PORTABLE GEIGER–MÜLLER COUNTERS

Three models of portable Geiger–Müller counters which were found useful in the detection of radioactive minerals are described. The models are similar in that in each the high voltage for the Geiger–Müller counter tube is supplied by means of a multivibrator circuit and the pulse from the G–M tube is fed to a trigger circuit which actuates headphones. In one model a neon tube discharge circuit is used to give one headphone pulse for every 10 from the G–M tube and a counting rate meter is provided. Details of circuit design and application are given. The circuit of a simple amplifier that may be used with a G–M tube at the end of a long three-conductor cable is given.