| The study of soft x-ray emission spectrum in laser-plasma interaction has been a subject of considerable importance for a variety of research investigations in laser driven inertial confinement fusion extreme ultraviolet (XUV) soft x-ray lasing, coherent high order harmonic generation etc. and potential applications of laser-produced plasmas as an x-ray source for microlithography, contact microscopy of biological cells, backlighting of imploding pellets etc. Quantitative analysis of the x-ray spectrum in the keV range is often used to derive diagnostic information on electron temperature, density, ionization states, and expansion velocity of the plasma as well as its spectral characterization for various applications. The X-ray emitted from laser-produced plasmas contains plentiful information in inertial confinement fusion (ICF). Abundant spectra of highly charged ions from laser plasmas have been obtained by using various crystal spectrographs. The spectra of elements have been used for determining electron temperature and electron density. In order to obtain the useful information, we have developed the Elliptical Crystal Spectrograph (ECS) in the 620-6200 Ev X-ray region based on elliptical geometry the theory.Optical system design for spectrometer has been developed taking the advantage of ellipse focusing geometry theory. The fundamental is that the ray emitted from a focus (front) of elliptical will flock together on the other focus (back) by the reflection on the elliptical surface. Through the aperture setting on the back focus, the x-ray will shoot on the detector and goes on record. Basic optical system constitution and characteristic parameter of the two-channel elliptical crystal spectrometer has presented. Research on parameter selection and craftworks of elliptical crystal analyzer has been explored.In this paper we present a theoretical evaluation of the performances of the elliptical curved crystal analyzers equipping the plasma diagnostic spectrometers of various fusion laboratories. Calculations have been performed by using a simple physical model developed to describe the diffraction properties of bent crystal. The generation mechanism of laser pulsed plasma x-ray and the theory basis of x-ray crystal diffraction has been discussed. The general characteristics are compared for the plane,convex, and concave crystal analyzers, which may be applied to the x-ray diagnosis. The unique advantages of the elliptical analyzer for precise spectral measurements are noted and detailed descriptions of its geometrical and physical optics are presented.Basic way of construction design for spectrometer has been described particularly. An adjustment method has been advanced which make the two channel crystals as a unity. With the comprising of two aiming scheme, the better scheme has been chosen. The dispersion degree of wavelength along the detection circle, the relationship between the luminosity magnitude dβ/dχ and dispersion angle dp, and the effect of an off-axis position of a source point, these three facts that contribute to the spectral line precision are deeply analyzed. The conclusion that directs the optimizing design has presented.We have designed, fabricated ,and installed a spectrographs at ShengGuang-II facility and Xingguang II .Compared with grating spectrographs, crystal spectrographs are simpler, easier to use, and have higher collecting efficiency and better resolution. This spectral region is analyzed with fixed elliptical curved crystals and different 2d-spacing of crystals in the 0.4-2.6nm range. The paper analyzes the dispersive principle of ECS and system design.The experiment using the vacuum system on the spectrometer, demonstrated that the vacuum degree in the spectrometer was up to 6 × 10~-3Pa, satisfying the working requirement of streak camera. The aiming experiment using a simulate point source demonstrate that the aiming scheme satisfied the target chamber effectively and conveniently.To determine x-ray yields, we needed accurate measurements of the x-ray spectrum produced by... |
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