Comparing soft X-ray pulses induced by different metallic plasmas

In this work, we report on the characterization of pulsed soft X-rays emitted from laser-produced plasma by different targets. The measurements were performed in a vacuum stainless-steel chamber at 10-7mbar. The plasma was generated by a pulsed KrF excimer laser of 248nm laser wavelength, operating with a single shot regime and having pulses of 23ns full width at half maximum. The beam was focused on pure Si, Cu and Ta targets. The laser energies were 40, 80 and 120mJ. The beam was focused on a spot of about 0.01cm2 with a resulting irradiance of 1.7, 3.5 and 5.2x108Wcm-2. The detector used was a very sensitive Faraday cup which, when properly biased, was able to record time-resolved signals of X-rays and to estimate their energy. The X-ray energy values found were compared with the ion temperature of the target plasma, fitting the time-resolved ion current signals by the shifted Maxwell-Boltzmann velocity distribution.