DIN EN 61788-11:2012-04

Copper or aluminium is used as stabilizer material in multifilamentary Nb₃Sn superconductors and works as an electrical shunt when the superconductivity is interrupted. It also contributes to recovery of the superconductivity by conducting the heat generated in the superconductor to the surrounding coolant. The resistivity of copper used in the composite superconductor in the cryogenic temperature region is an important quantity which influences the stability of the superconductor. The residual resistance ratio is defined as a ratio of the resistance of the superconductor at room temperature to that just above the superconducting transition. In this International Standard, the test method for the residual resistance ratio of Nb₃Sn composite superconductors is described. The curve method is employed for the measurement of the resistance just above the superconducting transition. Other methods are described in Annex A. This part of IEC 61788 covers a test method for the determination of the residual resistance ratio of Nb₃Sn composite superconductors. The method is intended for use with superconductor specimens that have a monolithic structure with rectangular or round cross section, a residual resistance ratio less than 350 and cross-sectional area less than 3 mm², and have received a reaction heat-treatment. Ideally, it is intended that the specimens be as straight as possible; however, this is not always the case, thus care must be taken to measure the specimen in its as received condition. All measurements are done without an applied magnetic field. The method described in the body of this standard is the "reference" method and optional acquisition methods are outlined in Annex A. The responsible committee is K 184 "Supraleiter" ("Superconductors") of the DKE (German Commission for Electrical, Electronic and Information Technologies) at DIN and VDE.