Design and performance of the ADMX SQUID-based microwave receiver

TL;DR

This paper details the design and performance of a SQUID-based microwave receiver used in the ADMX experiment to detect axion particles, highlighting its low noise and suitability for ultra-weak signal detection.

Contribution

The paper introduces a specialized SQUID-based microwave receiver with low noise performance tailored for axion detection in the ADMX experiment.

Findings

Achieved a noise temperature of 1 K with the SQUID amplifier.

Demonstrated a noise equivalent power of 1.1x10^-24 W/√Hz.

Operated successfully in the 812-860 MHz frequency range.

Abstract

The Axion Dark Matter eXperiment (ADMX) was designed to detect ultra-weakly interacting relic axion particles by searching for their conversion to microwave photons in a resonant cavity positioned in a strong magnetic field. Given the extremely low expected axion-photon conversion power we have designed, built and operated a microwave receiver based on a Superconducting QUantum Interference Device (SQUID). We describe the ADMX receiver in detail as well as the analysis of narrow band microwave signals. We demonstrate the sustained use of a SQUID amplifier operating between 812 and 860 MHz with a noise temperature of 1 K. The receiver has a noise equivalent power of 1.1x10^-24 W/sqrt(Hz) in the band of operation for an integration time of 1.8x10^3 s.