Abstract
The paper presents experimental results obtained on “Kanal-2” facility. Laser radiation focusing on the surface of plane magnesium targets created the high temperature plasma, which emitted X-ray and vacuum ultraviolet (VUV) radiation. This radiation spectrum was investigated with two spectrographs: the mica crystal spectrograph (working range 8.2 ? - 9.6 ?) and the grazing incidence VUV spectrograph (working rage 30 ? - 130 ?). A set of beryllium stepwise attenuators appended the diagnostic complex and allowed us to get an approximated picture of a continuous spectrum within the range of 2.2 ? - 6.2 ?. The estimation of the plasma electron temperature Te from the ratio between the intensity of the dielectronic satellites and the resonance line gives Te ~ 180 eV. The ratio between the intensity of the resonance and intercombination lines gives the electron density of the emitting zone ne ~ 2 × 1019 cm-3. Some lines observed within the spectral range of 8.5 ? - 9.1 ? belong to none of the transitions of Mg ions. Perhaps the observed spectrum is determined by the transitions in so-called hollow ions of Mg, i.e. in the ions with unfilled inner shells. The spectra obtained with the grazing incidence spectrograph and with the minimum-directioned discrepancy iteration method of spectrum reconstruction from the attenuation curve in the beryllium stepwise attenuators are also presented.
Highlights
Despite the fact that a lot of works have been devoted to the study of plasma X-ray radiation produced at focusing the high-power laser radiation on the solid target surface (e.g. [1,2,3,4,5]), many problems still remain to be unsolved
The model of a local thermodynamic equilibrium (LTE) and the corona model (CM) widely using at calculations have the restricted areas of feasibility, and both can appear unsuitable for values of electronic temperature and density having a place in experiment
Note that the intensities of those lines are significantly smaller as compared to the intensity of the resonance line w of He-like Mg XI ion, and this is indicative of the fact that the number of Mg XII ions in the plasma is essentially smaller than the number of Mg XI ions
Summary
Despite the fact that a lot of works have been devoted to the study of plasma X-ray radiation produced at focusing the high-power laser radiation on the solid target surface (e.g. [1,2,3,4,5]), many problems still remain to be unsolved. [1,2,3,4,5]), many problems still remain to be unsolved Such factors as small size of the studied object (10−1 10−2 cm), short lifetime (~10−9 s), high temperature (100 - 1000 eV) and density (1019 - 1022 cm−3) put forward strict requirements to the means of such plasma diagnostics. The study of hard (1 Å - 20 Å) and soft (20 Å - 200 Å) X-ray radiation is the most informative means of plasma diagnostics. If at the stage of formation and heating of plasma produced with the laser radiation reshapes a quasi-equilibrium charge structure of ions, at the subsequent stages of retraction, it can appear essentially non-equilibrium. The model of a local thermodynamic equilibrium (LTE) and the corona model (CM) widely using at calculations have the restricted areas of feasibility, and both can appear unsuitable for values of electronic temperature and density having a place in experiment
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