高电流密度实心电子束均匀磁场聚焦电子枪的设计

Design of High-Current-Density, Pencil-Beam Electron Gun with Uniform Magnetic Field Focusing

针对W波段小型化扩展互作用器件对电子枪及其对电子束的需求,设计了采用均匀磁场聚焦的高电流密度实心电子束电子枪。首先考虑现阶段阴极发射能力和扩展互作用器件对电子束的需求下完成了静电电子枪的设计;在此基础上,将电子枪分为静电聚焦区、过渡区和均匀磁场区三个部分,通过理论计算得出了理想的均匀聚焦磁场分布。在此基础上建立了高电流密度实心电子束均匀磁场聚焦电子枪的三维粒子仿真模型,工作电压为17 kV,阴极发射电流为19.3 A/cm2的条件下得到了压缩比为33,束电流为668 mA,平均束半径为0.182 mm,平均束电流密度为642.4 A/cm2的高电流密度实心电子束。仿真结果表明,该电子束在半径为0.25 mm的电子通道内的流通率达到了100%,理论计算和三维粒子仿真的结果符合得很好。

The high-current-densitypencil - beam electron gun with the uniform magnetic field focusing was modeled, approximated, simulated, and designed to meet the increasing demands of the miniaturization of the W - band extended interaction devices. First, the electron gun was divided into three parts： an electrostatic focusing zone, transition zone, and a uniform magnetic field zone. Next the ideal; uniform focusing magnetic field was theoretically calculated. Finally, the characteristics of the high-current-density, electron beam were evaluated with the 3D model of the electron gun, formulated with the calculated uniform magnetic field. The calculated results included： at a working voltage of 17 k V, the beam current of 668 rnA from the space-charge-limited emission cathode, the average beam radius of 0.182 mm in the uniform magnetic fieldcorresponding to a compression ratio of 33 ,and the average beam current density of 642.4 A/ cm2 and an emission current density of 19.3 A/ cm2 . The transmission efficiency of the electron beam through a beam tunnel 0.50 mm in diameter was simulated to be 100% . The theoretical calculated and 3D particle-in-cell simulated results were found to be in good agreement.