<title>Line x-ray emission from Al targets irradiated by high-intensity variable-length laser pulses</title>

The absolutely calibrated K-shell spectra emitted form short-living aluminum plasma at laser intensities of 5 by 1015- 4 by 1018 W/cm2 are reported. The experiments performed with the constant energy, variable-length laser pulse are modeled by the 1D hydrodynamics code including non-linear resonance absorption of the laser radiation, fast electron acceleration and energy transfer into the target. The characteristic features of the measured and the post- processed spectra are outlined; the scaling rules for the conversion efficiency of the laser radiation into the line x-ray emission are discussed.