We demonstrate electromagnetic induction imaging with an unshielded, portable radio frequency atomic magnetometer scanning over the target object. This configuration satisfies standard requirements in typical applications, from security screening to medical imaging. The ability to scan the magnetometer over the object relies on the miniaturization of the sensor head, the active compensation of the ambient magnetic field, and the implementation of a dedicated procedure to extract high-quality images from the recorded spatial dependent magnetic resonance. The procedure is shown to be effective in suppressing the detrimental effects of the spatial variation of the magnetic environment.

We demonstrate through-skin electromagnetic induction imaging of pilot-holes in an aluminum block concealed by a 0.41 mm thick aluminum shield with a 1.49 kg mechanically translatable radio frequency atomic magnetometer. The pilot-holes are identified and localized with submillimeter accuracy both with and without the Al shield. We utilize a dual-frequency technique to isolate the image of the target while removing the effect of the shielding from the image. Imaging accuracy is shown to be robust in a range of different operating conditions and immune to the effect of a thermal insulator between the shielding and the target. The approach introduced here finds direct application in aircraft wing manufacture and is competitive with existing approaches.

This work addresses the issue of imaging of corrosion under insulation in pipelines. We demonstrate imaging of recesses of variable depth in an aluminium plate covered by insulation, using a mechanical-translatable atomic magnetometer. This work validates the technology in settings close to real-world scenarios. The technology is of direct impact to the Oil & Gas Industry.

Real-world applications of atomic magnetometers require the ability to operate them with high-sensitivity in the presence of magnetic noise. In the present work, high-sensitivity operation of unshielded atomic magnetometers in a magnetically noisy environment is demonstrated. The distinguishing feature of the demonstrated approach is the implementation of active in-situ bias field stabilization using multiple fluxgate magnetometers. This is combined with the use of a counter-propagating pump and triple-pass probe configuration, to maximize the atomic polarization and the probe rotation respectively, so to reach high-sensitivity. The improvement in sensitivity of the unshielded system with respect to previous realizations is fully characterized, with the contributions of the different modifications of the apparatus individually quantified. The presented set-up is suitable for the detection of long-range magnetic fields, where shielding or differential measurements using multi-sensor set-ups do not constitute viable options.

High-sensitivity operation of a radio-frequency atomic magnetometer (RF-AM) requires careful setting of the system parameters, including the lasers intensity and detuning, and the vapour cell temperature. The identification of the optimal operating parameters, which ensures high sensitivity, is typically performed empirically and is often a lengthy process, which is especially labour intensive if frequent retuning of the magnetometer is required to perform different tasks. This paper demonstrates an efficient approach to RF-AM performance optimisation which relies on an open-loop optimisation technique based on Uniform Design (UD). This paper specifically describes the optimisation of an unshielded RF-AM based on a 4-factor-12-level UD of the experimental parameters space. The proposed procedure is shown to lead to the efficient optimisation of the atomic magnetometer at different frequencies, and is applicable to both AC and DC sensitivity optimisation. The procedure does not require any detailed knowledge of the model underlying the operation of the RF-AM and is effective in reducing the number of experimental runs required for the optimisation. It is ideally suited to self-calibration of devices without human supervision.