针对北京正负电子对撞机二期工程(BEPCⅡ)在高流强下运行经常出现的突然丢束问题,研制了基于逐束团测量的丢束监测系统。束流位置探头(BPM)的四路电极信号作为监测系统的信号源,四路高速模数转换器(ADC)和现场可编程门阵列(FPGA)进行模拟信号的数字化和数字信号的处理。通过获取丢束前每个束团的位置和流强等信息来分析引起丢束的原因。结合加速器硬件情况,长时间对丢束监测系统数据的分析,以及设计的对比实验,深入研究丢束问题。系统对高频系统故障、束流不稳定性和磁铁电源系统不稳定等原因引起的丢束现象可以做出准确的判断,进而为加速器稳定运行提供优化方向。

A new prototype system for bunch-by-bunch beam position measurement has been designed and built to monitor and analyse the beam loss in the Beijing Electron-Positron ColliderⅡ(BEPCⅡ) storage ring. The fast ADC is used to sample the analog signals from the beam position monitor, then the digital signal is processed further using programmable gate array (FPGA). The beam information can be obtained by means of bunch-by-bunch, such as bunch position, bunch current and bunch tune. Based on system monitoring and data analysis for long terms, as well as the dedicated machine experiments, it’s relatively clear for operators to understand some trip events, especially the beam loss caused by the high-frequency cavity trip, tune drift and multiple bunch instability. The study proves that the system is very useful for the operation of accelerator.