Design and performance validation of a compact hybrid-magnet beam expansion and collimation system

To enhance the transmission characteristics of electron beams, this paper presents a beam expansion and collimation system (BECS) that integrates Halbach permanent magnets with electromagnets. Under the constraint of the beamline length of 1.9 m, the system effectively expands the beam radius from 0.7 to 25 mm. Concurrently, it increases the proportion of the beam with a divergence angle below 0.05 mrad from 3.6% to 52.31%, thereby suppressing internal Coulomb repulsion and significantly suppressing the divergence angle. A tolerance analysis verifies the superior robustness of the BECS against injection errors, magnet misalignments, and fabrication imperfections, for which specific compensation strategies are proposed. Simulation results show that the system dynamically adjusts the excitation currents of quadrupole and solenoid magnets to compensate for energy deviations and remanent field discrepancies, while the skew quadrupole corrects deflection errors, ensuring stable beam operation and high collimation. This system provides a promising electron beam control solution with broad application prospects for active space experiments and high-performance beam control applications.