Cyclotron Radiation Emission Spectroscopy in resonant cavities for the Project 8 neutrino mass experiment

Project 8 is a next-generation experiment aiming to directly measure the neutrino mass using the tritium endpoint method with a targeted sensitivity of 40 meV. The completed phases I and II have established a new measuring technique, Cyclotron Radiation Emission Spectroscopy (CRES), as a precise measuring technique of the endpoint spectrum and extracted an upper limit on the neutrino mass from a small volume of tritium. The next development phase will demonstrate CRES on a large source volume, culminating in a pilot-scale CRES experiment with atomic tritium. A promising option is a mode-filtered, cylindrical resonant cavity in which cyclotron radiation from magnetically trapped beta electrons couples only to the lowest eigenmode(s), maximizing effective volume and minimizing signal complexity.

I will show recent progress in the experimental design, focusing on a small scale proof-of-concept cavity CRES apparatus (CCA) to demonstrate CRES in cavities at previously benchmarked CRES frequencies of ~26 GHz. In addition to 83m-Krypton transition line measurements, an electron gun will be validated as a new calibration tool for subsequent experimental setups.