A SUPERCONDUCTING MAGNETOMETER/GRADIOMETER FOR ADVANCED GEOPHYSICAL IMAGING

THERE HAS RECENTLY BEEN INCREASED INTEREST IN THE USE OF ACTIVE ELECROMAGNETIC MEASUREMENTS TO PROVIDE IMPROVED IMAGING OF SUBSURFACE STRUCTURES, PARTICULARLY FOR ENHANCED OIL RECOVERY AND ENVIRONMENTAL ISSUES SUCH AS GROUND WATER CONTAMINATION, UNDERGROUND PETROLEUM LEAKS, AND REMEDIATION OF HAZARDOUS WASTE SITES. BOREHOLE-TO-BOREHOLE AND SURFACE-TO-BOREHOLE MEASUREMENTS ARE OF PARTICULAR INTEREST SINCE THEY PROVIDE BETTER INFORMATION ABOUT THE SUBSURFACE STRUCTURE THAN A SURFACE-TO-SURFACE MEASUREMENT. ALTHOUGH INDUCTION COILS ARE AVAILABLE FOR USE IN BOREHOLES, IT IS DIFFICULT TO GET GOOD SENSITIVITY TO HORIZONTAL FIELDS. THESE COILS ARE EXPENSIVE AND/OR PHYSICALLY LARGE WHICH TENDS TO LIMIT THEIR WIDESPREAD USE. RECENT ADVANCES IN THE PERFORMANCE OF SUPERCONDUCTING QUANTUM INTERFERENCE DEVICE (SQUID) SENSORS MADE FROM THE NEW HIGH-TEMPERATURE SUPERCONDUCTORS HAVE BEEN SIGNIFICANT. IT IS NOW POSSIBLE TO USE THESE SENSORS TO BUILD COMPACT, LOW-NOISE, MULTI-ELEMENT MAGNETOMETER ARRAYS. PHASE I WILL DEVELOP A SIMPLE PROTOTYPE MAGNETOMETER SYSTEM INCORPORATING ONE OR MORE HIGH-TEMPERATURE SQUID SENSORS. THIS MAGNETOMETER WILL BE INTERFACED TO A RUGGEDIZED DATA ACQUISTION SYSTEM AND ITS PERFORMANCE AND NOISE LEVEL MEASURED IN A VARIETY OF OPERATING CONDITIONS.