BEPCⅡ逐束团双反馈系统运行试验研究

Research of the double feedback system operating in BEPCⅡ

逐束团反馈控制是抑制束流不稳定性最好的方法,未来的环形正负电子对撞机(Circular Electron Positron Collider,CEPC)等超大型装置的环周长为100 km,束流不稳定增长时间为毫秒量级,这要求束流振荡能在十几圈甚至几圈内被抑制,意味着反馈系统提供的阻尼时间要很短,传统的数字反馈系统显然难以实现。一些缩短阻尼时间的方法相继被提出,其中之一是在储存环中采用若干套束流反馈系统作用于同一束流上,通过阻尼效果的叠加以减少总系统阻尼时间。本文工作主要利用北京正负电子对撞机二期(Beijing Electron Positron Collider Ⅱ,BEPCⅡ)同步模式外环上两个条带kicker的有利条件,开展双反馈系统带束实验研究,一套是自行研制的逐束团数字横向反馈系统,另一套是Dimtel公司生产的商用逐束团数字反馈系统,分别测量各系统以及双系统的阻尼时间。实验测得商用系统的阻尼时间是0.93 ms,自研反馈系统的阻尼时间为2.98 ms,双反馈系统的阻尼时间为0.70 ms,验证双反馈系统能够有效缩短阻尼时间。

[Background] Digital bunch-by-bunch feedback control is the best way to control bunch instability. It will be applied to the super collider to suppress the beam oscillation within a dozen or even several cycles. The damping time of circular electron positron collider (CEPC) and FCC-ee ( Future Circle Collider e^-e^+) is very short, but it is impossible to realize through using traditional digital feedback system.[Purpose] This study aims to cure the coupled-bunch instability by using a dual-feedback control system to reduce the damping time for BEPCⅡ(Beijing Electron Positron Collider Ⅱ).[Methods] Several feedback systems operate simultaneously and act on the same time beam in storage ring can superimpose the damping effect and then reduce the damping time of the system. With the favorable condition of two stripline kicker located on the outer ring, we make a experimental research about double feedback system in BEPCII synchrotron mode. Among the double feedback system, one system is the self-make digital bunch-by-bunch transverse feedback system based commercial card, the other system is the commercial feedback system produced by the Dimtel company.[Results] The damping time of commercial feedback system is measured as 0.93 ms, the damping time of self-make digital bunch-by-bunch transverse feedback system based commercial card is measured as 2.98 ms, and the damping time of double feedback system is measured as 0.70 ms.[Conclusions] Several feedback systems work simultaneously can effectively reduce the damping time turn by turn.