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Title: Effect of low temperature baking in nitrogen on the performance of a niobium superconducting radio frequency cavity

Here, we report the rf performance of a single-cell superconducting radiofrequency cavity after low temperature baking in a nitrogen environment. A significant increase in quality factor has been observed when the cavity was heat treated in the temperature range of 120-160 °C with a nitrogen partial pressure of ~25 mTorr. This increase in quality factor as well as the Q-rise phenomenon (anti-Q-slope) is similar to those previously obtained with high temperature nitrogen doping as well as titanium doping. In this study, a cavity N 2-treated at 120 °C and at 140 °C, showed no degradation in accelerating gradient, however the accelerating gradient was reduced by ~25% with a 160 °C N 2 treatment, compared to the baseline tests after electropolishing. Sample coupons treated in the same conditions as the cavity were analyzed by scanning electron microscope, x-ray photoelectron spectroscopy and secondary ion mass spectroscopy revealed a complex surface composition of Nb 2O 5, NbO and NbN (1-x)O x within the rf penetration depth. Furthermore, magnetization measurements showed no significant change on bulk superconducting properties.
Authors:
ORCiD logo [1] ; ORCiD logo [2] ; ORCiD logo [2] ; ORCiD logo [2] ; ORCiD logo [1]
  1. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
  2. Florida State Univ., Tallahassee, FL (United States). National High Magnetic Field Lab. (MagLab). Applied Superconductivity Center
Publication Date:
Report Number(s):
JLAB-ACC-17-2626; DOE/OR/23177-4306
Journal ID: ISSN 2469-9888; PRABCJ
Grant/Contract Number:
SC0009960; FG02-09ER41638; NSF-DMR-1157490; AC05-06OR23177; SC 0009960
Type:
Published Article
Journal Name:
Physical Review Accelerators and Beams
Additional Journal Information:
Journal Volume: 21; Journal Issue: 3; Journal ID: ISSN 2469-9888
Publisher:
American Physical Society (APS)
Research Org:
Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Florida State Univ., Tallahassee, FL (United States)
Sponsoring Org:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25); North Carolina State Univ., Raleigh, NC (United States); National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 36 MATERIALS SCIENCE; 43 PARTICLE ACCELERATORS; Nb; superconducting radio frequency cavities; nitrogen; microstructure; surface chemistry; XPS; SIMS; magnetization
OSTI Identifier:
1424820
Alternate Identifier(s):
OSTI ID: 1425205; OSTI ID: 1425400