Numerical Simulation of the PEP - II Beam Position Monitor

We use MAFIA to analyze the PEP-II button-type beam position monitor (BPM). Employing proper termination of the BPM into a coaxial cable, the output signal at the BPM is determined. Thus the issues of signal sensitivity and power output can be addressed quantitatively, including all transient e ects and wake elds. Besides this rst quantitative analysis of a true BPM 3D structure, we nd that internal resonant modes are a major source of high value narrow-band impedances. The e ects of these resonances on coupled-bunch instabilities are discussed. An estimate of the power dissipation in the ceramic vacuum seal under high current operation is given. Presented at the Workshop on Collective E ects and Impedance for B-Factories, Tsukuba, Japan, June 12-17, 1995 Work supported by Department of Energy, contract DE-AC03-76SF00515.