Generation of hot plasma at solid density by high-contrast ultra-short laser pulses

We have generated a high-density plasma by focusing frequency-doubled Ti-Sapphire laser pulses at lambda = 395 nm and a duration of 150 fs on flat solid targets at an intensity of approximate to 10(17) W/cm(2). Using solid Al targets tamped by a thin surface layer of MgO we measured the Al K-shell emission. The measured resonance lines (Ly(alpha), He-alpha and He-beta) and their Li-like and He-like satellites are extremely broad. In addition, we observed clear center of gravity red shifts of the main lines by using the cold K-alpha line as a reference. The temporal duration of the K-shell emission, measured by an X-ray streak camera, is approximate to 2.5 ps. Analysis of the spectra yields an effective electron temperature of approximate to 300 eV and an electron density of approximate to (7-10) x 10(23) cm(-3). A very weak emission of cold Al K-alpha indicates a low level of energy deposited by fast electrons in the solid. Essential for achieving these results is the suppression of early time expansion of the Al target by using both, a high-contrast laser pulse and a tamped target. (C) 2000 Elsevier Science Ltd. All rights reserved.