Variable temperature total AC loss and stability characterization facility

The design of a versatile ac loss and stability characterization facility for high temperature superconducting materials suitable for variable temperature measurements is described. A non-metallic vessel inside a transverse field double-helix magnet acts as the measurement chamber. A cryocooler cools the samples to a target measurement temperature between 35 and 80 K. The facility is suitable for measurements on samples as long as 15 cm with ac transport current and ac background magnetic field, both at variable frequency. The facility allows for sample rotation to vary its orientation with respect to the magnetic field. Initial temperature measurements showed that the sample could be maintained at uniform temperature to +/- 0.5 K. AC loss measurements performed on a precursor setup, identical in concept, confirmed the suitability of the double-helix magnet design and cryocooler based cooling arrangement.