Space Charge Distortion of the Electric Field in a Plane-Parallel Ionization Chamber

The effect of space charge on the electric field in a plane-parallel ionization chamber is considered. It is shown that the electric field strength at the plates is considerably higher than in the centre of the gap, even when recombination losses amount to only a few per cent. Consequently, in a chamber which is provided with a system of guard wires or plates, the ` saturation curve ' obtained experimentally may show polarity effects due to changes in the volume from which ions are collected.