相对论速调管中间腔与调制电子束间的非线性互作用

在强流相对论电子束驱动的相对论速调管放大器中, 由于强流和高场强的影响, 尤其是中间腔具有高Q值, 微波腔与电子束之间的非线性作用很明显, 严重影响器件性能. 根据麦克斯韦方程组以及电子在微波场作用下运动方程给出了中间腔的束-波互作用自洽方程. 从这些方程出发, 研究了调制深度和调制频率对间隙电压幅度和相位的影响. 对比常规速调管的等效电路模型, 自洽公式给出的间隙电压幅值同粒子模拟结果更接近, 尤其是较高调制深度的情况. 同时器件带宽随调制深度的增加而变宽, 这也同粒子模拟结果一致. 由此设计了一个S波段高增益相对论放大器, 在LTD (长脉冲螺旋线)加速器上开展了相应的实验工作, 实验上获得了1.1 GW的输出功率, 器件增益49 dB. 关键词： 相对论速调管 非线性互作用 自洽方程

Nonlinear interaction between modulated electron beam and the intermediate cavity of RKA

In the relativistic klystron driven by intense relativistic electron beam, due to the influences of intense current and high electric field, especially the high Q value for the intermediate cavity, the nonlinear interaction between the intermediate cavity and the electron beam is very strong. It will significantly affect the performance of the device. According to the Maxwell equations and one-dimensional motion equation of electron, the self-consistent equation of the beam-wave interaction is obtained in the intermediate cavity. Based on these equations, the influences of the modulation depth and the modulation frequency on the amplitude and phase of gap voltage are studied respectively. The voltage amplitude obtained by the self-consistent equation is close to the voltage amplitude of particle in cell simulation, especially under the higher modulation depth compared with that obtained from the equivalent circuit model of conventional klystron. Meanwhile, the bandwidth of device becomes wide with the increase of the modulation depth. Finally, an S-band high-gain RKA is designed, and the corresponding experiments are done on the LTD accelerator. The output power with 1.1 GW is obtained, the gain is 49 dB.
Keywords： RKA nonlinear interaction self-consistent equation