Research On The Multilayer-coated Gratings In Vacuum-ultraviolet Wavelength Of Synchrotron Radiation Seya-Namioka Monochromator

Vacuum ultraviolet (VUV) light source have comprehensive application in the cosmic physics, chemistry, lift science, materials science, et al. . Synchrotron radiation facility has become an important light source in the VUV spectrum for its broadband continuous spectrum, high brightness, better straightness, highly polarized, and other sources can not compare the performance. As most of the synchrotron radiation beam lines are adopting grating monochromators to produce monochromatic light, the performance of gratings give the key on the quality of the synchrotron radiation light. However, the efficiencies of both gratings and mirrors below the wavelength 110 nm are difficult to improve because all the available materials strongly absorb radiations.In order to improve the quality of monochromatic light, this thesis is focusing on the investigation of synchrotron radiation multilayer gratings in VUV spectrum, which includes grating design, fabrication, efficiency measurement and analysis, and suppression of higher order harmonics. The main works of this thesis are as follows:(1) The design and fabrication of synchrotron radiation multilayer gratings. The grating was designed to work on the Seya-Namioka monochromator, and sub-quarterwave multilayer which is based on the superposition of various highly radiation-absorbing materials is employed on the grating fabrication to enhance the diffraction efficiency. For the design of multilayer coating, the sub-quarterwave multilayer theory and material selection rule are introduced, and four optimized multilayer films are given. For the design of grating, rigorous vector diffraction theory which base on the RCWM and PCGrate are use to calculate two kinds of multilayer gratings, respectivily. The simulation results show that, the efficiencies of multilayer gratings are nearly two times of the single-layer gratings. Then laminar multilayer gratings were fabricated using holograph and reactive ion beam etching with CHF3, and the profile parameters measured by Atomic Force Microscope indicate that the fabricated groove profiles well meet our design goal.(2) Measurement error analysis and correction method research in the VUV spectrum at the beamline U27 of the Hefei Light Source (HLS).A general correction method for the efficiency measurement of optical components in the 45-110 nm range is proposed to eliminate the contamination of higher-order harmonics. The validity of this correction method was verified by measuring the reflectivity of Au mirror. Then a detailed measurement error analysis and the corresponding resolution methods are given to improve the measurement accuracy on the U27 beamline. Finally, the correction method was applied on the measurement of synchrotron radiation grating. The measurement results show that, the efficiencies of multilayer gratings are obviously larger then the single-layer gratings, and it can achieve the anticipated target very well.(3) The design of higher order harmonics suppressor.According to the practical conditions of the beamline U27, HLS, three method which are base on mirrors, gratings and filters respectively, have been proposed to suppress the higher order harmonics of the wavelength 45-110 nm. The design of each structure and the corresponding harmonics suppression effect were given and analysised in detail. These methods can greatly improve the monochchromaticity without any structural alterations of the beamline.