The Effects of Dielectrics on Axion Searches using Resonant Cavities*

The existence of an axion may be the key to solving the strong CP problem and understanding dark matter. Therefore, searching for axions is of great interest to the physics community. Many axion searches use the haloscope technique, which is typically performed with a resonant microwave cavity immersed in a strong magnetic field. In such cavities, dielectric materials are sometimes used to tune the resonant frequency of these cavities or to reduce the power losses along the wall. However, this can have adverse effects on the sensitivity to an axion. Understanding the consequences of inserting dielectrics requires careful study and in this talk I will present our findings regarding the effect of dielectrics on axion signal power and scan rate. Our results suggest that for searches using the lowest TM mode, the amount of dielectric material in a resonant cavity should be minimized wherever possible.