Design and Characterization of a 26GHz Cavity for Phase III of the Project 8 Experiment

Project 8 aims to probe the absolute neutrino mass scale down to 40meV through measurement of the atomic tritium beta-decay spectrum endpoint, via cyclotron radiation emission spectroscopy(CRES). In CRES, the cyclotron frequency of an electron induced by an external magnetic field is inversely related to its kinetic energy, thereby allowing reconstruction of the beta-decay spectrum through measurement of the cyclotron frequency. The collaboration is developing CRES in a phased approach, where Phase I demonstrated measurement of cyclotron radiation from single electrons and Phase II provided the first neutrino mass limit from tritium using CRES. The next step before the final measurement culminates in Phase IV is demonstrating high-exposure/large-volume CRES to surpass statistics limitations seen in Phase II. While the first two phases utilized a waveguide to measure the cyclotron radiation, extensive R&D indicates that a microwave resonant cavity is best suited for scaling up CRES. This talk will cover important considerations underlying measurement of cyclotron radiation using a cavity, and both design and characterization of a 26GHz copper cavity that will be used in a proof-of-concept experiment, the Cavity CRES Apparatus(CCA), in Phase III of the Project 8 experiment.