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Field-dependent surface resistance for superconducting niobium accelerating cavities

Superconducting cavities made from niobium allow accelerating gradients of about 50  MV/m close to the theoretical limit. Quite often, however, the rf losses increase with the gradient faster than quadratic. This observation is equivalent with a decrease of the quality factor Q with the gradient, ca...

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Detalles Bibliográficos
Autor principal: Weingarten, Wolfgang
Publicado: 2011
Materias:
Acceso en línea:https://dx.doi.org/10.1103/PhysRevSTAB.14.101002
https://dx.doi.org/10.1103/PhysRevAccelBeams.24.069902
http://cds.cern.ch/record/1419185
Descripción
Sumario:Superconducting cavities made from niobium allow accelerating gradients of about 50  MV/m close to the theoretical limit. Quite often, however, the rf losses increase with the gradient faster than quadratic. This observation is equivalent with a decrease of the quality factor Q with the gradient, called “Q slope” for intermediate gradients, and “Q drop” for larger ones. The paper provides an explanation by an elementary model based on the two-fluid theory of rf superconductivity and applies it to experimental data for a large variety of cavity tests.