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Spatially resolved soft x-ray spectroscopy of femtosecond-laser-induced plasmas

Time-integrated spatially resolved emission spectra of soft x-rays were obtained in the case of 100-fs-laser irradiation of tantalum and aluminum targets by controlling the time intervals between the main pulse and artificial pre-pulse. The intensities of the main pulse and pre-pulse were fixed to 1.3x1016 and 2.0x1014 W/cm2. X-ray intensities were enhanced more than several ten fold at the optimal pulse-separation time of 2 ns. We confirmed that the main emission area for each target was less than 50-μm long from the target surface. In contrast to the small size of main emission area, we observed that line emissions from the aluminum target expanded far from the target.