Performance improvement of a box-and-grid type discrete-dynode electron multiplier using a monotonically decreasing voltage divider.

We propose a monotonically decreasing voltage divider of 7:6:6:5:5:4:4:4:2 instead of the constant one to improve the gain and its stability of a nine-dynode box-and-grid type discrete-dynode electron multiplier (BG-DEM) under electron bombardment. Experiment and simulation results demonstrate that the new voltage divider enables the BG-DEM to achieve a gain of 1.0 × 105 at the operating voltage of 1300 V with a significant enhancement of 112.8% and an operating voltage of 1775 V at the gain of 106 with a considerable reduction of 7.3%, attributed to the improvement of the electron magnifications of D2-D6 and the electron collection efficiencies of D2-D4. Furthermore, the monotonically decreasing voltage divider also decreases the gain decay rate to 4.1%/h with a substantial reduction of 22.6% owing to the increase of the interaction areas between electrons and dynodes of D2-D9 and the reduction of the initial electron magnifications of D7-D9. Overall, the proposed monotonically decreasing voltage divider presents a greatly convenient and effective approach for the design of the electrical parameters of BG-DEM, satisfying the requirement for more sensitive and stable detection of the charged particles in the precision instruments.