Dependence of Transport-Current Losses in MgB2 Superconducting Wire on Temperature and Frequency

Abstract—AC losses of a monofilamentary MgB2 wire in a self-field are experimentally evaluated at various temperatures and frequencies. The alternating transport currents are applied to the straight sample wire, and the AC losses are observed electrically with a lock-in amplifier. The temperature of the sample wire is adjusted by a conduction cooling with gaseous helium, and the stability is below ±0.1 K near a fixed temperature. The temperature dependence of the transport-current losses is almost reproduced with a theoretical expression based on the Bean model, though the experimental results of the transport-current losses slightly depend on the frequency. Index Terms—AC loss, alternating transport current, lock-in amplifier, magnesium-diboride monofilamentary wire