eeFACT2016 - List of Keywords (cavity)

Paper	Title	Other Keywords	Page
TUT2H2	Injector Linac Upgrade and New RF Gun Development for SuperKEKB	ion, gun, emittance, laser	74
	T. Natsui, D. Satoh, M. Yoshida, R. Zhang, X. Zhou KEK, Ibaraki, Japan
	The SuperKEKB commissioning has finally started. The final goal of luminosity is 40 times higher than KEKB. The injector upgrade is required to obtain the low emittance and high charge beam corresponding to the short beam life and small injection acceptance of the SuperKEKB ring. In the injector linac, several new instruments have been installed. Flux Concentrator (FC) was developed for high charge positron beam production. The target bunch charge of positron beam is 4 nC. The new damping ring will be used for positron beam to reduce beam emittance to 10 mm-mrad. However, electron beam must be reached to 20 mm-mrad normalized emittance at 5 nC beam charge without damping ring. Thermionic gun was used for KEKB injector and it was able to generate enough beam charge. However, its emittance is too large. Therefor we developed photo cathode S-band RF gun. This new RF gun has unique accelerating cavity which called quasi-travelling wave side coupled cavity. Laser system for this photo cathode has been also developed. The laser system is constructed with Yb:YAG thin disk for high power and pulse shaping. I will illustrate the RF gun, laser system and several new injector linac systems.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2016-TUT2H2
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TUT2H4	Top-up Injection Schemes for HEPS	ion, injection, kicker, operation	85
	Z. Duan, J. Chen, Y. Jiao, Y.M. Peng, Q.Y. Wang, G. Xu, P. Zhang IHEP, Beijing, People's Republic of China
	Funding: Natural Science Foundation of China (No.11605212) Top-up injection has become standard mode of operation for most third generation light sources, and has also been suc- cesfully applied in electron-positron circular colliders like KEKB and PEP-II. For next generation ultra-low emittance storage rings approaching the diffraction limit of X-rays, take the High Energy Photon Source (HEPS) for example, top-up injection is a basic requirement but non-trivial to im- plement. The very small dynamic aperture is insufficient for traditional off-axis injection scheme, instead, a novel on-axis injection scheme was recently proposed for HEPS, based on RF gymnastics of a double-frequency RF system. This paper will describe the physical mechanism of this scheme, related RF issues, and the implications for top-up injection.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2016-TUT2H4
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TUT3AH2	Instability Issues in CEPC	ion, impedance, damping, coupling	108
	N. Wang, W. Chou, J. Gao, D.J. Gong, J. He, Q. Qin, Y.S. Sun, D. Wang, Y. Wang, G. Xu, Y. Zhang, H.J. Zheng IHEP, Beijing, People's Republic of China K. Ohmi, D. Zhou KEK, Ibaraki, Japan
	The CEPC is a high energy circular electron-positron collider under design. Large bunch population is required to achieve the design luminosity. Instabilities driven by the coupling impedance are possible limitations for reaching high machine performance. An updated impedance model, including the resistive wall and the main vacuum components, has been obtained for the main ring. Based on the impedance model, the collective instability issues of the beam with the partial-double ring design are discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2016-TUT3AH2
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WET2H4	New Cavity Techniques and Future Prospects	ion, niobium, superconducting-cavity, SRF	173
	P. Sha Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China J.Y. Zhai IHEP, Beijing, People's Republic of China
	Funding: This study was supported by National Key Programme for S&T Research and Development (Grant NO.: 2016YFA0400400) and National Natural Science Foundation of China (Grant NO.: 11505197) In the recent decades, Superconducting cavities have been widely used to accelerate electron, positron, and ions. Most SRF cavities are made from bulk niobi-um till now, which has developed fast in the past years and is hard to advance more. Take 1.3 GHz 9-cell cavi-ty for example, the quality factor (Q) can keep above 10¹⁰ when the accelerating field (Eacc) reach 40 MV/m, which nearly touch the theoretical limitation of Q and Eacc for bulk niobium. For large superconducting accelerators in future (FCC, CEPC, etc), Q and Eacc should be increased significantly compared to now, which can reduce the cryogenic power and use fewer cavities. So new cavity material and techniques are being studied at accelerator laboratories, while Nitro-gen doping (N-doping) and Nb3Sn have developed quickly and been paid attention to mostly [1]. N-doping can increase Q by one time for 1.3 GHz 9-cell cavity, which have been adopted by Linac Coherent Light Source II (LCLS-II) at SLAC [2]. [1],Alexander Romanenko, Bulk Nb Based SRF Technology, FCC Week 2016. [2],Camille M Ginsburg, LCLS-II Cryomodules at FNAL & JLAB, TTC 2016.
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WET2H7	LLRF Controls Including Gap Transients at KEKB and Plans for SuperKEKB	ion, controls, LLRF, simulation	177
	T. Kobayashi, K. Akai KEK, Ibaraki, Japan
	Features of LLRF control systems in KEKB and SuperKEKB will be reviewed, and the evaluation of the bunch gap transient effect on beam phase will be presented for SuperKEKB. The RF systems of KEKB are being reinforced to handle triple as large beam power for upgrade to SuperKEKB. Furthermore, a new LLRF control system, which is based on a recent digital control technique, has been developed. For nine RF stations, among a total of thirty, the LLRF control system has been replaced with new ones. They were worked successfully in the Phase-1 commissioning. Bunch phase shift along the bunch train due to a bunch gap transient is a concern. In KEKB operation, a rapid phase change was observed at the leading part of the train, which was not predicted. Our new simulation study clarified that the rapid phase change is caused by a transient loading in the three-cavity system of ARES. And the new simulation shows that the phase change will be much large in SuperKEKB. The main issue is the difference in beam phase change between the two rings for the asymmetry colliding. The measures by means of mitigation of the relative beam phase difference between the two rings will be also suggested.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2016-WET2H7
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WET3AH2	High Efficiency Klystron Development for Particle Accelerators	ion, klystron, electron, bunching	185
	D.A. Constable Lancaster University, Lancaster, United Kingdom A.Yu. Baikov MFUA, Moscow, Russia G. Burt, V.C.R. Hill, C. Lingwood Cockcroft Institute, Lancaster University, Lancaster, United Kingdom I.A. Guzilov JSC Vacuum Devices Basic Technologies, Moscow, Russia A. Jensen SLAC, Menlo Park, California, USA R.D. Kowalczyk L-3, Williamsport, Pennsylvania, USA R. Marchesin TED, Velizy, France C. Marrelli ESS, Lund, Sweden I. Syratchev CERN, Geneva, Switzerland
	Upcoming large scale particle accelerators, such as the Future Circular Collider (FCC), the Compact Linear Collider (CLIC) and the International Linear Collider (ILC) are expected to require RF drive on the order of 100 MW. Therefore, efforts to improve the efficiency of the specific RF source is of significant interest to the particle accelerator community. Klystrons are an attractive choice as the RF source, with the current state of the art tubes offering efficiencies up to 70%. The High Efficiency International Klystron Activity (HEIKA) collaboration seeks to improve upon this by considering novel methods of electron bunching. Such methods include the core oscillation method (COM), the bunching-alignment-collection (BAC) method, as well as the use of harmonic cavities. The theory behind these bunching methods will be discussed, along with their suitability for specific particle accelerators. In addition, results from numerical simulations predicting klystrons with efficiencies larger than 80% will be presented. Early experimental testing of tubes employing the BAC method will also be presented, demonstrating the efficiency improvements that the scheme offers.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2016-WET3AH2
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WET3BH1	Improvement of Efficiency of Klystron to Apply the CPD Method	ion, klystron, electron, radiation	192
	K. Watanabe KEK, Ibaraki, Japan
	A high power RF system for the particle accelerators needs large electrical power in the operation. An improvement of efficiency is also always required as a technology component for the energy saving. To improve efficiency of a high-power source, the CPD (Collector Potential Depression) method already was applied a Gyrotron to recovery the electrical energy form the collector loss. The CPD is an energy-saving scheme that recovers the kinetic energy of the spent electrons after generating rf power. A CPD klystron (E37703 CPD) was fabricated at 2013, to recycle an existing klystron of Toshiba E3786. The purpose of our study is to demonstrate the proof-of-principle of the CPD method to apply a klystron. A plane of R&D of CPD klystron at KEK will be reported in this meeting.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2016-WET3BH1
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THS2H4	SRF Working Group Summary	ion, HOM, SRF, damping	223
	R.A. Rimmer JLab, Newport News, Virginia, USA
	Summary of Superconducting RF: This working group focused on the status and challenges of superconducting Radio Frequency (SRF) cavities and systems for present and future high luminosity lepton colliders, the so-called 'factories'. Submissions covered the state of the art of SRF cavity designs, HOM damping, high power couplers, operational experiences and the needs of future colliders. Active work on similar SRF systems for the electron complex of a future electron ion collider (EIC) was presented. Much of this technology is also useful for next generation high brightness light sources and other applications.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2016-THS2H4
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Paper

Title

Other Keywords

Page

TUT2H2

Injector Linac Upgrade and New RF Gun Development for SuperKEKB

ion, gun, emittance, laser

74

T. Natsui, D. Satoh, M. Yoshida, R. Zhang, X. Zhou
KEK, Ibaraki, Japan

The SuperKEKB commissioning has finally started. The final goal of luminosity is 40 times higher than KEKB. The injector upgrade is required to obtain the low emittance and high charge beam corresponding to the short beam life and small injection acceptance of the SuperKEKB ring. In the injector linac, several new instruments have been installed. Flux Concentrator (FC) was developed for high charge positron beam production. The target bunch charge of positron beam is 4 nC. The new damping ring will be used for positron beam to reduce beam emittance to 10 mm-mrad. However, electron beam must be reached to 20 mm-mrad normalized emittance at 5 nC beam charge without damping ring. Thermionic gun was used for KEKB injector and it was able to generate enough beam charge. However, its emittance is too large. Therefor we developed photo cathode S-band RF gun. This new RF gun has unique accelerating cavity which called quasi-travelling wave side coupled cavity. Laser system for this photo cathode has been also developed. The laser system is constructed with Yb:YAG thin disk for high power and pulse shaping. I will illustrate the RF gun, laser system and several new injector linac systems.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2016-TUT2H2

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TUT2H4

Top-up Injection Schemes for HEPS

ion, injection, kicker, operation

85

Z. Duan, J. Chen, Y. Jiao, Y.M. Peng, Q.Y. Wang, G. Xu, P. Zhang
IHEP, Beijing, People's Republic of China

Funding: Natural Science Foundation of China (No.11605212)
Top-up injection has become standard mode of operation for most third generation light sources, and has also been suc- cesfully applied in electron-positron circular colliders like KEKB and PEP-II. For next generation ultra-low emittance storage rings approaching the diffraction limit of X-rays, take the High Energy Photon Source (HEPS) for example, top-up injection is a basic requirement but non-trivial to im- plement. The very small dynamic aperture is insufficient for traditional off-axis injection scheme, instead, a novel on-axis injection scheme was recently proposed for HEPS, based on RF gymnastics of a double-frequency RF system. This paper will describe the physical mechanism of this scheme, related RF issues, and the implications for top-up injection.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2016-TUT2H4

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

TUT3AH2

Instability Issues in CEPC

ion, impedance, damping, coupling

108

N. Wang, W. Chou, J. Gao, D.J. Gong, J. He, Q. Qin, Y.S. Sun, D. Wang, Y. Wang, G. Xu, Y. Zhang, H.J. Zheng
IHEP, Beijing, People's Republic of China
K. Ohmi, D. Zhou
KEK, Ibaraki, Japan

The CEPC is a high energy circular electron-positron collider under design. Large bunch population is required to achieve the design luminosity. Instabilities driven by the coupling impedance are possible limitations for reaching high machine performance. An updated impedance model, including the resistive wall and the main vacuum components, has been obtained for the main ring. Based on the impedance model, the collective instability issues of the beam with the partial-double ring design are discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2016-TUT3AH2

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

WET2H4

New Cavity Techniques and Future Prospects

ion, niobium, superconducting-cavity, SRF

173

P. Sha
Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China
J.Y. Zhai
IHEP, Beijing, People's Republic of China

Funding: This study was supported by National Key Programme for S&T Research and Development (Grant NO.: 2016YFA0400400) and National Natural Science Foundation of China (Grant NO.: 11505197)
In the recent decades, Superconducting cavities have been widely used to accelerate electron, positron, and ions. Most SRF cavities are made from bulk niobi-um till now, which has developed fast in the past years and is hard to advance more. Take 1.3 GHz 9-cell cavi-ty for example, the quality factor (Q) can keep above 10¹⁰ when the accelerating field (Eacc) reach 40 MV/m, which nearly touch the theoretical limitation of Q and Eacc for bulk niobium. For large superconducting accelerators in future (FCC, CEPC, etc), Q and Eacc should be increased significantly compared to now, which can reduce the cryogenic power and use fewer cavities. So new cavity material and techniques are being studied at accelerator laboratories, while Nitro-gen doping (N-doping) and Nb3Sn have developed quickly and been paid attention to mostly [1]. N-doping can increase Q by one time for 1.3 GHz 9-cell cavity, which have been adopted by Linac Coherent Light Source II (LCLS-II) at SLAC [2].
[1],Alexander Romanenko, Bulk Nb Based SRF Technology, FCC Week 2016.
[2],Camille M Ginsburg, LCLS-II Cryomodules at FNAL & JLAB, TTC 2016.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2016-WET2H4

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WET2H7

LLRF Controls Including Gap Transients at KEKB and Plans for SuperKEKB

ion, controls, LLRF, simulation

177

T. Kobayashi, K. Akai
KEK, Ibaraki, Japan

Features of LLRF control systems in KEKB and SuperKEKB will be reviewed, and the evaluation of the bunch gap transient effect on beam phase will be presented for SuperKEKB. The RF systems of KEKB are being reinforced to handle triple as large beam power for upgrade to SuperKEKB. Furthermore, a new LLRF control system, which is based on a recent digital control technique, has been developed. For nine RF stations, among a total of thirty, the LLRF control system has been replaced with new ones. They were worked successfully in the Phase-1 commissioning. Bunch phase shift along the bunch train due to a bunch gap transient is a concern. In KEKB operation, a rapid phase change was observed at the leading part of the train, which was not predicted. Our new simulation study clarified that the rapid phase change is caused by a transient loading in the three-cavity system of ARES. And the new simulation shows that the phase change will be much large in SuperKEKB. The main issue is the difference in beam phase change between the two rings for the asymmetry colliding. The measures by means of mitigation of the relative beam phase difference between the two rings will be also suggested.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2016-WET2H7

Export •

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

WET3AH2

High Efficiency Klystron Development for Particle Accelerators

ion, klystron, electron, bunching

185

D.A. Constable
Lancaster University, Lancaster, United Kingdom
A.Yu. Baikov
MFUA, Moscow, Russia
G. Burt, V.C.R. Hill, C. Lingwood
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
I.A. Guzilov
JSC Vacuum Devices Basic Technologies, Moscow, Russia
A. Jensen
SLAC, Menlo Park, California, USA
R.D. Kowalczyk
L-3, Williamsport, Pennsylvania, USA
R. Marchesin
TED, Velizy, France
C. Marrelli
ESS, Lund, Sweden
I. Syratchev
CERN, Geneva, Switzerland

Upcoming large scale particle accelerators, such as the Future Circular Collider (FCC), the Compact Linear Collider (CLIC) and the International Linear Collider (ILC) are expected to require RF drive on the order of 100 MW. Therefore, efforts to improve the efficiency of the specific RF source is of significant interest to the particle accelerator community. Klystrons are an attractive choice as the RF source, with the current state of the art tubes offering efficiencies up to 70%. The High Efficiency International Klystron Activity (HEIKA) collaboration seeks to improve upon this by considering novel methods of electron bunching. Such methods include the core oscillation method (COM), the bunching-alignment-collection (BAC) method, as well as the use of harmonic cavities. The theory behind these bunching methods will be discussed, along with their suitability for specific particle accelerators. In addition, results from numerical simulations predicting klystrons with efficiencies larger than 80% will be presented. Early experimental testing of tubes employing the BAC method will also be presented, demonstrating the efficiency improvements that the scheme offers.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2016-WET3AH2

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

WET3BH1

Improvement of Efficiency of Klystron to Apply the CPD Method

ion, klystron, electron, radiation

192

K. Watanabe
KEK, Ibaraki, Japan

A high power RF system for the particle accelerators needs large electrical power in the operation. An improvement of efficiency is also always required as a technology component for the energy saving. To improve efficiency of a high-power source, the CPD (Collector Potential Depression) method already was applied a Gyrotron to recovery the electrical energy form the collector loss. The CPD is an energy-saving scheme that recovers the kinetic energy of the spent electrons after generating rf power. A CPD klystron (E37703 CPD) was fabricated at 2013, to recycle an existing klystron of Toshiba E3786. The purpose of our study is to demonstrate the proof-of-principle of the CPD method to apply a klystron. A plane of R&D of CPD klystron at KEK will be reported in this meeting.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2016-WET3BH1

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

THS2H4

SRF Working Group Summary

ion, HOM, SRF, damping

223

R.A. Rimmer
JLab, Newport News, Virginia, USA

Summary of Superconducting RF: This working group focused on the status and challenges of superconducting Radio Frequency (SRF) cavities and systems for present and future high luminosity lepton colliders, the so-called 'factories'. Submissions covered the state of the art of SRF cavity designs, HOM damping, high power couplers, operational experiences and the needs of future colliders. Active work on similar SRF systems for the electron complex of a future electron ion collider (EIC) was presented. Much of this technology is also useful for next generation high brightness light sources and other applications.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2016-THS2H4

Export •

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