Calibration of Button Type Beam Position Monitor for HLS Ⅱ

According to the high precision requirements of the Hefei Light Source major maintenance and reconstruction project, a new button type beam position monitor (BPM) was designed for HLS Ⅱ electron storage ring. The characteristic impedance and distributed capacitance of button pickup were measured by time-domain reflectometer (TDR), and scaling coefficient of the new BPM was determined through antenna method. The TDR test results show that the impedance of pickup is 50 Ω which matches the cable impedance, and the capacitance is about 2.9 pF which meets design requirements. Furthermore, the intuitive mapping diagram and calibration factor of beam position were obtained by antenna scanning. Compared with the design value, the sensitivity deviation of new BPM is less than 0.5% in the vertical direction and less than 2.8% in the horizontal direction.