Underwater Operations of an Atomic Magnetometer for Magnetic Anomaly Detection

Since the early part of the twentieth century highly-sensitive magnetometers have become a critical tool for detecting underwater objects through magnetic anomaly detection (MAD). Optically-pumped atomic magnetometers (OPMs) are an ideal candidate for operating in an underwater environment due to their ability to provide an absolute, scalar measurement of the local magnetic field. The University of Adelaide has been developing an OPM, based on non-linear magneto-optical rotation (NMOR) of polarisation, which has achieved a sensitivity of order 100 fT/rtHz at Earth’s field at relevant target frequencies, representing 20-fold improvement over existing MAD sensors.

I will present our work developing a deployable NMOR magnetometer designed to enable novel approaches to MAD. I’ll discuss the design and lab-based performance of our compact magnetometer heads, as well as our latest efforts towards testing these heads in real-world environments. As demonstrations of the capability of our device we will show results detecting a kg-scale steel object using a pair of magnetometers, as well as magnetometers operating in a maritime environment detecting a surface craft passing up to 15 metres above the sensors, in partnership with Defence Science and Technology Group