Author: Kelley, M.J.
Paper Title Page
TUPOTK042 Challenges to Reliable Production Nitrogen Doping of Nb for SRF Accelerating Cavities 1311
 
  • C.E. Reece, M.J. Kelley, E.M. Lechner, A.D. Palczewski
    JLab, Newport News, Virginia, USA
  • J.W. Angle, M.J. Kelley
    Virginia Polytechnic Institute and State University, Blacksburg, USA
  • F.A. Stevie
    NCSU AIF, Raleigh, North Carolina, USA
 
  Funding: This work was authored by JSA LLC under U.S. DOE contract DE-AC05-06OR23177. This material is based on work supported by the U.S. DOE Early Career Award to A. Palczewski, with supplemental support from DOE BES via the LCLS-II HE R&D program. J. Angle’s support was from the Office of High Energy Physics, under grant DE-SC-0014475 to Virginia Tech.
Over the last several years, alloying of the surface layer of niobium SRF cavities has been demonstrated to beneficially lower the superconducting RF surface resistance. Nitrogen, titanium, and oxygen have all been demonstrated as effective alloying agents, occupying interstitial sites in the niobium lattice within the RF penetration depth and even deeper, when allowed to thermally diffuse into the surface at appropriate temperatures. The use of nitrogen for this function has been often termed ’nitrogen doping’ and is being applied in the LCLS-II and LCLS-II HE projects. We report characterization studies of the distribution of nitrogen into the exposed niobium surface and how such distribution is affected by the quality of the vacuum furnace environment in which the doping takes place, and the complexity of nitride crystal growth on different grain orientations of surface niobium. Using state-of-the-art quantification methods by dynamic secondary ion mass spectrometry (SIMS) depth profiling in niobium, we identify several phenomena involving furnace-sourced contamination. We also highlight a potential issue with N2 flow constraints from the flange ’caps’ used during heat treatments.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOTK042  
About • Received ※ 07 June 2022 — Revised ※ 09 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 05 July 2022
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TUPOTK059 Modeling O and N Alloying in Nb for SRF Applications 1354
 
  • E.M. Lechner, M.J. Kelley, A.D. Palczewski, C.E. Reece
    JLab, Newport News, Virginia, USA
  • J.W. Angle, M.J. Kelley
    Virginia Polytechnic Institute and State University, Blacksburg, USA
  • F.A. Stevie
    NCSU AIF, Raleigh, North Carolina, USA
 
  Funding: This work was coauthored by Jefferson Science Associates LLC under U.S. DOE Contract No. DE-AC05-06OR23177 and grant No. DE-SC-0014475 to Virginia Tech for the support of J. Angle.
N and O-alloyed superconducting radio frequency cavities exhibit extraordinary quality factors. Developing diffusion models that describe interstitial N and O in Nb is important for optimizing alloyed cavity quality factors and accelerating gradients. N and O-alloyed Nb samples are examined with SEM AND SIMS and their diffusion profiles modeled.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOTK059  
About • Received ※ 08 June 2022 — Revised ※ 10 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 17 June 2022
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)