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CV2246 Military GM tube.
Geiger counters are instruments that can detect and measure radioactivity. They do so using a Geiger Mueller (GM) tube. The original design of the GM tube by H Geiger and E W Mueller in 1928 hasn't changed very much. Radiation, as it passes through the GM tube, ionizes the gas within the tube. This ionization, create a momentary conductive path between the wire at the centre of the tube (Anode) and the wall of the tube (Cathode). The momentary conductive path creates a electrical pulse that results in a 'click sound. This conductive path is quickly quenched by the halogen gas inside the GM tube. By measuring the number of the clicks, the instrument indicates the radiation levels.
A cut away drawing of a typical Geiger Mueller (GM) tube is shown below. The wall of the GM tube is a thin metal (cathode) cylinder surrounding a centre electrode (anode). The metal wall of the GM tube serves as the cathode of the GM Tube. The front of the tube is a thin Mica window sealed to the metal cylinder. The thin mica window allows the passage and detection of the weak penetrating alpha particles. The GM tube is first evacuated then filled with Neon, Argon plus Halogen gas.
GM tube basic construction.
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