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Title: Cryogenic rf test of the first SRF cavity etched in an rf Ar/Cl2 plasma

Abstract

An apparatus and a method for etching of the inner surfaces of superconducting radio frequency (SRF) accelerator cavities are described. The apparatus is based on the reactive ion etching performed in an Ar/Cl2 cylindrical capacitive discharge with reversed asymmetry. To test the effect of the plasma etching on the cavity rf performance, a 1497 MHz single cell SRF cavity was used. The single cell cavity was mechanically polished and buffer chemically etched and then rf tested at cryogenic temperatures to provide a baseline characterization. The cavity’s inner wall was then exposed to the capacitive discharge in a mixture of Argon and Chlorine. The inner wall acted as the grounded electrode, while kept at elevated temperature. The processing was accomplished by axially moving the dc-biased, corrugated inner electrode and the gas flow inlet in a step-wise manner to establish a sequence of longitudinally segmented discharges. The cavity was then tested in a standard vertical test stand at cryogenic temperatures. The rf tests and surface condition results, including the electron field emission elimination, are presented.

Authors:
 [1];  [2];  [1];  [2];  [1];  [2];  [1]
  1. Old Dominion Univ., Norfolk, VA (United States)
  2. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
Publication Date:
Research Org.:
Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Nuclear Physics (NP); USDOE Office of Science (SC), High Energy Physics (HEP)
OSTI Identifier:
1641619
Alternate Identifier(s):
OSTI ID: 1414016
Report Number(s):
JLAB-ACC-16-2299; DOE/OR/23177-3878; arXiv:1605.06494
Journal ID: ISSN 2158-3226; TRN: US2201868
Grant/Contract Number:  
SC0014397; AC05-06OR23177
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
AIP Advances
Additional Journal Information:
Journal Volume: 7; Journal Issue: 12; Journal ID: ISSN 2158-3226
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Vacuum apparatus; Physics of gases; Etching; Electrical properties and parameters; Plasma processing; Cryogenics; Chemical elements; Surface collisions; Superconductivity; Transition metals

Citation Formats

Upadhyay, J., Palczewski, A., Popović, S., Valente-Feliciano, A.-M., Im, Do, Phillips, H. L., and Vušković, L. Cryogenic rf test of the first SRF cavity etched in an rf Ar/Cl2 plasma. United States: N. p., 2017. Web. doi:10.1063/1.4991888.
Upadhyay, J., Palczewski, A., Popović, S., Valente-Feliciano, A.-M., Im, Do, Phillips, H. L., & Vušković, L. Cryogenic rf test of the first SRF cavity etched in an rf Ar/Cl2 plasma. United States. https://doi.org/10.1063/1.4991888
Upadhyay, J., Palczewski, A., Popović, S., Valente-Feliciano, A.-M., Im, Do, Phillips, H. L., and Vušković, L. 2017. "Cryogenic rf test of the first SRF cavity etched in an rf Ar/Cl2 plasma". United States. https://doi.org/10.1063/1.4991888. https://www.osti.gov/servlets/purl/1641619.
@article{osti_1641619,
title = {Cryogenic rf test of the first SRF cavity etched in an rf Ar/Cl2 plasma},
author = {Upadhyay, J. and Palczewski, A. and Popović, S. and Valente-Feliciano, A.-M. and Im, Do and Phillips, H. L. and Vušković, L.},
abstractNote = {An apparatus and a method for etching of the inner surfaces of superconducting radio frequency (SRF) accelerator cavities are described. The apparatus is based on the reactive ion etching performed in an Ar/Cl2 cylindrical capacitive discharge with reversed asymmetry. To test the effect of the plasma etching on the cavity rf performance, a 1497 MHz single cell SRF cavity was used. The single cell cavity was mechanically polished and buffer chemically etched and then rf tested at cryogenic temperatures to provide a baseline characterization. The cavity’s inner wall was then exposed to the capacitive discharge in a mixture of Argon and Chlorine. The inner wall acted as the grounded electrode, while kept at elevated temperature. The processing was accomplished by axially moving the dc-biased, corrugated inner electrode and the gas flow inlet in a step-wise manner to establish a sequence of longitudinally segmented discharges. The cavity was then tested in a standard vertical test stand at cryogenic temperatures. The rf tests and surface condition results, including the electron field emission elimination, are presented.},
doi = {10.1063/1.4991888},
url = {https://www.osti.gov/biblio/1641619}, journal = {AIP Advances},
issn = {2158-3226},
number = 12,
volume = 7,
place = {United States},
year = {Tue Dec 19 00:00:00 EST 2017},
month = {Tue Dec 19 00:00:00 EST 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Citation Metrics:
Cited by: 3 works
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Figures / Tables:

FIG. 1 FIG. 1: (a) Schematic diagram of experimental setup of single cell cavity plasma etching system. (b) The photo of experimental setup to plasma etch single cell SRF cavity.

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Works referenced in this record:

Cavity preparation/assembly techniques and impact on Q, realistic Q-factors in a module, review of modules
journal, February 2006


Improving the work function of the niobium surface of SRF cavities by plasma processing
journal, April 2016


Evaluation of the diffusion coefficient of fluorine during the electropolishing of niobium
journal, August 2010


Apparatus and method for plasma processing of SRF cavities
journal, May 2016

  • Upadhyay, J.; Im, Do; Peshl, J.
  • Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 818
  • https://doi.org/10.1016/j.nima.2016.02.049

Etching mechanism of niobium in coaxial Ar/Cl 2 radio frequency plasma
journal, March 2015


Plasma sputtering robotic device for in-situ thick coatings of long, small diameter vacuum tubesa)
journal, May 2015


Mirror-smooth surfaces and repair of defects in superconducting RF cavities by mechanical polishing
journal, November 2012


Plasma processing of large curved surfaces for superconducting rf cavity modification
journal, December 2014


Improved surface treatment of the superconducting TESLA cavities
journal, January 2004

  • Lilje, L.; Antoine, C.; Benvenuti, C.
  • Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 516, Issue 2-3
  • https://doi.org/10.1016/j.nima.2003.08.116

Reversal of the asymmetry in a cylindrical coaxial capacitively coupled Ar/Cl 2 plasma
journal, November 2015

  • Upadhyay, Janardan; Im, Do; Popović, Svetozar
  • Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, Vol. 33, Issue 6
  • https://doi.org/10.1116/1.4932562

Works referencing / citing this record:

Argon metastable and resonant level densities in Ar and Ar/Cl2 discharges used for the processing of bulk niobium
journal, September 2019


Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.