Short sample critical current measurements using a superconducting transformer

We have developed a superconducting transformer (SCT) for measuring critical current in large composite superconductors for high field and high current applications such as those used in fusion magnets. It consists of a 700-turn primary and a one-turn secondary coil of which the sample conductor is a constituent. A current of up to 100 A in the primary induces a current calculated at greater than 25 kA in the secondary. A 7.5 tesla magnet provides the background field. The secondary current is measured using a Hall probe and a Rogowski coil. The device is calibrated against superconducting critical current US NBS SRM number1457. Theory, design, and test results of the device are presented