SHINE腔式BPM系统射频信号调理前端研制  

Development of RF Signal Conditioning Front-end for Cavity BPM of SHINE

作　　者：陈健[1] 陈方舟 冷用斌 CHEN Jian;CHEN Fangzhou;LENG Yongbin(Shanghai Advanced Research Institute,Chinese Academy of Science,Shanghai 201204,China;Shanghai Institute of Applied Physics,Chinese Academy of Science,Shanghai 201800,China)

机构地区：[1]中国科学院上海高等研究院,上海201204 [2]中国科学院上海应用物理研究所,上海201800

出　　处：《原子能科学技术》2022年第10期2124-2132,共9页Atomic Energy Science and Technology

基　　金：上海市市级科技重大专项(2017SHZDZX02);国家重点研究开发项目(2016YFA0401903,2016YFA0401900)。

摘　　要：基于低温超导直线加速器的上海硬X射线自由电子激光装置(SHINE)需1个分辨率可达200 nm的束流位置测量系统,以实现电子束与光子束在波荡器中的紧密相互作用和能量交换。现已研制的束流位置测量系统不能完全满足上述要求,为此,基于对关键技术指标的分配,设计研制了一个由C波段腔式探头、低噪声系数的单路下变频至低中频的射频信号调理前端以及专用数字信号束流位置处理器构成的CBPM系统样机。而作为连接腔式探头和数字信号采集电子学之间的桥梁,射频信号调理前端(radio frequency front-end,RF前端)的结构和性能也直接决定了CBPM系统的性能。本文从SHINE对CBPM系统的整体需求为出发点,分析了系统对射频信号调理前端的指标分配,提出了一种放大器开关切换型RF前端的方案设计,并成功搭建了1套可模拟束流条件的离线全锁相采样测试平台。此外,在上海软X射线自由电子激光装置(SXFEL)中搭建了测试平台并完成了射频信号调理前端的带束性能评估,束流实验结果表明,在束团电荷量为100 pC、系统动态范围在±100μm的条件下,采用腔式探头射频信号一分二的评估方法,位置分辨率可达71 nm,优于设计指标需求。The SHINE based on the superconducting linear accelerator is the first quasi-continuous wave hard X-ray free electron laser user facility under construction in China.It has the characteristics of high repetition rate of 1 MHz max,low bunch charge about 100 pC and large scale about 3.1 km.In order to reduce the decay of the output power of FEL radiation,it requires a beam position monitor(BPM)system with resolution of two hundred nanometers to realize the close interaction and energy exchange between the electron beam and the photon beam in the undulator.The BPM system that has been developed for SXFEL cannot fully meet the requirements.Therefore,based on the quantitative relationship between the relative amplitude extraction uncertainty of the cavity BPM signal and the main parameters of each subsystem,as well as the reasonable allocation of key technical indicators,a prototype of cavity BPM system was designed and developed,which consists of a C-band cavity BPM pickup,a radio frequency(RF)front-end with the character of signal-channel down converted RF signal to low intermediate frequency(IF)signal and low noise figure,and a dedicated digital BPM signal processor.As a bridge between the cavity pickup and the digital BPM signal processor,the structure and performance of the RF front-end also determine the performance of the CBPM system directly.In this paper,based on the SHINE’s demand for cavity BPM system,the key technical indicators of the RF front-end were analyzed,the scheme of amplifier switching type RF front-end was proposed,and the advantages of the RF front-end schemes with amplifier switching type and the adjustable attenuation type were compared and analyzed by the method of parametric simulation.And an off-line full phase-locked sampling test bench which can simulate beam conditions is also successfully built for the first time.In addition,the beam test bench was built in SXFEL facility and the performance evaluation of the RF front-end was completed.Based on the evaluation method of power divided,

关 键 词：SHINE 腔式BPM系统 射频信号调理前端 性能评估 

分 类 号：TL506[核科学技术—核技术及应用]