Design And Performance Of Single-order Multilayer Diffraction Gratings

The single-order diffraction grating has the diffraction characteristics of generating 0-order and conjugate ± 1-order,which can effectively suppress the high-order diffraction.This kind of diffraction characteristic which produces pure spectrum makes the single-stage diffraction grat-ing have important application value in X-ray diagnosis of laser plasma.However,when the energy of the incident X-ray reaches the order of several keV,the penetration of the X-ray be-comes stronger with the increase of its energy,and the deflection and light distribution ability of the traditional transmission single-stage diffraction grating to the energy band X-ray de-creases,which causes most of the diffraction light to focus on the 0-stage,thus affecting the diffraction efficiency of the 1-stage.In recent years,the appearance of multilayer grating has solved the problem of grating application in X-ray with high energy.By combining the high reflectivity of multilayer to X-ray and the light splitting ability of grating,multilayer grating can provide high level 1 diffraction efficiency to the incident X-ray.However,there are a series of higher-order diffraction in the spectrum of the multilayer grating.The multilayer structure in the multilayer grating can not only enhance the first-order diffraction efficiency,but also inev-itably enhance the diffraction efficiency of the higher-order diffraction.In this paper,a kind of multilayer single-order diffraction grating named quasi-sinusoidal multilayer grating is designed according to the structure of quasi-sinusoidal single-order dif-fraction grating.Combined with the diffraction characteristics of the single-stage diffraction grating and the reflection characteristics of the multilayer mirror,the quasi-sinusoidal multi-layer grating has new diffraction characteristics.In the depth direction,the periodic multilayer structure can provide high reflectivity of X-ray,and in the horizontal direction,the quasi sine grating structure can effectively suppress high-order diffraction.Therefore,the multilayer sin-gle-stage diffraction grating combines the excellent characteristics of the two,so that the X-ray with energy of several keV can still obtain high light intensity and monochromaticity X-ray,when incident at normal angle or grazing incidence.The quasi sinusoidal multilayer grating designed in this paper is expected to provide the high diffraction efficiency X-ray spectrum of black cavity radiation with several keV energy bands for ICF.The main contents of this paper are as follows:The first chapter introduces the principle of laser driven ICF,the detection of laser plasma X-ray and the content and significance of this paper.The second chapter reviews the derivation of scalar diffraction theory and the design ideas of several single-stage diffraction gratings,including binary sinusoidal diffraction grating,quasi sinusoidal grating,random grating,inclined rectangular hole grating and trapezoidal transmis-sion grating.At the end of this chapter,the limitation of the spectral range of transmission sin-gle-stage diffraction grating is analyzed.In the third chapter,we study the multi-layer mirror applied in X-ray optics.We focus on the calculation of the multi-layer reflectivity and the design of MATLAB program.In the fourth chapter,the diffraction characteristics of multilayer gratings and single-order multilayer gratings are studied,including the application of X-ray diffraction theory in multi-layer gratings and the analysis of the difference between the diffraction characteristics of mul-tilayer gratings and traditional gratings.Besides,we design a single-order multilayer diffraction grating for several keV X-rays,and analyze the diffraction distribution of the designed multi-layer grating at 3kev and 5kev energy points,as well as the conditions for obtaining high dif-fraction efficiency at-1 diffraction order.