合肥光源储存环同时运行长短束团方案的概念设计研究

项目名称： 合肥光源储存环同时运行长短束团方案的概念设计研究

项目编号： No.11475167

项目类型： 面上项目

立项/批准年度： 2015

项目学科： 数理科学和化学

项目作者： 李为民

作者单位： 中国科学技术大学

项目金额： 98万元

中文摘要： 短束团在同步辐射光源中有非常重要的意义，不仅用于产生时间分辨光谱研究的短同步光脉冲，还可以产生高功率相干THz辐射。目前电子储存环中发展了多种技术用于产生短电子束团，如等时性储存环、激光切片技术、偏转腔技术等，获得了良好的效果，也暴露出明显不足。如等时性储存环中束流强度弱，与其它用户研究不兼容；激光切片技术中，短脉冲辐射光通量弱，重复频率低；偏转腔技术中，短束团只针对个别束线存在，无法满足多用户的需求。本项目将研究在合肥光源储存环上如何产生短束团。实验上，研究储存环准等时性模式下，应用现有高次谐波腔压缩电子束团长度。理论上研究储存环增加2套主动式谐波腔，实现储存环中长-短束团同时运行模式。通过数值仿真研究，确定最佳谐波腔参数，评估束流耦合阻抗、束团非均匀填充、相干同步辐射等对束流动力学的影响，准确预测储存环中长和短束团的表现。最后根据物理要求完成高次模阻尼的高次谐波腔的参数设计和数值模拟。

中文关键词： 电子储存环；超短束团；束流动力学；数值仿真；高次谐波腔

英文摘要： Short electron bunch has interesting application in synchrotron radiation light source, such as production of powerful coherent THz radiation, Time Resolving spectrum analysis, etc. Except for linac-based SR light source, various methods were developed for production of short electron bunch or short radiation pulse, for example, laser-slicing method, isochronous storage ring, crab cavity pair technique, etc. Although the results are very exciting, the defects are also remarkable. In the isochronous storage ring, other usual beamlines can't work well due to very low beam intensity. The photon flux of short radiation pulse is very weak in laser slicing method due to tiny electrons and low repetition frequency. In crab cavity pair scheme, short radiation pulse is only available to single or several beamlines, it is not enough for multi-user research platform. Our aim is to study production of short electron bunch globally in Hefei Light Source storage ring. First, based on available conditions of HLS storage ring, except for lowering momentum compaction factor of the ring, passive 4th harmonic cavity can be used to reduce bunch length futher in quasi-isochronous operation mode. The dependance of bunch length on momentum compaction factor, parameters of basic and harmonic RF cavities, beam intensity will be studied experimentally. Then, considering the empty long straight section of HLS storage ring, conceptual design study of simulataneous long and short bunch operation mode would be made with two additional active harmonic cavities. Compromising and combining bunch length, beam intensity and beam lifetime, main parameters of RF system will be optimized. The final beam performance can be estimated by numerical emulation software of electron storage ring, where the impedance-driven effects, non-uniform filling effects, coherent synchrotron radiation effects, etc, will be taken into consideration. According to physical requirements of conceptual design, we will design two harmonic cavities with HOM damper using electro-magnetic simulation code CST-MWS. Through theoretical analysis of longitudinal beam dynamics, numerical emulation of electron storage ring, technical design of key components-harmonic cavities, the feasibility of new simultaneous long and short bunch operation mode will be approved.

英文关键词： electron storage ring;ultra-short bunch;beam dynamics;numerical emulation;higher harmonic cavity