SRF2019 - List of Authors (Chu, Q.W.)

Paper	Title	Page
MOP085	The Destructive Effects to the RF Coupler by the Plasma Discharge	285
	A.D. Wu, Q.W. Chu, H. Guo, Y. He, S.C. Huang, T.C. Jiang, C.L. Li, Z.Q. Lin, F. Pan, Y.K. Song, T. Tan, W.M. Yue, S.H. Zhang, H.W. Zhao IMP/CAS, Lanzhou, People’s Republic of China
	The low temperature RF plasma was proved an effec-tive method to clean the niobium surface and relieve the field emission effect for the SRF cavities. In the case of half-wave resonators, these cavities were usually powered via the fundamental coupler with the electric coupling. Thus, coupler antennas were fixed in the intense electric field region, and this region was where the plasma rou-tinely ignited. Therefore, the ceramic window of coupler taken the risk of breakdown under the sputtering of ions and heating loads that may be caused by the plasma drift and diffusion from the electric field region. In this paper, the plasma ignition for surface cleaning on the HWR cavity and its coupler was investigated, and the power transmission, temperature raising and vacuum degradation were tested to characterize the adverse impacts on the ceramic window. Finally, the solution was proposed to figure these issues.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP085
About •	paper received ※ 22 June 2019 paper accepted ※ 02 July 2019 issue date ※ 14 August 2019
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TUP076	Electrochemical Deposition of Nb₃Sn on the Surface of Cu Substrates	624
SUSP005	use link to see paper's listing under its alternate paper code
	M. Lu, Q.W. Chu, Y. He, Z.Q. Lin, F. Pan, T. Tan, Z.Q. Yang IMP/CAS, Lanzhou, People’s Republic of China
	Coating superconducting Nb₃Sn thin film on the inner surface of a superconducting RF cavity is one of the most promising approaches to improve the performance of the accelerating cavity. Compared with traditional evaporation and sputtering, electrochemical coating has the advantages on process simplicity, low cost and mass production. However, the conventional electroplating, because of its low growth temperature and aqueous reaction environment, tends to produce porous, loosely bonded, and often contaminated film. All these properties result in excessive pinning center and deteriorate the superconducting radio frequency cavities performance. In this paper, a new method including multi-layer electroplating and heat treatment is used to deposit Nb₃Sn thin film on top of copper substrates. Important growth parameters, e.g. electrical current density, layer thickness ratio, and annealing temperature are studied. The morphology of the film surfaces was observed by scanning electron microscope (SEM) and the structure of the film was analyzed by X-ray diffraction (XRD). The results showed that a flat and uniform Nb₃Sn layer on copper can be obtained, and the thickness is about 7 micron.
	Poster TUP076 [0.716 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP076
About •	paper received ※ 23 June 2019 paper accepted ※ 01 July 2019 issue date ※ 14 August 2019
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THP010	The Mechanism of Electropolishing of Niobium from Choline Chloride-based Deep Eutectic Solvents	852
	Q.W. Chu, H. Guo, S.C. Huang, A.D. Wu, Z.M. You IMP/CAS, Lanzhou, People’s Republic of China
	Funding: National Natural Science Foundation (11705252) The mechanism of electropolishing of niobium (Nb) from choline chloride-based deep eutectic solvent (DES) was studied by anodic polarization tests and electrochemical impedance spectroscopy (EIS) using a Nb rotating disk electrode (RDE). Based on the results of an anodic polarisation test, the electropolishing of Nb is mass transport controlled. EIS results are consistent with the compact salt film mechanism for niobium electropolishing in this electrolyte. The influence of rotation rate, applied potential and electrolyte temperature on the electropolishing mechanism of Nb was investigated. As the applied potential positively shift, Rct, Rp and L increase, CPE decrease and Rs unchanged. The increase in rotation rate and electrolyte temperature leads to a decrease of Rs, Rct, Rp and L, and an increase of CPE.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP010
About •	paper received ※ 18 June 2019 paper accepted ※ 02 July 2019 issue date ※ 14 August 2019
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THP064	The Cryostat Results of Carbon Contamination and Plasma Cleaning for the Field Emission on the SRF Cavity	1038
	A.D. Wu, Q.W. Chu, H. Guo, Y. He, S.C. Huang, C.L. Li, F. Pan, Y.K. Song, T. Tan, P.R. Xiong, W.M. Yue, S.H. Zhang, H.W. Zhao IMP/CAS, Lanzhou, People’s Republic of China
	The field emission effect is the mainly limitation for the operating of SRF cavities in higher gradient with stability. In this paper, the experiments were performed to evaluate the impact of the carbon contaminants and plasma cleaning on the performance of SRF cavity. Contamination mechanism was classified into cryogenic adsorption with weak strength and chemical deposition with strong strength. For the weak strength condition, the methane was injected into the SRF cavity during vertical test to make a cryogenic adsorption layer on the inner surface of the cavity. The results revealed that the performance of SRF cavity degraded by methane physical adsorption, but the performance can be recovered by thermal cycle the cavity to 300K and pump methane out. For the strong strength condition, the chemical deposited dirty layer of carbon contamination was produced by using of Ar/CH₄ mixed PECVD method, and the SRF cavity performance was deteriorated by the severe field emission. Finally, carbon deposited cavity was treated by the Ar/O2 plasma, and its results revealed that the field emission removed greatly and the gradient was increased.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP064
About •	paper received ※ 20 June 2019 paper accepted ※ 01 July 2019 issue date ※ 14 August 2019
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FRCAB3	The Design of an Automated High-Pressure Rinsing System for SRF Cavity and the Outlook for Future Automated Cleanroom on Strings Assembly	1216
	H. Guo, Q.W. Chu, Y. He, C.L. Li, Y.K. Song, T. Tan, Z.M. You IMP/CAS, Lanzhou, People’s Republic of China
	High-pressure rinsing (HPR) and cavity assembly are two critical steps in cavity post-processing. Traditionally, high-pressure rinsing processing is based on ultra pure water system, pump, rinsing wand and simple-functional control system; cavity assembly processing is based on simple fixtures, wrenches, bolts and nuts. Beside the equipments, at least two operators are required in either of these two processing. Operators and their actions could bring mistakes and cause extra airborne particle contamination in cleanroom. To avoid the risk from labors, a robot has been introduced in IMP cleanroom for HPR assisting and assembly assisting. Labor cost and cavity RF test results are compared between the circumstances with and without robot assisting. In this work, an automated HPR system that has been designed and will be installed in IMP cleanroom will be presented. In addition, a future automated cleanroom on strings assembly will be discussed as well.
	Slides FRCAB3 [6.203 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-FRCAB3
About •	paper received ※ 03 July 2019 paper accepted ※ 12 July 2019 issue date ※ 14 August 2019
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FRCAB6	The Effect of Helium Processing and Plasma Cleaning for Low Beta HWR Cavity	1228
THP065	use link to see paper's listing under its alternate paper code
	S.C. Huang, Q.W. Chu, Y. He, C.L. Li, A.D. Wu, S.X. Zhang IMP/CAS, Lanzhou, People’s Republic of China
	The commissioning of the 25 MeV high power and high intensity proton Linac demo for CiADS showed that the performance of the SRF cavities was mainly limited by field emission inside the cavities. Therefore, the techniques of helium processing and reactive oxygen plasma cleaning have been developed to mitigate field emission issues. We performed an experiment with a low beta HWR cavity exposed to air directly and processed by helium and reactive oxygen. In this paper, the details of the experiment will be described, the efficiency of helium processing and plasma cleaning will be compared and discussed
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-FRCAB6
About •	paper received ※ 23 June 2019 paper accepted ※ 01 July 2019 issue date ※ 14 August 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

The Destructive Effects to the RF Coupler by the Plasma Discharge

285

A.D. Wu, Q.W. Chu, H. Guo, Y. He, S.C. Huang, T.C. Jiang, C.L. Li, Z.Q. Lin, F. Pan, Y.K. Song, T. Tan, W.M. Yue, S.H. Zhang, H.W. Zhao
IMP/CAS, Lanzhou, People’s Republic of China

The low temperature RF plasma was proved an effec-tive method to clean the niobium surface and relieve the field emission effect for the SRF cavities. In the case of half-wave resonators, these cavities were usually powered via the fundamental coupler with the electric coupling. Thus, coupler antennas were fixed in the intense electric field region, and this region was where the plasma rou-tinely ignited. Therefore, the ceramic window of coupler taken the risk of breakdown under the sputtering of ions and heating loads that may be caused by the plasma drift and diffusion from the electric field region. In this paper, the plasma ignition for surface cleaning on the HWR cavity and its coupler was investigated, and the power transmission, temperature raising and vacuum degradation were tested to characterize the adverse impacts on the ceramic window. Finally, the solution was proposed to figure these issues.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP085

About •

paper received ※ 22 June 2019 paper accepted ※ 02 July 2019 issue date ※ 14 August 2019

Export •

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

TUP076

Electrochemical Deposition of Nb₃Sn on the Surface of Cu Substrates

624

SUSP005

use link to see paper's listing under its alternate paper code

M. Lu, Q.W. Chu, Y. He, Z.Q. Lin, F. Pan, T. Tan, Z.Q. Yang
IMP/CAS, Lanzhou, People’s Republic of China

Coating superconducting Nb₃Sn thin film on the inner surface of a superconducting RF cavity is one of the most promising approaches to improve the performance of the accelerating cavity. Compared with traditional evaporation and sputtering, electrochemical coating has the advantages on process simplicity, low cost and mass production. However, the conventional electroplating, because of its low growth temperature and aqueous reaction environment, tends to produce porous, loosely bonded, and often contaminated film. All these properties result in excessive pinning center and deteriorate the superconducting radio frequency cavities performance. In this paper, a new method including multi-layer electroplating and heat treatment is used to deposit Nb₃Sn thin film on top of copper substrates. Important growth parameters, e.g. electrical current density, layer thickness ratio, and annealing temperature are studied. The morphology of the film surfaces was observed by scanning electron microscope (SEM) and the structure of the film was analyzed by X-ray diffraction (XRD). The results showed that a flat and uniform Nb₃Sn layer on copper can be obtained, and the thickness is about 7 micron.

Poster TUP076 [0.716 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP076

About •

paper received ※ 23 June 2019 paper accepted ※ 01 July 2019 issue date ※ 14 August 2019

Export •

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

THP010

The Mechanism of Electropolishing of Niobium from Choline Chloride-based Deep Eutectic Solvents

852

Q.W. Chu, H. Guo, S.C. Huang, A.D. Wu, Z.M. You
IMP/CAS, Lanzhou, People’s Republic of China

Funding: National Natural Science Foundation (11705252)
The mechanism of electropolishing of niobium (Nb) from choline chloride-based deep eutectic solvent (DES) was studied by anodic polarization tests and electrochemical impedance spectroscopy (EIS) using a Nb rotating disk electrode (RDE). Based on the results of an anodic polarisation test, the electropolishing of Nb is mass transport controlled. EIS results are consistent with the compact salt film mechanism for niobium electropolishing in this electrolyte. The influence of rotation rate, applied potential and electrolyte temperature on the electropolishing mechanism of Nb was investigated. As the applied potential positively shift, Rct, Rp and L increase, CPE decrease and Rs unchanged. The increase in rotation rate and electrolyte temperature leads to a decrease of Rs, Rct, Rp and L, and an increase of CPE.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP010

About •

paper received ※ 18 June 2019 paper accepted ※ 02 July 2019 issue date ※ 14 August 2019

Export •

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

THP064

The Cryostat Results of Carbon Contamination and Plasma Cleaning for the Field Emission on the SRF Cavity

1038

A.D. Wu, Q.W. Chu, H. Guo, Y. He, S.C. Huang, C.L. Li, F. Pan, Y.K. Song, T. Tan, P.R. Xiong, W.M. Yue, S.H. Zhang, H.W. Zhao
IMP/CAS, Lanzhou, People’s Republic of China

The field emission effect is the mainly limitation for the operating of SRF cavities in higher gradient with stability. In this paper, the experiments were performed to evaluate the impact of the carbon contaminants and plasma cleaning on the performance of SRF cavity. Contamination mechanism was classified into cryogenic adsorption with weak strength and chemical deposition with strong strength. For the weak strength condition, the methane was injected into the SRF cavity during vertical test to make a cryogenic adsorption layer on the inner surface of the cavity. The results revealed that the performance of SRF cavity degraded by methane physical adsorption, but the performance can be recovered by thermal cycle the cavity to 300K and pump methane out. For the strong strength condition, the chemical deposited dirty layer of carbon contamination was produced by using of Ar/CH₄ mixed PECVD method, and the SRF cavity performance was deteriorated by the severe field emission. Finally, carbon deposited cavity was treated by the Ar/O2 plasma, and its results revealed that the field emission removed greatly and the gradient was increased.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP064

About •

paper received ※ 20 June 2019 paper accepted ※ 01 July 2019 issue date ※ 14 August 2019

Export •

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

FRCAB3

The Design of an Automated High-Pressure Rinsing System for SRF Cavity and the Outlook for Future Automated Cleanroom on Strings Assembly

1216

H. Guo, Q.W. Chu, Y. He, C.L. Li, Y.K. Song, T. Tan, Z.M. You
IMP/CAS, Lanzhou, People’s Republic of China

High-pressure rinsing (HPR) and cavity assembly are two critical steps in cavity post-processing. Traditionally, high-pressure rinsing processing is based on ultra pure water system, pump, rinsing wand and simple-functional control system; cavity assembly processing is based on simple fixtures, wrenches, bolts and nuts. Beside the equipments, at least two operators are required in either of these two processing. Operators and their actions could bring mistakes and cause extra airborne particle contamination in cleanroom. To avoid the risk from labors, a robot has been introduced in IMP cleanroom for HPR assisting and assembly assisting. Labor cost and cavity RF test results are compared between the circumstances with and without robot assisting. In this work, an automated HPR system that has been designed and will be installed in IMP cleanroom will be presented. In addition, a future automated cleanroom on strings assembly will be discussed as well.

Slides FRCAB3 [6.203 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-FRCAB3

About •

paper received ※ 03 July 2019 paper accepted ※ 12 July 2019 issue date ※ 14 August 2019

Export •

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

FRCAB6

The Effect of Helium Processing and Plasma Cleaning for Low Beta HWR Cavity

1228

THP065

use link to see paper's listing under its alternate paper code

S.C. Huang, Q.W. Chu, Y. He, C.L. Li, A.D. Wu, S.X. Zhang
IMP/CAS, Lanzhou, People’s Republic of China

The commissioning of the 25 MeV high power and high intensity proton Linac demo for CiADS showed that the performance of the SRF cavities was mainly limited by field emission inside the cavities. Therefore, the techniques of helium processing and reactive oxygen plasma cleaning have been developed to mitigate field emission issues. We performed an experiment with a low beta HWR cavity exposed to air directly and processed by helium and reactive oxygen. In this paper, the details of the experiment will be described, the efficiency of helium processing and plasma cleaning will be compared and discussed

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-FRCAB6

About •

paper received ※ 23 June 2019 paper accepted ※ 01 July 2019 issue date ※ 14 August 2019

Export •

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