Geiger counter

A Geiger counter (or Geiger–Müller counter) is an instrument that is used for the measure of radiation.

Construction

A Geiger counter consists of an cylindrical metal tube, the Cathode, with an wire, the Anode, in it. The wire is fixed at a small opening at the side. The whole container includes a filling gas and does only work, when it´s affiliated to a power source.

Function

As the Geiger counter is associated to the power source, an electric field arises. Upon the penetration of radioactive radiation through the opening, the filling gas gets ionized. In case of the electric field the ions move to the Geiger counter wall, while the electrons go to the wire. The electrons become faster and turn into an electron avalanche. This electron avalanche causes a current surge, that can be registered by the counter.