高传输通过率带状电子注聚焦与传输特性的研究

Investigation on focus and transport characteristics of high transmission rate sheet electron beam

大宽高比的非轴对称带状电子注在微波和毫米波真空电子器件中具有显著的技术优势与应用潜力.采用轴向均匀磁场可以聚焦和传输带状电子注,且具有易于实现电子注与磁场的匹配和调节、聚焦强流电子注以及无传输截止电压限制等优点,但面临严重的Diocotron不稳定性.结合单粒子模型理论和冷流模型理论,对带状电子注传输特性进行的研究及其数值计算表明,通过详细设计带状注电子光学系统物理参数,增强聚焦磁场并在传输通道高度方向上选择较大的电子注填充比,可以有效降低Diocotron不稳定性对带状电子注的影响,并实现其长距离稳定传输.通过对应用于W波段带状注器件的电子枪及电子光学系统三维仿真和参数优化,解决了小尺寸和高精度结构所带来的对准、装配和焊接等工艺与技术问题,完成了带状电子注聚焦与传输实验高真空密封束管的研制.实验获得的电子枪压缩和成形的椭圆带状电子注截面为10mm×0.7mm,且在电子注电压为20—80kV,电流为0.64—4.60A时,在长度为90mm的漂移通道内带状电子注传输的通过率达到95%以上.该结果优于目前国际上采用周期永磁聚焦进行带状电子注传输通过率92%的实验结果.

The investigation on focus and transport characteristics of sheet electron beam has been a key technique for the development of high-power microwave and millimeter-wave vacuum electronic devices.Compared with the period permanent magnetic system to transport the sheet electron beam,the uniform magnetic focusing system has many advantages,such as easily adjusting and matching the magnet with the beam,focusing the intensity electron beam,no cut off beam voltage restriction,etc.However,the Diocotron instability of the sheet electron beam in the uniform magnetic field can produce the distortion,deformation,vortex and oscillation to destroy the beam transportation.In this paper,the single-particle model and the cold-fluid model theory and calculation are used to indicate that if the electron optics system parameters of the sheet beam are designed more carefully,the magnitude of uniform magnetic field and the filling factor of the beam in transport tunnel are increased appropriately,the Diocotron instability can be reduced,even vanished completely to transport the sheet beam effectively in a long distance.To verify the above conclusion,the electron gun with the ellipse cathode and the electron optics system are designed and optimized with the three-dimensinal simulation software in detail.After the complex assembly and weld process with the small geometry and high precision,the W-band sheet electron beam tube is manufactured and tested.The sheet beam cross section of 10 mm×0.7 mm is achieved experimentally with the one-dimensional compression and formation of electron gun.Also,with a beam voltage of 20—80 kV,and beam current of 0.64—4.60 A,the experimental transmission rate of sheet beam electron tube manufactured is more than 95% with a drift length of 90 mm,which is higher than the periodic cusp magnetic field transport experiment result of 92% obtained recently.