Compact gantry systems are critical for minimizing the footprint and cost of proton therapy facilities. This study presents the design and evaluation of a compact proton therapy gantry that utilizes a short source-to-axis distance (SAD) downstream scanning configuration along with high-field magnets made of FeCo alloy. Multi-objective beam optics optimization, which was carried out with COSY-INFINITY code and NSGA-III algorithm, enabled achromatic transport and sub-5.5 mm (2σ) beam spots at the isocenter. Dipole magnets are designed using FeCo alloy with a high saturation flux density. This allows the bending radius to be reduced to 1.35 m while lowering magnet and gantry weight, with field uniformity maintained below 0.0281%. These results demonstrate the feasibility of a lightweight and compact gantry scenario, offering a practical solution for miniaturized proton therapy facilities.

Compact gantry,FeCo alloy Magnet,Beam optics,Proton therapy