X-RAY-EMISSION FROM SHORT-PULSE LASER PLASMAS

Highly intense picosecond and subpicosecond laser pulses interacting w ith solids can create hot and dense plasmas which emit x-ray pulses in a broad spectral range from less than or equal to 100 eV up to MeV. T he duration of these x-ray pulses depends on the transient behaviour o f the relaxation and recombination mechanisms, as well as on the lifet ime of energetic electrons produced via nonlinear processes in the pla sma. This paper reports experiments using a 1.5-ps laser pulse with hi gh constrast ratio (up to 10(10)) and intensities up to 10(18) W cm(-2 ) irradiating solid targets. Both the line spectrum characteristics of a magnesium plasma, recorded using crystal spectrometers with high sp ectral resolution, and kinetic calculations have allowed the deduction of plasma parameters in the process of plasma evolution. In addition, hard x-ray pulses from a tantalum plasma were measured and their scal ing was explained as bremsstrahlung emission from energetic electrons. Absolute dose values of x-ray pulses are given.