High Critical Temperature Superconducting Wire Based Flux Transformers

Flux transformers are currently used for signal detection with high sensitivity magnetometers like SQUIDS , as an alternative to direct coupling between the magnetometer and the sample. To avoid extra noise, most of them are made of superconducting material, namely low critical temperature (Tc) wires and high Tc thin films. We build flux transformers with high Tc Bi-2223 commercial wires operating at 77 K. Because the loops are closed by tin soldering, the device has a residual resistance of a few muOmega . We present the magnetic flux transfer characteristics and the calculations of the noise induced in the detection chain by this kind of flux transformer in two configurations: the untuned flux transformer and the tuned flux transformer.