Superconducting quantum interference filters operated in commercial miniature cryocoolers

Superconducting Quantum Interference Filters (SQIF´s) are multi-loop arrays of Josephson junctions possessing unconventional grating structures. The flux-to-voltage transfer function of SQIF´s is unique and has a single delta-peak like characteristics at zero applied magnetic field. The fault tolerance of SQIF´s allows them to be realized in standard high-temperature grain boundary Josephson junction technology. We have successfully designed high-temperature YBCO SQIF´s with voltage swings of more than 3 mV and a rather large dynamical range. This large dynamical range allows high-Tc SQIF´s to be operated in commercial miniature cryocoolers at 50 K-80 K without any significant problems. Typical parasitic oscillations which are induced by the 55 Hz driven compressor of the cryocooler do not degrade the performance of SQIF´s. Even if SQIF´s are operated fully unshielded no significant degradation of the performance has been observed.