HIL testing of a compact Beam Position Monitor diagnostic for particle accelerators

Abstract

Beam Position Monitors (BPM) are fundamental diagnostics in particle accelerators widely used in circular and linear accelerators. Their purpose is to give a measurement of the transversal center of mass position of a beam under study as well as to act as monitor of the longitudinal shape of the particle bunches conforming the beam. The main objective of this work is to describe a compact BPM diagnostic and a prototype for Hardware-In-the-Loop (HIL) testing of such devices. The system includes a test bench with the BPM, together with an analog front-end and an acquisition and monitorisation compact system. In particular, the diagnostic under study in this work uses 4 button type sensors, based on capacitive effect for noninterceptive measure of the beam. On the other hand, the digital acquisition and processing of the signals provided by the four BPM sensors need very fast sampling rates, which are typically in the range of hundreds of MHz in accordance with the usual working frequencies in particle accelerators, requiring high performance ADCs. NI FlexRIO solutions can be used in this working range, using subsampling techniques. The main advantage of this approach is the total integration of the FlexRIO technology in the ecosystem provided by NI hardware and software and the flexibility of the development using LabVIEW. In this way, the system is easily reconfigurable and ble to possible new requirements. In this case, a NI PXIe-7961R FlexRIO FPGA card is used, in conjunction with two different modules: two acquisition cards with maximum sampling rate of 50MS/s and 250MS/s, respectively. All the functionalities and calculations needed in fast real-time are implemented in the FPGA, while other functions are executed in a real-time controller, which plays the host role in the current implementation of the prototype. The work describes the results obtained with the prototype and its implementation details. In addition, the calibration procedure of the BPM device is outlined.