Achromatic beamline design for a laser-driven proton therapy accelerator
Kedong Wang, Kejun Zhu, Matthew Easton, Yujia Li, Chen Lin, X. Q. Yan
Abstract
A new laser-driven proton therapy facility is being designed by Peking University. The protons will be produced by laser--plasma interaction, using a 2-PW laser to reach proton energies up to 100 MeV. We hope that the construction of this facility will promote the real-world applications of laser accelerators. Based on the experimental results and design experience of existing devices in Peking University, we propose a beam transmission system which is suitable for the beam produced by laser acceleration, and demonstrate its feasibility through theoretical simulation. It is designed with two transport lines to provide both horizontal and vertical irradiation modes. We have used a locally-achromatic design method with new canted-cosine-theta (CCT) magnets. These two measures allow us to mitigate the negative effects of large energy spread produced by laser-acceleration, and to reduce the overall weight of the vertical beamline. The beamline contains a complete energy selection system, which can reduce the energy spread of the laser-accelerated beam enough to meet the application requirements. The users can select the proton beam energy within the range 40--100 MeV, which is then transmitted through the rest of the beamline. A beam spot with diameter of less than 15 mm and energy spread of less than 5% can be provided at the horizontal and vertical irradiation targets.