粒子加速器消色散节中相干同步辐射效应抑制的理论与实验研究

The effect of the coherent synchrotron radiation (CSR) becomes evident, and leads to increased beam energy spread and transverse emittance dilution, as the emittance and bunch length of the electron beams are continuously pushed down in present and forthcoming high-brightness light sources and linear colliders. This effect cannot be cancelled in conventional achromats and studies on suppressing this effect in achromats are essentially required to achieve the expected machine performance that is evaluated without considering the CSR effect. The applicants have proposed the CSR "point-kick" model and the "two-dimensional CSR-kicks" analysis method and achieved generic CSR-suppression conditions for a two-dipole achromat. In this project, the applicant will perform the verification experiment for the proposed CSR-suppression scheme in a dogleg on the accelerator of the Shanghai Deep Ultraviolet FEL. Meanwhile, the applicants will theoretically and numerically investigate effective and generic CSR-suppression approaches for other kinds of achromats,such as TBA and MBA. Eespecially, efforts will be made to look for a feasible scheme for bunch compressors to simutaneously improve the performance of the bunch compression and suppress the CSR-induced emittance growth. Till now the analysis methods for the CSR effect are always based on the linearization of the CSR effect in a dipole. The applicants will study the effect of a full CSR wake,and find an effective way to suppress this effect. The goal of these studies is to achieve leading international results in the field of the CSR study, which will build solid conditions and accumulate technical reservations for the design and construction of the next-generation, high-brightness colliders and light sources in China.

在电子加速器中，随着束流品质不断提高，相干同步辐射（CSR）开始变得显著，使束流在通过消色散节时产生横向发射度增长。在消色散节内有效抑制CSR效应，对保持束流品质、实现机器预期指标，有着十分重要的意义。本项目申请人在线性化CSR效应基础上提出"二维-点力"分析方法，利用该方法得到DBA及dogleg中完全抵消CSR线性效应的一般性条件，并提出相应的CSR效应抑制方案。本项目计划在SDUV-FEL实验平台上开展dogleg内CSR抑制方案验证实验。同时，本项目计划利用"二维-点力"分析方法，开展TBA、MBA等消色散结构中的CSR效应抑制研究；结合束团压缩机制研究，探索同时实现束团压缩优化和CSR效应抑制的可行方案；研究实际CSR尾场效应及其抑制方法。本项目的目标是在CSR研究领域取得国际领先的成果，并为我国未来建设新一代高亮度粒子对撞机和先进光源提供直接的借鉴和参考。

在电子加速器中，随着束流品质不断提高，相干同步辐射（CSR）开始变得显著，使束流在通过消色散节时产生横向发射度增长。在消色散节中有效抑制CSR效应，对保持束流品质、实现机器预期性能指标，有着十分重要的意义。.课题组在深入研究CSR效应的基础上，提出“二维-点力”分析方法，并将其应用于DBA、TBA、包含多个DBA的弧区束团压缩器等消色散节中。在实验研究方面，与上海应用物理所及意大利FERMI-FEL实验室合作，提出CSR效应抑制验证实验。不过由于拟开展实验的SDUV-FEL（位于合作单位上海应用物理研究所）因故停止运行，无法开展实际束流实验研究。.课题组在加速器领域国内外重要期刊及国际会议发表多篇文章，口头报告2次，激发了意大利FERMI-FEL实验室S. Di Mitri博士、美国LBNL实验室M. Venturini博士、美国JLAB实验室C.Y. Tsai博士等同行的相关研究，并在紧致型ERL、大型粒子对撞机Fcc-ee，上海软X射线FEL等加速器设计中得到应用。