上海光源逐束团数据采集系统研制

Research of bunch by bunch data acquisition system in SSRF

为进一步提升光源性能,需要对加速器非线性束流动力学问题、宽带束流阻抗问题、恒流模式下注入脉冲引入的束流位置扰动问题进行研究,从而优化新增设备阻抗、优化束团填充模式、优化注入模式,提高不稳定性流强阈值。而逐束团诊断技术的研究,是达成上述目标的技术基础。上海光源研制了一套逐束团数据采集系统,该系统主要由RF前端、数据采集卡和EPICS软件三部分组成。RF前端将束团信号展宽到2 ns,利用四路采样率为125 MHz的ADC组成等效的500 MHz逐束团采样,利用EPICS实现后续信号处理。在线测试结果表明,系统可准确检测逐束团位置信息,并可获得逐束团工作点,为机器研究提供了有力手段。

Background： In order to improve the synchrotron performance in the constant current mode, attentions should be paid to problems such as non-linear beam dynamics, broadband beam impedance, and position disturbance, etc. Purpose： To address these problems, a bunch by bunch data acquisition system （BBDAQ） is implemented for real-time bunch position monitoring, as well as the off-line data analysis for the Shanghai Synchrotron Radiation Facility （SSRF） storage ring. It can be applied to optimize new equipment impedance, filling pattern, injection mode, and raise threshold value of current instability. Methods： This BBDAQ developed at SSRF consists a RF front end to filter and expand bunch signal to 2 ns, a data acquisition and processing card to sample bunch signal with four 125-MHz ADCs, which make an equivalent 500-MHz sampling rate, and the EPICS for post-processing to give bunch position and tune value. Results： Online experimental results show that the system can measure bunch by bunch position and tune value successfully. Conclusion： The development of bunch by bunch data acquisition system provides an efficient tool to analyze beam impedance, coupling instability, nonlinear dynamics. It makes further improvement of synchrotron performance visible.