Test results of an apparatus for calorimetric measurement of AC losses in superconductors

A description is given of a novel method to measure calorimetrically AC losses in superconducting samples. The boil-off gas is stored below the liquid helium level in a measuring tube. Losses in the range of 1 mW up to 100 mW can be measured with an accuracy of 3%. Results of measurements of AC losses in superconducting wires are presented. In contrast to measurements with gas-flow meters, there is a negligible background signal and an excellent reproducibility as all measurements are performed at the temperature of boiling helium