Demonstration of sensitivity increase in mercury free-spin-precession magnetometers due to laser-based readout for neutron electric dipole moment searches

TL;DR

This paper demonstrates that laser-based $^{199}$Hg co-magnetometers significantly enhance signal-to-noise ratio and sensitivity in neutron electric dipole moment experiments compared to traditional lamp-based systems.

Contribution

It introduces a laser-based $^{199}$Hg co-magnetometer with over five times improved signal-to-noise ratio and an improved data model for better system parameter extraction.

Findings

Over five times increased signal-to-noise ratio with laser-based magnetometer

Consistent data description using the new model for both laser and lamp sources

Meets sensitivity requirements for next-generation neutron EDM experiments

Abstract

We report on a laser based $^{199}$Hg co-magnetometer deployed in an experiment searching for a permanent electric dipole moment of the neutron. We demonstrate a more than five times increased signal to-noise-ratio in a direct comparison measurement with its $^{204}$Hg discharge bulb-based predecessor. An improved data model for the extraction of important system parameters such as the degrees of absorption and polarization is derived. Laser- and lamp-based data-sets can be consistently described by the improved model which permits to compare measurements using the two different light sources and to explain the increase in magnetometer performance. The laser-based magnetometer satisfies the magnetic field sensitivity requirements for the next generation nEDM experiments.