Neutron detector

Claim 1

IN AN APPARATUS FOR RADIOLOGICAL LOGGING OF BORE HOLES, A HOUSING ADAPTED TO BE LOWERED INTO A BORE HOLE, SAID HOUSING COMPRISING A SOURCE OF NEUTRONS ARRANGED TO RADIATE NEUTRONS INTO THE FORMATIONS SURROUNDING SAID HOLE WHEREBY GAMMA RAYS AND NEUTRONS ARE DIRECTED TOWARDS SAID HOLE AS A RESULT OF INTERACTION OF SAID NEUTRONS WITH SAID FORMATION, A CRYSTAL CONVENIENTLY DISTANT FROM SAID SOURCE, SAID CRYSTAL BEING SENSITIVE TO THERMAL NEUTRONS, FAST NEUTRONS, AND GAMMA RAYS AND ADAPTED TO PRODUCE A LIGHT IMPULSE IN RESPONSE TO A THERMAL NEUTRON, FAST NEUTRON, OR TO A GAMMA RAY, ANOTHER CRYSTAL SURROUNDING SAID FIRST CRYSTAL, SAID OTHER CRYSTAL BEING SELECTIVELY SENSITIVE TO GAMMA RAYS AND FAST NEUTRONS AND ADAPTED TO PRODUCE A LIGHT IMPULSE IN RESPONSE TO A GAMMA RAY OR A FAST NEUTRON, A FIRST PHOTOMULTIPLIER RESPONSIVE TO A LIGHT IMPULSE IN SAID FIRST CRYSTAL TO PRODUCE A CORRESPONDING CURRENT IMPULSE, A SECOND PHOTOMULTIPLIER RESPONSIVE TO A LIGHT IMPULSE IN SAID SECOND CRYSTAL TO PRODUCE A CORRESPONDING CURRENT IMPULSE, AN ANTICOINCIDENCE NETWORK CONNECTED TO SAID TWO PHOTOMULTIPLIERS FOR PROVIDING AN OUTPUT SIGNAL AT THE OCCURENCE OF AN IMPULSE AT SAID FIRST PHOTOMULTIPLIER THAT IS NOT SIMULTANEOUS WITH AN IMPULSE AT SAID SECOND PHOTOMULTIPLIER, A COUNTING RATE CIRCUIT CONNECTED TO SAID ANTICOINCIDENCE NETWORK FOR PROVIDING A VOLTAGE REPRESENTING THE RATE OF OCCURENCE OF ITS OUTPUT SIGNALS, MEANS FOR DETERMINING THE DEPTH TO WHICH SAID HOUSING IS LOWERED, AND MEANS FOR SEPARATELY RECORDING THE OUTPUTS OF SAID CIRCUITS IN CORRELATION WITH DEPTH.