偏轴双腔互比型腔式束流位置监测器

Cavity beam position monitor based on two off-axis resonant cavities by comparison method

提出一种利用偏轴双腔来监测电子束位置的新方法,根据谐振腔归一化分流阻抗参数分析了其工作原理和主要特性。偏心束流在偏轴谐振腔中激发出较强的偶极模TM110信号,根据两腔输出的偶极模信号幅度比可直接测量束流的中心偏移量。偶极模信号幅度变化反映了束流的偏移方向,省去了鉴相工作,简化了前端接收电路的的设计,基模抑制问题已被解决。利用MAFIA和HFSS软件对本征模进行仿真,并分析了模式耦合特性,仿真结果验证了新结构的可行性。

A new concept for monitoring electron beam position based on two off-axis cavities is proposed, main performances of the beam position monitor are discussed using its main parameters, such as normalized shunt impedence. Two off-axis cavities excited dipole mode TM110 by off-center beam provides microwave signals strong enough for the detection of beam position, which can be measured directly by the ratio of the dipole mode amplitude from two cavities. The change of dipole mode amplitude reflects the beam displacement. RF front-end circuits are simplified by the method without phase detection and the common mode is heavily suppressed. Eigenmode characteristics as well as mode coupling coefficient between two cavities are studied by MAFIA and HFSS simulations, which prove the function of the new structure.