Abstract: A discrete discharging model is built up, based on analyzing the discharging course of a double grid aircounter (DGAC) . A new optimization method of DGAC parameter design is developed. The study shows that theworking voltage is closely r elated to the geometr ic parameter of DGAC, the sensitivity of the circuit and the numberof discharges. Exper iment shows t hat t he novelmethod can be used in parameter design of DGAC; not only can it effectively avoid one-sidedness by the traditional design, but also the hardware circuit design of control systems is veryeasy and trustwort hy.

Key words: sensor system, non destructive testing, low energy electron, working voltage