Research Of X-ray Bent Crystal Spectrometer With Uniform Dispersion For Dense Plasmas Diagnostics

X-ray plasma spectroscopy, which plays a significant role in the field of inertial confinement fusion(ICF), offers a powerful tool for investigating of plasma formation and evolution mechanisms and for diagnosing the plasma conditions as well. Focusing bent crystal spectrometers based on Bragg diffraction are commonly employed to study the high-energy density plasma sources. The measured x-ray spectrum provides fruitful information of plasma parameters, including electron temperature with its gradient, electron density with its gradient, the opacity and etc. Consequently, developments of novel diagnostic tools and methods are crucial parts of ICF research, which are also important complements to high-energy density physics.To expand the application of bent crystals in ICF area and to meet the growing demands of diagnosing the complicated x-ray spectra from high-Z target materials used on “Shengguang” laser facility and the Z-pinch Primary Test Stand(PTS), we have conducted a research on the uniform dispersion crystal spectrometers. This project is supported by National Natural Science Foundation of China(No.10876044, No. No.11005098) and the Laboroary Directed Research and Development(LDRD) project of Princeton Plasma Physics Laboroary, Princeton University funded by the U. S. Department of Energy(No. DE-AC02-09CH-11466). This thesis focuses on the raised scientific issues in complex spectra identifications together with the weak X-ray Thomson scattering signals measurements and aims at exploring new types of x-ray spectrometers for hot and warm dense plasmas diagnostics. The main works are as following:① The thermodynamic equilibrium model, the coronal model and the collisional-radiative model used for describing different plasma conditions are introduced. The x-ray spectra emitting and broadening mechanisms are discussed as well as the spectral profile features. Also discussed are the electron temperature and density diagnostic methods based on the the K-shell self-emission spectra, which provide theory foundations for the analyzation and interprataion of experimental data.② A varity of existed singly-focusing spectrometers, including Johann-, von Hamos- and conicial- instruments are summarized. To overcome the drawback of varing linear dispersion and to satisfy the needs of complex spectra measurements, a uniform dispersion concept has been proposed. The equations of the crystal bent curve and the spectrometer performance parameters are mathematically derived. Numerical calculations show the feasibility of uniform dispersion and high spectral resolution capability. While for the double-focusing spectrometer with spatial resolution using spherically bent crystal, the possibility of approximated uniform dispersion of such a spectrometer is investigated. Also deduced are the accurate photon throughput formulas along with the results of proof-of-principle experiments.③ The developed dual-channel uniform dispersion crystal spectrometer is tested on “Yang” accelerator for measuring the K-shell x-ray spectra from Al wire-array imploading Z-pinch plasmas and the unform dispersion of recorded spectra is successfully realized. Using the spectra from mica bent crystal, the electron temperature, the electron density and the ion temperatures are inferred. The radial gradient of electron temperature of cylindrical plasma is determinded from the line and continuum emissions. A comparison of Langmuir dips from plasma perturbation and spectral line shifts from quantum mechanics theory gives a self-consistent electron density value.④ According to the special measurement requirements of warm dense matters, the principles of detecting and diagnosing warm dense plasmas with X-ray Thomson scattering technique are introduced. The requirements of probes and spectrometers for weak signals acquiring are also analyzed. A dual-channel spherically bent crystal spectrometer is construced for XRTS measurement and characterized, showing the capability of high spectral(~ 4000) and spatial(~ 18 μm) resolution. The shock-compressed warm dense plasmas are probed by the x-ray free electron laser. The spatially-resolved scattered x-ray spectra are recorded with the developed spectrometer and the spatial profile compressions due to laser shocks are laso observed.