Space charge effects in a thin rectangular proportional counter

We recently reported on a “twin-peaks effect” found for a thin rectangular proportional counter. In this work we develop a simple model for the space-charge effect during the drift process of primary electrons and simulate the twin-peaks effect for incident α-rays. The “first peak” is thus explained by a time distribution of arrival of the primary electrons at the multiplication region, while the ‘second peak” can be qualitatively explained as a result of competition between diffusion and recombination.