Apparatus for calorimetric measurements of losses in MgB_2 superconductors exposed to alternating currents and external magnetic fields

摘要

Inexpensive superconducting wires with low AC losses would open up for a large superconductor market in AC electrical power applications. One candidate for this market is the MgB_2 conductor. In the development of an AC optimized superconductor, high-quality measurements of the AC losses under applicationlike conditions must be available. This article describes an apparatus built for this purpose. The measurement method is calorimetric. The temperature increase of the superconductor sample is measured and compared to the temperature increase due to a heater with known heat input. The system is designed for measurements of losses due to magnetic fields combined with transport currents. Results from tests verifying the capabilities of the system are given, as well as from initial AC loss measurements on a tape-shaped MgB_2 superconductor.