Test and Simulation for the Response of PLS-II Button-type Beam Position Monitor

For the upgrade project of the Pohang Light Source (PLS-II), button-type beam position monitors (BPM) have been made and tested. The BPMs have been tested on a test stand using a metallic wire connected to a 500 MHz RF signal generator. During the test of the BPMs, some of the BPMs show a response different from that of the others. The response of these BPMs was usually asymmetric and tilted. In this research, we did simulations to figure out which factors affected the response of BPM. For the simulations, we use the MATLAB code which is made of ALBA-cells and Diamond. Using this code, we studied the effect of defective button geometry on the response of BPM system and made defective BPMs combinations of geometry that minimized the asymmetry and the tilt of the response. From these results, we can use a defective BPM unit with another defective BPM unit that has a complementary button geometry.