首页|Analytical study and correction investigation of fringe-field effects for sector-based energy analysis systems
Analytical study and correction investigation of fringe-field effects for sector-based energy analysis systems
Wang, Miss Yan Zeng, Miss Yifeng Xiao, Mr. Dongyun Hu, Mr. Hao Liu, Dr. KaiFeng Ping, Dr. Tan Hu, Dr. Tongning
Analytical study and correction investigation of fringe-field effects for sector-based energy analysis systems
Analytical study and correction investigation of fringe-field effects for sector-based energy analysis systems
摘要
Beam momentum spread is regarded as a key parameter for evaluating the performance of high-quality electron beam injectors in large-scale scientific facilities, while magnetic-deflection-based energy analysis systems are widely employed to obtain energy-spectrum information. However, in conventional ideal hard-edge approximation models, the fringe-field effects of the dipole magnet are neglected. As a result, the additional horizontal broadening introduced at the system end by the initial vertical distribution of the bunch through transverse coupling under the action of the fringe field is not taken into account, which limits the measurement accuracy of the momentum spread of low-energy bunches. To address this issue, the particle transport characteristics including higher-order transport effects are analytically derived based on the equation of motion for MeV-scale electron beams under a gate-function-based fringe-field approximation model. On this basis, a correction method based on the transverse profile of the beam spot image at the system exit is proposed, and the conventional formula for calculating the momentum spread is modified accordingly. Subsequently, the method is extended to a multi-particle statistical model to reduce the measurement error of the momentum spread. Finally, virtual tests are carried out based on the HuTeX (Test bench of X-band beam injector at Huazhong University of Science and Technology) experimental platform under construction. The results demonstrate that the horizontal broadening and measurement error of the momentum spread introduced by the initial vertical distribution under the action of the fringe field can be effectively suppressed by combining the fringe-field correction with the third-order compensation. Within the current range of beam-parameter measurements, the measurement error of the momentum spread is almost completely corrected by the proposed method under the gate-function model. Furthermore, the relative measurement error can still be suppressed to within 2%, even when measured magnetic-field data containing multipole components are used. This study effectively mitigates the interference with energy-spectrum diagnostics caused by the initial vertical distribution under fringe-field effects, which provides reliable theoretical support and engineering guidance for high-precision diagnostics of high-quality electron beam injectors.