Mobile magnetic anomaly detection using a field-compensated high-T-c single layer SQUID gradiometer

High-Tc single layer SQUID gradiometers are useful for measuring small localized magnetic fields in the presence of much larger background interference. Such sensors have been used extensively for eddy-current non-destructive evaluation and biomagnetic measurements, where the sensor is stationary or scanned in a straight line. However for magnetic anomaly detection (MAD) and geophysical exploration it is necessary that gradiometers can undergo rotation and vibration in the Earth's magnetic field without degrading their sensitivity. We describe a portable system that uses background field cancellation techniques to allow a gradiometer's orientation to change during magnetic mapping applications without compromising its sensitivity. We describe the system setup and demonstrate its capability to detect a magnetic target whilst undergoing random motion in a laboratory environment.