Low-Noise, Broadband SQUID Amplifiers for Low-Impedance Signal Sources

Matching the impedance of a signal source to the input of an amplifier yields the lowest-noise amplification. Using conventional, semiconductor amplifiers requires impedance matching networks that inherently limit bandwidth. Superconducting Quantum Interference Devices (SQUIDs) offer inherently low impedance amplifiers with virtually unlimited bandwidth. High-temperature superconductor (HTS) SQUIDs can operate with crycoolers that render the cryogenics transparent to a user. Phase I will develop a theoretical noise model for HTS SQUID amplifiers with wideband electronics and validate it experimentally. Phase I will establish the sensor performance improvements achievable with the new amplifier technology, leading to integration of a prototype amplifier with a sensor system in Phase II. Together with new, wideband SQUID electronics developed by the firm with IBM, they enable a new, low-impedance amplifier technology of unprecedentedly low noise, wide bandwidth, high dynamic range, and high common mode rejection ratio. The technology finds application wherever low-impedance sensors produce small signals. Applications of interest to BMDO include IR and X-ray detector arrays.