Study Of Cavity Geometries for The Project 8 Neutrino Mass Experiment

Project 8 is an experiment being developed that aims to measure the effective absolute electron (anti-)neutrino mass, which would have implications on particle physics and cosmology. Project 8 uses a method called CRES, cyclotron radiation emission spectroscopy, where electrons emitted with neutrinos in tritium beta decay are put into a cyclotron motion induced by a magnetic field inside a cavity. The frequency of the coherent radiation emitted from these electrons is then used to calculate their energy, which can then be used to reconstruct the rest mass of the electron anti-neutrino in the emission through conservation of energy. In this project, we studied different geometries of a prototype layered cavity to maximize the cavity volume to reduce tritium gas density while keeping the TE₀₁₁ mode. We used HFSS to design models with different geometries and analyzed their resonant frequencies. We compared simulation data with VNA measurements of a prototype cavity to see how well the model matched our results. We also fitted the resonances in the data and found the Q-factor of each geometry. We repeated this process using a new, copper coupling piece, and found that it matched the model much better. Additionally, an etalon cavity model utilizing crossed confocal resonators is proposed to increase the volume covered by antinodes.