Symmetry Breaking in Haloscope Microwave Cavities

Abstract

Axion haloscope detectors use microwave cavities permeated by a magnetic field to resonate photons that are converted from axions due to the inverse Primakoff effect. The sensitivity of a detector is proportional to the form factor of the cavity's search mode. Transverse symmetry breaking is used to tune the search modes for scanning across a range of axion masses. However, numerical analysis shows transverse and longitudinal symmetry breaking reduce the sensitivity of the search mode. Simulations also show longitudinal symmetry breaking leads to other undesired consequences like mode mixing and mode crowding. The results complicate axion dark matter searches and further reduce the search capabilities of detectors. The findings of a numerical analysis of symmetry breaking in haloscope microwave cavities are presented.