Speaker
Description
The imaging accuracy of proton radiography critically depends on the beam transfer matrix defined by magnetic lenses. However, fringe field effects introduce nonlinear magnetic components, causing deviations from the ideal hard-edge model and limiting the performance of con-ventional optics designs. In this study, we systematically investigate methods for precise characterization and mitigation of magnetic lens fringe fields for an 18 MeV proton radiography experimental platform. Pole-face shimming and end-cutting techniques are applied to suppress higher-order harmonics and enhance field uniformity within the effective region. The fringe field distribution is further quantified using a three-dimensional Enge coefficient fitting method and incorporated into beam optics matching software for accurate simulation. Based on point-to-point imaging performance, the quadrupole magnet structure and gradient strength are co-optimized. Full-scale particle tracking simulations validate the effectiveness of the proposed design, demonstrating high imaging fidelity under realistic fringe field conditions. This work provides a reliable technical approach for the optimized design of high-precision proton radiography lens systems
