geigerMüller

The Geiger-Müller tube, often referred to in a broader sense as a Geiger counter, is a gas-filled radiation detector that registers individual ionizing events by producing a brief electrical pulse when radiation passes through the detector. It was developed by Hans Geiger and Walther Müller in 1928 and has since become one of the most widely used portable instruments for detecting ionizing radiation.

Construction and operation center on a thin-walled tube filled with a low-pressure inert gas, typically a noble gas such as argon or neon, mixed with a quenching agent (organic vapors or halogen compounds). A central anode wire is maintained at a high positive voltage relative to the surrounding cathode. An incident ionizing particle creates ion pairs in the gas; the strong electric field accelerates these ions, triggering a self-sustaining discharge that produces a characteristic, easily counted pulse. The pulse height is relatively independent of the radiation energy, which means the tube provides a count rate rather than energy spectroscopy.

Key characteristics include a definite dead time after each detected event, during which the tube is temporarily insensitive. The response depends on the applied voltage; too little voltage yields no discharge, while excessive voltage can cause continuous discharge. Detection efficiency varies with radiation type and the tube’s window and geometry, with alpha detection requiring a thin window and gamma detection relying on scattering and wall interactions.

Applications span survey meters, laboratory instrumentation, health physics, industrial safety, and homeland security. While simple and robust, the Geiger-Müller tube does not provide energy information and is often complemented by other detectors when spectroscopic data are needed.