METHOD AND APPARATUS FOR STABILIZING THE GAIN OF A PHOTOMULTIPLIER

摘要

1418726 Stabilizing gain of photo-multiplier SCHLUMBERGER INLAND SERVICES INC 24 Jan 1973 [24 Jan 1972] 3602/73 Heading G1A The gain of a photo-multiplier is stabilized by measuring variations in the mean output current of the photo-multiplier and compensating said variations by modifying the illumination of the photocathode of the detector. Variations in gain, and thus mean current, may be due to temperature changes or sudden changes in illumination. In the arrangement described, a photo-emissive diode 13 is used to modify the illumination, being embedded in an epoxy resin disc-shaped light guide mounted between the scintillator 12 and the photocathode 11. Mean current is measured by an operational amplifier 22 having a capacitative feedback loop so as to act as an integrator and compared with a reference level 28 in further operational amplifier 26. Changes in intensity of diode 13 are in such a direction as to maintain the mean current constant. The signal relating to the radiation field under investigation is filtered by capacitor 20, to remove the D.C. background level.