Diamond quantum sensors for non-destructive testing

The nitrogen-vacancy (NV) centre in diamond has emerged in the past two decades as a unique multi-modal sensor, combining the excellent sensitivity and accuracy of quantum sensors in a solid diamond, small and easy-to-integrate while offering extremely high spatial resolution. NV centres in diamond are especially good magnetometers, providing an absolute vectorial measurement of the magnetic field. Founded in 2023, KWAN-TEK is a start-up company pioneering in the development of NV-based sensors for industrial applications. In the context of non-destructive evaluation (NDE), several techniques rely on the magnetic field for controlling the state of a metal, either with static measurement (magnetoscopy, magnetic flux leakage) or with dynamic measurements (Eddy current testing, Barkhausen noise, incremental permeability). All these techniques have specific limitations linked to the sensors used for the implementation and could benefit from the use of absolute sensors with high resolution and sensitivity like NV sensors. Additionally, in the context of NDE in the nuclear industry, the small size of the fibered NV sensors and the robustness of diamonds could be key to deploying NDE in constraint spaces or in harsh environments. In this paper, we recall the underlying principle of NV physics before presenting the experimental work carried out at KWAN-TEK. We will illustrate the advantages of the technique for NDE and recent implementation of eddy current sensing is discussed.