D波段行波管电子光学系统设计

Design of electronic optics system for D-band traveling wave tube

摘要:

提出一种用于D波段行波管的电子光学系统设计方案，包括电子枪和永磁聚焦系统，并进行了验证。电子枪采用经典皮尔斯电子枪结构，阴极发射面的外层设置阴极套壳，抑制阴极边缘杂散发射；采用圆柱形控制极替代锥形控制极，同时在聚焦极加负偏压，调节电子注的压缩状态。所设计电子枪工作电压为19 kV，提供电子注电流57 mA，注腰半径为0.068 mm，射程为14.9 mm。为在半径0.15 mm的电子通道中稳定地聚焦和传输电子注，永磁聚焦系统采用周期永磁聚焦系统。峰值磁场为布里渊磁场的2.9倍，增加了电子注刚性。模拟结果显示，传输的电子注最大波动半径小于0.1 mm。按所设计的电子光学系统加工组装了试验流通短管，测试结果显示电子注电流为49.83 mA，收集极电流为49.6 mA，对应电子注流通率达到99.5%，实现了设计目标。

Abstract:

A design of the electro-optical system for D-band Travelling Wave Tubes (TWTs), including an electron gun and a Periodic Permanent Magnet(PPM) focusing system, is presented and verified. The electron gun utilizes the classical Pierce electron gun structure, the outer layer of the cathode emission surface is set with a cathode sleeve to suppress stray emission at the edge of the cathode, and a cylindrical control electrode is used instead of a conical control electrode, and a negative bias is added to the focusing electrode to adjust the compression state of the electron injection. The electron gun can provide a beam current 57 mA with the beam waist radius of 0.068 mm and the shooting distance of 14.9 mm at the beam voltage of 1.9 kV. A sleeve tube is attached on the cathode to block the electron emission from the edge of the cathode. A cylindrical focusing electrode is used in the electron gun for adjusting the beam focusing state. To stably focus and transmit the electron beam in the beam tunnel of 0.15 mm radius, a PPM focusing system is employed. The peak magnetic field is 2.9 times the Brillouin magnetic field to increase the rigidity of electron injection. The simulated result shows the fluctuation radius of the electron beam is less than 0.1 mm. In order to validate the effectiveness of the D-band TWT electro-optical system, the electron gun and the PPM focusing system have been machined and assembled. The experimental results show the beam current is 49.83 mA, and the collector current is 49.6 mA. The beam transmission rate of 99.5% are obtained by carefully adjusting the PPM system, which achieves the design goal.