NSRL光谱辐射标准和计量线偏振性和光谱纯度研究

This project is to establish an Au-Si-Au triple-mirror reflection polarizer with suppression of higher-order harmonics. This polarizer has an integrated filtering effect and higher-order harmonics can be suppressed directly with the proposed polarizer in the proper energy region. Au film provides promising performance in the energy range of 10-100eV, especially the highest degree of polarization. Silicon’s cutoff edge is acts as the blocking element for higher photon energy. Quantitatively measuring polarization of SR is a base of performance research of polarization optical element, Polarization performance of SR affect the metrology accuracy of polarization optical element directly. In the wavelength range of 5-140nm, a transmission grating (TG) is used to determine the contribution of higher-order harmonics at spectral radiation standard and metrology beamline (U26) in NSRL. TG is used to quantitatively research the higher-order contribution after suppressed by different material filters and different thickness filters in the proper energy region. TG is also used to research the higher-order contribution after suppressed by the triple-mirror reflection polarizer. Suppressing higher-order effectively can provide more purity spectra for detector calibration and performance research of optical element in the region of 5-140nm, and this can improve the metrology accuracy..Spectral radiation standard and metrology beamline is dedicated to EUV spectra metrology, a grazing incidence sperical grating monochromator is used to split the continuous light source. Usually grazing incidence grating monochromator can cover a wide photon energy region. Since the angle of incidence has to be small enough to reflect at the highest photon energies, there is an abundance of higher-order diffracted light at the low end of the photon energy range. For the existing beamline where the design cannot readily be altered, it is the simplest and effect method to use transmission filters suppressing higher-order harmonics. Higher-order homonics can be suppressed but it is impossible to eliminated, so to know the contribution of higher-order quantitatively is also important, it can be used to modify the experiment data.

建立Au-Si-Au三镜反射兼俱高次谐波抑制的偏振仪，提高入射光的偏振性和定量测量NSRL计量站同步辐射偏振性，为极紫外偏振光学元件研究提供基础。利用高线密度透射光栅定量研究计量线的高次谐波分布，定量研究计量线所覆盖的5-140nm波段不同滤片材料和同一材料不同厚度滤片对高次谐波的抑制作用，研究三镜反射偏振仪对45-120nm高次谐波的抑制作用。为5-140nm波段探测器定标和光学元件性能测试提供高纯度的光谱，以提高计量精度。.计量光束线是我国极紫外光谱计量的实验平台。同步辐射偏振性研究直接影响偏振元件的计量精度。入射的同步辐射光经光栅单色器分光后，其出射光总是伴有高次谐波。对于已经建成的光束线，要改变光学设计和现有结构来抑制高次谐波是困难的，滤片抑制高次谐波是简单和有效的；即使采用了高次谐波抑制手段，也会有残存高次谐波，为了提高光谱纯度和计量精度，需要定量研究高次谐波，以修正实验数据.

光谱辐射标准和计量光束线(计量线)是我国极紫外光谱计量的平台。随着我国太空科学的飞速发展，极紫外光谱计量的需求越来越迫切。要提高光谱计量精度就要采用有效的方法抑制高次谐波以提高入射的光谱纯度和了解同步辐射的偏振性。入射的同步辐射光经光栅单色器分光后其出射光总是伴随有高次谐波，对于已经建成的光束线要改变光栅单色器的结构来抑制高次谐波是困难的，滤片抑制高次谐波是简单和有效的，三镜反射机构可以安装在后置镜出射光后，不改变整体光栅单色器的结构，且对较高级次的谐波抑制是有效的。实验测试结果表明各波段合适的滤片和三镜反射机构相结合可以更有效的抑制高次谐波、提高光谱纯度。在30-50nm波段，以前由于高次谐波的含量高，几乎不能使用，现在光谱纯度提高到96%以上。.本课题先研究了计量线本身高次谐波的定量分布,建立了三镜反射机构并完成在线安装调试。然后实验测试了Si、Al、Al/Mg/Al、LiF和MgF等滤片分别对各个不同波段高次谐波的抑制效果；研究了三镜反射机构单独使用时对高次谐波的抑制效果，三镜反射机构对二级以上更高级次的谐波有明显的抑制效果；研究了三镜反射机构和Si、Al、Al/Mg/Al滤片相结合时对高次谐波的抑制效果。两者结合时高次谐波的抑制效果最好：5-40和105-140nm波段，光谱纯度100%； 40-50nm波段，光谱纯度可以到96%。本项目还研究了计量线光谱的偏振度，在12nm附近偏振度在95%。