Z-pinch The Soft X-ray Continuous Spectrum Measurement

To diagnose the spatial distribution and status of plasmas in Z-pinches at different time is the only way to understand the principle plasmas follow and then to control the pinch process for application. Ions, electrons and photons interact with each other fiercely during this process, which makes it possible to obtain the dynamic information of those particles without interrupting them through detecting the x-ray emissions. Through the x-ray spectrum, temperature of radiation field, ion density, radiating shock etc can be acquired. Limited by the driving ability of domestic facility, most emitted x-rays in Z-pinch dynamic hohlraum are in sub kilo electron volt energy range while line radiations superimpose on continuum. High resolving power is required for obtaining useful information, which makes severe demands on spectroscopic technology. To search a suitable method meeting requirements for soft x-ray spectrum measurement is the purpose of this dissertation.In this paper, flat-field gratings selected as dispersion components and imaging plate as recording medium constitute a spectrometer. Dispersion property, energy range and spectral resolving power are analyzed with the gratings ray tracing theory. Since high spectral orders of can't be ignored, complexity of extraction from spatial distribution of dispersive x-ray is explained. After extraction process is transformed into linear equations, it's pointed out that the solution can't be determined in math and that more constraints must be added from physical consideration. Different constraints added make an essential distinction among various extraction methods. According to the comparison of iterative method and basis function expansion method, the latter with B-spline basis function is selected for experimental spectrum extraction and in advance is tested numerically on extracting precision and anti-noise performance for both single peak and multiple peaks spectrum, which insures the validity of extraction.Soft x-ray spectrum measurement for normal wire array with foam, dense wire array with foam and tungsten wire array without foam were all done and B-spline expansion method was implemented on extraction. Stability and precision of this method were confirmed again by experimental result while its disadvantage of losing detail for fine structure of spectrum was also demonstrated. Spectra of three types of wire array were compared combining power measurement. Spectral resolving power E/ΔE was estimated to be 61 from the full width at half maximum of a line radiation at about 367eV.