Geiger Counter

A Geiger counter is an electronic instrument for detecting and measuring ionizing radiation, using a Geiger-Müller tube to register alpha particles, beta particles and gamma rays through the ionization they cause inside the tube. The tube is filled with an inert gas at low pressure that becomes briefly conductive when a high-energy particle passes through it, producing an electrical pulse that is then amplified enough for simple electronics to count and display, which is what makes the device both cheap and practical. The detection principle was worked out in 1908 by Hans Geiger under Ernest Rutherford at the University of Manchester, but the practical, sealed Geiger-Müller tube able to detect beta and gamma radiation as well as alpha particles was not built until 1928, by Geiger and Walther Müller.