The Raether limit is the physical limiting value of the multiplication factor (M) or
gas gain in an ionization avalanche process (
Townsend avalanche
The Townsend discharge or Townsend avalanche is a gas ionisation process where free electrons are accelerated by an electric field, collide with gas molecules, and consequently free additional electrons. Those electrons are in turn accelerated an ...
).
Even though, theoretically, it seems as if M can increase without limit (exponentially), physically, it is limited to about M < 10
8 or αx < 20 (where α is the first
Townsend coefficient and x is the length of the path of ionization, starting from the point of the primary ionization.
Heinz Raether
Heinz Artur Raether (14 October 1909 — 31 December 1986) was a German physicist. He is best known for his theoretical and experimental contributions to the study of surface plasmons, as well as for Kretschmann-Raether configuration, a commonly- ...
postulated that this was due to the effect of the space charge on the electric field.
[proportional counter The proportional counter is a type of gaseous ionization detector device used to measure particles of ionizing radiation. The key feature is its ability to measure the energy of incident radiation, by producing a detector output pulse that is ''pro ...]
* ''The Mechanism of the Electric Spark By Leonard Benedict Loeb, John M. Meek''. Stanford University Press, 1941
* ''High Voltage Engineering'', M S Naidu, V Kamarju. Tata McGraw-Hill Education, 2009
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