A method to evaluate RRR of superconducting cavities

The Residual Resistivity Ratio (RRR) is defined as ⇢(300 K)/⇢(10 K) where ⇢ is the surface resistivity in the normal conducting state of the material. RRR is related to the impurity content in the material and then it represents a strong indication on how good the material is. In this paper we will develop an useful method to measure RRR for superconducting cavities during cryogenic tests