Investigation of multi-intensity compensation for a medical proton therapy facility using the quadrupole scanning method

Abstract

Abstract In cyclotron-based particle therapy facilities, when degrading from maximum to minimum energy use, strong beam loss on degraders and collimators results in a ratio of current up to 10 3 . Considering patient safety and precision, the beam intensity should vary with energy by a factor of approximately quadrupole scanning and the Monte Carlo method . The main design features of the beamline, detailed optimization process of beam optics, transmission calculation, and intensity compensation have been done successfully. A passive scheme of defocusing high energy beams at specific collimators was adopted as the final solution. In the intensity compensation scheme, the beam optics and transmission were implemented with different strategies depending on the energy range. Studies reported that intensity compensation should be divided into different parts. Regarding low energies, there is only one beam optic design and the field values of all magnets should be scaled with beam rigidity. Moreover, the intensity of the primary beam cannot be increased to compensate for the poor transmission. At high energies, beam losses in the degrader system cause beam intensity variations over two orders of magnitudes. This could be limited by producing intentional losses at selected collimators.