We present a novel four-channel OPM sensor for magnetoencephalography that utilizes a two-color pump/probe scheme on a single optical axis. We characterize its performance across 18 built sensor modules. The new sensor implements several improvements over our previously developed sensor including lower vapor-cell operating temperature, improved probe-light detection optics, and reduced optical power requirements. The sensor also has new electromagnetic field coils on the sensor head which are designed using stream-function-based current optimization. We detail the coil design methodology and present experimental characterization of the coil performance. The magnetic sensitivity of the sensor is on average 12.3 fT/rt-Hz across the 18 modules while the average gradiometrically inferred sensitivity is about 6.0 fT/rt-Hz. The sensor 3-dB bandwidth is 100 Hz on average. The on-sensor coil performance is in good agreement with the simulations.
@article{arxiv.2312.14623,
title = {A Four-channel Optically Pumped Magnetometer for a Magnetoencephalography Sensor Array},
author = {Joonas Iivanainen and Tony R. Carter and Jonathan E. Dhombridge and Timothy S. Read and Kaleb Campbell and Quinn Abate and David M. Ridley and Amir Borna and Peter D. D. Schwindt},
journal= {arXiv preprint arXiv:2312.14623},
year = {2023}
}