X-RAY SPECTROSCOPIC STUDY OF HIGH-TEMPERATURE PLASMAS BY CURVED CRYSTAL SPECTROMETER
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概要
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Extensive studies have been carried out on the structures of x-ray spectra from highly stripped ions of first transition elements and their behaviour in a high-temperature plasma using a high-resolution crystal spectrometer. Calculations are made on the design and the use of a curved crystal spectrometer for plasma diagnostics. A Johann type crystal spectrometer for measuring the x-ray lines has been constructed on the basis of the calculations. Characteristics of curved crystals of LiF, Ge and quartz used for measurement of Kα_<1,2> characteristic lines from the first transition elements are investigated. The resolving power and reflectivity of these crystals are tabulated. The spectral resolution and sensitivity of the curved crystal spectrometer (crystal : LiF (200), bending radius : 100cm) are measured with a position-sensitive detector of photodiode array calibrated using a proportional counter. A vacuum spark has been constructed for producing a high-temperature plasma which emits the x-ray lines from the highly stripped ions. The results of the experimental studies for the x-ray spectroscopic measurements carried out using the spectrometer are as follows. Spatially resolved Fe Kα spectra were first measured in a single shot and a visible image-converter camera and x-ray pinhole camera were used in order to examine the structure of the plasma produced by the vacuum spark. They show the evident proof that the vacuum spark plasma has two different structures. One is a thermalized. point plasma (≲10μm) of high temperature and high density. The other is an extended plasma (∿3mm) associated with non-thermal electrons, which consists of iron ions in lower charge states. The x-ray lines from the extended plasma have been observed. Kα lines from iron ions in some charge state are shifted to the long-wavelength side of Kα lines from singly ionized iron ions. The transition energies of the TiVI-XIII Kβ lines are determined and some weak satellite lines are first found. All the x-ray lines associated with K-shell from the point plasma have been observed for iron element. The transition wavelengths of He-like resonance series lines up to ls6p-1s^2 were determined for the first time. A highly resolved Kα spectrum of FeXXIV and FeXXV has been observed and plasma parameters were determined : n_e≃10^<21>cm^<-3>, T_e≃2.2keV, ionization temperature T_z≃0.8keV and T_i≲4keV. The structures of He-like Kα and Li-like Kβ satellites are described in detail. Kα lines of Ti through Zn have been observed from the point plasma. The transition wavelengths of the He-like resonance lines are first determined under careful experimental procedures. The results are compared with theoretical predictions and are in good agreement with ones given by Safronova. The predictions, however, include uncertainties in relativistic and QED corrections. More accurate theoretical values are needed for comparison with these experimental data.
- 核融合科学研究所の論文
- 1983-07-00