RFQ低电平控制系统频率跟踪与幅相反馈的设计与实现

Design and implementation of frequency tracking and amplitude-phase feedback in RFQ low level control system

射频四极场(Radio Frequency Quadrupole,RFQ)的动态调谐一般是通过控制腔翼和腔壁上冷却水的水温来实现的。为了方便RFQ老练和调试过程中的功率提升,设计了一个使用直接数字合成技术(Direct Digital Synthesis,DDS)和锁相环(Phase-locked Loop,PLL)技术的RFQ低电平控制系统,该系统可以同时实现对RFQ谐振频率的动态跟踪与幅相反馈控制。即使冷却水没有达到热平衡,RFQ也可以加载功率并形成加速场。该控制系统在以FIR(Finite Impulse Response)滤波器为基础的模拟腔实验平台上进行了测试。测试结果表明:该方案能在对虚拟腔谐振频率进行跟踪的同时,实现±0.5%的幅度稳定度和±0.5o的相位稳定度。

[Background] The dynamic tuning of a radio frequency quadrupole（RFQ） is generally achieved via thermal regulation over the vanes and walls. However it takes tens of minutes to reach nominal power. [Purpose] The dynamic tracking of the RFQ＇s resonant frequency and the amplitude-phase feedback control will make it possible for the RFQ to be powered and form an acceleration field quickly, even though the cooling water of the RFQ does not reach thermal equilibrium. [Methods] An RFQ low-level control system implemented with direct digital synthesis（DDS） and phase-locked loop（PLL） technology was designed and tested at an experimental platform based on a simulation cavity. [Results] The test results show that this scheme can achieve the tracking of resonant frequency with ±0.5% amplitude stability and ±0.5o phase stability. [Conclusion] The performance of system meets expectation, and reaches acquired accuracy.