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Plasma processing of large curved surfaces for superconducting rf cavity modification [electronic resource].

Published
Washington, D.C. : United States. Dept. of Energy. Office of Science, 2014.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy
Physical Description
Article numbers 122,001 : digital, PDF file
Additional Creators
Thomas Jefferson National Accelerator Facility (U.S.), United States. Department of Energy. Office of Science, and United States. Department of Energy. Office of Scientific and Technical Information
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Summary
In this study, plasma based surface modification of niobium is a promising alternative to wet etching of superconducting radio frequency (SRF) cavities. The development of the technology based on Cl2/Ar plasma etching has to address several crucial parameters which influence the etching rate and surface roughness, and eventually, determine cavity performance. This includes dependence of the process on the frequency of the RF generator, gas pressure, power level, the driven (inner) electrode configuration, and the chlorine concentration in the gas mixture during plasma processing. To demonstrate surface layer removal in the asymmetric non-planar geometry, we are using a simple cylindrical cavity with 8 ports symmetrically distributed over the cylinder. The ports are used for diagnosing the plasma parameters and as holders for the samples to be etched. The etching rate is highly correlated with the shape of the inner electrode, radio-frequency (RF) circuit elements, chlorine concentration in the Cl2/Ar gas mixtures, residence time of reactive species and temperature of the cavity. Using cylindrical electrodes with variable radius, large-surface ring-shaped samples and d.c. bias implementation in the external circuit we have demonstrated substantial average etching rates and outlined the possibility to optimize plasma properties with respect to maximum surface processing effect.
Report Numbers
E 1.99:jlab-acc--14-1903
E 1.99: doe/or/23177--3118
doe/or/23177--3118
jlab-acc--14-1903
Subject(s)
Note
Published through SciTech Connect.
12/15/2014.
"jlab-acc--14-1903"
" doe/or/23177--3118"
"ArticleNumber: 122001"
Physical Review Special Topics. Accelerators and Beams 17 12 ISSN 1098-4402; PRABFM AM
Upadhyay, J.; Im, Do; Popović, S.; Valente-Feliciano, A.; Phillips, L.; Vušković, L.
Funding Information
AC05-06OR23177
SC0007879
View MARC record | catkey: 23758690