Numerical calculation of the electromagnetic coupling strength between the electrodes of a beam-position monitor

The PF 2.5-GeV linac is now being upgraded for the KEKB project. A stripline-type beam-position monitor is under development in order to easily handle the beam orbits of primary high-current electron beams for producing a sufficient number of positrons. The spatial dimensions of the mechanical monitor components were decided during its design. In the monitor design, it is particularly important to determine the opening angle of the electrode, because larger electromagnetic couplings between the electrodes generate a larger nonlinearity concerning pick-up signals. The opening angle of the electrode was decided based on a numerical calculation which considered the charge-simulation method. This report summarizes the method and results of the numerical calculation in detail. (author)