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Title: Physics and material science of ultra-high quality factor superconducting resonator

The nitrogen doping into niobium superconducting radio frequency cavity walls aiming to improve the fundamental mode quality factor is the subject of the research in the given work. Quantitative nitrogen diffusion into niobium model calculating the concentration profile was developed. The model estimations were confirmed with secondary ion mass spectrometry technique measurements. The model made controlled nitrogen doping recipe optimization possible. As a result the robust reproducible recipe for SRF cavity walls treatment with nitrogen doping was developed. The cavities produced with optimized recipe met LCLS–II requirements on quality factor of 2.7 ∙ 1010 at acceleration field of 16 MV/m. The microscopic effects of nitrogen doping on superconducting niobium properties were studied with low energy muon spin rotation technique and magnetometer measurements. No significant effect of nitrogen on the following features was found: electron mean free path, magnetic field penetration depth, and upper and surface critical magnetic fields. It was detected that for nitrogen doped niobium samples magnetic flux starts to penetrate inside the superconductor at lower external magnetic field value compared to the low temperature baked niobium ones. This explains lower quench field of SRF cavities treated with nitrogen. Quality factor improvement of fundamental mode forced to analyze themore » high order mode (HOM) impact on the particle beam dynamics. Both resonant and cumulative effects caused by monopole and dipole HOMs respectively are found to be negligible within the requirements for LCLS–II.« less
Authors:
 [1]
  1. Univ. of Chicago, IL (United States)
Publication Date:
OSTI Identifier:
1221362
Report Number(s):
FERMILAB-THESIS--2015-19
TRN: US1601314
DOE Contract Number:
AC02-07CH11359
Resource Type:
Thesis/Dissertation
Research Org:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 36 MATERIALS SCIENCE; NIOBIUM; NITROGEN; QUALITY FACTOR; CRITICAL FIELD; SUPERCONDUCTING CAVITY RESONATORS; MASS SPECTROSCOPY; RF SYSTEMS; ION MICROPROBE ANALYSIS; TEMPERATURE RANGE 0273-0400 K; ELECTRONS; MUON SPIN RELAXATION; COMPARATIVE EVALUATIONS; CONCENTRATION RATIO; DOPED MATERIALS; PARTICLE BEAMS; BEAM DYNAMICS; DIPOLES; MAGNETOMETERS; WALLS; MEAN FREE PATH; MAGNETIC FLUX; PENETRATION DEPTH; ABUNDANCE; DIFFUSION; OPTIMIZATION; SURFACES; MAGNETIC FIELDS; STANFORD LINEAR ACCELERATOR CENTER; LIGHT SOURCES