通过选择适当电子初始的横纵向速度比,并引进坡度磁场的方法,来提高同轴腔电子回旋微波激射器效率.非线性模拟表明,用这种办法可以将德国卡尔斯鲁研究中心研制的同轴腔电子回旋微波激射振荡器的实验效率,从26.7%提高到31.5%.这种效率放大的物理机制是:坡度磁场改变了相对论电子的运动条件,有效地改善了波束互作用过程中电子的群聚状态,使电子束有更多的动能转换为电磁能,从而提高了电子束的换能效率.

To enhance the efficiency of a coaxial-cavity free-electron maser,a method by employing a tapered magnetic field is proposed. Nonlinear simulation indicates that the efficiency of 26.7% measured in the FZK experiment might be enhanced up to 31.5% by a proper taper of the axial magnetic field. The mechanism of the efficiency enhancement is that the tapered magnetic field changes the condition of the electrons' motion and improves the bunching of the electrons in the interaction between the electron beam and the wave.