SRF2019 - List of Keywords (plasma)

Paper	Title	Other Keywords	Page
MOP004	Preparation of Pb-Photocathodes at National Centre for Nuclear Research in Poland – State of the Art	cathode, electron, laser, gun	25
	J. Lorkiewicz, I. Cieślik, P.J. Czuma, A.M. Kosińska, R. Nietubyć NCBJ, Świerk/Otwock, Poland J.K. Sekutowicz DESY, Hamburg, Germany
	Funding: We are currently using a financial support within "PolFEL - Polish Free Electron Laser" cofounded by the European Regional Development Fund. R&D activities related to preparation of the superconducting Pb photocathode layer on niobium substrate are ongoing at the National Centre for Nuclear Research (NCBJ) in cooperation with DESY, HZDR, HZB, BNL and other research institutes. The activities are part of the R&D program at DESY for the cw-upgrade of E-XFEL and for the newly approved free electron laser facility PolFEL to be built and operated at NCBJ. The optimization results obtained for the lead deposition on niobium and smoothing of the coated layers are reported. The photocathodes samples were tested for their surface morphology, microstructure and quantum efficiency in terms of the impact on the operation of all-superconducting RF electron injector, proposed for both facilities.
	Poster MOP004 [1.446 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP004
About •	paper received ※ 23 June 2019 paper accepted ※ 29 June 2019 issue date ※ 14 August 2019
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MOP085	The Destructive Effects to the RF Coupler by the Plasma Discharge	cavity, experiment, vacuum, coupling	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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THP044	RF Characterization of Novel Superconducting Materials and Multilayers	cavity, niobium, SRF, site	950
	T.E. Oseroff, M. Liepe, Z. Sun Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA B. Moeckly STI, Santa Barbara, California, USA M.J. Sowa Veeco-CNT, Medford, USA
	Cutting edge SRF technology is likely approaching the fundamental limitations of niobium cavities operating in the Meissner state. This combined with the obvious advantages of using higher critical temperature superconductors and thin film depositions leads to interest in the RF characterization of such materials. A TE mode niobium sample host cavity was used to characterize the RF performance of 5" (12.7 cm) diameter sample plates as a function of field and temperature at 4 GHz. Materials studied include MgB₂ and thin film atomic layer deposition (ALD) NbN and NbTiN on Nb substrates. These higher critical temperature superconductors all having coherence lengths on the order of a few nm. It is therefore likely that defects on the order of the coherence lengths will cause early flux penetration well before the theorized superheating field of an ideal superconducting surface. Superconductor-insulator-superconductor (SIS) multilayers have been proposed as a mechanism of arresting these early penetration flux avalanches and are therefore studied here as well, using the same NbN and NbTiN films, but over thin layers of insulating AlN on Nb substrates.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP044
About •	paper received ※ 02 July 2019 paper accepted ※ 03 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	cavity, SRF, experiment, cryogenics	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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FRCAB6	The Effect of Helium Processing and Plasma Cleaning for Low Beta HWR Cavity	cavity, experiment, SRF, ion-effects	1228
	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
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FRCAB7	Plasma Processing to Reduce Field Emission in LCLS-II 1.3 GHz SRF Cavities	cavity, radiation, vacuum, HOM	1231
	B. Giaccone, J. Zasadzinski IIT, Chicago, Illinois, USA P. Berrutti, B. Giaccone, A. Grassellino, M. Martinello Fermilab, Batavia, Illinois, USA M. Doleans ORNL, Oak Ridge, Tennessee, USA D. Gonnella, G. Lanza, M.C. Ross SLAC, Menlo Park, California, USA
	Plasma cleaning for LCLS-II 9-cell 1.3 GHz cavities is under study at Fermilab. Starting from ORNL method, we have developed a new technique for plasma ignition using HOMs. Plasma processing is being applied to contaminated and field emitting cavities, here are discussed the first results in terms of Q and radiation vs E measured before and after treatment. Further studies are ongoing to optimize plasma parameters and to acquire statistics on plasma cleaning effectiveness.
	Slides FRCAB7 [14.701 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-FRCAB7
About •	paper received ※ 23 June 2019 paper accepted ※ 04 July 2019 issue date ※ 14 August 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Other Keywords

Page

MOP004

Preparation of Pb-Photocathodes at National Centre for Nuclear Research in Poland – State of the Art

cathode, electron, laser, gun

25

J. Lorkiewicz, I. Cieślik, P.J. Czuma, A.M. Kosińska, R. Nietubyć
NCBJ, Świerk/Otwock, Poland
J.K. Sekutowicz
DESY, Hamburg, Germany

Funding: We are currently using a financial support within "PolFEL - Polish Free Electron Laser" cofounded by the European Regional Development Fund.
R&D activities related to preparation of the superconducting Pb photocathode layer on niobium substrate are ongoing at the National Centre for Nuclear Research (NCBJ) in cooperation with DESY, HZDR, HZB, BNL and other research institutes. The activities are part of the R&D program at DESY for the cw-upgrade of E-XFEL and for the newly approved free electron laser facility PolFEL to be built and operated at NCBJ. The optimization results obtained for the lead deposition on niobium and smoothing of the coated layers are reported. The photocathodes samples were tested for their surface morphology, microstructure and quantum efficiency in terms of the impact on the operation of all-superconducting RF electron injector, proposed for both facilities.

Poster MOP004 [1.446 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP004

About •

paper received ※ 23 June 2019 paper accepted ※ 29 June 2019 issue date ※ 14 August 2019

Export •

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

MOP085

The Destructive Effects to the RF Coupler by the Plasma Discharge

cavity, experiment, vacuum, coupling

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)

THP044

RF Characterization of Novel Superconducting Materials and Multilayers

cavity, niobium, SRF, site

950

T.E. Oseroff, M. Liepe, Z. Sun
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
B. Moeckly
STI, Santa Barbara, California, USA
M.J. Sowa
Veeco-CNT, Medford, USA

Cutting edge SRF technology is likely approaching the fundamental limitations of niobium cavities operating in the Meissner state. This combined with the obvious advantages of using higher critical temperature superconductors and thin film depositions leads to interest in the RF characterization of such materials. A TE mode niobium sample host cavity was used to characterize the RF performance of 5" (12.7 cm) diameter sample plates as a function of field and temperature at 4 GHz. Materials studied include MgB₂ and thin film atomic layer deposition (ALD) NbN and NbTiN on Nb substrates. These higher critical temperature superconductors all having coherence lengths on the order of a few nm. It is therefore likely that defects on the order of the coherence lengths will cause early flux penetration well before the theorized superheating field of an ideal superconducting surface. Superconductor-insulator-superconductor (SIS) multilayers have been proposed as a mechanism of arresting these early penetration flux avalanches and are therefore studied here as well, using the same NbN and NbTiN films, but over thin layers of insulating AlN on Nb substrates.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP044

About •

paper received ※ 02 July 2019 paper accepted ※ 03 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

cavity, SRF, experiment, cryogenics

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)

FRCAB6

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

cavity, experiment, SRF, ion-effects

1228

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)

FRCAB7

Plasma Processing to Reduce Field Emission in LCLS-II 1.3 GHz SRF Cavities

cavity, radiation, vacuum, HOM

1231

B. Giaccone, J. Zasadzinski
IIT, Chicago, Illinois, USA
P. Berrutti, B. Giaccone, A. Grassellino, M. Martinello
Fermilab, Batavia, Illinois, USA
M. Doleans
ORNL, Oak Ridge, Tennessee, USA
D. Gonnella, G. Lanza, M.C. Ross
SLAC, Menlo Park, California, USA

Plasma cleaning for LCLS-II 9-cell 1.3 GHz cavities is under study at Fermilab. Starting from ORNL method, we have developed a new technique for plasma ignition using HOMs. Plasma processing is being applied to contaminated and field emitting cavities, here are discussed the first results in terms of Q and radiation vs E measured before and after treatment. Further studies are ongoing to optimize plasma parameters and to acquire statistics on plasma cleaning effectiveness.

Slides FRCAB7 [14.701 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-FRCAB7

About •

paper received ※ 23 June 2019 paper accepted ※ 04 July 2019 issue date ※ 14 August 2019

Export •

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