Raether limit

The Raether limit is the physical limiting value of themultiplication factor (M) or gas gain in an ionizationavalanche process (Townsend avalanche).Even though, theoretically, it seems as if M can increasewithout limit (exponentially), physically, it is limited toabout M < 108 or x < 20 (where is the rst Townsendcoecient and x is the length of the path of ionization,starting from the point of the primary ionization.Heinz Raether postulated that this was due to the eectof the space charge on the electric eld.The multiplication factor or gas gain is of fundamentalimportance for the operation of the proportional counterionising radiation detector.

1 Sources Electron avalanches and breakdown in gases. HeinzRaether, Butterworths 1964

The Mechanism of the Electric Spark By LeonardBenedict Loeb, John M. Meek. Stanford UniversityPress, 1941

High Voltage Engineering, M S Naidu, V Kamarju.Tata McGraw-Hill Education, 2009

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