采用MAGIC 2.5D模拟软件, 建立了X波段11.424 GHz相对论大功率速调管放大器的高频结构模型。该模型由5个简单药盒型谐振腔组成, 包括1个输入腔、3个中间腔和1个输出腔。研究了该模型的高频特性, 初步设计漂移管及各谐振腔结构参数, 再结合热腔模拟, 研究了输入腔的吸收匹配问题, 依据各腔体对基波电流逐级调制情况, 优化配合各腔体的间隙等结构参数, 从而获得电子束的最佳调制状态, 最后通过调节外加均匀磁场大小获得百MW功率输出, 结果表明: 在加速电压520 kV、束电流460 A、外加磁场0.4 T的条件下, 当注入信号功率为1 kW时, 基波电流调制深度达162%, 最终输出功率105 MW, 效率43.5%, 增益50 dB。

An X-band high power relativistic klystron amplifier is studied using a 2.5 dimensional PIC code MAGIC in this paper. The presented klystron is composed of five nose-cone removed pillbox cavities, including an input cavity, three middle cavities, and an output cavity. The absorption of the injected microwave is studied, and the gaps of idler cavities are optimized according to the fundamental harmonic modulated current when an electron beam propagates through every cavity. Finally, after optimization of the guiding magnetic field, the output microwave is obtained with an average power of 105 MW when the diode voltage is 520 kV, beam current 460 A, the guiding magnetic field 0.4 T and the seeding power 1 kW. The efficiency reaches 43.5% with a gain of 50 dB, when the fundamental current modulation depth reaches 162%.