression is difficult only by using KEKB components. In order to deal with this problem, new components we developed support μ=-1, -2, and -3 mode instabilities, and we improved the performance and usability as compared to existing components. We schedule studies using a beam at Phase-II.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB115

Export •

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