Advances in sensor development and demonstration of superconducting gradiometers for mobile operation

During the 1980s a SQUID-based superconducting gradiometer prototype utilizing bulk niobium and wire superconducting components cooled by liquid helium was developed by the US Navy. This sensor was successfully utilized in demonstrations for sea mine countermeasures and for the detection of UneXploded Ordnance (UXO). Advances in this sensor technology are being pursued for longer detection ranges and for more versatile operation. An advanced sensor prototype using all thin film niobium circuits and a new liquid helium cooling concept has been built to provide significant increases in sensitivity. In addition, a high Tc sensor concept using liquid nitrogen refrigeration has been developed to reduce package size and to simplify logistic and support requirements for field operation. This paper will review the current status and plans of this program, specifically describing the recent advances in sensor development and results from the demonstration to detect UXO.