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Vacancy-Hydrogen Dynamics in Samples during Low Temperature Baking

Wenskat, M.; Bate, C.; Cizek, J.; Liedke, M. O.ORC; Butterling, M.; Hirschmann, E.; Wagner, A.ORC; Reschke, D.; Weise, H.
The recent discovery of a modified low temperature baking process established an increased accelerating gradient of TESLA shaped cavities through reduction of surface losses.
A possible explanation for the performance gain is the suppression of lossy nanohydrides via defect trapping, with vacancy-hydrogen (v+nH) complexes forming at the lower temperatures. Utilizing Doppler broadening Positron Annihilation Spectroscopy, Positron Annihilation Lifetime Spectroscopy and Nuclear Reaction Analysis, samples made from European XFEL niobium sheets and cavity cut-outs were investigated. The evolution of vacancies, hydrogen and their interaction at different temperature levels have been studied during in-situ and ex-situ annealing and in-situ cooldowns.
Measurements of niobium samples and a correlation between RF, material properties, and v+nH distribution in cavity cut-outs have been carried out.
Keywords: PAS, Nb, superconductivity, defects, hydrogen


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Publ.-Id: 30619