Ion losses in a plane-parallel ionisation chamber irradiated with a pulsed electron beam

Saturation curves for a plane-parallel ionisation chamber have been studied in a pulsed electron beam of 5.2 MeV initial energy as a function of chamber voltage, chamber depth and charge density liberated per pulse. It is shown that, if ion losses by diffusion and by initial recombination are appropriately considered, the remaining ion losses by volume recombination can be described by Boag's theory. The constant mu in this theory has been determined to be (2.7 +/- 0.1) x 10(10) V m C-1. This value is consistent with data on charge collection characteristics obtained using the same ionisation chamber exposed to continuous radiation from beta-sources.