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Some comments on the relation between ionisation and ionisation current in gases at high pressures

Published online by Cambridge University Press:  24 October 2008

W. R. Harper
Affiliation:
St John's College; Wills Physics Laboratory, University of Bristol

Extract

The phenomena which limit saturation in a high pressure ionisation chamber are examined with particular reference to the rôle played by preferential recombination. The complexity of the phenomena is discussed in detail in order to bring out the scope and limitations of the simple theory of preferential recombination and the conditions which a more complete theory would have to satisfy. It is pointed out that in a number of recent papers on the subject fundamental aspects of the problem have been overlooked, and the significance of these omissions is discussed.

Type
Research Article
Copyright
Copyright © Cambridge Philosophical Society 1933

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References

* Broxon, , Phys. Rev. 42, 321 (1932)CrossRefGoogle Scholar.

As pointed out by Zanstra, and Clay, , Phys. Rev. 41, 679 (1932).CrossRefGoogle Scholar

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Ordinary recombination is here defined as the recombination that occurs when the ions have become distributed at random.

Preferential recombination is here defined as recombination between an ejected electron (or negative ion if it has become one) and its parent positive ion.

** Initial recombination is the recombination that occurs when the ions are still distributed in a more or less columnar form, i.e. when there are localised regions of ionic concentration greater than the mean for a large volume of the gas. Initial recombination will, however, henceforward be taken to exclude that form of it which is preferential recombination.

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* It is difficult to estimate from the curves how considerable, but perhaps 30% of the ionisation was lost by preferential and initial recombination, and for reasons already given a large fraction of this must have been lost by preferential recombination.

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It should be mentioned that the interpretation of experimental results is often rendered unnecessarily difficult by authors neglecting to mention either the applied field or the magnitude of the ionisation—or sometimes even both. The ratio of ionisation to ionisation current does not of course depend on the magnitude of the ionisation when only preferential and initial recombination limit the ionisation current (unless the ionisation is very large), but when ordinary recombination plays a part the ratio does depend on the magnitude of the ionisation.

§ Zeits. für Phys. 75, 570 (1932)Google Scholar. See also Broxon, , Phys. Rev. 40, 1022 (1932)CrossRefGoogle Scholar, and Gingrich, , Phys. Rev. 41, 679 (1932).CrossRefGoogle Scholar

* Loc. cit.Google Scholar