Abstract
ACCURATE experimental data are lacking for Townsend's ionization coefficient α/p for electrons drifting through helium, when the ratio X/p of electric field to pressure is small. As has been pointed out by Loeb1, however, it is possible in this instance to calculate α/p from the relation2 where W is the drift velocity of the electrons, v the speed of an electron which has energy V in its random motion, f(V) the energy distribution function in the random motion, I the ionization energy, and P(V) the probability of ionization for an electron with energy V per unit random path at unit pressure, since the form of f(V) has been determined with considerable accuracy by Smit3.
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References
Loeb, “Fundamental Processes of Electrical Discharge in Gases", 365 (New York, 1939).
Emeleus, Lunt, and Meek, C. A., Proc. Roy. Soc., A, 156, 394 (1936).
Smit, Physica, 3, 543 (1936).
Dunlop, M.Sc. thesis, Belfast (1948).
Druyvesteyn and Penning, Rev. Mod. Phys., 12, 97 (1940).
Loeb, op. cit., 192.
Townsend and MacCallum . Phil. Mag. 17, 678 (1934).
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DUNLOP, S. Townsend's Ionization Coefficient for Helium. Nature 164, 452 (1949). https://doi.org/10.1038/164452a0
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DOI: https://doi.org/10.1038/164452a0
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