Use of a Victoreen 500 electrometer to determine ionization chamber collection efficiencies

An investigation has been made of the Victoreen 500 electrometer's capability to predict saturation corrections for ionization chamber measurements. This electrometer has been provided with a switch that reduces the polarizing voltage on the chamber to 40% of its normal value. It can be demonstrated theoretically that ion chamber measurements at two separate voltages should be sufficient to determine the saturation correction, for both pulsed beams and continuous radiation. Tests were made with the Victoreen 500 which indicated that this is the case. Saturation corrections of up to 10% have been demonstrated for both pulsed and continuous beams and these can be predicted using the Victoreen 500 electrometer to within 1%.