Research On Key Technologies Of A Window-type X-ray Crystal Spectrograph

The X-ray spectra emitted from laser-produced plasmas contain plentiful information. It is a powerful tool to carry out plasma diagnosis and to study the formation and evolution of the plasmas as well. In order to obtain the high precise experimental data, to detect the phenomenon which has been predicted by the theory, and to discover the new variation of line intensities in the laser-plasma spectral measurement, it is necessary for a novel effective x-ray spectrographs and detecting technology to be developed such as a novel Johann, and spherically or torroidally bent crystal spectrometer due to their increasing luminosity, and high spectral and spatial resolution. In recent years, research of the elliptically crystal spectrometer became hot topic gradually. Compare with the spherically curved crystal spectrometer, although the elliptically curved crystal spectrometer has shortcoming in the measured spectral resolution, signal-to-noise ratio, and spatial resolution,it has the merits of a large spectral range measurement, a large working distance to the source, a real crossover point, no aberration, and a feasible collimation. In this thesis, the theoretical system of the elliptically curved crystal spectrograph was studied by the Bragg equation and the elliptical self-focusing geometric principle, and it was analyzed for the drawback of the elliptically curved crystal spectrometer in the practical application. The idea was firstly proposed to solve the shortcming and demonstrated its feasibility accordingly. And then, a window-type novel x-ray crystal spectrometer was put forward based on the elliptically curved crystal analyzer. It was coupled to an x-ray CCD camera, and a set of system had been designed and constructed. The spectrograph is useful in the experiments of x-ray diagnostics, for example in x-ray lasers, inertial confinement fusion (ICF), laser-matter interaction, and so on. In this paper, the atomic physics mechanism, emission, absorbing and spectrum structure of the keV x-ray spectra were also studied in details both experimentally and theoretically. Detailed contents are given as follows:(1)In views of the x-ray laser target chamber on the SG-II high-power laser facility and the experimentally physical demands, the key influencing factors, such as the elliptical eccentricity and the spectral detection angle, on the angular dispersion, the spectral resolution,and the photometric parameter were studied by the elliptical self-focusing geometric principle. In order to increase the spectral and spatial resolution, using ray tracing code and optical path function, optimization calculation was carried out for an elliptical crystal spectrometer. For the requirements of the high spectral resolution and good signal-to-noise ratio, a window-type novel x-ray crystal spectrometer was presented according to the calculation results that the photometric parameter was simulated in the elliptically curved crystal analyzer.(2) Based on the distinguishing feature of a window-type novel x-ray crystal spectrometer, the characteristics of the coated material of the grazing incidence flat reflection mirror, the crystal integrated reflectivity, and the filter transmissivity were also studied, respectively. The optical system of the pre-grazing incidence mirror was designed. A large area (Φ100 mm) flat mirror was fabricated. It was optimized for the optical path of the window-type x-ray crystal spectromter/s system. The spectrograph was developed. The line transmission function for a spectrographic system, combining with a large area flat mirror as pre-positive optic system, and a filter, was given. The energy window was numerically simulated.(3) Beginning with basic principle of aberration theory, the strict theory model of wavelength error was established and the influencing factors on the errors of wavelength were analyzed in the window-type x-ray crystal spectrometer coupled to x-ray CCD, and a set of syetem, The wave front aberration theory and ray tracing code indicate that the spectrometric system has good spectral resolution (λΔλ) better than 1000. Compare with the elliptically curved crystal spectrometer, the improvement of signal-to-noise ratio is about 3 times.(4) On the basis of the self-designing window-type x-ray crystal spectrometer coupled to x-ray CCD, a window-type novel x-ray spectral measuremental and diagnostical system was set up, aligning scheme is designed, and the K-shell emissions of the laser-produced Al and Ti plasma, and M-band radiation of the laser-produced Au plasma were measured, respectively. The measured results presented high signal-to-noise ratio x-ray spectra. Some spectral lines were classified, and the measured spectral resolution of the spectrograph was given. At the same time, the error correction of the measured spectral line intensity was also proposed.(5) Based on the self-designing window-type x-ray crystal spectrometer coupled to x-ray CCD, and a set of syetem, some issues related to the experimental measurements of the keV x-ray, such as the diffraction efficiency of crystal, the geometrical factors and x-ray CCD camera quantum efficiency, were discussed. According to the theoretical models, and measured spectral results, the diagnostic method of laser-produced plasma's kinetic parameters was also pointed out.