缩短自由电子激光放大器饱和长度的研究

缩短自由电子激光器中的束-波互作用饱和长度，能够有效地降低加速器、摇摆器以及整体器件的成本。为探索缩短束-波互作用饱和长度的途径，本文作者采用非线性数值模拟方法，研究自由电子激光放大器中关键参数对束-波互作用饱和长度的影响。以一种红外自由电子激光放大器为例，对摇摆器磁场振幅在3 000 Ga做±10%较大调整，对应的饱和长度5.92 m，仅缩短0.11 m(减少不足2%); 通过对摇摆器周期、电子束能量、激光波长的搭配进行优化，当摇摆器周期为3.8 cm、电子束能量为105 MeV、激光波长为853 nm时达到最优，使饱和长度缩短到4.35 m(减少26.5%)。结果表明:摇摆器振幅对饱和长度的影响不大，但电子束能量、摇摆器周期、激光波长三者之间的恰当匹配至关重要，可明显缩短对应的束-波互作用饱和长度。  

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 nu-merical simulation method .Taking an infrared FEL amplifier as example , a range of ＆#177;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 am-plitude has a slight influence on shortening the saturation length , whereas the proper matching of the wiggler period , the laser wave-length and the electron-beam energy is able to greatly shorten the saturation length and increase the saturation power .