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  • The Definitive Search for Dark Matter Axions

    Schematic of the ADMX receiver chain showing the path from the cavity microwave signal at the left to near-audio downconverted signal at the right.

    The ADMX receiver is sensitive to 0.01 yoctowatts of power. That's equivalent to less than one axion decay within the cavity per minute.


    The ultra-low noise microwave receiver makes the experiment possible. The dominant background is thermal noise arising from the cavity and the receiver electronics. Signals from the cavity are amplified by an exotic cryogenic Superconducting QUantum Interference Device (SQUID) amplifier followed by ultralow noise cryogenic HFET amplifiers. The receiver then downconverts mirowave cavity frequencies to a a lower frequency that can be easily digitized and saved.

    We have demonstrated that the SQUID amplifier allows for quantum limited power sensitivity. The receiver chain is sensitive to powers smaller than 0.01 yoctowatts; this is the world's lowest-noise microwave receiver in a production environment.