The Study Of Optical System For Solar Extreme Ultraviolet Imaging Spectrometer

In recent years, people are increasingly concerned about the activity of solar andthe change of space environment as the development of space technology.Hyper-spectral imaging observation of solar in the EUV is an important method forthe study of solar atmosphere’s physical characteristics. Solar EUV imagingspectrometer is used to observe the EUV spectral radiation with spatial resolution.The information of the EUV radiation is important condition for the research of themechanism of solar activity like corona heating and solar wind acceleration.Therefore, carrying out the study of optical system for solar EUV imagingspectrometer is of great significance.This paper focus on the key technologies which required for the developmentprocess of optical system for solar EUV imaging spectrometer, including: opticalsystem design, toroidal substrate fabrication and testing, EUV holographic gratingdesign and fabrication, and toroidal profile testing etc.The characteristic of EUV detection is summarized. Every optical structure ofthe EUV imaging spectrometer is analyzed and comparison, the structure ofdispersive imaging spectrometer with telescope system and concave grating isselected. Working theory of dispersive imaging spectrometer, the imaging anddispersion theory of concave grating are introduced. The aberration correcting theoryof toroidal uniform-line-space grating and toroidal varied-line-space grating are given.According to the application requirements of solar activity’s observations,combined with the domestic and international development status of solar EUVimaging spectrometer, performance parameters for solar EUV imaging spectrometerare drew up. The characteristics of every optical element for EUV imagingspectrometer are discussed, the specific optical elements are choice. Two opticalsystems for solar EUV imaging spectrometer are designed for different structures,the design progresses, design results, results of tolerance analysis and the opticaltransmission efficiency are given respectively.Fabrication process of super-smooth toroidal substrate is described, methods oftesting the radius of the toroidal surface are studied, and radius of the toroidalsurface is tested by the spherical-model method. Measurement methods for theroughness of super-smooth toroidal surface are studied, roughness of the substratesurface is tested by atom force microscope and optical profiler respectively, the testresult reveal that the surface has up to the standard of super-smooth. Two kinds ofEUV grating groove are designed according to the scalar diffraction theory. Thehologram ion beam etching process is described, and the EUV grating is fabricated.Two kinds of broad-band EUV multilayer are designed, the grating is coated withone design result, and deposition process of EUV multilayer is given.Aim at the problem of toroidal surface’s profile cannot be tested byinterferometer directly, methods of null compensating testing toroidal surface withcylindrical lens and orthorhombic plane plate are present, the compensating theoriesof these methods are given, the error source and error estimated value are summedup, typical optical paths are designed for a typical toroidal surface by every method,total errors are calculated, optical paths and total error calculated results show thefeasibility of these methods.