Radiation borehole logging

Claim 1

APPARATUS FOR LOGGING AN EARTH FORMATION TRAVERSED BY A BOREHOLE COMPRISING A PAIR OF VERTICALLY SPACED NEUTRON SOURCES, ONE OF SAID SOURCES PRODUCING NEUTRONS HAVING SUFFICIENT ENERGY TO CAUSE DISINTEGRATION OF 8O16 NUCLEI AND THE OTHER OF SAID SOURCES PRODUCING NO NEUTRONS HAVING SUFFICIENT ENERGY TO CAUSE DISINTEGRATION OF 8O16 NUCLEI, MEANS FOR VERTICALLY MOVING THE NEUTRON SOURCES ALONG A BOREHOLE, MEANS INCLUDING A FIRST DETECTOR FOR CONTINUOUSLY PRODUCING A FIRST ELECTRICAL SIGNAL HAVING A MAGNITUDE THAT IS A FUNCTION OF THE RATE AT WHICH A SELECTED CLASS OF PENETRATING RADIATION ENTERS THE BOREHOLE ADJACENT ONE NEUTRON SOURCE, MEANS INCLUDING A SECOND DETECTOR SAPCED FROM SAID FIRST DETECTOR AND HAVING SUBSTANTIALLY THE SAME CHARACTERISTICS AS SAID FIRST DETECTOR FOR CONTINUALLY PRODUCING A SECOND ELECTRICAL SIGNAL HAVING A MAGNITUDE THAT IS A FUNCTION OF THE RATE AT WHICH SAID SELECTED CLASS OF PENETRATING RADIATION ENTERS THE BOREHOLE ADJACENT THE OTHER NEUTRON SOURCE, MEANS FOR PRODUCING A THIRD ELECTRICAL SIGNAL HAVING A MAGNITUDE THAT IS PROPORTIONAL TO THE MAGNITUDE OF THE FIRST SIGNAL AT A TIME DISPLACEMENT THAT SUBSTANTIALLY EQUALS THE TIME REQUIRED FOR ONE NEUTRON SOURCE TO TRAVEL THE VERTICAL DISTANCE BETWEEN THE NEUTRON SOURCES, AND MEANS FOR PRODUCING AN OUTPUT ELECTRICAL SIGNAL HAVING A MAGNITUDE THAT IS A FUNCTION OF THE MAGNITUDE OF THE SECOND SIGNAL AND THE THIRD SIGNAL, AND MEANS FOR RECORDING THE OUTPUT SIGNAL VERSUS THE DEPTH OF SAID ONE NEUTRON SOURCE IN THE BOREHOLE.