Magnetic induction sensor based on a dual-frequency atomic magnetometer

We propose and demonstrate a combined static- and oscillating-field alkali atom magnetometer and use it as a magnetic induction tomography sensor. The magnetometer realizes simultaneous measurements of the static and oscillating magnetic fields using two different Zeeman transitions of a single sensor. This approach dramatically enhances the long-term stability and sensitivity of detection of low-conductivity objects. Using our dual-frequency magnetometer, we detect small containers with salt water with conductivity as low as 0.55 S/m. We achieved a conductivity measurement uncertainty of 0.18 S/m with a 10-s integration time. This performance is sufficient to distinguish between healthy and malignant tissue in the human body. The dual-frequency magnetometer can also be used as a self-stabilized radio-frequency magnetometer.