Eddy current imaging with an atomic radio-frequency magnetometer

TL;DR

This paper demonstrates a highly sensitive atomic magnetometer-based eddy current imaging technique capable of resolving sub-millimeter features and discriminating materials by conductivity at frequencies up to 250 kHz.

Contribution

It introduces a novel application of an alkali-vapor cell magnetometer for high-resolution conductivity mapping and material discrimination in eddy current imaging.

Findings

Resolved sub-mm features in conductive objects

Characterized frequency response up to 250 kHz

Discriminated materials based on conductivity response

Abstract

We use a radio-frequency $^{85}$Rb alkali-vapor cell magnetometer based on a paraffin-coated cell with long spin-coherence time and a small, low-inductance driving coil to create highly resolved conductivity maps of different objects. We resolve sub-mm features in conductive objects, we characterize the frequency response of our technique, and by operating at frequencies up to 250 kHz we are able to discriminate between differently conductive materials based on the induced response. The method is suited to cover a wide range of driving frequencies and can potentially be used for detecting non-metallic objects with low DC conductivity.