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

2021; American Institute of Physics; Volume: 119; Issue: 8 Linguagem: Inglês

10.1063/5.0059464

1520-8842

Eric Lechner, Jonathan W. Angle, F. A. Stevie, Michael J. Kelley, Charles Reece, Ari Palczewski,

Physics of Superconductivity and Magnetism

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 Q0) previously expected only from 800 °C diffusive alloying with N.