RF surface resistance tuning of superconducting niobium via thermal diffusion of native oxide

RF surface resistance tuning of superconducting niobium via thermal diffusion of native oxide

Recently, Nb superconducting radio frequency cavities vacuum heat treated between 300 and 400 °C for a few hours have exhibited very high quality factors (∼5 × 1010 at 2.0 K). Secondary ion mass spectrometry measurements of O, N, and C show that this enhancement in RF surface conductivity is primari...

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Bibliographic Details
Published in:Applied physics letters Vol. 119; no. 8
Main Authors: Lechner, E. M., Angle, J. W., Stevie, F. A., Kelley, M. J., Reece, C. E., Palczewski, A. D.
Format: Journal Article
Language:English
Published: Melville American Institute of Physics 23-08-2021
American Institute of Physics (AIP)
Subjects:
Alloying
annealing
Applied physics
CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
crystallization
depth profiling techniques
Heat treatment
Holes
Niobium
particle accelerators
Q factors
Radio frequency
Secondary ion mass spectrometry
Superconductivity
surface conductivity
Surface resistance
Thermal diffusion
thermal diffusivity
thin films
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Summary:Recently, Nb superconducting radio frequency cavities vacuum heat treated between 300 and 400 °C for a few hours have exhibited very high quality factors (∼5 × 1010 at 2.0 K). Secondary ion mass spectrometry measurements of O, N, and C show that this enhancement in RF surface conductivity is primarily associated with interstitial O alloying via dissolution and diffusion of the native oxide. We use a theory of oxide decomposition and O diffusion to quantify previously unknown parameters crucial in modeling this process. RF measurements of a vacuum heat-treated Nb superconducting radio frequency cavity confirm the minimized surface resistance (higher Q 0) previously expected only from 800 °C diffusive alloying with N.
Bibliography:USDOE Office of Science (SC), High Energy Physics (HEP)
AC05-06OR23177; SC0014475
USDOE Office of Science (SC), Nuclear Physics (NP)
JLAB-ACC-21-3401; DOE/OR-23177-5222; arXiv:2106.06647
ISSN:0003-6951
1077-3118
DOI:10.1063/5.0059464