Design of a cryogenic photocathode gun with a novel TM02 mode coupler for low emittance

分类： 核科学技术 >> 辐射物理与技术 提交时间： 2025-05-19

Jiahao.Tian Cheng.Wang

摘要： The application of radiofrequency (RF) electron guns operating at cryogenic temperatures can enhance theperformance of a photoinjector. The low emittance and increased brightness of the electron beams resultingfrom the high gradient in the cryogenic photoinjector make it possible to improve the performance of new lightsources. As an upgrading scheme for the Shanghai Soft X-ray Free-Electron Laser (SXFEL), this study exploresa novel photocathode RF gun by introducing the TM02 mode into the cathode cell of a 2.6-cell electron gun,which improves the RF performance, particularly in terms of the monopole field. Furthermore, the optimizedcathode cell with the TM02 mode can reduce the errors resulting from installation and decrease the dark currentwith alternative cathodes. In this study, the beam dynamics in a photoinjector were optimized using a 500 pC,5 ps beam, and its feasibility was examined. This paper presents the entire RF design process, including theadjustment of the RF structure, coupler design, local field, and multipole mode suppression to provide theoreticalguidance for subsequent manufacturing and assembly.

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