A quasilinear theory is developed for free-electron lasers in which intense electron beams with a significant velocity dispersion are used to implement the kinetic regime of electron–wave interaction. Under the assumption that the field is stored in a high-Q cavity, stationary distributions of the spectral density of excited cavity modes are found for various levels of the excess of the beam current above the threshold. It is shown that, if the excess is large, the energy distribution of the electrons that exit the cavity includes a plateau with the width proportional to the generation spectrum width. Parameters are estimated for long pulse free-electron lasers that can be implemented on the basis of linear induction accelerators. It is shown that the energy of high-dispersion electron beams can be efficiently converted into broadband terahertz radiation.

为自由电子激光器开发了一种拟线性理论，其中使用具有显着速度色散的强电子束来实现电子波相互作用的动力学机制。假设该字段存储在一个高Q对于超过阈值的束流的各种水平，发现激发腔模式的光谱密度的平稳分布。结果表明，如果过剩量较大，则出腔电子的能量分布包括一个宽度与产生谱宽度成正比的平台。可以在线性感应加速器的基础上实现的长脉冲自由电子激光器的参数估计。结果表明，高色散电子束的能量可以有效地转换为宽带太赫兹辐射。