中文摘要：

近年来的实验表明，在相对论微波器件中，填充适当密度的等离子体可提高器件的束波互作用效率、输出功率和工作频率。在该类器件的理论分析中，常常利用电磁流体模型来研究电子束和等离子体。从麦克斯韦方程组和电子的运动方程出发，导出了相对论电子束和磁化等离子体的等效介电张量，所得结果为该类器件的理论分析提供了方便。

英文摘要：

In recent years, it was found experimentally that injecting plasma into the relativistic microwave apparatus enhanced the interaction efficiency, the output power and the operating frequency much more than the vacuum case. Plasma also can greatly improve the transmission quality of electron beam. Therefore, much attention has been attracted to the study of the plasma waveguide. Among those theoretical analyses of the apparatus, electron beam and plasma are often studied by electromagnetic fluid model. The expressions of the dielectric tensors of relativistic electron beam and magnetized plasma are derived from the Maxewell＇ s equations and the electron motion equations. The results can be convenient for theoretical analyses of the apparatus.