Author: Sethna, J.P.
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TUFUA1 The Field-Dependent Surface Resistance of Doped Niobium: New Experimental and Theoretical Results 340
  • J.T. Maniscalco, M. Ge, P.N. Koufalis, M. Liepe
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • T. Arias, D. Liarte, J.P. Sethna, N. Sitaraman
    Cornell University, Ithaca, New York, USA
  We present systematic work investigating how different doping and post-doping treatments affect the BCS surface resistance at 1.3~GHz and higher frequencies. We examine the field-dependent BCS resistance at many temperatures as well as the field-dependent residual resistance and use the results to reveal how impurity species and concentration levels affect the field-dependent RF properties. We further demonstrate the importance of thermal effects and their direct dependence on doping level. We use the tools of Density Functional Theory to work towards an {\em ab initio} model of electron overheating to theoretically confirm the impact of doping, create a full model that includes thermal effects to predict the field dependent resistance, and show that the predictions of the model agree with results from doped and non-doped cavities ({\em e.g.} the strength of the anti-Q-slope and the high-field Q slope). Finally, we use our experimental results to systematically assess and compare theories of the field-dependent BCS resistance, showing that the current theory on smearing of the density of states is incomplete.  
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About • paper received ※ 01 July 2019       paper accepted ※ 02 July 2019       issue date ※ 14 August 2019  
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