Optical design and higher-order aberrations with the superconducting gantry based on limited ramping fields

Abstract

One of the major challenges in proton therapy is the cost and scale of the treatment facility, which depends mainly on the dimensions of the gantry. A potential method that promises to make the gantry lighter and more compact is superconducting magnet technology. However, the rapid ramping requirements during energy modulation are the primary reason for magnet quenching. To alleviate these restrictions, we propose a superconducting bending section consisting of a TBA lattice for a gantry optical design. With only three magnetic field settings needed to deliver 70–200 MeV proton beams, it achieves ±10% large momentum acceptance owing to its significant dispersion function suppression capabilities. Another feature that contributes to reducing the footprint is the installation of a degrader on the proposed gantry, allowing the degraded beam to be guided directly to the isocenter without being filtered by the Energy Selection System. For verifying the feasibility of the concept, we assess the possibility of beam scraping in the beam path and beam spot distortion at the isocenter. These efforts are accomplished by modeling realistic field distributions with ANSYS Maxwell and then performing 7th-order transfer mapping through COSY Infinity. Regarding the influence of broad energy spread on beam depth dose distribution, TOPAS is used to simulate and compare the integrated depth dose for various therapeutic energies.