SRF2017 - List of Authors (Zhai, J.Y.)

Paper	Title	Page
MOPB028	HOM Coupler Design for CEPC Cavities	115
	H.J. Zheng, F. Meng, 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) In this paper，it will be presented the higher order mode (HOM) coupler design for the Circular Electron-Positron Collider (CEPC) 650 MHz 2-cell cavity. The higher order modes excited by the intense beam bunches must be damped to avoid additional cryogenic loss and multi-bunch instabilities. To keep the beam stable, the impedance budget and the HOM damping requirement are given. A double notch coaxial HOM coupler, which will be mounted on the beam pipe, is planned to extract the HOM power below the cut-off frequency of the beam pipe. This paper summarizes the RF design of the HOM coupler, tolerance analysis, thermal analysis as well as mechanical structures.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB028
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MOPB069	Design of the High Power Input Coupler for CEPC Main Ring Cavity *	216
	T.M. Huang, Q. Ma, J.Y. Zhai IHEP, Beijing, People's Republic of China K.X. Gu Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China
	The main ring cavities of CEPC project are two-cell el-liptical superconducting cavities operating at 650 MHz in CW mode. Each cavity equips with one high power input coupler and each coupler has to deliver at least 300 kW of CW RF power to the beam. A variable coupling from 10⁵ to 2·10⁶ is required to meet different operation modes. Considering the cavities working with high quali-ty factor up to 2·10¹⁰, the coupler assembled with cavity in class 10 clean room is strongly recommended to protect the cavity from contamination. Also, low cryogenic heat loss is one of the important issues for a large scale CW operation machine. Some of the above requirements should be compromise. Therefore, it's a big challenge to design a high power input coupler fulfilling the above requirements simultaneously. A new coupler that employs 75 Ω coaxial line sections, a planar ceramic disk win-dow, a coaxial to waveguide transition and a coupling adjusting actuator has been designed. In this paper, the RF design, thermal stress analysis and preliminary me-chanical design of the coupler are presented.
	Poster MOPB069 [0.735 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB069
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MOPB071	The Recent Research of HOM Damper for Superconducting Cavity in IHEP	223
	F. Meng, T.M. Huang, H.Y. Lin, Q. Ma, W.M. Pan, J.Y. Zhai, P. Zhang, H.J. Zheng 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) For high current accelerator, the efficient higher-order mode (HOM) damping is always an important issue. HOM damper with microwave absorbing material is a key component for high power and broadband HOM damping application. To pursue the high damping efficiency, some ideal material with good microwave absorbing capacity is essential during the RF design and fabrication phase. Sometimes the selection and test of material is the first step and also a long step. This paper will present the recent work on HOM dampers for BEPCII 500MHz cavity and CEPC 650MHz cavity in IHEP.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB071
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TUXAA01	CEPC SRF System Design and Challenges	332
	J.Y. Zhai, Y.L. Chi, J. Dai, J. Gao, R. Ge, D.J. Gong, R. Han, T.M. Huang, S. Jin, Z.Q. Li, B. Liu, Z.C. Liu, Q. Ma, F. Meng, Z.H. Mi, G. Pei, Q. Qin, P. Sha, Q.Y. Wang, T.X. Zhao, H.J. Zheng IHEP, Beijing, People's Republic of China C. Pagani Università degli Studi di Milano & INFN, Segrate, Italy
	Funding: Work supported by National Key Programme for S&T Research and Development of China (Grant NO.: 2016YFA0400400) CEPC is a 100 km circular electron positron collider operating at 90-240 GeV center-of-mass energy of Z, W and Higgs bosons. CEPC and its successor SPPC, a 100 TeV center-of-mass super proton-proton collider, will ensure the elementary particle physics a vibrant field for decades to come. The conceptual design report (CDR) of CEPC will be completed in the end of 2017 as an important step to move the project forward. In this contribution, CEPC SRF system CDR design and challenges will be introduced, including the system layout and parameter choices, configuration at different operation energies, transient beam loading and its compensation, cavity fundamental mode (FM) and higher order mode (HOM) induced coupled bunch instabilities (CBI) and the beam feedback requirement, etc. The SRF technology R&D plan and progress as well as the SRF infrastructure and industrialization plan are discussed at last.
	Slides TUXAA01 [9.124 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUXAA01
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TUPB005	Developed Spoke Cavity Module for Main Linac of China ADS HOM Simulations and Damping Scheme for CEPC Cavities	393
	Z.Q. Li, J.S. Cao, Y.L. Chi, F.S. He, S.P. Li, H.Y. Lin, Q. Ma, Z.H. Mi, W.M. Pan, P. Sha, B. Xu, J.Y. Zhai, X.Y. Zhang IHEP, Beijing, People's Republic of China
	During past five year, two kind of spoke of Beta equal 0.21 and 0.40 were developed at IHEP CAS, the spoke cavity of beta 0.21 was adopted to accelerate proton from 10 to 32MeV, and 32 to 160MeV for beta 0.40 spoke cavity. Up to now, two kind of naked spoke cavities have been test in vertical, also the module of beta 0.21 spoke cavity, which equipped the liquid helium jacket, magnetic shield layer and frequency tuner has been fulfilled and test, the performance of all of components reach the design requirements.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB005
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TUPB032	Study on 650MHz 5-cell Prototype Cavities at IHEP	448
	S. Jin, J. Gao, D.J. Gong, Z.C. Liu, P. Sha, J.Y. Zhai, T.X. Zhao, H.J. Zheng IHEP, Beijing, People's Republic of China
	CEPC Pre CDR pointed that the 650 MHz 5-cell SRF cavity could be a candidate for the main ring of the single-ring pretzel scheme at the Higgs energy in 2015. Then EM design of 5-cell cavities were published later. So, the study on the fabrication of a 5-cell prototype cavity with waveguide HOM couplers were carried on at IHEP. In the paper, we will mainly report the mechanical design and fabrication progress of the 5-cell prototype. Besides, fabrication of a bare 2-cell prototype cavity was also carried on according to the further study after Pre-CDR. Challenges and possible solutions for the prototypes development will also be discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB032
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TUPB036	R&D of CEPC Cavity	463
	P. Sha Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China B. Liu, Z.H. Mi, J.Y. Zhai, X.Y. Zhang, H.J. Zheng 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) CEPC will use 650 MHz cavities for the collider (Main Ring) and 1.3 GHz cavities for the Booster. Each booster cryomodule contains eight 1.3 GHz 9-cell cavities, which is similar as LCLS-II. Each collider cryomodule contains six 650 MHz 2-cell cavities, which is totally new. So our R&D of CEPC cavity mainly focuses on the 650 MHz 2-cell cavity. A cryomodule which consists of two 650 MHz 2-cell cavities has began in early 2017. In this thesis, the RF and mechanical design is displayed with Helium Vessel. Besides, multipacting is analyzed. In order to achieve high Q, N-doping is also studied.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB036
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TUPB038	Mechanical Design of a 650 MHz Superconducting RF Cavity for CEPC	471
	X.Y. Zhang Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China F.S. He, Q. Ma, Z.H. Mi, P. Sha, 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) The 650 MHz superconducting RF cavities have been proposed by IHEP for the Circular Electron-Positron Collider (CEPC). The major components are a 2-cell elliptical cavity, end groups, stiffness and helium vessel, which have been optimized to meet the design requirement. The minimization of the Lorentz force detuning and the sensitivity of resonance frequency to Helium pressure variations was the main goal of the optimization. Also detailed stress analysis, tuning and microphonics performance of dresses cavity will be presented in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB038
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TUPB084	EP System Development at IHEP	586
	S. Jin, J. Dai, J. Gao, D.J. Gong, F.S. He, Z.Q. Li, Z.C. Liu, P. Sha, J.Y. Zhai, P. Zhang, T.X. Zhao IHEP, Beijing, People's Republic of China
	Electropolishing (EP) System is a critical facility for SRF cavity treatment, especially for high performance cavities which are necessary for several great projects like LCLS-II, CEPC, Shanghai XFEL, and so on. So, an EP system was under development at IHEP. At this stage, we would like a horizontal EP facility. Main purpose is for elliptical SRF Nb cavities like 500MHz single cell cavities. Besides, it should be compatible for other frequency cavities, such as 650MHz and 1.3GHz cavities. In this paper, we will mainly report the preliminary design for the EP system. Several key points in the design will be also discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB084
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THPB037	Cavity Fundamental Mode and Beam Interaction in CEPC Main Ring	825
	D.J. Gong, J. Gao, D. Wang, J.Y. Zhai IHEP, Beijing, People's Republic of China
	Circular electron positron collider (CEPC) is design as a particle factory for Higgs, W and Z. The preliminary study is undertaken for CEPC cavity fundamental mode and beam interaction in this paper. The baseline of CEPC is DR scheme, the alternative is the APDR scheme. Beam loading effects and the corresponding longitudinal beam dynamics of both CEPC DR and APDR are elaborated in this article. The phase shift and voltage decrease are calculated by the analytic formula and the program. Furthermore, the longitudinal coupled-bunch instability is also studied. At last, the RF parameters are calculated for CEPC 100km APDR, in order to match the machine parameters and relieve the beam loading effects.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-THPB037
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Paper

Title

Page

HOM Coupler Design for CEPC Cavities

115

H.J. Zheng, F. Meng, 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)
In this paper，it will be presented the higher order mode (HOM) coupler design for the Circular Electron-Positron Collider (CEPC) 650 MHz 2-cell cavity. The higher order modes excited by the intense beam bunches must be damped to avoid additional cryogenic loss and multi-bunch instabilities. To keep the beam stable, the impedance budget and the HOM damping requirement are given. A double notch coaxial HOM coupler, which will be mounted on the beam pipe, is planned to extract the HOM power below the cut-off frequency of the beam pipe. This paper summarizes the RF design of the HOM coupler, tolerance analysis, thermal analysis as well as mechanical structures.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB028

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MOPB069

Design of the High Power Input Coupler for CEPC Main Ring Cavity *

216

T.M. Huang, Q. Ma, J.Y. Zhai
IHEP, Beijing, People's Republic of China
K.X. Gu
Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China

The main ring cavities of CEPC project are two-cell el-liptical superconducting cavities operating at 650 MHz in CW mode. Each cavity equips with one high power input coupler and each coupler has to deliver at least 300 kW of CW RF power to the beam. A variable coupling from 10⁵ to 2·10⁶ is required to meet different operation modes. Considering the cavities working with high quali-ty factor up to 2·10¹⁰, the coupler assembled with cavity in class 10 clean room is strongly recommended to protect the cavity from contamination. Also, low cryogenic heat loss is one of the important issues for a large scale CW operation machine. Some of the above requirements should be compromise. Therefore, it's a big challenge to design a high power input coupler fulfilling the above requirements simultaneously. A new coupler that employs 75 Ω coaxial line sections, a planar ceramic disk win-dow, a coaxial to waveguide transition and a coupling adjusting actuator has been designed. In this paper, the RF design, thermal stress analysis and preliminary me-chanical design of the coupler are presented.

Poster MOPB069 [0.735 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB069

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

MOPB071

The Recent Research of HOM Damper for Superconducting Cavity in IHEP

223

F. Meng, T.M. Huang, H.Y. Lin, Q. Ma, W.M. Pan, J.Y. Zhai, P. Zhang, H.J. Zheng
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)
For high current accelerator, the efficient higher-order mode (HOM) damping is always an important issue. HOM damper with microwave absorbing material is a key component for high power and broadband HOM damping application. To pursue the high damping efficiency, some ideal material with good microwave absorbing capacity is essential during the RF design and fabrication phase. Sometimes the selection and test of material is the first step and also a long step. This paper will present the recent work on HOM dampers for BEPCII 500MHz cavity and CEPC 650MHz cavity in IHEP.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB071

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TUXAA01

CEPC SRF System Design and Challenges

332

J.Y. Zhai, Y.L. Chi, J. Dai, J. Gao, R. Ge, D.J. Gong, R. Han, T.M. Huang, S. Jin, Z.Q. Li, B. Liu, Z.C. Liu, Q. Ma, F. Meng, Z.H. Mi, G. Pei, Q. Qin, P. Sha, Q.Y. Wang, T.X. Zhao, H.J. Zheng
IHEP, Beijing, People's Republic of China
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy

Funding: Work supported by National Key Programme for S&T Research and Development of China (Grant NO.: 2016YFA0400400)
CEPC is a 100 km circular electron positron collider operating at 90-240 GeV center-of-mass energy of Z, W and Higgs bosons. CEPC and its successor SPPC, a 100 TeV center-of-mass super proton-proton collider, will ensure the elementary particle physics a vibrant field for decades to come. The conceptual design report (CDR) of CEPC will be completed in the end of 2017 as an important step to move the project forward. In this contribution, CEPC SRF system CDR design and challenges will be introduced, including the system layout and parameter choices, configuration at different operation energies, transient beam loading and its compensation, cavity fundamental mode (FM) and higher order mode (HOM) induced coupled bunch instabilities (CBI) and the beam feedback requirement, etc. The SRF technology R&D plan and progress as well as the SRF infrastructure and industrialization plan are discussed at last.

Slides TUXAA01 [9.124 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUXAA01

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TUPB005

Developed Spoke Cavity Module for Main Linac of China ADS HOM Simulations and Damping Scheme for CEPC Cavities

393

Z.Q. Li, J.S. Cao, Y.L. Chi, F.S. He, S.P. Li, H.Y. Lin, Q. Ma, Z.H. Mi, W.M. Pan, P. Sha, B. Xu, J.Y. Zhai, X.Y. Zhang
IHEP, Beijing, People's Republic of China

During past five year, two kind of spoke of Beta equal 0.21 and 0.40 were developed at IHEP CAS, the spoke cavity of beta 0.21 was adopted to accelerate proton from 10 to 32MeV, and 32 to 160MeV for beta 0.40 spoke cavity. Up to now, two kind of naked spoke cavities have been test in vertical, also the module of beta 0.21 spoke cavity, which equipped the liquid helium jacket, magnetic shield layer and frequency tuner has been fulfilled and test, the performance of all of components reach the design requirements.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB005

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TUPB032

Study on 650MHz 5-cell Prototype Cavities at IHEP

448

S. Jin, J. Gao, D.J. Gong, Z.C. Liu, P. Sha, J.Y. Zhai, T.X. Zhao, H.J. Zheng
IHEP, Beijing, People's Republic of China

CEPC Pre CDR pointed that the 650 MHz 5-cell SRF cavity could be a candidate for the main ring of the single-ring pretzel scheme at the Higgs energy in 2015. Then EM design of 5-cell cavities were published later. So, the study on the fabrication of a 5-cell prototype cavity with waveguide HOM couplers were carried on at IHEP. In the paper, we will mainly report the mechanical design and fabrication progress of the 5-cell prototype. Besides, fabrication of a bare 2-cell prototype cavity was also carried on according to the further study after Pre-CDR. Challenges and possible solutions for the prototypes development will also be discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB032

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TUPB036

R&D of CEPC Cavity

463

P. Sha
Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China
B. Liu, Z.H. Mi, J.Y. Zhai, X.Y. Zhang, H.J. Zheng
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)
CEPC will use 650 MHz cavities for the collider (Main Ring) and 1.3 GHz cavities for the Booster. Each booster cryomodule contains eight 1.3 GHz 9-cell cavities, which is similar as LCLS-II. Each collider cryomodule contains six 650 MHz 2-cell cavities, which is totally new. So our R&D of CEPC cavity mainly focuses on the 650 MHz 2-cell cavity. A cryomodule which consists of two 650 MHz 2-cell cavities has began in early 2017. In this thesis, the RF and mechanical design is displayed with Helium Vessel. Besides, multipacting is analyzed. In order to achieve high Q, N-doping is also studied.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB036

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TUPB038

Mechanical Design of a 650 MHz Superconducting RF Cavity for CEPC

471

X.Y. Zhang
Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China
F.S. He, Q. Ma, Z.H. Mi, P. Sha, 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)
The 650 MHz superconducting RF cavities have been proposed by IHEP for the Circular Electron-Positron Collider (CEPC). The major components are a 2-cell elliptical cavity, end groups, stiffness and helium vessel, which have been optimized to meet the design requirement. The minimization of the Lorentz force detuning and the sensitivity of resonance frequency to Helium pressure variations was the main goal of the optimization. Also detailed stress analysis, tuning and microphonics performance of dresses cavity will be presented in this paper.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB038

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TUPB084

EP System Development at IHEP

586

S. Jin, J. Dai, J. Gao, D.J. Gong, F.S. He, Z.Q. Li, Z.C. Liu, P. Sha, J.Y. Zhai, P. Zhang, T.X. Zhao
IHEP, Beijing, People's Republic of China

Electropolishing (EP) System is a critical facility for SRF cavity treatment, especially for high performance cavities which are necessary for several great projects like LCLS-II, CEPC, Shanghai XFEL, and so on. So, an EP system was under development at IHEP. At this stage, we would like a horizontal EP facility. Main purpose is for elliptical SRF Nb cavities like 500MHz single cell cavities. Besides, it should be compatible for other frequency cavities, such as 650MHz and 1.3GHz cavities. In this paper, we will mainly report the preliminary design for the EP system. Several key points in the design will be also discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB084

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THPB037

Cavity Fundamental Mode and Beam Interaction in CEPC Main Ring

825

D.J. Gong, J. Gao, D. Wang, J.Y. Zhai
IHEP, Beijing, People's Republic of China

Circular electron positron collider (CEPC) is design as a particle factory for Higgs, W and Z. The preliminary study is undertaken for CEPC cavity fundamental mode and beam interaction in this paper. The baseline of CEPC is DR scheme, the alternative is the APDR scheme. Beam loading effects and the corresponding longitudinal beam dynamics of both CEPC DR and APDR are elaborated in this article. The phase shift and voltage decrease are calculated by the analytic formula and the program. Furthermore, the longitudinal coupled-bunch instability is also studied. At last, the RF parameters are calculated for CEPC 100km APDR, in order to match the machine parameters and relieve the beam loading effects.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-THPB037

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