Delayen, J.R. De Silva, S.U. Park, H. JACoW Publishing Geneva, Switzerland 2226-0366 978-3-95450-194-6 10.18429/JACoW-LINAC2018-TUPO035 English 405-407 TUPO035 cavity experiment electromagnetic-fields SRF superconducting-cavity Contribution to a conference proceedings 2019 2019-01 https://doi.org/10.18429/JACoW-LINAC2018-TUPO035 http://jacow.org/linac2018/papers/tupo035.pdf Cryogenic tests of superconducting cavities yield an average surface resistance as a function of the peak surface magnetic field. An analytical formalism has been developed to extract the actual field dependence of the surface resistance from cavity tests and is applied to coaxial cavities and cavities of more complex geometries.