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

Factors influencing polarization control with crossed undulator in soft X-ray free electron lasers

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。

The crossed undulator is an effective method for polarization control in soft x-ray free electron lasers（FELs）.Influencing factors were statistically analyzed for polarization control with a crossed undulator in self-amplified spontaneous（SASE） FELs.The effects of the coherence length of radiation,and the relative slippage length and power difference of the two field components were analyzed,and the principles for optimizing an polarization control scheme with a crossed undulator were proposed.These principles are that： the radiation should have good longtitudinal coherence,the relative slippage length of the field components should be short,and the power difference of the two field components should be small.This work provides a theoretical basis for optimization of polarization control scheme with crossed undulator.