基于谐振腔的超级陶粲装置注入器束团长度与电荷量监测器设计

Design of bunch length and charge monitor based on cavity resonator for injector of Super Tau-Charm Facility

超级陶粲装置(Super Tau Charm Facility,STCF)是前沿的新一代正负电子对撞机,其对高精度、高亮度的要求对加速器技术提出了重大挑战。由于该装置储存环束流寿命极短且动力学孔径较小,为了保证注入效率,需要精确测量注入束团长度及电荷量等参数,从而监测注入过程,这对束流诊断方法及设备提出了更高的要求。基于谐振腔特征模式信号提取直线加速器束流信息的监测技术具备较高的信噪比,且属于非拦截测量,有潜力满足高品质直线加速器的在线高分辨测量需求。本文针对STCF注入器束流参数及测量需求,进行了谐振腔束团长度和电荷量监测器的物理设计与仿真。利用电磁仿真软件CST(Computer Simulation Technology)建模设计了两个Pill-Box型谐振腔,并对其结构进行优化。仿真结果表明,对于束团长度与电荷量的仿真测量误差分别达到3.3%和0.02%,依据同类型谐振腔式探头的在线测试结果,推算该监测器束团长度测量分辨率有望达到100 fs@1.5 nC,电荷量测量相对分辨率好于0.07%,能够满足STCF的束团长度及电荷量的诊断需求,后续将制作实物以进行在线测试。

[Background]The Super Tau Charm Facility(STCF)is a new generation electron-positron colliders at the forefront of high precision,and its high brightness requirements pose a major challenge to accelerator technology.Resonant cavity-based monitors utilize characteristic mode signals for non-intercepting,high signal-to-noise ratio measurements,hence may meet the online high-resolution measurement requirements of various high-quality linear accelerators.[Purpose]This study aims to address the challenges posed by the short lifetime and the small dynamic aperture of the storage ring beams in the STCF by developing high-resolution monitoring techniques for bunch length and charge to ensure efficient injection and precise measurement of these parameters.[Methods]According to the beam parameters and measurement requirements of the STCF injector,the physical design and simulation of the resonator bunch length and charge monitor were carried out.Two Pill-Box cavities were designed by using Computer Simulation Technology(CST)modeling,and their structures were optimized.Subsequently,the beam load in the CST particle studio for simulation was conducted to analyze influences of beam tilt and lateral offset on the measurement accuracy,and the measuring resolutions of bunch length and charge were evaluated using cavity beam position monitor(CBPM).[Results]Simulation results show that the measurement errors of bunch length and charge are 3.3%and 0.02%,respectively.According to the online test results of the same type monitor,it is estimated that the resolution of bunch length of the monitor is expected to reach 100 fs@1.5 nC,and the relative resolution of charge measurement is better than 0.07%.[Conclusions]The currently designed monitor meets the diagnostic requirements of bunch length and charge of STCF,it will be manufactured in future for online testing.