Stabilized scintillation counter using photomultiplier

Claim 1

IN A SCINTILLATION COUNTER COMPRISING A CRYSTAL AND A PHOTOMULTIPLIER PROVIDED WITH A PHOTOCATHODE AND A PLURALITY OF ELECTRODES INCLUDING AN ANODE, A VOLTAGE SOURCE AND A RESISTANCE NETWORK FOR SUPPLYING POTENTIAL DIFFERENCES TO SAID ELECTRODES, SAID CRYSTAL BEING ADAPTED TO PRODUCE SCINTILLATIONS IN RESPONSE TO IRRADIATION BY NUCLEAR RAYS FROM THE ENVIRONMENT AND SAID COUNTER BEING ADAPTED TO PERFORM A MEASUREMENT OF THE INTENSITY OF SAID RAYS, A LIGHT SOURCE ARRANGED TO ILLUMINATE SAID PHOTOCATHODE WITH A STEADY, UNVARYING, CONTINUOUS, STANDARD ILLUMINATION DURING SAID MEASUREMENT, SAID ILLUMINATION PRODUCING A D.C. PHOTOMULTIPLIER ANODE CURRENT, AND SAID SCINTILLATIONS PRODUCING PHOTOMULTIPLIER ANODE CURRENT PULSES, A FIRST ELECTRIC SIGNAL CHANNEL FOR SELECTIVELY TRANSMITTING VARIATIONS IN SAID D.C. PHOTOMULTIPLIER CURRENT AND A SECOND ELECTRIC SIGNAL CHANNEL FOR SELECTIVELY TRANSMITTING SAID PULSES AND MEANS CONTROLLED BY SAID FIRST SIGNAL CHANNEL FOR AUTOMATICALLY INCREASING AT LEAST ONE OF SAID POTENTIAL DIFFERENCES WHEN SAID D.C. CURRENT DECREASES AND FOR DECREASING AT LEAST ONE OF SAID POTENTIAL DIFFERENCES WHEN SAID D.C. CURRENT INCREASES, SO AS TO MAINTAIN THE SENSITIVITY OF SAID COUNTER SUBSTANTIALLY CONSTANT DESPITE VARIATIONS IN THE VOLTAGE OF SAID SOURCE.