Three data-selection approaches for beam position monitor offline calibration

In this study, we describe the fabrication of an electrostatic beam position monitor (BPM) for beam diagnostic systems. Calibration of the BPM pickup requires both sensitivity and curve fitting owing to manufacturing tolerances following fabrication. To calibrate the BPM, we developed a BPM calibration system that comprises a wire-based test bench and readout electronics. We considered three difference-over-sum (DOS) data selection methods: DOSdiag, DOSaxis, and DOSall, to understand their impact on calibration accuracy. Each method selected specific DOS data, and we compared their characteristic curves. Consequently, we analyzed the calibration results by performing linear, 3rd-order, 5th-order, and two-dimensional (2D) 3rd-order polynomial fitting. Each of the three DOS data selection methods was examined to illustrate their advantages and limitations in terms of calibration accuracy and required amount of data. The results obtained demonstrated that choosing the appropriate DOS data-selection approach could be employed for the BPM offline calibrations, achieving minimized calibration errors and optimized response characteristics with polynomial curve fitting.