DIN EN 61788-4:2017-01

Copper, Cu-Ni, Cu/Cu-Ni or aluminum is applied as a matrix material for stabilization in Nb-Ti and Nb₃Sn compound superconductors and acts as an electrical shunt resistor when superconductivity is interrupted. It also helps restore superconductivity by dissipating heat generated in the superconductor to the outside of the coolant. The low temperature resistivity of the copper used in a compound superconductor is an important parameter that affects the stability of the superconductor. The residual resistivity ratio is defined as the ratio of the resistance of the superconductor at room temperature to the resistance immediately above the transition to superconductivity. This Part 4 of the IEC 61788 series of International Standards specifies the measurement procedure for determining the residual resistance ratio of Nb-Ti and Nb₃Sn compound superconductors. The method with measured voltage curves is used for the measurement of the resistance immediately above the transition from normal to superconductivity. Other methods are described in A.3. This part of IEC 61788 deals with a measurement method for determining the residual resistance ratio (RRR) of Nb-Ti composite superconductors with Cu, Cu-Ni, Cu/Cu-Ni and Al matrix and Nb₃Sn composite superconductors. This method is intended for use with superconductors that have a monolithic structure with a rectangular or circular cross-section, a residual resistance ratio less than 350, and a cross-sectional area less than 3 mm². A reaction heat treatment was performed on the samples in the case of Nb₃Sn. The responsible committee is DKE/K 184 "Supraleiter" ("Superconductors") of the DKE (German Commission for Electrical, Electronic and Information Technologies) at DIN and VDE.