Development and Evaluation of an Airborne Superconducting Quantum Interference Device-Based Magnetic Gradiometer Tensor System for Detection, Characterization and Mapping of Unexploded Ordnance

摘要

The objective of this project was to develop and demonstrate an airborne full-tensor magnetic gradiometer for detection and precision mapping of UXO. The system was based on a liquid nitrogen-cooled high-temperature Superconducting QUantum Interference Device (SQUID) developed in a project funded by the U.S. Department of Energy and the U.S. Navy's Explosive Ordnance Disposal Technology Division. This SQUID sensor was to be integrated with the airborne geophysical platform originally deployed by Oak Ridge National Laboratory (ORNL) and now by Battelle. This project included the design and testing of the SQUID sensor and characterization of the noise signatures in flight. Processing and analysis tools for the tensor data were developed to reduce or remove the noise signatures and to maximize the detection thresholds at large sensor-target offsets. The high-temperature SQUID proved successful in stationary operation, for which it was originally designed. On a moving platform, numerous technical problems with the instrument arose, some of which could not be resolved or even explained. Continuous review of ongoing research in the field indicates that a low-temperature (liquid helium) intrinsic gradiometer system would be better suited to a moving platform despite the added complexity of a pressurized cryogenic vessel. Such a system is already in operation in a towed-bird helicopter, and stinger-mounted fixed-wing configuration. Its use as an electromagnetic receiver may also produce some benefit by virtue of operating in the system's lowest noise bandwidth.