Noise measurements in multiloop superconducting interferometers

Abstract Noise measurements on multiloop dc SQUIDs, fabricated with Nb-NbOx-PbAuIn and Pb-alloy Josephson tunnel junctions and well coupled with the external world by an input coil, we performed in flux locked loop mode. To achieve this task, we built a reliable low-cost control electronics to detect the voltage output of the SQUID. The results show that for multiloop dc SQUIDs with single-junction critical currents larger than 20 ?A and an inductive parameter ? L less than 4.5, an intrinsic white-energy spectral density of about ...