喇曼型无引导场自由电子激光实验的理论计算

SIMULATION OF RAMAN FREE ELECTRON LASER WITHOUT AXIAL GUIDING MAGNETIC FIELD

用三维程序CAGⅡ对西南应用电子学研究所在EPA-74脉冲加速器上所作的FEL(自由电子激光)实验进行了数值模拟,分析计算了输入功率、摇摆器磁场振幅、自发辐射频率、电子能量、束流强度和发射度等参数变化时对饱和位置、饱和功率和效率的影响。在对实验参数中的电子能量作合理调整的条件下,数值模拟的增益系数大约为70dB/m,是实验值的80％。因此饱和位置比实验推后20％到40％。饱和功率高出大约3倍。经折算后大约为1MW,与实验结果比较接近。考虑到实验的复杂情况可认为理论结果同实验结果基本符合。

Based on single particle theory and under the paraxial and adiabatic approximations , Only the wiggler field is considered in the equations of electron trajectories and longitudinal motion equations of electron are averaged over the period of wiggler , λw. We derived a set of coupled nonlinear differential equations of both TEmn and TMmn modes in a loss -free cylindrical waveguiede. The space charge potential is considered and the longitudinal guiding field is neglected . Using the data obtained in the EPA - 74 FEL experiment , the models are computed by 3-D CAG FEL II code. The computational results show that the saturation position z= 130 - 150cm , the saturation power P≈1MW and the gain G = 70dB/m , in the scope of experiment parameters .