上海同步辐射装置波荡器光源空间相干性的研究

Research on spatial coherence of undulator source in Shanghai synchrotron radiation facility

利用高斯-谢尔光源模型理论与交叉谱密度函数在自由空间传输的规律,研究了上海同步辐射装置波荡器光源(BL15U)的空间相干性;讨论了预聚焦镜、单色器对光束空间相干性的影响;实验测量了单色光狭缝S2处光束的横向相干长度(Z方向).理论计算表明,S2处光束的横向相干长度为66.5μm,但实验测量结果为27μm.理论与实验相差较大的原因是由于S2上游光学元件预聚焦镜或单色器1期性高频振动导致了光束空间相干性的退化.实验结果表明,上海同步辐射装置波荡器光源已有较强的空间相干性,可以满足微米尺度的硬X射线相干性实验.

Firstly,based on the Gaussian-schell model source theory and the propagation of cross-spectral density function in free space, the spatial coherence of undulator source（BL15U） in Shanghai Synchrotron Radiation Facility is studied.Secondly,the influences of pre-focusing mirror and the monochromator on the beam spatial coherence are discussed.Finally,the spatial coherent length at mono slit S2 is measured.The spatial coherent length at S2 theoretically is 66.5μm,but experimentally is 27μm.This difference is due to the high frequency vibration of pre-focusing mirror or monochromato.Nevertheless,high coherent hard X ray beams can be obtained at the location of experimental sample and many coherent experiments can be fulfilled on this beamline.