A study of electric field distribution in Benjamin type proportional counter using finite element method.

Tissue equivalent proportional counters (TEPCs)  are commonly based on the Benjamin type of concept. Initially the electric field is optimized by pulse height measurement methods and only one optimum solution was established at that time. In this paper, the electric field distribution is analyzed and optimized using a three-dimensional finite element method. The calculations show that the characteristics of the radial electric field distribution of this type of counters can be equated to cylindrical counters using a pair of appropriate field shaping electrode. Furthermore, the paper analyzes the axial electric field distribution and the possibility of achieving a uniform electric field along its anode while reducing the size of Benjamin type proportional counter design down to 1/10 of currently feasible values with respect to the thinnest available anode wire diameters.