Portable Single-Beam Atomic Total-Field Magnetometer for Stand-off Magnetic Sensing

TL;DR

This paper presents a portable, single-beam atomic magnetometer capable of detecting magnetic anomalies at stand-off distances in unshielded environments, suitable for field applications.

Contribution

The development of a compact, all-optical scalar atomic magnetometer with high sensitivity and operational range in unshielded environments is introduced as a novel portable sensing solution.

Findings

Achieved a noise floor below 6 pT/√Hz near 80 Hz.

Demonstrated detection of transient magnetic signatures from elevator motion.

Operated effectively at distances up to 10 meters in unshielded environments.

Abstract

Optically pumped atomic magnetometers (OPAMs) offer high sensitivity at room temperature and are increasingly considered for portable magnetic sensing in geomagnetic-field environments. Here we report a handheld-scale, single-beam scalar $^{87}$Rb OPAM with a sensor-head volume of approximately 110 mL. The device operates in an all-optical Bell-Bloom configuration and uses digital lock-in, dispersive tracking of the $^{87}$Rb Larmor resonance, implemented with a hybrid electronics stack that combines in-house control hardware with commercial modules. A single frequency-modulated laser beam performs both pumping and probing without RF coils. In an unshielded indoor environment, the magnetometer exhibits a noise floor below 6 pT/$\sqrt{\mathrm{Hz}}$ near 80 Hz and a measurement bandwidth of 200 Hz. In an unshielded Earth-field deployment, we detect repeatable transient magnetic signatures from a controlled elevator motion sequence and quantify standoff observability over sensor-elevator distances from 1.25 m to 10 m. These results show that compact scalar OPAMs can provide bandwidth and range-resolved event sensitivity suitable for field-deployable magnetic anomaly detection and infrastructure monitoring in realistic geomagnetic environments.