HIGH SENSITIVITY OPTICAL MAGNETOMETER

RESEARCHERS ARE DEVELOPING AN INNOVATIVE MAGNETIC FIELD SENSING TECHNIQUE THAT ACHIEVES VERY HIGH SENSITIVITY FOR EARTH SURVEYING APPLICATIONS, BUT UNLIKE ALL COMPETING SQUID TECHNOLOGIES, DOES NOT REQUIRE ANY COOLING. THE NEW MAGNETOMETER USES NEWLY DEVELOPED OPTICAL MATERIALS AND INTERFEROMETRIC PHASE MEASUREMENT TECHNIQUE. THE SYSTEM CONSISTS OF A SMALL SENSOR HEAD (2 INCH CUBE) CONTAINING ONLY PASSIVE, NON-CONDUCTIVE OPTICAL MATERIALS AND AN OPTICAL/ELECTRONIC PROCESSING UNIT CONNECTED TOGETHER VIA OPTICAL FIBER. THE SENSOR HEAD CAN BE IMPLEMENTED AS A FIRST OR SECOND ORDER GRADIENT SENSOR; HOWEVER, THE EXTRAORDINARY LINEARITY AND DYNAMIC RANGE OF THE TECHNIQUE ALLOWS HIGH RESOLUTION OPERATION WITHIN THE EARTH'S DC MAGNETIC FIELD (FIELD BIASING IS NOT REQUIRED). THE OPERATING PRINCIPLE IS THE ACCURATE MEASUREMENT OF THE FARADAY ROTATION OF AN OPTICAL BEAM IN AN ADVANCED, HIGH VERDET COEFFICIENT, OPTICAL CRYSTAL. RESEARCHERS HAVE DEMONSTRATED THE MEASUREMENT CONCEPT WITH A 10 MM LONG BY 1.5 MM DIAMETER TRANSDUCER ELEMENT AND ACHIEVED 0.5 NT/HZ MINIMUM DETECTABLE FIELD. FURTHER DEVELOPMENT DURING THE PROGRAM WILL DEVELOP A THREE AXIS SENSOR AND IMPROVE THE PERFORMANCE TO THE 10(-14) T/ HZ RANGE, COMPARABLE TO SQUID SENSORS. THE SENSOR BANDWIDTH IS FROM DC TO 50 KHZ OR MORE.