Systematic Uncertainties in RF-Based Measurement of Superconducting   Cavity Quality Factors
  Q0 determinations based on RF power measurements are subject to at least three potentially large systematic effects that have not been previously appreciated. Instrumental factors that can systematically bias RF based measurements of Q0 are quantified and steps that can be taken to improve the determination of Q0 are discussed. 
J.P. Holzbauer, Yu. Pischalnikov, D.A. Sergatskov, W. Schappert, S.   Smith
physics.acc-ph