ADMX Extended Frequency Range (EFR): Searching for 2-4GHz axions with 18 cavities

ADMX (Axion Dark Matter eXperiment) is the world-leading search for QCD axion dark matter in the μeV mass range. ADMX detects axions via their conversion to photons under a strong magnetic field in a high-Q resonant cavity. ADMX-EFR is designed to use an array of 18 cavities and coherent power combining to cover a range from 2-4GHz (8-16μeV axion mass) with DFSZ benchmark sensitivity in a 3 year operation using a designated 9.4T MRI magnet at Fermilab. In this talk we outline the conceptual design of EFR based on experience and R&D from previous ADMX runs and present a detailed sensitivity estimate for EFR.