The AC Losses Of A Kind Of Iron-based Superconducting Tape

In February2008, a research team of Tokyo, Japan Institute of Industry led by Professor Hosono’s, found that superconductivity can be realized at temperature of26K by doping F element in parent material LaFeAsO. Subsequently, scientists in various countries devoted to study of series of new iron-based superconducting materials, then a variety of iron-based superconducting materials with various formulations were successfully prepared and their transition temperature continuously increase either. Chinese scientists in this field have achieved prominent results and prepared a variety of iron-based superconducting materials, Chinese scientists in this field have achieved prominent results, prepared a variety of iron-based superconducting materials, but there are few reports on their AC loss characteristics.Based on referring to relative reports on AC losses of superconductor, the AC loss mechanism of superconductor and theoretical calculation method of superconducting slab according to the Bean critical model are firstly described in this paper. Furthermore, three kinds of measurement methods which include magnetic, electric and calorimetric methods are systematically introduced and analyzed for measuring AC losses of superconductors. In order to measure the hysteresis loss of iron-based superconductor, one designed a set of AC loss measurement set-up by employing the pick-up coil method. Various components of set-up including pick-up coil, compensation coil, compensation circuit, specimen form, AC superconducting magnet, low-frequency AC power, cryostat, amplifiers, data acquisition system are designed and fabricated. Consequently, one finished a set of AC loss measurement set-up for hysteresis loss in accordance with IEC standard.Calibrations of the set-up were performed by SQUID magnetometer and pick-up coils methods with using pure lead standard samples. It is shown that the set-up meets requirement of AC loss measurement. Then, one measured the hysteresis loss of iron-based superconducting tape with single core manufactured by PIT process by using the calibrated measurement set-up at liquid helium temperature4.2K. Comparing with calculating results of hysteresis loss from single core iron-based superconductor and eddy current loss from iron sheath in sample, the measurement results is proportional to frequency of AC background magnetic field, so that the AC losses of iron-based superconductor dominates and eddy current loss can be neglected since it is proportional to square of frequency.