高亮度电子束相空间调制、传输与微束团不稳定性研究

Performance improvement of modern particle accelerators, serving as a unique platform for multidisciplinary research, is of critical importance to the breakthrough of cutting-edge researches. In pursuit of the high-brightness electron beam and the rapid progress of associated technologies, effects of collective beam instabilities have played an essential role to the overall machine performance. Quantitative studies of high-brightness electron beam dynamics and computational efficiency have posed great challenges to numerical particle tracking simulation because of existing numerical noise by limited number of simulation particles. Starting from Vlasov analysis of plasma kinetic theory, which is free from numerical noise and the computing issue, we formulate the phase space evolution during the beam transport in the presence of the coherent synchrotron radiation and the space charge effect. In this proposal, a more complete theory of single-pass microbunching dynamics will be constructed and is applied to the sensitivity analysis of the existing schemes of high-brightness electron phase space modulations for advanced light sources. The developed semi-analytical Vlasov solver is particularly suitable to the microbunching analysis, as it takes much less computational effort than the particle tracking simulations, while it is general and therefore provides a quick and accurate performance estimation for the high-brightness electron transport lattice design. It is expected that the analysis based on this proposal can shed light on the lattice design that aims to suppress or control the microbunching or phase space modulation in a high-brightness electron transport line.

许多前沿科学的突破依赖于粒子加速器性能的提升。随着电子源技术的快速进展，电子束亮度获得提升，却也加剧束流集体不稳定性对整体效能的影响。近年来在高亮度电子微束团动力学的研究，粒子跟踪模拟受数值噪音影响，对结果量化与计算效率产生极大挑战。为免除数值噪声与计算效率的困难，本研究从等离子体Vlasov分析出发，确立以高亮度电子束相空间调制、传输、微束团不稳定性为主轴，揭示电子束在相干同步辐射与空间电荷效应影响下，其相空间在传输过程中的演变。本项目将建立更完整的微束团动力学理论，并应用到先进光源相空间调制方案灵敏度分析。基于本项目开发的分析工具有课题针对性，因此计算效率远高于粒子跟踪模拟程序。同时具一般性，能提供加速器社群对高亮度电子传输段设计的微束团动力学有初步且准确的评估。在加速器磁聚焦结构设计中，抑制电子微束团不稳定性非常重要，研究成果将为相关设计与相空间调制方案提供更坚实的理论指导。

近年来加速器社群对高亮度电子微束团动力学的研究与日俱增，粒子跟踪模拟受数值噪声影响，对结果量化与计算效率产生极大挑战。..为避免数值噪声问题，本项目从等离子体动理学理论出发，建立了更完整的微束团动力学理论，包含相干同步辐射、空间电荷等集体效应与近距离小角度、多次碰撞产生的束内散射效应。在本项目支持下，利用MATLAB结合ELEGANT，开发了半解析快速分析工具，提供加速器社群对高亮度电子传输段设计的微束团动力学有初步且准确的评估。课题组与加速器领域国内外同行合作(北京高能物理研究所焦毅研究员、意大利FERMI实验室Simone DiMitri研究员、DESY的秦伟伦博士)，将开发的半解析工作应用在实际磁聚焦结构设计中，为抑制电子微束团不稳定性与研究成果将为相关设计与相空间调制方案提供更坚实的理论指导。..为缓解微束团集体效应分析对数值计算的极大挑战，针对近年提出的稳态微聚束机制，本项目开展了基于宏粒子模型的半解析研究，分析了微束团单次与多次经过激光调制器增强腔的集体效应动力学。课题组与加速器领域国内外同行合作(清华大学唐传祥教授课题组、美国斯坦福大学赵午教授)，项目研究成果将为稳态微聚束储存环设计与激光调制器设计提供理论指导。