Definition : Devices designed primarily to sense ionizing radiation from alpha and beta particles at a low counting rate; some tubes can also detect high-level gamma radiation. These devices typically consist of a metallic tube (or insulated tube but internally covered with a conductive layer) that works as the cathode and a wire placed inside the tube that works as the anode; the tube is filled with an inert gas (e.g., helium, argon). Geiger tubes have a thin (e.g., mica) window that allows entering of alpha and beta particles; some tubes using glass windows can measure only beta particles. The passage of ionized particles through the tube creates an avalanche of charged particles that produce an audible click for each particle (Geiger counting). Geiger tubes are used as the main component of radiation counters and low-level environmental ionizing radiation detectors.
UMDC code : 23518