Analytical and Numerical Ray Tracing of X-Ray Lasers

Soft x-ray lasers in 10-30nm range are now routinely produced in hot plasmas generated either by a laser from a solid target or by an electrical discharge in a capillary. Such an x-ray laser is a convenient tool for future applications, such as probing dense plasmas of interest for fusion experiments. Their short wavelength enables plasma diagnosis beyond the capabilities of optical lasers, because the high critical plasma density ({approx}{lambda}{sup 2}) limits the optical beam propagation. In our paper, we present analytical and numerical ray tracing of an x-ray laser in dense amplifying plasmas. A general analytical formula for a beam propagation has been developed for a gradient plasma. The simplified analytical formulaes enable better understanding of processes involved. They also simplify optimization of the beam propagation and ''mapping'' the parameter space for further studies by numerical codes. We discuss implications for a transient x-ray laser that is produced from a slab target by a (sub-)picosecond laser pulse

SOLORZANO, ÁNGELES Y ROSARIO [Material gráfico]

Copia digital. Madrid : Ministerio de Educación, Cultura y Deporte, 201

Effective gain and Stark profile calculations in the recombination scheme x-ray lasers

International audienceStark profile functions of Al10+ lasing lines in recombining plasmas are calculated. Due to electron-emitter collisions and dynamic ion microfields, the 3d-4f and 3d-5f lines at 10.57 and 15.47 nm, respectively, are broadened by a large amount, compared to thermal Doppler broadening. Consistently with experiments, an effective gain is derived from intensity of the X-ray beam, versus plasma length. A lowering of the effective and the spectral peak gains, with respect to the commonly used Doppler gain, is noticed. Effective and peak values differ by less than 13% for transitions at 15.47 nm, and by less than 10% for those at 10.57 nm. Comparison with experimental results is discussed. Calculations seem to indicate that there is no gain at 10.57 nm, due to a large Stark broadening

Density-induced continuum resonances and quasi-bound states in the collisional-radiative equilibrium of dense plasmas

The aim of this work is to improve the treatment of density effects in non local thermodynamic equilibrium plasmas. The density effect on atomic structure (wavefunctions and energy levels) is modeled by an ion-sphere potential. The modification of the atomic potential, continuum lowering and appearance of resonances are shown. In particular, we show that the continuum resonances are linked to the electrons in the subshells passed into the continuum. Their presence determine the existence of partially bound configurations, which must be taken into account in the collisional-radiative model. We introduce in the set of rate equations a supplementary ionization process due to the plasma environment. This process (and its inverse) enters into the balance of all of the other process. It is equivalent to tunneling ionization where an outer electron located above the ionization threshold (and trapped by the potential barrier) crosses the barrier. As an application, we studied the influence of temperature and density on the average ionization and the ionic populations of a carbon plasma. We compared these calculations with the traditional method based on the chemical picture with continuum lowering

Opacity and radiative power losses calculations

International audienceIn this contribution we present results on opacity and radiative power losses in laser-produced plasmas. We focus our attention on the inner shell transition array 1s-2p in an aluminum plasma. At high densities, electron, Doppler and ion Stark broadening play a role in line merging. This is why the PPP line shape code developed at Universite de Provence was adapted to calculate opacity and radiative power losses in Al and Ge ions. Atomic physics data required in PPP calculations is provided by an MCDF code. Comparison with experiments is discussed. (c) 2009 Elsevier B.V. All rights reserved

Theoretical predictions for the polarization of X-ray laser lines in the presence of a directed beam of hot electrons

The 19.6 nm laser line due to a 3p - 3s, J=0-1 transition in Ne-like Ge ions was found to be polarized parallel to the target plane with a degree of polarization of -53 % by Kawachi et al. (1995). They intepret it as a consequence of a an unbalanced population of the 3s magnetic sublevels. Kieffer et al. (1993) have shown that, during plasma heating, some electrons could be accelerated preferentially in the same direction as the pump laser. In the present work, we shall show that such anisotropic electrons can give a small difference in populations of the 3s sublevels. The 3s level spontaneous emission to the ground level is linearly polarized and can be reabsorbed by the Ne-like ion ground state which amplifies the population of the 3s levels, as well as it increases the different sublevel populations. The 3p-3s X-ray laser amplification depending on the 3s level population becomes polarized but with an opposite sign to the absorbed radiation from the ground level

Temporal coherence of the ni-like palladium x-ray laser in the transient pumping scheme

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Copper neon-like X-ray laser modeling including hyperfine structure levels

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