K$_{\alpha}$ conversion efficiency from rare gas jets irradiated by ultra short laser pulses

The absolute laser conversion efficiency to K$_{\alpha }$-like inner shell x-rays (integrated from K$_{\alpha }$ to K$_{\beta })$ is observed to be an order of magnitude higher in argon gas jets than in solid targets due to enhanced emission from higher ionization stages following ultra short pulse laser irradiation. Excluding the higher ionization stages, the conversion efficiency to near-cold K$_{\alpha }$ is the same in argon gas jets as in solid targets. In krypton gas jets, we present conversion efficiency exclusively into near-cold K$_{\alpha }$ and K$_{\beta }$. This work was performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory, through the Institute for Laser Science and Applications, under contract DE-AC52-07NA27344.