Calibration of Hall sensor AC loss measurements

Accurate measurements of the magnetic AC loss in short samples of conductor are essential for the design of superconducting power devices and guide the development of superconducting wire with low AC losses. The authors report quantitative AC loss measurements at power frequencies at 77 K obtained with a Hall sensor magnetometer (HSM) using a calibration method which involves assumptions about the current distribution within the sample. The samples included strips of pure silver and multi-filamentary Bi-2223 tapes. A comparison using AC susceptometry and their Hall sensor magnetometer technique shows good agreement between the two methods for both the HTS and silver tape samples. In the case of the silver tapes the results also agree with the predicted power loss. AC susceptometer measurements were made using a pick-up coil enclosing the entire sample so that the global magnetic moment was measured, including any effects of the sample ends. The HSM results are unaffected by sample end-currents. The comparison confirms the accuracy of the calibrated HSM technique.