Distributed microwave damping filters for superconducting quantum interference devices

We describe a distributed thin-film filter for the broad-band damping of microwave resonances in thin-film superconducting strip lines and coils used in Nb endash Al/AlOx endash Nb superconducting quantum interference devices (SQUIDs). The filter consists of an array of 14 μm diameter thin-film Au endash Cu dots which are insulated from the strip lines or coils by an SiO2 layer. Damping occurs via eddy current induced in the dots. Our measurements show that the filter removes resonance steps from the current endash voltage curves of SQUIDs which are coupled to the coils and reduces white noise associated with the resonances. copyright 1997 American Institute of Physics