SRF2017 - List of Authors (Meng, F.)

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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MOPB054	Design of Fundamental Power Coupler for High Intensity Heavy-ion Accelerator	183
	B. Bing, T.M. Huang, Q. Ma, F. Meng, W.M. Pan 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
	A single-window coaxial coupler at warm has been designed for high intensity heavy-ion accelerator. The coupler is designed to handle 100 kW CW power of 325 MHz and is currently being fabricated. T-bend transition and doorknob have been taken into account. The length of the T-bend short circuit is sensitive to S parameters and contributes to the online adjustment of VSWR in RF conditioning. The doorknob type is adopted to realize the transition from a half-height WR 2300 waveguide to a coaxial line ended with a coupling antenna. This paper describes the RF design, thermal stress and heat load analysis of the coupler as well as multipacting simula-tions.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB054
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MOPB070	The Improvement of the Power Coupler for CADS SC Spoke Cavities	220
	T.M. Huang, B. Bing, X. Chen, H.Y. Lin, Q. Ma, F. Meng, W.M. Pan, G.W. Wang 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
	Twenty superconducting spoke cavities mounted in three cryomodules (CM1, CM2 and CM4) were in-stalled in the CADS, a test facility of 10 mA, 25 MeV CW proton linac. Each cavity was equipped with one coaxial type fundamental power coupler (FPC). Fatal window crack was observed during the test cryomod-ule (TCM) commissioning. A series of experiments were subsequently implemented and eventually at-tributed the window crack to the electron bombard-ment from cavity field emission (FE). Improvements covering the coupler cleaning and assembly proce-dure, the structure and position modifications were thus implemented, aiming to reduce the cavity contam-ination and avoid the window damaged by cavity FE electrons. This paper will describe how the coupler window damaged by cavity field emission and the improve-ments for cure. In addition, the performances of FPCs for CM1, CM2 and CM4 were compared.
	Poster MOPB070 [0.613 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB070
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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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TUPB004	HOM damping with an enlarged beam tube for HEPS 166.6 MHz SC cavities	389
	H.X. Hao, Z.Q. Li, F. Meng, P. Zhang, X.Y. Zhang IHEP, Beijing, People's Republic of China
	The 166.6 MHz superconducting cavities have been proposed for the High Energy Photon Source (HEPS) storage ring, which is initiated by the Institute of High Energy Physics in Beijing. Their higher order modes (HOMs) have to be damped sufficiently in order to limit coupled-bunch instabilities and parasitic mode losses. In order to keep the beam stable, the impedance budget and the HOM damping requirement are given. As one HOM damping option, an enlarged beam tube allows HOMs to propagate and subsequently be absorbed by downstream HOM dampers installed on the inner surface of the beam tube. And the conventional coaxial HOM coupler, which will be mounted on the big beam tube, is planned to extract the HOM power below the cut-off frequency of the beam pipe.
	Poster TUPB004 [1.132 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB004
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TUPB034	The 166.6 MHz Proof-of-principle SRF Cavity for HEPS-TF	454
	P. Zhang, J. Dai, H.X. Hao, T.M. Huang, Z.Q. Li, H.Y. Lin, Q. Ma, F. Meng, Z.H. Mi, W.M. Pan, Y. Sun, G.W. Wang, Q.Y. Wang, X.Y. Zhang IHEP, Beijing, People's Republic of China
	Funding: This work has been supported by HEPS-TF project and also partly supported by Pioneer "Hundred Talents Program" of Chinese Academy of Sciences. The 166.6 MHz superconducting RF cavities have been proposed for the High Energy Photon Source (HEPS), a 6 GeV kilometer-scale light source. The cavity is of quarter-wave type made of bulk niobium with β =1. Each cavity will be operated at 4 K providing 1.2 MV accelerating voltage and 145 kW of power to the electron beam. During the HEPS - Test Facility (HEPS-TF) phase, a proof-of-principle cavity of 166.6 MHz has been designed in IHEP and manufactured in Beijing. The subsequent BCP was conducted in Ningxia, while HPR, cleanroom assembly and 120 degree baking was done in IHEP. The cavity was finally vertical tested at both 4K and 2K in IHEP. The cavity Q0 at nominal gradient at 4 K was measured to be 2.4·10⁹ with Epeak of 42 MV/m and Bpeak of 65 mT. The maximum Epeak and Bpeak reached 86MV/m and 131 mT respectively at both 4 K and 2 K, and the corresponding Q0 was measured to be 5.10⁸ (4 K) and 3.3·10⁹ (2 K). The residual surface resistance was measured to be 2.3 nOhm.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB034
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WEYA04	The R&D on TEM-type SRF Cavities for High-current Applications at IHEP
	F.S. He, J.P. Dai, J. Dai, N. Gan, H.X. Hao, H. Huang, T.M. Huang, X. Huang, Z.Q. Li, H.Y. Lin, R.L. Liu, Q. Ma, X. Ma, F. Meng, Z.H. Mi, W.M. Pan, X.H. Peng, P. Sha, Y. Shao, G.W. Wang, Q.Y. Wang, Z. Xue, P. Zhang, X.Y. Zhang IHEP, Beijing, People's Republic of China
	Funding: This work has been supported partly by Pioneer 'Hundred Talents Program' of Chinese Academy of Science. The recent SRF R&D efforts on TEM-type cavities at IHEP have been strongly linked to two large projects: high current proton linac for ADS and High Energy Photon Source (HEPS). A CW 10 MeV proton injector and part of the 25 MeV main linac for the CADS project are developed at IHEP. 14 SRF spoke012 cavities for the injector have been commissioned with 10.6mA proton beam at 10.67MeV; while 6 SRF spoke021 cavities for the main linac have been assembled into cryomodule in Lanzhou. 166.6 MHz quarter-wave β=1 cavities were proposed for HEPS storage ring, required by the planned on-axis beam accumulation injection scheme. Each 166.6 MHz cavity will be operated at 4 K providing 1.2 MV accelerating voltage and 145 kW of power to the electron beam. A proof-of-principle cavity has been manufactured and vertical tested recently with a success. HOM damping is currently being designed. The development progress of the 6 types of spoke, HWR, QWR cavities, and their ancillaries, as well as the spoke cavity performance during beam operation, will be addressed.
	Slides WEYA04 [2.904 MB]
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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

Export •

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

MOPB054

Design of Fundamental Power Coupler for High Intensity Heavy-ion Accelerator

183

B. Bing, T.M. Huang, Q. Ma, F. Meng, W.M. Pan
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

A single-window coaxial coupler at warm has been designed for high intensity heavy-ion accelerator. The coupler is designed to handle 100 kW CW power of 325 MHz and is currently being fabricated. T-bend transition and doorknob have been taken into account. The length of the T-bend short circuit is sensitive to S parameters and contributes to the online adjustment of VSWR in RF conditioning. The doorknob type is adopted to realize the transition from a half-height WR 2300 waveguide to a coaxial line ended with a coupling antenna. This paper describes the RF design, thermal stress and heat load analysis of the coupler as well as multipacting simula-tions.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB054

Export •

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

MOPB070

The Improvement of the Power Coupler for CADS SC Spoke Cavities

220

T.M. Huang, B. Bing, X. Chen, H.Y. Lin, Q. Ma, F. Meng, W.M. Pan, G.W. Wang
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

Twenty superconducting spoke cavities mounted in three cryomodules (CM1, CM2 and CM4) were in-stalled in the CADS, a test facility of 10 mA, 25 MeV CW proton linac. Each cavity was equipped with one coaxial type fundamental power coupler (FPC). Fatal window crack was observed during the test cryomod-ule (TCM) commissioning. A series of experiments were subsequently implemented and eventually at-tributed the window crack to the electron bombard-ment from cavity field emission (FE). Improvements covering the coupler cleaning and assembly proce-dure, the structure and position modifications were thus implemented, aiming to reduce the cavity contam-ination and avoid the window damaged by cavity FE electrons. This paper will describe how the coupler window damaged by cavity field emission and the improve-ments for cure. In addition, the performances of FPCs for CM1, CM2 and CM4 were compared.

Poster MOPB070 [0.613 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB070

Export •

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

Export •

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

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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TUPB004

HOM damping with an enlarged beam tube for HEPS 166.6 MHz SC cavities

389

H.X. Hao, Z.Q. Li, F. Meng, P. Zhang, X.Y. Zhang
IHEP, Beijing, People's Republic of China

The 166.6 MHz superconducting cavities have been proposed for the High Energy Photon Source (HEPS) storage ring, which is initiated by the Institute of High Energy Physics in Beijing. Their higher order modes (HOMs) have to be damped sufficiently in order to limit coupled-bunch instabilities and parasitic mode losses. In order to keep the beam stable, the impedance budget and the HOM damping requirement are given. As one HOM damping option, an enlarged beam tube allows HOMs to propagate and subsequently be absorbed by downstream HOM dampers installed on the inner surface of the beam tube. And the conventional coaxial HOM coupler, which will be mounted on the big beam tube, is planned to extract the HOM power below the cut-off frequency of the beam pipe.

Poster TUPB004 [1.132 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB004

Export •

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

TUPB034

The 166.6 MHz Proof-of-principle SRF Cavity for HEPS-TF

454

P. Zhang, J. Dai, H.X. Hao, T.M. Huang, Z.Q. Li, H.Y. Lin, Q. Ma, F. Meng, Z.H. Mi, W.M. Pan, Y. Sun, G.W. Wang, Q.Y. Wang, X.Y. Zhang
IHEP, Beijing, People's Republic of China

Funding: This work has been supported by HEPS-TF project and also partly supported by Pioneer "Hundred Talents Program" of Chinese Academy of Sciences.
The 166.6 MHz superconducting RF cavities have been proposed for the High Energy Photon Source (HEPS), a 6 GeV kilometer-scale light source. The cavity is of quarter-wave type made of bulk niobium with β =1. Each cavity will be operated at 4 K providing 1.2 MV accelerating voltage and 145 kW of power to the electron beam. During the HEPS - Test Facility (HEPS-TF) phase, a proof-of-principle cavity of 166.6 MHz has been designed in IHEP and manufactured in Beijing. The subsequent BCP was conducted in Ningxia, while HPR, cleanroom assembly and 120 degree baking was done in IHEP. The cavity was finally vertical tested at both 4K and 2K in IHEP. The cavity Q0 at nominal gradient at 4 K was measured to be 2.4·10⁹ with Epeak of 42 MV/m and Bpeak of 65 mT. The maximum Epeak and Bpeak reached 86MV/m and 131 mT respectively at both 4 K and 2 K, and the corresponding Q0 was measured to be 5.10⁸ (4 K) and 3.3·10⁹ (2 K). The residual surface resistance was measured to be 2.3 nOhm.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB034

Export •

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

WEYA04

The R&D on TEM-type SRF Cavities for High-current Applications at IHEP

F.S. He, J.P. Dai, J. Dai, N. Gan, H.X. Hao, H. Huang, T.M. Huang, X. Huang, Z.Q. Li, H.Y. Lin, R.L. Liu, Q. Ma, X. Ma, F. Meng, Z.H. Mi, W.M. Pan, X.H. Peng, P. Sha, Y. Shao, G.W. Wang, Q.Y. Wang, Z. Xue, P. Zhang, X.Y. Zhang
IHEP, Beijing, People's Republic of China

Funding: This work has been supported partly by Pioneer 'Hundred Talents Program' of Chinese Academy of Science.
The recent SRF R&D efforts on TEM-type cavities at IHEP have been strongly linked to two large projects: high current proton linac for ADS and High Energy Photon Source (HEPS). A CW 10 MeV proton injector and part of the 25 MeV main linac for the CADS project are developed at IHEP. 14 SRF spoke012 cavities for the injector have been commissioned with 10.6mA proton beam at 10.67MeV; while 6 SRF spoke021 cavities for the main linac have been assembled into cryomodule in Lanzhou. 166.6 MHz quarter-wave β=1 cavities were proposed for HEPS storage ring, required by the planned on-axis beam accumulation injection scheme. Each 166.6 MHz cavity will be operated at 4 K providing 1.2 MV accelerating voltage and 145 kW of power to the electron beam. A proof-of-principle cavity has been manufactured and vertical tested recently with a success. HOM damping is currently being designed. The development progress of the 6 types of spoke, HWR, QWR cavities, and their ancillaries, as well as the spoke cavity performance during beam operation, will be addressed.

Slides WEYA04 [2.904 MB]

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