FPGA Design of the digital acquisition chain to test and implement ALPS, the new Beam Position Monitor for the Super Proton Synchrotron at CERN

This thesis presents the firmware design and the data analysis to test and implement part of the acquisition chain of ALPS (A Logarithmic Position Monitor), the new beam position monitor of the Super Proton Synchrotron (SPS) at CERN, the European Organization for Nuclear Research. CERN provides particle accelerators and detectors to accelerate beams of particles and observe their collisions and the SPS is the second larger circular machine in the accelerator complex. The SPS beam position monitor, the system that measures the transverse position of the accelerated particle beams along the pipe, is now under redesign. In the BPM acquisition chain the signal from the sensor is first conditioned by the analog front-end, then digitalised in the digital front-end and transmitted to the back-end for being processed. The goal of the thesis is the conception of firmware modules and analysis tools integrated with the acquisition chain, aiming to acquire and analyse data to qualify the system and finally implement the digital processing modules to extract the position information. I designed the back-end FPGA (Field Programmable Gate Array) firmware and the control software to test the analog front-end prototype, based on logarithmic amplifiers. The design is based on a synchronous static finite state machine, interfacing with the high-speed digital link to the front-end and with the machine timing from the accelerator. It is parametrizable and controllable by software online. Every modules and the whole firmware have been simulated and later tested in the lab. With the full acquisition chain I made data acquisition in the lab, with a signal generator beam emulator, and in the tunnel, with actual beam signals. The analysis of the data acquired allowed to characterise the front-end prototype in terms of linearity, intensity dependence and resolution, individuating limits and strong points. The data collected are also the base of the second step of the thesis, aimed to explore the digital processing tools that can be implemented in FPGA to extract the position information. I studied and implemented a parametrizable algorithm to recognise the specific event linked to the position extraction. I designed the module to calculate the beam orbit, the position averaged at a programmable bandwidth, based on a IIR (Infinite Integral Response) digital filter with selectable bandwidth; the filter has an external control that adapts the bandwidth according to the read-out frequency. I developed also the modules to calculate the trajectory and the capture, the position measured turn by turn, respectively for all the beam batches and for a selected batch. All the modules are designed to be instantiated in parallel, as the logic building blocks of a more complex hierarchical system, adapting on-going to the future developments of the analog front-end. In conclusion, this document offers several FPGA based solutions for acquiring and processing Beam Position Data from circular machines; all the modules designed are simulated and, for the most part, they are also already verified with actual beam data.