Author: Ge, M.
Paper Title Page
WEOTEV03 Toward Stoichiometric and Low-Surface-Roughness Nb3Sn Thin Films via Direct Electrochemical Deposition 710
 
  • Z. Sun, G. Gaitan, M. Ge, K. Howard, M. Liepe, T.E. Oseroff, R.D. Porter
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • T. Arias, Z. Baraissov, M.M. Kelley, D.A. Muller, J.P. Sethna, N. Sitaraman
    Cornell University, Ithaca, New York, USA
  • K.D. Dobson
    University of Delaware, Newark, Delaware, USA
 
  Reducing surface roughness and attaining stoichiometry of Nb3Sn superconducting films are required to push their superheating field to the theoretical limit in SRF cavities. As such, we explore direct electrochemical processes that minimize involving foreign elements to deposit high-quality Sn, Nb, and NbxSn films on Nb and Cu surfaces. These films are then thermally annealed to Nb3Sn. We find that smooth Sn pre-depositions via electroplating on Nb surfaces significantly reduce the average roughness of resultant Nb3Sn to 65 nm, with a dramatic reduction in power intensity at medium special frequencies. Structural and superconducting properties demonstrate a Nb3Sn A15 phase with a stoichiometry of 25 at% Sn. This process is being scaled-up to a 3.9 GHz cavity. Moreover, preliminary results on electroplating on Cu surface show that Nb plating undergoes a slow growth rate while subsequent Sn plating on the plated Nb surface can be controlled with varied thickness. The Nb plating process is currently being optimized.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-WEOTEV03  
About • Received ※ 09 July 2021 — Revised ※ 09 August 2021 — Accepted ※ 21 August 2021 — Issue date ※ 16 January 2022
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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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