能散度与发射度模块在太赫兹FWTWT模拟中的应用

Applications of electron kinetic and angular spread modules for Terahertz Folded-Waveguide Traveling Wave Tube simulation

研制了三维全电磁粒子模拟大规模并行程序NEPTUNE3D的能散度和发射度模块,主要用于评估电子出射速度和方向分布对太赫兹折叠波导行波管(FWTWT)性能的影响。将能散度和发射度模块应用到0.22 THz的FWTWT器件粒子模拟中,结果表明:能散度主要通过改变器件束压范围,使其偏离束波互作用共振电压范围,导致器件性能下降;发射度反映电子发射角的发散,同时影响纵向与横向电子速度,电子横向速度的增加导致其更易碰撞通道内壁,使电子总数下降,导致器件性能下降;若束压保持不变,电子横向速度的增加势必导致轴向速度的减小,破坏束波同步条件,导致器件性能进一步下降。

For analyzing the influence of emitted electrons velocity and direction distribution on the performance of terahertz Folded Waveguide Traveling Wave Tube（FWTWT）, the kinetic and angular spread modules of a massively parallel 3-D fully electromagnetic and Particle In Cell（PIC） code named NEPTUNE3D are designed. The above modules are applied to the simulation of 0.22 THz FWTWT successfully. The simulated results could be concluded as followings. The kinetic spread alters the range of electron-beam voltage distribution which destroys the oscillation voltage relation between electron beam and electromagnetic wave, therefore causes the degrading of device performance. The angular spread reflects the distribution of emission angle which alters electron transverse and axial velocities. As the increasing of transverse velocity, many electrons will collide with the inner-wall of tube which causes the degrading of device performance. At the same time, considering the constant beam voltage, the decreasing of electron axial velocity could destroy the synchronous condition between beam and wave, which causes the device performance degrading furthermore.