Axial high-temperature RF SQUID gradiometer system for geomagnetic prospecting

In order to implement the geomagnetic prospecting in unshielded environment, an axial high-temperature radio frequency superconducting quantum interference device (RF SQUID) gradiometer system operating in liquid nitrogen at 77K is proposed in the paper. The gradiometer consists of two RF SQUID magnetometers, each with sensitivity better than 30 fT/Hz^1/2. The gradiometer baseline is adjustable from 6 cm to 10 cm. The SQUID electronics we designed is automated and the working points are adjusted by the integrated microcontroller. The system maintains continuously two RF SQUID magnetometers in the flux-locking condition. According to a long-term experiment, it is indicated that the gradiometer system developed by us demonstrated a good performance in the application of geomagnetic prospecting.