Method and apparatus for detecting neutrons in the presence of other radiation

Claim 1

A SYSTEM FOR MAKING A RADIOACTIVITY LOG OF A WELL THAT COMPRISES A SUBSURFACE INSTRUMENT ADAPTED TO BE LOWERED AND RAISED IN A WELL, SAID SUBSURFACE INSTRUMENT COMPRISING A SOURCE OF NEUTRONS, A PLURALITY OF INDEPENDENT SCINTILLATION MEDIA ELECTROSTATICALLY AND OPTICALLY SHIELDED FROM ONE ANOTHER, A NEUTRON-CAPTURING MATERIAL DISPOSED ABOUT SAID PLURALITY OF INDEPENDENT SCINTILLATION MEDIA WHEREBY SEPATATE PRODUCT OF THE REACTIONS RESULTING FROM NEUTRON CAPTURE PRODUCE SCINTILLATIONS IN SEPARATE SCINTILLATION MEDIAL, SEPARATE PHOTOMULTIPLIERS FOR EACH OF SAID MEDIA FOR PRODUCING PROPORTIONALLY RELATED ELECTRICAL PULSES WHEN EXPOSED TO SCINTILLATIONS IN SAID MEDIA, SEPARATE AMPLIFIERS CONNECTED TO EACH PHOTOMULTIPLIER, SEPARATE DISCRIMINATORS CONNECTED TO EACH AMPLIFIER FOR ELIMINATING DARK CURRENT PULSES PRODUCED IN THE RESPECTIVE PHOTOMULTIPLIERS, MEAN FOR SHAPING EACH SERIES OF AMPLIFIED PULSES TO MAKE ALL PULSES THE SAME SIZE AND SHAPE, AND MEANS FOR COMBINING ALL SERIES OF SHAPED PULSES; MEANS FOR TRAVERSING THE WELL WITH SAID SUBSURFACE INSTRUMENT; MEANS FOR TRNASMITTING PULSES, SAID MEANS COMPRISING MEANS FOR EARTH; AND MEANS AT THE SURFACE OF THE EARTH FOR RECEIVING SAID TRANSMITTED PULSES, SAID MEANS COMPRISING MEANS FOR SUPPRESSING FROM THE COMBINED PULSES THOSE PULSES LESS THAN DOUBLE HEIGHT WHEREBY THE REMAINING PULSES ARE INDICATIVE OF SIMULTANEOUS DETECTION BY AT LEAST TWO OF SAID PLURALITY OF INDEPENDENT SCINTILLATION MEDIA, MEANS FOR DERIVING A DIRECT-CURRENT SIGNAL PROPORTIAONALLY RELATED TO THE RATE OF OCCURRENCE OF SAID PULSES OF AT LEAST DOUBLE HEIGHT, AND MEANS FOR RECORDING SAID DIRECT-CURRENT SIGNAL IN CORRELATION WITH THE DEPTH IN THE WELL AT WHICH DETECTION OCCURRED.