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Effect of high temperature heat treatments on the quality factor of a large-grain superconducting radio-frequency niobium cavity
Physical Review Accelerators and Beams
  • P Dhakal, Thomas Jefferson National Accelerator Facility
  • G Ciovati, Thomas Jefferson National Accelerator Facility
  • G R Myneni, Thomas Jefferson National Accelerator Facility
  • K E Gray, Argonne National Laboratory
  • N Groll, Argonne National Laboratory
  • P Maheshwari, North Carolina State University
  • D M McRae, Florida State University
  • Robert D Pike, College of William and Mary
  • T Proslier, Argonne National Laboratory
  • F Stevie, North Carolina State University
  • R P Walsh, Florida State University
  • Q Yang, Norfolk State University
  • J Zasadzinzki, Illinois Institute of Technology
Document Type
Article
Publication Date
4-10-2013
Abstract

Large-grain Nb has become a viable alternative to fine-grain Nb for the fabrication of superconducting radio-frequency cavities. In this contribution we report the results from a heat treatment study of a large-grain 1.5 GHz single-cell cavity made of “medium purity” Nb. The baseline surface preparation prior to heat treatment consisted of standard buffered chemical polishing. The heat treatment in the range 800–1400°C was done in a newly designed vacuum induction furnace. Q0 values of the order of 2×1010 at 2.0 K and peak surface magnetic field (Bp) of 90 mT were achieved reproducibly. A Q0 value of (5±1)×1010 at 2.0 K and Bp=90  mT was obtained after heat treatment at 1400°C. This is the highest value ever reported at this temperature, frequency, and field. Samples heat treated with the cavity at 1400°C were analyzed by secondary ion mass spectrometry, x-ray photoelectron spectroscopy, energy dispersive x ray, point-contact tunneling, and x-ray diffraction, and revealed a complex surface composition which includes titanium oxide, increased carbon, and nitrogen content but reduced hydrogen concentration compared to a non-heat-treated sample.

Citation Information
P Dhakal, G Ciovati, G R Myneni, K E Gray, et al.. "Effect of high temperature heat treatments on the quality factor of a large-grain superconducting radio-frequency niobium cavity" Physical Review Accelerators and Beams Vol. 16 Iss. 042001 (2013)
Available at: http://works.bepress.com/robert-pike/156/