NSRL注入器束团长度测量系统初步设计

Preliminary design of the bunch length measurement system for NSRL injector

合肥光源注入器升级改造接近完成。为了更好地分析其束流品质,为储存环提供更高品质的束流,针对合肥光源设计了一套利用横向偏转腔(Transverse Deflecting Structure,TDS)测量分析束流纵向品质的系统。利用TDS分析束流纵向品质精度高,功能多样,优势明显。本文TDS采用外围开槽盘荷波导结构,给出了该结构具体尺寸及相关参数计算,并对计算结果做了简要分析处理。根据该结构在注入器的安装位置,对束团长度测量系统进行了物理设计,并分别使用MATLAB程序和PARMELA模拟了束团通过该结构的状态分布,得到了符合预期的纵向束团长度测量结果。

Background： With the development of design and construction technology in accelerator fields, high-quality beam brings challenges to beam diagnostics. Purpose： To meet the strict requirements, new beam measurement techniques have emerged. One of them is the Transverse Deflecting Structure（TDS） method that possesses advantages of versatility and high precision. This paper aims to design a TDS Structure for longitudinal measurements. Methods： Based on the work on TDS by scientists around the world, the Computer Simulation Technology-MICROWAVE STUDIO（CST-WS） software was applied to design a TDS cell structure-Disk loaded waveguide structure with two peripheral recesses matched to Hefei Light Source（HLS） parameters. Beam dynamics simulations are executed by using MATLAB and PARMELA to show the evolution of the bunch distribution in the structure, respectively. Results： Dimensions of this TDS, the field type and the resulting dispersion curve are obtained. And the impacts on the operating frequency of feature sizes are explicated. Conclusion： This structure can get the desired deflection field type. Stabilizing mode method can realize stable ~25.5 MHz frequency separation, which can be proved effective through CST simulations. Characteristic dimension b impacts the operating frequency most, and dr impacts changes most for different polarization modes. MATLAB and PARMELA simulation are consistent.