AN ADVANCED PULSED NEUTRON LOGGING TOOL

PULSED NEUTRON LOGGING INSTRUMENTS ARE ROUTINELY USED TO MEASURE POROSITY AND FORMATION COMPOSITION IN BOREHOLES. HOWEVER, THE AVERAGE 14 MEV NEUTRON FLUX OF ABOUT 10(8) N/SEC AVAILABLE WITH EXISTING TOOLS LIMITS THEIR CAPABILITIES. A NEW TYPE OF NEUTRON SOURCE IS PLANNED THAT IS EXPECTED TO PROVIDE AVERAGE FLUXES OF >10(9) N/SEC AT 14 MEV AND >10(7) N/SEC AT 2.45 MEV. THIS SOURCE INCLUDES AN ADVANCED ION GENERATOR, WHICH IS EXPECTED TO OFFER A VERY HIGH FRACTIONAL OUTPUT (>90%) OF ATOMIC IONS CRITICAL FOR ACHIEVING HIGH NEUTRON FLUXES, AND A DISTRIBUTED ION EXTRACTION GEOMETRY. THE LATTER IS IMPORTANT FOR MINIMIZINGTARGET HEATING AND SPUTTERING AND THEREBY INCREASING SOURCE LIFETIME. IF SUCCESSFULLY DEVELOPED, THIS NEUTRON SOURCE WILL PROVIDE SUBSTANTIAL BENEFITS INCLUDING: (1) HIGHER LOGGING SPEEDS, (2) REDUCED BOREHOLE EFFECTS, (3) INCREASED COUNT RATES, (4) INCREASED STATISTICAL ACCURACY, AND (5) GREATER DEPTHS OF INVESTIGATION. THE PHASE I OBJECTIVE IS TO DEMONSTRATE THE BASIC TECHNICAL FEASIBILITY OF THE SOURCE CONCEPT. THIS OBJECTIVE IS BEING ACCOMPLISHED BY PERFORMING THE FOLLOWING TASKS: (1) DESIGNING AND ASSEMBLINGA THIN-WIRE ION SOURCE EXPERIMENT, (2) PERFORMING MEASUREMENTS OF THE SOURCE CHARACTERISTICS AND DETERMINING THE FRACTIONAL YIELD OF ATOMIC IONS, AND (3) DEVELOPING THE CONCEPTUAL DESIGN FOR A THIN-WIRE NEUTRON SOURCE (TWNS) LOGGING SYSTEM. SUCCESS IN PHASE I WILL PROVIDE A FIRM FOUNDATION FOR DEVELOPMENT OF A LABORATORY PROTOTYPE TWNS LOGGING TOOL IN PHASE II.