Study on Saturation Length in a Free-electron Laser Amplifier

The cost of a free-electron laser (FEL) can be substantially reduced by shortening the saturation length of the beam-wave interaction. In order to study the way of shortening the saturation length of the beam-wave interaction, the authors research the impact of the key parameters on the free electron laser amplifier to the saturation length of the beam-wave interaction by nonlinear numerical simulation method. Taking an infrared FEL amplifier as example, a range of ±10% variation around 3000 Gauss results in a saturation length shortening of 0.11 m from 5.92 m (less than 2%), but optimizing the wiggler period, the electron beam energy and the light wavelength shortens the saturation length to 4.35 m (about 26.5%).In the present paper, results show that the wiggler amplitude has a slight influence on shortening the saturation length, whereas the proper matching of the wiggler period, the laser wavelength and the electron-beam energy is able to greatly shorten the saturation length and increase the saturation power.