The investigation of x-ray emission from laser-irradiated solid targets is motivated both by the effort to create a new type of bright x-ray source for different applications including material science and time resolved x-ray diffraction for biology and by the needs of the plasma diagnostics. Line emission from highly ionized media or their probing by external x-ray sources is the most efficient and sometimes the only tool capable of providing detailed information on plasma conditions.

Radiation transport in x-ray lines is modelled as a postprocessor to 1D hydrocode in planar geometry. The spectrum of K-shell line emission is calculated together with a self-consistent description of the excitation kinetics. In the implemented model for the simulation of non-equilibrium line transfer, the coupling is carried out by an iterative procedure, where the populations are obtained by linearization while the line transfer is computed within the core saturation approximation and with complete frequency redistribution [1].

Here, the impact of laser prepulse on the x-ray spectra emitted from solid Al target heated by a short moderate intensity laser pulse is investigated. The laser target interaction is described by means of a 1D hydrocode [2]. The postprocessor is used to find the optimum separation between the prepulse and main laser pulse in order to reach the maximum laser energy conversion into the emission in the selected x-ray line. The energy emitted in the selected spectral lines is compared to the experimental measurements [3].

The detailed features of the line x-ray spectra from laser irradiated solid targets are presented, including the impact of fast electron generation by resonance absorption. The feasibility of postprocessing the results of two-dimensional hydrocode [4] is discussed.

References

[2] Andreev,A.A. - Limpouch,J.: Ion Acceleration in Short-Pulse Laser-Target Interactions. J. Plasma Phys. 62, pp. 179--193, 1999.

[3] Andreev,A.A. - Limpouch,J. - Nakano,H.: Optimal enhancement of x-ray line emission from plasma by shaping of short high-intensity laser pulses. Photonics West, LASE2000, San Jose, 22.-28.1 2000, oral 3934-15, Proc. SPIE 3934 (in print).

[4] Iskakov,A.B. et al - Limpouch,J.: Two-Dimensional Model of Thermal Smoothing of Laser Imprint in a Double-Pulse Plasma. Phys. Rev. E61, pp. 842--847, 2000.

This research has been supported by the Grant Agency of the Czech Republic grant No. 202/97/1186.

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