Project 8: Single-Electron Spectroscopy via Relativistic Cyclotron Radiation

The Project 8 experiment seeks to determine the neutrino mass via the precise measurement of the electron energy in beta decays. We have developed a novel technique called Cyclotron Radiation Emission Spectroscopy (CRES), which allows single electron detection and characterization through the measurement of cyclotron radiation emitted by magnetically-trapped electrons produced by a gaseous radioactive source. The advantages of this technique include scalability, excellent energy resolution, and low backgrounds. A prototype using a waveguide-coupled $^{83\mathrm{m}}$Kr source in a $1~\mathrm{T}$ magnetic field was constructed, and used to demonstrate the viability of this technique. We have recently reported the first observation and measurement of single-electron cyclotron radiation, emitted by the internal conversion electrons (at $17.8~\mathrm{keV}$ and $30.4~\mathrm{keV}$) released in the decay of $^{83\mathrm{m}}$Kr. We present the latest results of the ongoing prototype run, with a focus on signal detection and analysis techniques leading to an improved energy resolution of $O(1~\mathrm{eV})$.