CIRCUIT FOR STABILIZING THE GAIN OF A STAGE CONTAINING A PHOTOELECTRON MULTIPLIER.

Difficulties in using photoelectron multiplier (pem) in portable radiometric instruments are associated with the significant time instability of the amplifying properties of the pem, the pronounced effect of the supply voltage on its gain, and the long (0. 5-1 h) time required for the settling of the operating point after turn-on. The purpose of the work described in this paper was to create a supply and stabilized circuit which ensures a constant gain of at worst 0. 1% for maximum simplicity and minimal dimensions. The circuit operates as follows: monitoring light pulses generated by a AL102B diode are applied to the photocathode of a FEU-13 pem. Voltage pulses are isolated across the resistor R//1 and are then applied to the input of the discriminator based on the differential amplifier via a compound emitter-follower. Pulses having an amplitude which exceeds the discrimination threshold are amplified, normalized, and applied to the input of the counting-rate meter. Then the smoothed voltage is used to control the power supply of the pem. The gain varies by 0. 07% when the supply voltage varies by 12%. The power drawn is 0. 5 W. The time constant of the circuit is 0. 5 sec.