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High Quality Content by WIKIPEDIA articles! The Raether limit is the physical limiting value of the multiplication factor (M) or gas gain in an ionization avalanche process (Townsend avalanche). Even though, theoretically, it seems as if M can increase without limit (exponentially), physically, it is limited to about M 108 or x 20 (where is the first Townsend coefficient and x is the length of the path of ionization, starting from the point of the primary ionization. The multiplication factor or gas gain is of fundamental importance for the development of proportional counters. A Townsend avalanche is a cascade reaction involving electrons in a region with a sufficiently high electric field. This reaction must also occur in a medium that can be ionized, such as air. It is exploited in devices such as Geiger counters and Proportional counters to detect and measure the energy of an ionizing radiation. Incoming radiation ionizes one of the atoms or molecules in the medium. The positive ion drifts towards the cathode, while the free electron drifts towards the anode of the particular device.
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