Numerical analysis of the space charge effect in the MWPC beam monitor

A transient gain reduction process of the multi-wire beam profile monitor was numerically investigated for the detailed design of geometric parameters. In order to consider the space-charge effect, we developed a numerical code based on the drift-diffusion model. To find the relations between the gain reductions of the output signal and the space-charge distributions, the calculations were performed for the time period of ∼10 - 100 μs, which is much longer than the time required by ions to travel from the anode to the cathode. We found the ion distributions to be quasi-stationary for the successive beam injection of ∼108 - 109 pps. (author)