根据激光驱动质子束流低发射度、短脉冲、单束团低电量的性质, 研究腔式束流位置探测器(BPM)测量激光加速器产生的质子束团横向位置的可行性问题。针对质子束团的大横向分布和发散角问题, 推导了其通过腔式BPM的输出信号, 结果表明该信号与集中从束团对称中心、倾斜一定角度通过的束流产生的输出信号相同。依据上述原理, 使用CST软件进行了腔式BPM的设计和仿真, 确定了矩形谐振腔波导耦合的方案。讨论了该方案的腔式BPM对于激光加速束流的适用性和不同激光驱动质子束流参数的分辨率, 并针对PW级激光加速系统进行了分辨率估算。

According to low-emittance, short-pulse and low-charge-in-single-bunch properties of laser-driven proton beam, we study the feasibility of cavity beam position monitor (BPM) to measure the transverse position of proton beam generated by laser accelerator. In view of the large transverse distribution and divergence angle of proton beam, we derive the output signal when it goes through the cavity BPM, and the result shows that the output signal is identical to that generated by the beam passing through the symmetry center of the transverse distribution and at a certain angle of inclination. Based on the above principle, we use CST software to design and simulate cavity BPM, and determine the scheme of rectangular cavity with coupling waveguide. We discuss the applicability of this scheme for laser-accelerated beam and the resolution of different laser-driven proton beam parameters, and estimate the resolution of PW laser acceleration system.