Fluxon induced surface resistance and field emission in niobium films at 1.5 GHz

The surface resistance of superconducting niobium films induced by the presence of trapped magnetic flux, presumably in the form of a pinned fluxon lattice, is shown to be modified by the presence of a field emitting impurity or defect. The modification takes the form of an additional surface resist...

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Bibliographic Details
Published in:Physica. C, Superconductivity Superconductivity, 2001-09, Vol.361 (1), p.31-39
Main Authors: Benvenuti, C., Calatroni, S., Darriulat, P., Peck, M.A., Valente, A.-M., Van 't Hof, C.A.
Format: Article
Language:English
Subjects:
Electron field emission
Flux pinning
RF cavities
Surface impedance
Thin films
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Summary:The surface resistance of superconducting niobium films induced by the presence of trapped magnetic flux, presumably in the form of a pinned fluxon lattice, is shown to be modified by the presence of a field emitting impurity or defect. The modification takes the form of an additional surface resistance proportional to the density of the fluxon lattice and increasing linearly with the amplitude of the microwave above a threshold significantly lower than the field emission threshold. Such an effect, precursor of electron emission, is observed here for the first time in a study using radiofrequency cavities operated at their fundamental 1.5 GHz frequency. The measured properties of the additional surface resistance severely constrain possible explanations of the observed effect.
ISSN:0921-4534
1873-2143
DOI:10.1016/S0921-4534(01)00284-2