Standardization of the pickup coil method for AC loss measurement of three-component superconducting wires

In order to extend the scope of the proposed standard of the pickup coil method for AC loss measurement in IEC/TC90-WG9, a round robin test (RRT) of AC loss measurement for three-component (Cu/Cu–Ni/Nb–Ti) superconducting wires has been carried out. Three kinds of three-component superconducting wires were supplied and two laboratories participated in the RRT. The frequency dependence of total AC loss was measured in an alternating transverse magnetic field with the amplitude of 0.5 and 1 T at 4.2 K in the frequency range between 0.01 and 20 Hz. The hysteresis loss per cycle was obtained as an extrapolated value of the total AC loss per cycle at f=0 Hz. The coupling loss was also obtained by subtracting the hysteresis loss from the total AC loss. From the RRT between the two laboratories, the coefficients of variation of hysteresis loss and coupling time constant were both within 2%. Consequently, it was found that the procedure of AC loss measurement for the three-component wires was in principle the same as that for the Cu/Nb–Ti composite ones by extending the upper point of the measuring frequency range from 1 Hz up to about 10 Hz.