Author: Holic, A.T.
Paper Title Page
SUPTEV007 Development of a System for Coating SRF Cavities Using Remote Plasma CVD 129
 
  • G. Gaitan, P. Bishop, A.T. Holic, G. Kulina, M. Liepe, J. Sears, Z. Sun
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Funding: This work was supported by the National Science Foundation under Grant No. PHY-1549132.
Next-generation, thin-film surfaces employing Nb3Sn, NbN, NbTiN, and other compound superconductors are destined to allow reaching superior RF performance levels in SRF cavities. Optimized, advanced deposition processes are required to enable high-quality films of such materials on large and complex-shaped cavities. For this purpose, Cornell University is developing a remote plasma-enhanced chemical vapor deposition (CVD) system that facilitates coating on complicated geometries with a high deposition rate. This system is based on a high-temperature tube furnace with a clean vacuum and furnace loading system. The use of plasma alongside reacting precursors will significantly reduce the required processing temperature and promote precursor decomposition. A vacuum quality monitor (VQM) is used to characterize the residual gases before coating. The CVD system has been designed and is currently under assembly and commissioning.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-SUPTEV007  
About • Received ※ 09 July 2021 — Accepted ※ 21 August 2021 — Issue date; ※ 10 February 2022  
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SUPTEV008 CW Operation of Conduction-Cooled Nb3Sn SRF Cavity 133
 
  • N.A. Stilin, A.T. Holic, M. Liepe, R.D. Porter, J. Sears, Z. Sun
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Significant progress in the performance of SRF cavities coated with Nb3Sn films during the last few years has provided an energy efficient alternative to traditional Nb cavities, thereby initiating a fundamental shift in SRF technology. These Nb3Sn cavities can operate at significantly higher temperatures than Nb cavities while simultaneously requiring less cooling power. This allows for the use of new cryogenic cooling schemes based on conduction cooling with robust, commercialized turn-key style cryocoolers. Cornell University has developed and tested a 2.6 GHz Nb3Sn cavity assembly which utilizes such cooling methods. These tests have demonstrated stable RF operation at 10 MV/m with measured thermal dynamics which match numerical simulations. These results also serve as a foundation for designing a new standalone SRF cryomodule which will use a pair of cryocoolers to cool a 1.3 GHz Nb3Sn cavity with an input coupler capable of supporting high beam current operation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-SUPTEV008  
About • Received ※ 22 June 2021 — Accepted ※ 13 August 2021 — Issue date; ※ 08 November 2021  
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THPFDV005 Superconducting RF Performance of Cornell 500 MHz N-Doped B-Cell SRF Cavitiy 764
 
  • M. Ge, T. Gruber, A.T. Holic, M. Liepe, J. Sears
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  The Cornell SRF group is working on rebuilding a 500 MHz B-cell cryomodule (CRYO-2 BB1-5) as a spared cryomodule for the operation of the CESR ring. To minimize BCS surface resistance, achieve a high quality-factor (Q0), and increase maximum fields, we prepared the cavity’s surface with electropolishing and performed a 2/6 N2-doping. In this work, we report 4.2 K and 2 K cavity test results with detailed surface resistance analysis, showing improved performance, including significant higher fields.  
poster icon Poster THPFDV005 [0.712 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-THPFDV005  
About • Received ※ 05 July 2021 — Revised ※ 10 August 2021 — Accepted ※ 21 August 2021 — Issue date ※ 22 April 2022
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THPFDV006 Seebeck Coefficient Measurement at Cryogenic Temperatures for the LCLS-II HE Project 768
 
  • M. Ge, A.T. Holic, M. Liepe, J. Sears
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Reducing thermoelectric currents during cooldown is important to maintain high-quality factors (Q0) of the cavities in the LCLS-II HE cryomodules. The temperature-dependent Seebeck coefficients of the materials used in the cryomodules are needed for quantitative estimations of thermoelectric currents. In this work, we present a setup for cryogenic Seebeck coefficient measurements as well as the measured Seebeck coefficients of high-pure niobium at cryogenic temperatures between 4K and 200K.  
poster icon Poster THPFDV006 [0.505 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-THPFDV006  
About • Received ※ 29 June 2021 — Revised ※ 10 August 2021 — Accepted ※ 21 August 2021 — Issue date ※ 26 November 2021
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