A Transducer for Measuring the Field Quality in Superconducting Solenoids

The critical current of superconducting wires is measured at CERN in four test stations that use high-field superconducting solenoid magnets achieving up to 15 T. The reduction of the uncertainty in the critical-current measurements requires the field mapping of the solenoids in their operating condition. This paper presents the design and application of a solenoidal-field transducer based on a pair of nested induction coils, which are moved along the axis of the magnet. The system allows to extract the longitudinal and transverse field components as a function of the sensor's longitudinal position. The radial dependence of the magnetic flux density can be estimated directly from the nested coils of different diameters validated by applying the theory of pseudo-multipoles in solenoidal magnets. The results and uncertainties of the field mappings are presented.