Measurement of AC transport current loss in different kinds of superconducting tapes and wires in liquid helium

Low-temperature and high-temperature superconductors are used in liquid helium (LHe) as magnets and in other applications. AC transport current loss study is important for the use of these superconductors in alternating current regimes. The measurement of AC transport current loss under LHe conditions requires a measurement system with a special measurement device. A possible way to carry out the measurement is presented in this paper. The device described in this paper is based on the principle of a current transformer. The transport current is induced into one secondary turn formed by a superconducting sample. The LHe evaporation caused by the heating of the current leads at high currents and the measurement system dimensions are minimized. Our experimental setup enables us to determine the AC transport current loss of a superconducting tape or a wire in the self-field, in LHe up to a current of 2000 A at a frequency up to 300 Hz. The measurements are based on a lock-in technique. This paper presents and compares AC transport losses of YBa(2)Cu(3)O(7-x) (YBCO) coated conductor, Bi(2)Sr(2)Ca(2)Cu(3)O(10) (BSCCO) tape, NbTi wire and Nb(3)Sn tape measured up to their quench currents in LHe.