Stark broadened line profiles of neutral strontium lines in plasma conditions
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During more than twenty years, we are making a continuous effort to provide Stark-broadening parameters needed for research of astrophysical, laboratory and laser produced plasma. A review of our results is presented in Dimitrijević, 1996). Such data are of interest for the consideration of a number of problems in astrophysics, physics and technology as e.g. for stellar plasma diagnostic, opacity calculations, the investigation/modelling of stellar spectra or a particular line, laboratory plasma diagnostic, laser produced plasmas, thermonuclear research, plasma technology, as well as for different examinations of regularities and systematic trends for e.g. homologous atoms (Dimitrijević and Popović, 1989) or in general (Purić et al. 1991).Keywords:
Thermonuclear Fusion
Opacity
Line (geometry)
Previous computations of low-temperature Rosseland and Planck mean opacities from Alexander & Ferguson are updated and expanded. The new computations include a more complete equation of state (EOS) with more grain species and updated optical constants. Grains are now explicitly included in thermal equilibrium in the EOS calculation, which allows for a much wider range of grain compositions to be accurately included than was previously the case. The inclusion of high-temperature condensates such as Al2O3 and CaTiO3 significantly affects the total opacity over a narrow range of temperatures before the appearance of the first silicate grains. The new opacity tables are tabulated for temperatures ranging from 30,000 to 500 K with gas densities from 10-4 to 10-19 g cm-3. Comparisons with previous Rosseland mean opacity calculations are discussed. At high temperatures, the agreement with OPAL and Opacity Project is quite good. Comparisons at lower temperatures are more divergent as a result of differences in molecular and grain physics included in different calculations. The computation of Planck mean opacities performed with the opacity sampling method is shown to require a very large number of opacity sampling wavelength points; previously published results obtained with fewer wavelength points are shown to be significantly in error. Methods for requesting or obtaining the new tables are provided.
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A motional Stark effect diagnostic at the tokamak TEXTOR has been constructed and brought recently into operation. In contrast to diagnostics used on other tokamaks, this diagnostic reveals the direction of the magnetic field from the intensity ratio of the π and σ components of the emitted Balmer-α and not from a polarization measurement of a single line. Moreover, the complete spectrum is measured which allows determining the radial position of the measurement, and in principle the radial electric field.
Balmer series
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This paper summarizes the results of experiments carried out within about a decade in the Atomic and Plasma Physics group at Kiel University. These experiments aimed for the calibration of the Stark effect of Hydrogen spectral lines with special emphasis on the first line of the Balmer‐series. Broadening, shift and splitting constants obtained by independent diagnostic techniques provide the possibility to use the Stark effect of the Hydrogen lines as a tool for plasma diagnostics over a wide range of electron densities and electric field strengths. Moreover they may be used to check the theoretical calculations of the respective constants.
Balmer series
Hydrogen spectral series
Hydrogen line
Line (geometry)
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Thomson scattering (TS) is a powerful diagnostics for understanding the plasma conditions in high energy density experiments. With the aid of Monte Carlo simulation and statistical analysis, we demonstrated unreported high precisions of ne, Te, Ti, etc., via fitting the multiple-wavenumber spectra of ion-acoustic featured TS simultaneously. For instance, utilizing this method in the current typical conditions on SG-180kJ laser facility, the precisions of ne, Te would be better than 8% and 0.5%, respectively. We presented the fitting precisions at different cases and the chi-square trends of the single- and dual-branch TS. This diagnostic technique is found to be applicable within a wide range of plasma parameters and wavenumbers, which is practical to prompt much more precise plasma diagnostics in experiments.
Wavenumber
Thomson scattering
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The q profile plays a key role for plasma equilibrium and theories of magnetohydrodynamic instabilities. With the development of the motional Stark effect (MSE) diagnostic, accurate q(r,t) profiles have been measured and utilized for equilibrium and stability analysis. Improvements to the MSE diagnostic on TFTR include a new method for calibrating the system and increasing the number of sightlines from 12 to 21 channels. A technique that uses the known poloidal field at the edge of the plasma is utilized to calibrate each sightline. The major radius is moved over the course of a discharge such that the plasma edge covers each sightline radius. Then with several discharges at various plasma currents each channel is independently calibrated. This method has been compared to our earlier calibration technique using neutral beam injection into a gas filled torus and some differences in the calibration have been found that have been attributed to differences in the excitation and l mixing processes in the Stark spectrum.
Gyroradius
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Opacity
Formalism (music)
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A simplified theory relating the collector current to the grid bias and other plasma parameters has been developed for a multiple-gridded electrostatic energy analyzer. Experiments have shown that the theory is only approximately valid, but the temperature obtained agrees closely with that from a Langmuir probe. It is found that temperature measurements depend on the grid bias potentials and the ratios of grid hole radius to electron Debye length. As a result, the conditions for the best performance of the energy analyzer as an accurate diagnostic device have been determined. A theory has also been worked out for the second-order change in the electron distribution function due to a cyclotron damped wave. This, together with experimental results, will provide valuable information on the thermal anisotropy of a plasma.
Langmuir Probe
Electron temperature
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A method is described for measuring the opacity of anesthetic dental filling materials using a goniophotometer. Procedures are given for converting measured opacity values to those referred to a 70% reflectance background (C0.7 values) as required by existing specifications. The conversion is involved, and, since most available white surfaces have reflectance of about 80%, it is recommended that in future specifications opacity be recorded as C0.8 values. Opacity values for 28 materials are reported. It was found that the opacity of dental cement decreases for several days following preparation and that powder/liquid ratio has little effect, while pigmentation has a marked effect on opacity.
Opacity
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The present state of Stark plasma spectroscopy is discussed. The possibilities of measurements of electric field and related plasma parameters are considered. A brief theory of linear and nonlinear Stark effect is outlined. The specific features of Stark effect — shifts, splitting and related line broadening, forbidden transitions — are described for the electric fields of differing nature — correlated external static and alternative fields, plasma turbulence fields, microfields generated by charged particles. Techniques based on classical emission spectroscopy, and novel linear and nonlinear laser techniques are considered. It is shown that the application of recently developed coherent laser spectroscopic methods radically improves the possibilities of electric fields measurements for the high pressure range.
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We have developed a diagnostic to measure the motional Stark effect (MSE) on TEXTOR-94. This diagnostic allows us to measure locally the strength and direction of the magnetic field. Furthermore, the major radius of observation and the radial electric field are determined. Because the MSE diagnostic on TEXTOR-94 employs the full spectral information, in addition to the complete polarization, the measurements are independent from other experimental data. In this article we present the first preliminary results of the MSE diagnostic on TEXTOR-94.
Motional narrowing
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