QUALITY REQUIREMENTS OF ELECTRON BEAM IN FEL
自由电子激光器对电子束质量的要求

The effect of the monochromaticity of relativistic electron beam's energy on the small signal gain of free electron lasers is analyzed. For a certain pumping field, there is a critical energy divergency, over which the small signal gain will become negative. The shorter the wavelength and the longer the magnification length, the higher is the requirement of energy monochromaticity of electron beam for laser amplifiers. But the requirement of monochromaticity of electron beam for laser oscillators is much lower.