Calorimetric measurement of AC loss in ICCS conductors subjected to pulsed magnetic fields

A calorimetric apparatus was developed to measure the AC loss in internally-cooled cabled superconductors (ICCS) which were subjected to pulsed magnetic fields. The purpose of the measurement was to compare the losses of several superconducting wires being considered for use in ohmic heating coils for tokamak fusion devices. The apparatus consisted of a vacuum chamber containing two samples of ICCS, and a pulse coil set surrounded by a Bitter magnet which provided a steady background field. First, the composite enthalpies of the samples were determined, and then the response of each sample to pulsed fields was recorded. A plot of energy versus pulse rate was then constructed. Results are presented for several types of Nb3Sn wires (bronze process, internal tin, and jelly roll) at a 10 tesla background field and for pulse rates up to 150 tesla/second.