A Loss Measurement System in a Test Facility for High-current Superconducting Cables and Wires

The realisation of a 7 tesla/25 kA test facility for measuring the critical current density and the quench propagation velocity of high-current superconductors has already been reported [11. The test volume in this set-up is torus-shaped having a diameter of 0.2 m and a cross-section of 5 cm2. The test facility has been equipped with a set of AC coils and pick-up coils in order to perform AC loss measurements. A system of helium gas channels has been included to determine the helium boil-off for calibration and verification purposes. The amplitude of the AC magnetic field is limited to about 0.5 T at 10 Hz. A transport current of up to 25 kA, AC or DC, can be fed to the test conductor by means of a transformer. The facility provides means to perform loss measurements on large conductors at a relatively low cost. In order to test the AC loss measurement system a superconductor manufactured by Vacuumschmelze has been investigated. This NbTi superconductor for TORE SUPRA is a monolith with a mixed matrix, a cross-section of 5.6 x 2.8 mm2 and contains 10164 filaments. The characteristics of the AC loss measurement system as well as preliminary results of the loss measurements on the Vacuumschmelze conductor are reported here.