S波段多注相对论速调管的小信号理论

Small-signal theory of multiple-beam relativistic klystron amplifier

多注相对论速调管利用多注电子注并行工作,各电子注在传输过程中彼此独立,利于提高注波互作用效率,抑制杂模振荡。分析多注相对论速调管的小信号理论,从谐振腔内电场的场形函数出发确定了不同腔体结构的耦合系数的计算方法,得到了不同电子注形状、注数时的基波电流分量轴向变化过程,并进行模拟验证。结果表明:同轴谐振腔的间隙耦合系数要大于圆柱腔的间隙耦合系数,采用同轴谐振腔更有利于注波互作用;电子群聚过程与每注电子注的势能密切相关,提高电子注数目有助于得到更大的基波电流分量。在电子注电压600 kV、电流5 kA、间隙电压30 kV的条件下,输入腔后的基波电流分量达800 A。

Multiple beam relativistic klystrons use multiple parallel beamlets that propagate in individual channels but interact in common cavity gaps.Multiple-beam operation takes advantage of the low current and small radius of individual beamlet to avoid non-working mode oscillation and enable more efficient bunching and consequently higher efficiency.A small-signal theory of multiple-beam relativistic klystrons is developed and validated by simulation.The method of calculating the beam coupling coefficient is studied,assuming that the electric field is a function of gap distance.Properties of current modulation are investigated,obtaining a expression of scaling law for the fundamental component of the bunching current.The results indicate that the amplirude of the beam coupling coefficient is higher in the coaxial cavity,which is better for beam-wave interaction.The influences of potential energy of individual beamlet on current modulation are crucial,using more annular electron beams helps to have a bigger amplitude of ac current.Making use of electron beams of 600 kV/5 kA,gap voltage of 30 kV,theac current of multiple beamlets can reach 800 A behind the input cavity.