Synthetic Electron Source for Calibrating the Project 8 Neutrino Mass Experiment*

Project 8 is a next-generation neutrino mass experiment that uses Cyclotron Radiation Emission Spectroscopy (CRES) to measure the neutrino mass. CRES is a novel technique for β-decay spectroscopy that measures the frequency of the cyclotron radiation produced by energetic electrons trapped in a magnetic field. The cyclotron frequency can be directly converted into the energy spectrum, which yields the neutrino mass through measurement of the spectrum endpoint. The next phase of Project 8 seeks to measure the energy spectrum of molecular tritium β-decay in an O(10 cm³) free space volume, using a multi-channel phased antenna array. I present progress on the design and fabrication of a probe antenna that mimics the electromagnetic radiation produced by an electron in a magnetic trap. The synthetic electron/CRES source will enable benchtop experiments to test the phased array reconstruction techniques necessary for performing CRES in a large volume experiment. I give an overview of the synthetic CRES antenna design and development, and show initial measurements of the gain pattern from the first prototypes. Additionally, I will outline future applications of the synthetic CRES antenna for phased array reconstruction algorithm development as well as sketch out a calibration scheme for the Project 8 phased antenna array.

This work is supported by the US DOE Office of Nuclear Physics, the US NSF, the PRISMA+ Cluster of Excellence at the University of Mainz, and internal investments at all institutions.