Integrated optically pumped magnetometer for measurements within Earth's magnetic field

TL;DR

This paper introduces a portable, ultra-sensitive optically pumped magnetometer designed for measurements within Earth's magnetic field, demonstrating high sensitivity, bandwidth, and potential for practical geomagnetic applications.

Contribution

The paper presents a novel portable magnetometer using a MEMS-based Cs vapor cell with detailed design, noise analysis, and performance comparison to commercial SQUID systems.

Findings

Sensor noise level down to 140 fT/√Hz

Bandwidth of several 100 Hz

Performance comparable to SQUID systems

Abstract

We present a portable optically pumped magnetometer instrument for ultra-sensitive measurements within the Earth's magnetic field. The central part of the system is a sensor head operating a MEMS-based Cs vapor cell in the light-shift dispersed Mz mode. It is connected to a compact, battery-driven electronics module by a flexible cable. We briefly review the working principles of the device and detail on the realization of both, sensor head and electronics. We show shielded and unshielded measurements within a static magnetic field amplitude of 50 uT demonstrating a noise level of the sensor system down to 140 fT/\sqrt{Hz} and a sensor bandwidth of several 100 Hz. In a detailed analysis of sensor noise we reveal the system to be limited by technical sources with straightforward strategies for further improvement towards its fundamental noise limit of 12 fT/\sqrt{Hz}. We assess the parameters defining the sensor bandwidth by theoretical modeling based on the Bloch equations. Finally, we compare our sensors' performance to a commercial SQUID system in a measurement environment typical for geomagnetic observatory practice and geomagnetic prospection.