The effect of vacancies on the microwave surface resistance of niobium revealed by positron annihilation spectroscopy

A. Romanenko, C. J. Edwardson, P. G. Coleman, P. J. Simpson

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)

Abstract

Using variable-energy positron annihilation spectroscopy, we demonstrate that a different near-surface vacancy concentration accompanies drastic differences in surface resistance of superconducting niobium cavities for particle acceleration. Our data suggest that vacuum baking at 120 °C leads to the doping of a near-surface layer with vacancy-hydrogen complexes, and that higher vacancy-type defect concentration distinguishes electropolished from chemically etched cavities. Our findings may help to explain a strong dependence of cavity performance on heat and chemical treatments, and may be of interest to other physics fields including cavity quantum electrodynamics (QED), microresonators, and single photon detectors.
Original languageEnglish
Article number232601
JournalApplied Physics Letters
Volume102
Issue number23
DOIs
Publication statusPublished - 10 Jun 2013

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