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| TUYBA02 |
Thermal Boundary Resistance Model and Defect Statistical Distribution in Nb/Cu Cavities |
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- R. Vaglio
UniNa, Napoli, Italy
- V. Palmieri
INFN/LNL, Legnaro (PD), Italy
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The ‘Q-slope' problem strongly limits the application of niobium thin film sputtered cavities in high field accelerators. Here we consider the hypothesis that the Q-slope is related to local enhanced of the thermal boundary resistance at the Nb/Cu interface, due to poor thermal contact between film and substrate. We introduce a simple model that directly connects the Q versus Eacc curves to the distribution function f(RNb/Cu) of RNb/Cu thermal contact at the Nb/Cu interface over the cavity surface. Starting from the experimental curves, using inverse problem methods, we deduce the distribution functions generating those curves. The technique has been applied to cavities by different groups, including LNL/INFN and ISOLDE/CERN. In all cases to explain the data it is sufficient to assume that only a small fraction of the film over the cavity surface is in poor thermal contact with the substrate. The distribution functions typically follow a simple power-law statistical distribution and are temperature independent. The full analysis supports the hypothesis that the main origin of the Q-slope in thin film cavities is indeed related to bad adhesion at the Nb/Cu interface.
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Slides TUYBA02 [0.988 MB]
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| DOI • |
reference for this paper
※ https://doi.org/10.18429/JACoW-SRF2017-TUYBA02
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