在0.22 THz微电真空折叠波导行波管放大器(FWG-TWT)的设计中，为了保证在电子枪中产生的、具有所需电流密度的电子注能够稳定、成型地注入互作用区，并维持较高的电子通过率，需仔细设计磁场聚焦系统。本文在 FWG-TWT 中使用螺线管线圈和周期永磁聚焦系统(PPM)2种磁场结构来实现电子束流的稳定注入和传输。通过三维仿真软件对此电子光学系统进行模拟计算，重点考察了磁场的初始位置、磁感应强度峰值以及磁体厚度等对电子束传输特性的影响。仿真结果表明，在合理的参数范围内，电子注静态通过率可以接近100%，波动很小，能够实现束流的稳定注入和传输。%In the design of 0.22 THz Folded Waveguide Traveling-Wave Tube(FWG-TWT) which acts as an amplifier in terahertz sources,a magnetic focusing system is employed to ensure the beam from the electron gun moving into the beam-wave interaction region with high passing rate. The paper studies two kinds of magnetic focusing system,including solenoid and Periodic Permanent Magnet(PPM). Three-dimensional software is used to simulate the model and analyze how such parameters as magnetic pole position,period,flux density,even magnet pole’s thickness determine the beam’s transmission. The results show that the static passing rate of electron beam in the tunnel can almostly achieve 100%,with a small oscillating range of beam.
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