SQUID-Based Microwave Cavity Search for Dark-Matter Axions

Axions in the mu eV mass range are a plausible cold dark-matter candidate and may be detected by their conversion into microwave photons in a resonant cavity immersed in a static magnetic field. We report the first result from such an axion search using a superconducting first-stage amplifier (SQUID) replacing a conventional GaAs field-effect transistor amplifier. This experiment excludes KSVZ dark-matter axions with masses between 3: 3 mu eV and 3: 53 mu eV and sets the stage for a definitive axion search utilizing near quantum-limited SQUID amplifiers.