系统提出了一种新的腔式束流位置监测器(BPM), 即跑道型腔式BPM, 并使用微波工作室软件进行了理论研究和模拟计算, 提出了通用设计方法。跑道型腔式BPM的金属腔部分具有跑道形横截面, 引出束流位置偏移激励起的一对偶极模式作为束流位置信号。该方案的偶极模式极化方向固定, 频率分离, 可以解决随机误差产生的横向串扰问题, 其理论位置分辨力可以达到15 nm。

A new high brightness injector based on a new photocathode RF electron gun is planned to be installed at Hefei light source. To get high quality electron bunch, precise control of beam position is required. The positional resolution of the beam position monitor(BMP) system designed for RF electron gun should be higher than 10 μm. A new type of cavity BPM with racetrack cavity is designed. The racetrack cavity is a cavity with a racetrack cross section, so that it has a pair of dipole modes with different resonant frequency and fixed polarization direction. The cross-talk problem is then solved. The 3D model of the cavity is simulated in MWS, and the theoretical performance of racetrack BPM and the optimization method are analysed. The theoretical resolution of racetrack cavity BPM can be 15 nm.