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Abstract

A real-time beam profile monitor (BPM) has been developed for particle therapy and evaluated at the Heidelberg Ion Beam Therapy Center (HIT). The system is designed to provide real-time measurements of the ion beam position and width, thereby enabling precise radiation delivery in future clinical applications.

The BPM measures the one-dimensional projections of the beam using two layers of 250 µm scintillating fibers, which are read out by Hamamatsu S11865-64 photodiode arrays equipped with amplifier and integration circuits. The photodiode channels have dimensions of 0.7 mm (w) x 0.8 mm (h) with a pitch of 0.8 mm. The signals from the photodiodes are digitized on a custom PCB hosting voltage regulators and ADCs. Both the photodiodes and ADCs are controlled by a MAX 10 FPGA, which, in addition to signal control, performs ADC data packaging and beam profile reconstruction before transmitting the processed data via Ethernet to a PC equipped with dedicated data acquisition software.

This thesis investigates the signal characteristics of the SciFi-BPM, develops a tailored beam profile reconstruction algorithm, and implements it on the FPGA, enabling real-time determination of the beam position and width. Beam tests at HIT with protons and carbon ions demonstrated that the performance is sufficient for the majority of beam settings, specifically achieving an overall resolution better than 0.05 mm for the beam position and 0.12 mm for the beam width at high intensities.