Scintillation-type well logging device with two crystals responding separately to thermal neutrons and gamma rays

Claim 1

APPARATUS FOR LOGGING AN EARTH FORMATION TRAVERSED BY A BORE HOLE COMPRISING A CONTAINER ADAPTED TO BE PASSED THROUGH SAID BORE HOLE, A SOURCE OF NEUTRONS LOCATED IN SAID CONTAINER, A FIRST LUMINOPHOR RESPONSIVE TO THERMAL NEUTRONS AND A SECOND LUMINOPHOR RESPONSIVE TO GAMMA RADIATION LOCATED WITHIN SAID CONTAINER A PREDETERMINED DISTANCE FROM SAID SOURCE, MEANS FOR EQUALIZING THE LIGHT INTENSITY OF SCINTILLATIONS PRODUCED IN SAID FIRST AND SECOND LUMINOPHORS BY SECONDARY ELECTRONS OF LIKE ENERGIES, PHOTOSENSITIVE MEANS OPTICALLY COUPLED TO SAID FIRST AND SECOND LUMINOPHORS FOR DETECTING AND CONVERTING SAID SCINTILLATIONS INTO ELECTRICAL PULSES, ELECTRICAL MEANS FOR AMPLIFYING SAID ELECTRICAL PULSES, DISCRIMINATOR MEANS FOR ADJUSTING SAID ELECTRICAL MEANS TO REJECT PULSES PRODUCED BY THE DETECTION OF NUCLEAR RADIATIONS IN SAID FIRST AND SECOND LUMINOPHORS HAVING AMPLITUDES LESS THAN A PREDETERMINED VALUE, AND MEANS FOR RECORDING THE OUTPUT OF SAID ELECTRICAL MEANS AS A FUNCTION OF THE POSITION OF SAID CONTAINER IN SAID BORE HOLE.