同步辐射晶体单色器高次谐波在光学检测中的应用

Application of Synchrotron Radiation Crystal Monochromator with Higher-harmonics in Optical Detection

基于高次谐波的特性,在上海光源X光学测试线分别进行了吸收谱、成像和衍射相关检测实验,拓展了在线检测中同步辐射的光谱范围和应用场景。利用元素Se的K吸收边对光子能量为12.658 keV高次谐波进行测量,实现了Si(111)双晶单色器4.219 keV能量下限的标定;利用Si(111)晶体的光子能量12 keV高次谐波的衍射成像,研究了晶体热形变引起的Si(333)晶格面衍射的光斑畸变现象;利用双晶单色器出射的光子能量为60keV的高次谐波,完成了对Si(111)高能劳厄晶体摇摆曲线的测量。

The synchrotron is a machine which is used by physicists to produce high energy charged particles.The centripetal force acting on the relativistic electrons causes them to radiate electromagnetic radiation predominantly in vacuum ultraviolet and soft X-ray regions.The synchrotron radiation facility is a large,expensive,and complex organization,devoted to the provision of electromagnetic radiation to a wide range of experimental rigs,and service a community with diverse scientific backgrounds.Synchrotron radiation has the characteristics of high photon brilliance,high collimation and high purity.Double crystal monochromator is the core splitter in synchrotron radiation beamline.The diffraction beam produced by it contains fundamental and harmonic X-rays.As monochromators select from a given spectrum a series of harmonics whose wavelengths satisfy Bragg′s law for the monochromator diffracting planes,higher-order harmonics are still present in the spectrum after monochromatization with not negligible relative intensities.On the one hand,higher harmonics can reduce the monochromaticity of X-ray;on the other hand,higher harmonics have the characteristics of high resolution and high energy.In experiments,higher harmonics are usually used or suppressed according to the demands.High purity harmonics are obtained and fundamental waves are filtered by aluminum sheets of different thickness.Based on the characteristics of higher harmonics,the absorption spectrum,imaging and diffraction experiments are carried out on test beamline(09B)at Shanghai Synchrotron Radiation Facility(SSRF),which expanded the spectrum range and applications of synchrotron radiation at wavelength measurement.The lower limit of monochromator energy is an important feature for beamline.The lower limit of the monochromator energy in SSRF Beamline is 2 keV.There is no simple method to measure the lower limit of the monochromator energy at present.The lower limit of the monochromator energy can be easily measured by high order harmonic.The lower limit of 4.219 keV energy of Si(111)monochromator crystal is calibrated by measuring the K-edge absorption of element Se for third-order harmonic at 12 keV.Monochromaticity is an important criterion of beamline at synchrotron radiation,and thermal deformation of monochromator crystal affects photon energy bandwidth.The energy bandwidth of Si(333)crystal planes is 0.37"@30 keV.This value is on the same order of magnitude with the result of thermal deformation of crystal.It can be used in the detection of thermal deformation of crystal.The specular distortion of Si(333)lattice surface diffraction caused by thermal deformations of crystal Si(111)is studied by diffraction imaging with 12 keV higher harmonic.The ultrahard multifunctional X-Ray beamline in the phase II of SSRF with a photon energy range of30~120 keV,with Laue diffraction monochromator to select from a given spectrum.It is necessary to characterize it at wavelength measurement by high-energy X-rays in this range.The rocking curve of highenergy Laue crystals is measured by Laue diffraction with 60 keV higher harmonic.Based on the test beamline at Shanghai Synchrotron Radiation Facility,studying the applications using higher-order harmonic of crystal monochromator in three aspects.First,the lower limit of the energy of the double crystal monochromator is calibrated.Second,the thermal deformation of crystal is directly observed by X-ray imaging.Third,Characterization of rocking curves of Laue crystal monochromator at high energy.Utilizing monochromator higher-harmonics,a variety of high-precision detections has been successfully realized.This work extended the applied range of Test Beamline at Shanghai Synchrotron Radiation Facility.