When an ion chamber containing a low conductivity liquid is exposed to a very short pulse of ionizing radiation ∼ 10-7 seconds), the current in the external circuit is high during the pulse and then falls rapidly and nonexponentially towards zero. Further, the shape of the curve depends on both the delivered dose and the collecting field. A theoretical analysis of the liquid ion chamber under these conditions is given quantitating the effect of space charge and deriving expressions relating the observed current to the fundamental physical properties of the liquid. Experimental data for n-hexane are also shown covering six decades of both time and current for various collecting fields and incident doses for which data essentially establish the theoretical treatment. One-MeV electron beam irradiations were used ranging from 0.8 to 120 ma in pulse lengths from 10-8 to 10-6 second. Besides values for the recombination coefficient and other parameters, evidence is given of ionic charge multiplicity and free unattached electrons during the initial stages of the process.

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Copyright 1970 Academic Press, Inc.
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