Study Of A Compact Spectrometer For Near-Edge X-Ray Absorption Spectroscopy Under Grazing Incidence Conditions

Near-edge X-ray absorption fine structure spectrum(NEXAFS)contains the local structure information of absorbing atoms.Because of its wide application range and high sensitivity,NEXAFS has become one of the important means to study the structure of matter.At present,the NEXAFS spectrum is mainly based on the experimental equipment of synchrotron radiation source.However,the synchrotron radiation light source is very limited,the device volume is huge,the construction and operation and maintenance costs are too high,and the NEXAFS technology is difficult to meet.The more scientific research needs.In this thesis,the small spectrometer which is suitable for the measurement of near-edge X-ray absorption spectrum in laboratory is taken as the research target.Through theoretical analysis and experiment,the following research work is mainly carried out:1.A near-edge X-ray absorption spectrometer was designed and fabricated to study the NEXAFS spectrum of carbon.The laser plasma light source was used as the X-ray source,the concave variable line distance grating as the spectral element,the area CCD as the detector.In order to facilitate the installation and adjustment,the optical parameters of the optical system are optimized.2.In this paper,we propose a new method to extract the absorption spectrum from the reflection spectrum.Since the traditional method cannot be used to deal with the fine structure of the near-edge region.In this paper,we propose to use the ?-scaling correction method to get the absorption spectral directly from the Fresnel formula.3.Based on the theory of concave-period-varying grating aberration,analytical resolution and ray-tracing method are used to analyze the theoretical resolving power of the spectrometer,which proves that the design goal can be achieved.The signal-to-noise ratio(SNR)of the developed spectrometer was analyzed by using the data of each component in the system.The wavelength calibration method of the spectrometer is studied and the fitting model of the parameter fitting calibration method is deduced.4.The resolution of the spectrometer was measured by nitrogen plasma spectroscopy.It is about 666 at 4.4nm and the wavelength range is 2-5nm.The wavelength calibration was performed by using the parameter fitting method,and the actual structural parameters were calculated.The reflectance spectra of the polyimide were measured and the absorption spectra were obtained by the proposed extraction and absorption spectra.The peak position of the polyimide was characterized by the functional group of polyimide.