Stimulated Coherent Emission from Short Electron Bunches in Free Space

The peculiarities have been studied of the stimulated emission of a sheetlike electron bunch of finite length and transverse size passing through an undulator field. A two-dimensional model, based on a nonstationary parabolic equation, has been formulated and includes the effects of slippage and optical guiding as well as transverse electromagnetic energy diffraction and dissipation. It is shown that the emission from the electron bunch is composed of short coherent pulses (superradiation pulses) which are diffracted after escaping from the channel formed by the electron bunch.