Progress towards a Hybrid Superconducting Microwave Cavity for ADMX

Dark-matter axions can be detected by their resonant conversion into photons using microwave resonant cavities in an axial magnetic field. This is the basis of both the ADMX and ADMX-HF experiments currently under construction. The axion-photon conversion power is directly related to the quality factor (Q) of the microwave cavity used. To date copper cavities have been used with Q $\sim 10^5$ at frequencies of 1 GHz. However, superconducting cavities can regularly be made with Q $> 10^9$. Here we describe progress of R\&D efforts to make hybrid cavities with a superconducting barrel and normal copper end-caps that can maintain their superconducting properties and an enhanced Q in a magnetic field.