A Geiger-Müller tube, often called a Geiger tube or GM tube, is the key component of a Geiger counter or Geiger-Müller detector. It’s a sealed cylindrical device containing a gas mixture at low pressure and two electrodes: a central wire anode and a surrounding metal cathode.
When ionizing radiation, such as alpha, beta, or gamma rays, enters the tube, it ionizes the gas molecules along its path. This ionization causes a cascade effect, generating a measurable electrical pulse. The tube is designed to amplify these pulses, making them detectable by the counter’s electronics.
The detection process in a Geiger tube involves three main stages: ionization, multiplication, and detection. Initially, the radiation ionizes the gas, creating charged particles. These charges are then accelerated by an electric field within the tube, causing a chain reaction called a gas discharge, resulting in a substantial amplification of the original ionization event. Finally, the amplified signal is detected and registered by the Geiger counter’s electronics.
