Editing Geiger–Müller tube (section)

==Detection efficiency==
The efficiency of detection of a G–M tube varies with the type of incident radiation. Tubes with thin end windows have very high efficiencies (can be nearly 100%) for high energy beta, though this drops off as the beta energy decreases due to attenuation by the window material. Alpha particles are also attenuated by the window. As alpha particles have a maximum range of less than 50&nbsp;mm in air, the detection window should be as close as possible to the source of radiation. The attenuation of the window adds to the attenuation of air, so the window should have a density as low as 1.5 to 2.0&nbsp;mg/cm<sup>2</sup> to give an acceptable level of detection efficiency. The article on [[Stopping power (particle radiation)|stopping power]] explains in more detail the ranges for particles types of various energies.
The counting efficiency of photon radiation (gamma and X-rays above 25&nbsp;keV) depends on the efficiency of radiation interaction in the tube wall, which increases with the atomic number of the wall material. Chromium iron is a commonly used material, which gives an efficiency of about 1% over a wide range of energies.<ref name="centronics"/>