摘要:

The development of a set of stable implosions using indirectly driven plastic microspheres with argon (0.1 atm) doped deuterium (50 atm) has provided a unique source for testing the plasma spectroscopy of the high energy density imploded core. The core reaches electron densities of>1024&hthinsp;cm−3with temperatures of ∼ 1 keV and has been shown to be reproducible on a shot to shot basis. Moreover, it has been shown that not only the peak temperature and density are consistent, but that the temporal evolution of the mean temperature and density of the final phase of the implosion is also reproducible. These imploding cores provide a unique opportunity to test aspects of plasma spectroscopy that are difficult to study in other plasmas and to develop methods to test stable hydrodynamics. We will present experimental results and discuss spectroscopic analysis algorithms to determine consistent temperature and density fits to determine gradients in the plasma. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1370576

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

The fine structure observed in spectra of hydrogenic aluminum emitted from a constrained-flow plasma indicates the presence of the laser-induced satellites. The measured profiles of the Al Lyman line &bgr; exhibit peaks in the wings consistent with theoretical predictions of the line modification by strong single-frequency electric fields. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1370577

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

As it was experimentally shown earlier, there is an intense IR radiation in purely thermal emission spectra of dense sodium vapors. Based on the assumption that the wing profile is formed by buffer gas quasistatic broadening in nearest neighbor approximation, a theoretical model for the far wing of sodium D-lines was developed. The model described the experimental results within an order of magnitude, unlike to the standard theory of radiation transfer. However, the validity of this approximation at large detunings is not evident. Thus, the problem of the intense IR emission of dense vapors remains open. Its origin was also assigned to the influence of sodium clusters. In order to verify this hypothesis an investigation of absorption spectra of dense sodium vapors in a wide spectral range (0.35–1.1 &mgr;m) was carried out. For verification of the validity of the nearest neighbor approximation at large detunings, numerical calculations of the distribution function of ionic microfields in dense plasma were carried out. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1370578

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

The distortion of resonance line shapes due to the accumulation of a large number of satellite transitions is discovered by means of X-ray optical methods with simultaneous high spectral(&lgr;/&dgr;&lgr;≈8000)and spatial resolution(&dgr;x≈7&hthinsp;&mgr;m).Disappearance of theHe&agr;resonance line emission near the target surface is observed while Rydberg satellite intensity accumulates near the resonance line position.He&bgr;andHe&ggr;resonance line shapes are also shown to be seriously affected by opacity, higher-order line emissions from autoionizing states and inhomogeneous spatial emission. Opposite to resonance line emissions theHe&bgr;satellites originate only from a very narrow spatial interval. New temperature and density diagnostics employing the 1s2131′and 1s3131′-satellites are developed. Moreover, even-J components of the satellite line emissions were resolved in the present high resolution experiments. Line transitions from the autoionizing states 1s2131′are therefore also proposed for space resolved Stark broadening analysis and local high density probing. Theorists are encouraged to provide accurate Stark broadening data for the transitions1s2131′→1s221+hv.©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1370579

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

The interpretation of a measured x-ray spectrum from a carbon plasma induced by subpicosecond laser pulses [Wilhein, T., &etal;,J. Opt. Soc. Am. B15, 1235 (1998)] is reexamined. We calculate a synthetic Lyman spectrum emitted from a plasma layer at a given temperature and density, using a microscopic approach to the line shape in dense, non-ideal plasmas. Self-absorption is taken into account within a simple model considering one-dimensional radiation transport in a plasma layer. We infer a temperature ofT=106&hthinsp;Kand an electron density ofne=3×1021&hthinsp;cm−3.©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1370580

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

High density plasmas are produced in a special flashtube allowing variable filling up of a mixture of argon and hydrogen. On axis plasma parameters are in the range1–2.1018&hthinsp;cm−3for the electron density and1.7–2.1.104&hthinsp;Kfor the temperature. In those conditions, the FWHM of the BalmerH&agr;line are measured and compared with theoretical and other experimental values. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1370581

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

A new formalism has been elaborated for calculations of hydrogen line profiles emitted by dense plasmas. Calculated line shapes are broadened, shifted and asymmetrical. The formalism is very general and yields full line shapes, shifts and widths at relatively small number of assumptions. For this purpose a new basis of the appropriate subspace of the Hilbert space has been built. This basis gives an accurate description of the quadratic Stark effect and the interaction of the emitter with field gradients. A computer simulation has been used to determine the emitter perturbations by electrons and ions. Final results have been compared with experimental and theoretical findings of other authors. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1370582

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

The absorption phenomena is very important effect in optically thick plasmas. It is expressed by the radiative transfer which analyses interactions of the radiation field with the plasma. We present a model using a global absorption coefficient which takes in to account this effect and shows its dependence with the optical length of the plasma. The inhomogeneity of the medium has an effect influencing the redistribution of radiation in optically thick plasmas. Our results in lithium-like aluminum are in good agreement with experimental spectra. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1370583

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

The present work is devoted to the study of opacities for ultra-dense, hot, low Z plasmas. For those highly correlated plasmas, similar to some astrophysical situations and to implosion experiments, ionic and electronic correlation effects modify drastically the atomic and radiative properties. Up to now the quasi-molecular model has been shown to be efficient for an exact treatment of the spectral line shapes. The aim of this work is to use the same approach for the computation of the photo-excitation cross sections, the opacity and the emissivity characterizing ultra-dense and hot plasmas. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1370584

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

The standard static-ion/impact-electron theory of line broadening is assessed with calculations of hydrogen lines over a broad range of plasma conditions. In most cases, discrepancies between results from theory and experiments are explained by the neglect of ion-dynamics effects. Nevertheless, recent experiments involving high density but low temperature plasmas indicate that ion-dynamics/impact-electron models may seriously overestimate the broadening for such conditions. We show that the observed discrepancies are not due to the ion modeling but due to the impact approximation of the electrons in the Original Frequency Fluctuation Model (FFM). This situation arises for plasma conditions where the interactions with the electrons are a major broadening mechanism and quasi-static, i.e. non-binary, electron effects are important. An alternative approach to a binary collision operator is therefore proposed by means of the FFM code generalized to the two components (ions and electrons) of the plasma. Accurate simulations accounting for the electron plus ion field dynamics have been used to corroborate the FFM as applied to both ion and electron perturbers, and good agreement is found with recent experiments onH&agr;andP&agr;for dense but relatively cold plasmas. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1370585

出版商:AIP    

年代:1901

数据来源: AIP