Continuous Beam Scanning Intensity Control of a Medical Proton Accelerator Using a Simulink Generated FPGA Gain Scheduled Controller

Pablo Fernandez Carmona, Christian Bula, Michael Eichin, Grischa Klimpki, David Meer, Vinzenz Minnig, Serena Psoroulas, Damien Charles Weber, Cheng, Yung-Sen (Ed.), Schaa, Volker RW (Ed.), Chiu, Pei-Chen (Ed.), Li, Lu (Ed.) (+2 others)
At the Centre for Proton Therapy at the Paul Scherrer Institut we treat cancer patients using a fixed beam line and two gantries. The latter use a step-and-shoot technique to deliver dose covering the treatment volume with a grid of weighted proton bunches. Dose delivery for tumours moving under respiration (e.g. lung) is however challenging and not routinely performed because of the interplay between target and beam motions. At the Gantry 2 unit, we are implementing a novel continuous beam
more » ... lation concept called line scanning, aiming at realizing a faster dose delivery to allow for effective organ motion mitigation techniques such as rescanning and gating. The current should stabilise within 100 us, which is tough due to the non-linearity of the system and latency of the monitors. In this work we implemented a gain scheduled controller and a predictor by modelling the accelerator in Simulink and developing a controller using the frequency domain robust method. We used Mathwork's HDL Coder functionality to generate VHDL code that was implemented in an FPGA in the gantry control system. Latency, overshoot and dosimetric performance improved considerably compared to a classic PID.
doi:10.18429/jacow-pcapac2018-frcc2 fatcat:v6dywedqnvf5jokd2xagwaejnm