SlicedBREAD: Experimentally Measuring Axion Detection Efficiency of Dielectric Stacks in a BREAD-Like Testbed

The QCD axion is a proposed beyond-the-Standard-Model particle that could resolve the strong CP problem and constitute dark matter. Conventional haloscopes have achieved sensitivity to the QCD axion band, but remain limited by narrow-band tuning of the resonant cavity. The Broadband Reflection Experiment for Axion Detection (BREAD) utilizes novel parabolic reflector geometry to search for dark photon and axion dark matter across a broad gigahertz to terahertz frequency range. By incorporating layers of dielectric material, axion field-induced photon emission can be boosted by constructive interference between layers. In SlicedBREAD, we develop a dedicated W-band (75–110 GHz) testbed to evaluate dielectric stack power boost architectures for BREAD, aiming to increase axion detection efficiency beyond the standard reflector. This talk presents the progress towards designing a SlicedBREAD detector, focusing on the experimental apparatus, cryogenic integration, alignment, and microwave signal chain used to determine the power boost factor and axion detection efficiency. We also report preliminary W-band measurements of transmission and reflection versus frequency of various candidate dielectric stacks.