The Effect of Diffusion on the Analysis of Pulsed Radiolysis Drift Tube Experiments

Electron drift velocities have previously been calculated from the transient waveforms recorded with a pulsed radiolysis drift tube (PRDT) using a first order theory in which it is assumed that diffusion during the drift of the electrons to the anode effectively increases the drift distance. In this paper the modifications to the transient waveforms caused by diffusion have been analysed more accurately by using a model representation of a group of electrons drifting and diffusing in a uniform electric field between plane, parallel absorbing electrodes. It is shown that, when account is taken of loss of electrons to the electrodes by diffusion, the correction factor differs in both magnitude and sign from that assumed in the first order theory.