Two-Stage SQUID Amplifiers for Cryogenic Detector Readouts

This proposal describes an innovative two-stage SQUID-based amplifier and PC-based high-speed feedback electronics without flux modulation for low-impedance cryogenic detector readouts. The proposed amplifier consists of a sensitive input SQUID followed by a coherently modulated output SQUID array. The gain of the second stage is sufficient to allow the amplifier to be directly coupled to a room-temperature preamplifier, thereby eliminating the need for flux modulation and cooled impedance matching circuits and enabling wideband operation. The SQUIDs in the output array are damped to avoid resonances or distortions in the transfer characteristics, which improves the stability of the amplifier and simplifies operation, and enhances the large-signal bandwidth. All SQUID drive signals and loop parameters may be configured remotely via a Windows-based graphical user interface. Multi-channel configurations are supported. This effort directly benefits SEU programs and addresses specific needs for SQUID-based amplifiers for cryogenic detector readouts.