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The surface resistance of an RF superconductor depends on the surfacetemperature, the residual resistance and various superconductor parameters,e.g. the energy gap, and the electron mean free path. These parameters can bedetermined by measuring the quality factor Q0 of a SRF cavity in helium-bathsof different temperatures. The surface resistance can be computed from Q0 forany cavity geometry, but it is not trivial to determine the temperature of thesurface when only the temperature of the helium bath is known.  Traditionally, it was approximated that the surface temperature on the innersurface of the cavity was the same as the temperature of the helium bath. Thisis a good approximation at small RF-fields on the surface, but to determine thefield dependence of Rs, one cannot be restricted to small field losses.  Here we show the following: (1) How computer simulations can be used todetermine the inside temperature Tin so that Rs(Tin) can then be used toextract the superconducting parameters. The computer code combines thewell-known programs, the HEAT code and the SRIMP code. (2) How large an erroris created when assuming the surface temperature is same as the temperature ofthe helium bath? It turns out that this error is at least 10% at high RF-fieldsin typical cases.

Extracting superconducting parameters from surface resistivity by using inside temperatures of SRF cavities