ADMX Cold Electronics Design and Characterization*

The Axion Dark Matter eXperiment (ADMX) uses quantum limited electronics, in conjunction with a large volume microwave cavity in a 7.6 Tesla magnetic field, to place the most stringent limits on the QCD axion. The current ADMX G2 experiment is the only microwave cavity experiment to reach DFSZ sensitivities. The speed at which we can exclude axion mass parameter space depends on how well the experiment can amplify the microwave axion signal above the background electrical noise. Optimizing noise performance in the cold electronics is crucial for achieving high signal to noise ratio, since they are the first stage of amplification. As we move to frequencies above 1.5 GHz, higher cavity numbers (4 for ADMX run 2A and 18 for ADMX EFR) will necessitate an increase in complexity for the cold electronics system. We will discuss the design and characterization of the ADMX first stage, cold electronics used to achieve high scan speeds at DFSZ sensitivities, as well as how these electronic systems will evolve for multicavity experiments.