交叉型波荡器软X射线自由电子激光极化控制的影响因素

 交叉型波荡器是一种实现软X射线自由电子激光极化控制的有效方式。以自放大自发辐射自由光电子激光为例,采用统计的方法系统地分析了交叉型波荡器软X射线自由电子激光极化控制的影响因素。通过对光场相干长度、光脉冲两分量之间相对滑移长度和光场分量平均功率差异等的分析,给出了优化交叉型波荡器极化控制方案遵循的原则,即：辐射场相干时间尽可能长,光场分量相对滑移长度尽可能短,辐射场分量功率差异尽可能小等。该原则为交叉型波荡器软X射线自由电子激光极化控制方案的优化提供了依据。     

FEL振荡器的一维模拟计算

利用基于自由电子激光经典理论的一维模型的两个程序(MFEL1和FEL0),数值模拟了1.06μm自由电子激光振荡器的各物理参数的演化。MFEL1是考虑了Slippage效应的短脉冲多模计算程序,FEL0是没考虑Slippage效应的长脉冲单模计算程序。前者更能反映实际情况,后者能更细致地模拟光场与电子束在一次放大过程中的演化。计算表明,在短脉冲情况下,激光强度、品质、增益和能量抽取效率强烈依赖于电子束流强度,对一定范围的能散变化却不敏感;但在长脉冲情况下,上述物理量对能散在同样范围内的变化较为敏感。光强度的增益谱清楚地再现了小信号放大的Madey定理。在信号接近饱和时,增益谱的非零部分出现在远离共振频率的区域,这正是FEL中的边带不稳定性。     

短波自由电子激光放大器数值模拟

介绍在理论上研究自由电子激光(FEL)的MICFEL程序。MICEFL是以单粒子理论为基础的二维放大器程序。利用MICFEL计算的Paladin实验结果与FRED程序计算结果以及25米Paladin实验结果相比均基本符合。理论计算的结果显示了FEL增益光导的特性。     

孔耦合自由电子激光振荡器光场横向结构特性

 孔耦合输出对自由电子激光(FEL)振荡器腔内光场的横向结构有很大的影响, 在输出镜上横模之间发生很复杂的耦合转换。基于中物院远红外自由电子激光振荡器, 研究了 孔输出波导 FEL的数值模拟, 对孔耦合及其引起的腔内光场的变化给以特别的注意, 依据数 值结果, 分析了孔耦合FEL光场横向结构的特性。     

高增益自由电子激光饱和态分析的三维统计理论

考虑电子束横向发射度和电子β振荡,将2005年国际上提出的单通过高增益自由电子激光饱和状态分析的统计物理方法发展到三维情形。首先建立一种描述电子三维运动的归一化简化模型,推导了一维光场下包含电子横向运动的Vlasov方程。在螺旋型波荡器情形下通过引入横向运动守恒量发展了三维统计物理分析方法,并编写了相应计算程序,计算自由电子激光达到饱和时系统的光强增益、聚束因子。作为对比验证,编写包含N个电子自由电子激光系统的三维直接数值模拟程序,结果表明数值模拟和统计计算结果相一致。对比文献中一维模拟和一维统计理论计算结果,所得结果反映了电子束横向发射度以及电子在波荡器中的横向β振荡对饱和点参数的影响。     

增益介质中的光场本征模—自由电子激光的三维解与光导

给出了等效折射率横向分布为二次型函数情况下的三维光场方程的本征模。它是非厄密算符的双正交基。利用这套双正交基可以实现微扰展开来处理自由电子激光的三维问题。以光导现象为例,得到了由于电子束中心偏离而引起光束重心的离轴行为的方程。     

改型wiggler高次谐波自由电子激光的非线性理论分析

建立了改型wiggler自由电子激光的非线性理论,导出了自洽非线性方程组.用计算机模拟方法对改型wiggler高次谐波自由电子激光进行了分析,得到了电子在与光场相互作用,从线性调制到非线性饱和演化过程中的相空间群聚图、高次谐波的增益、抽取效率以及电子束能谱图,同时,还研究了电子束能散度对高次谐波的增益和效率的影响等.模拟结果证实了改型wiggler自由电子激光是实现短波长相干光辐射的重要途径之一. 关键词：     

FEL振荡器实验中电子束非理想入射和反射镜倾斜引起的三维效应模拟

用３－ＤＯＳＩＦＥＬ程序计算、分析了在自由电子激光振荡器实验中，电子束偏入射、斜入射和反射镜倾斜引起的各种三维效应对振荡器自由电子激光特性影响。     

FEL振荡器实验中电子束非理想入射和反射镜倾斜引起的三维效应模拟

用３－ＤＯＳＩＦＥＬ程序计算、分析了在自由电子激光振荡器实验中，电子束偏入射、斜入射和反射镜倾斜引起的各种三维效应对振荡器自由电子激光特性影响。     

SASE自由电子激光起振问题及统计特性的数值模拟

 介绍一种自放大自发辐射自由电子激光（SASE FEL）的自发辐射和电子束噪声的数学描述，运用修正的一维非定态程序，对SASE FEL 起振问题及光场统计特性进行了数值模拟，分析了自发辐射谱的发展过程及一定频带宽度内光场随机特性的统计规律，数值模拟结果与理论结果符合较好。     

Gain enhancement in two-stream free electron laser with planar wiggler and axial guide magnetic field

The theory for the two-stream free electron laser (FEL) consisting of a relativistic electron beam transported along the axis of a planar wiggler in the presence of an axial guiding magnetic field is proposed and investigated. The electron trajectories and the small signal gain are derived. The characteristic of the linear gain and the normalized maximum gain are studied numerically. The result shows that the normalized maximum gain is considerably enhanced in comparison with that of the single stream. The effect of the difference between the energies of the two beams in this configuration of FEL is also considered, and we find that the gain is affected by the energy differences between groups 1 and 2.     

自由电子激光的计算机模拟

本文使用1(2/2)维电磁相对论粒子程序对自由电子激光进行计算机模拟。在线性段,计算机模拟与用解析理论计算的增长率符合很好。与没有轴向引导磁场的自由电子激光相比,加一弱轴向引导磁场时,Wiggler场的强度可降得较低。加一强轴向引导磁场时,波能量达到饱和水平所需时间较短。     

Kinetic theory of a cyclotron-undulator hybrid fel in circular waveguide

In this paper, we model the cyclotron-undulator hydrid instability using the kinetic theory in circular waveguide geometry, following the generalized method of the field expansion in the guiding center coordinate system; and derive in detail the coupling coefficient for a cyclotron-undulator hybrid FEL operating at the fundamental harmonic of gyration and undulation. In our discussion, the effect of the transverse structure of the radiation fields is taken into account, but the undulator is considered as an ideally longitudinal one.     

Gain enhancement in two-stream free electron laser with a planar wiggler and an axial guide magnetic field

The theory for a two-stream free electron laser (FEL) consisting of a relativistic electron beam transported along the axis of a planar wiggler in the presence of an axial guiding magnetic field is proposed and investigated. The electron trajectories and the small signal gain are derived. The characteristic of the linear gain and the normalized maximum gain are studied numerically. The result shows that the normalized maximum gain is considerably enhanced in comparison with that of the single stream. The effect of the difference between the energies of the two beams in this configuration of FEL is also considered, and we find that the gain is affected by the energy differences between groups 1 and 2.     

Instability of Two-stream Free-electron Laser with an Axial Guiding Magnetic Field

A model of two-stream Free-Electron Lasers (FEL) with an axial guiding magnetic field (AGMF) is proposed and investigated in this paper. The dispersion relation is derived employing linear fluid theory. The characteristics of dispersion relation are analyzed in detail by numerical solutions, which show that the growth rate can be considerably enhanced and the operation frequency is significantly broader with the suitable of AGMF, separation velocity and beams’ relative density factor, and the occurrences of two-stream instability in FEL are stronger due to the presence of AGMF.     

磁场逐渐增强的摇摆器

研究了用磁场增强摇摆器来提高自由电子激光器效率的机制．采用KMR方程，考虑空间电荷效应，模拟计算发现自由电子激光器的效率有了很大的提高，而且电子束能散度越大，对提高自由电子激光器效率越有帮助．因此采用磁场增强摇摆器能充分利用加速器的能量来莸得更高的自由电子激光器能量 关键词：     

光速调管FEL的小信号增益理论

 利用自由电子激光（FEL）纵模统一理论，系统地分析了光速调管FEL的小信号增益理论，并对色散参数Nd、束流能散度和发射度的影响进行了讨论。     

New method for energy compensation of free electron laser

In this paper the theory of FEL operation in a longitudinal uniform magnetic field integrated with a synchronous precessing electro-magnetic field is expounded in view of the main problems in FEL development. A new energy compensation method is suggested as a new way and basis for the development of FEL research.