Future Directions in the Microwave Cavity Search for Dark Matter Axions

TL;DR

This paper reviews the current and future prospects of microwave cavity experiments for detecting axion dark matter, emphasizing technological advances needed for higher frequency searches and describing the ADMX-HF project as a key development platform.

Contribution

It outlines the technological challenges and proposed solutions for expanding axion searches across a broad mass range, including the development of advanced microwave detection techniques.

Findings

Current experiments are sensitive to plausible axion models.

Upgrades aim to achieve definitive low-mass axion detection.

ADMX-HF serves as a test-bed for high-frequency axion search technologies.

Abstract

The axion is a light pseudoscalar particle which suppresses CP-violating effects in strong interactions and also happens to be an excellent dark matter candidate. Axions constituting the dark matter halo of our galaxy may be detected by their resonant conversion to photons in a microwave cavity permeated by a magnetic field. The current generation of the microwave cavity experiment has demonstrated sensitivity to plausible axion models, and upgrades in progress should achieve the sensitivity required for a definitive search, at least for low mass axions. However, a comprehensive strategy for scanning the entire mass range, from 1-1000 $\mu$eV, will require significant technological advances to maintain the needed sensitivity at higher frequencies. Such advances could include sub-quantum-limited amplifiers based on squeezed vacuum states, bolometers, and/or superconducting microwave cavities. The Axion Dark Matter eXperiment at High Frequencies (ADMX-HF) represents both a pathfinder for first data in the 20-100 $\mu$eV range ($\sim$5-25 GHz), and an innovation test-bed for these concepts.