Research And Design Of UV-VUV Monochromator Based On Seya-Namioka Structure

The vacuum ultraviolet（VUV）band refers to a part of the electromagnetic spectrum with wavelengths between 100nm and 200nm.In this band,there are many atomic resonance lines,absorption lines,and radiation lines that provide a natural resolution mechanism for research on the composition of materials.Research in this band has broad application prospects in life sciences,material sciences,environmental sciences,atmospheric physics,solar physics,micro-nano devices and other fields.The monochromator is a basic instrument for research in the UV-VUV band and is important for improving the performance of various research instruments in the VUV band.Therefore,how to optimize and improve the performance of grating monochromators has been a research focus of scientific institutions in various countries and is also the key to improving the performance of a series of spectrometers with grating monochromators as their core structure,such as UV-VUV spectrophotometers and UV-VUV spectrometers.This paper studies the concave grating monochromator based on the Seya-Namioka configuration.Starting from the design and application of UV-VUV monochromators,this paper conducts systematic and in-depth research on concave grating monochromators using the structural design theory,error analysis theory,and optomechanical joint adjustment method as entry points.The main research content of this paper includes two aspects:optomechanical structure design theory and optomechanical joint adjustment.In the optical design of the monochromator,the grating line density is determined based on spectral resolution parameters and spectral range parameters,and a spectral resolution calculation model based on slit aperture parameters is established.In subsequent structural design,the development of a micro-motion slit for the monochromator is completed based on this.Through experimental testing,when the slit aperture is 0.015mm,the corresponding 313nm spectral resolution is 0.0696nm,which is consistent with the theoretical model of spectral resolution calculation.In the study of high-precision grating monochromator wavelength scanning mechanism,a wavelength output calculation model based on wavelength scanning mechanism structural parameters is first derived,and a linear wavelength scanning mechanism for monochromators is designed.Based on this,ring-by-ring analysis is performed to obtain errors that affect wavelength repeatability.The theoretical calculation model of wavelength repeatability of monochromators is obtained and error allocation is completed.Through experimental testing,within the full spectral range of monochromators,the wavelength repeatability of monochromators is better than 0.02nm,which proves the correctness of the theoretical calculation model of wavelength repeatability;wavelength linearity is better than 0.0126%,which proves the effectiveness of linear wavelength scanning mechanism design for monochromators.In the study of vacuum sealing design for monochromators,vacuum sealing principles are first analyzed and static sealing design for monochromators is completed.Then dynamic sealing structures corresponding to adjustable micro-motion slits and micro-motion grating axes are designed and simulated by analyzing their motion characteristics.Through experimental testing,the overall vacuum degree is better than 5.0×10^-3Pa and signal-to-noise ratio in VUV band is good,verifying effectiveness of vacuum sealing design.In optomechanical joint adjustment research,an optomechanical joint adjustment process for concave grating monochromators based on Seya-Namioka configuration was integrated and best matching method for concave grating entrance/exit slit and wavelength accuracy correction theory were proposed.An innovative solution was proposed for correcting wavelength accuracy of monochromators.In order to improve wavelength accuracy index of monochromators,factors affecting wavelength accuracy of monochromators were analyzed ring by ring based on wavelength output equation of monochromators;zero position deviation parameter of grating axis and pendulum length parameter of grating axis were separated out as two adjustable parameters;based on this zero position deviation parameter was introduced into wavelength correction theory to establish a structural correction method for concave grating monochromator wavelength accuracy based on dual parameters;combined with calibration correction to form a comprehensive correction method for wavelength accuracy;experiments were conducted on both monochromator developed in this paper and another one developed in laboratory;after correction by this method measured wavelength accuracy was better than±0.085nm verifying effectiveness of this correction method.