Photonic Band Gap resonators for HAYSTAC

Axion haloscopes are detectors used to search for dark matter axions via their conversion to photons. Haloscopes rely in part on the use of tunable electromagnetic resonators to enhance the converted photon signal. Existing haloscopes use traditional microwave cavities that support many fundamental eigenmodes. However, only a limited subset of the cavity modes can be used for data collection. Mode mixing and crowding limit the available tuning range in current cavities and pose challenges for accessing new regions of parameter space. Photonic Band Gap (PBG)-based resonators allow for the confinement of the modes of interest while eliminating unwanted modes. By eliminating mode crossings, PBG resonators can provide larger uninterrupted tuning ranges and avoid mode crowding at higher frequencies. In this talk, we present updates on the ongoing development of tunable PBG resonators for HAYSTAC and results from testing a first prototype design.