DEVELOPMENT OF A PULSED MHD SOURCE FOR ELECTROMAGNETIC SOUNDING

INFORMATION OBTAINED FROM THE MEASUREMENT OF THE ELECTRICAL CONDUCTIVITY OF THE EARTH'S CRUST IS OF GREAT VALUE IN THE EXPLORATION FOR AND THE DELINEATION OF RESOURCES. THIS INFORMATION CAN ALSO SIGNIFICANTLY ENHANCE UNDERSTANDING OF THE EVOLUTION OF THE CRUST, ITS CURRENT COMPOSITION AND STRUCTURE, AND THE FORCES WITHIN IT. THE PREFERRED METHOD OF ELECTROMAGNETIC SOUNDING (EMS) IS TO INDUCE AN ELECTRIC CURRENT AT THE SURFACE AND MEASURE INDUCED MAGNETIC FIELDS AS THIS PULSE DIFFUSES AND DECAYS INTO THE CRUST. TO MAKE USE OF THE FULL CAPABILITIES OF AN EMS SYSTEM, A PORTABLE, HIGH POWER PULSE SOURCE AND A DETECTION SYSTEM WITH A HIGH SIGNAL-TO-NOISE DETECTION CAPABILITY ARE REQUIRED. CURRENTSWITH PEAK AMPLITUDES IN THE RANGE OF 10 KA AND ABOVE WITH DURATIONS OF A FEW SECONDS ARE REQUIRED. USUALLY, AN INDEPENDENT SOURCE MUST BE PROVIDED AT EMS SITES BECAUSE THEY LACK ELECTRIC UTILITY GRID CAPABILITY. THE MAGNETOHYDRODYNAMIC (MHD) GENERATOR IS IDEALLY SUITED FOR THIS KIND OF DUTY. COMBINED WITH AN EMS SYSTEM, THE MHD GENERATOR CAN GREATLY INCREASE THE DIPOLE MOMENT OBTAINABLE AND YIELD SUBSTANTIAL IMPROVEMENTS IN PERFORMANCE. PHASE I OF THIS PROJECT INVOLVES A SYSTEM STUDY TO OPTIMIZE AN EMS SYSTEM USING AN APPROPRIATELY MODIFIED EXISTING PULSED MHD GENERATOR, A DEFINITION OF THE INSTRUMENTATION AND DATA HANDLING SUBSYSTEM REQUIRED, AND THE SELECTION OF A FIELD TEST PROGRAM FOR A PHASE II PROTOTYPE SYSTEM DEMONSTRATION. THE OVERALL EMS-MHD SYSTEM PERFORMANCE WILL BE ESTABLISHED, THE ECONOMICS OF THE METHOD WILL BE ASSESSED AND THE STEPS TO BE TAKEN TO ENSURE THAT IT MEETS APPLICABLE ENVIRONMENTALREGULATIONS WILL BE IDENTIFIED.