Spectroscopic studies of Cr VI species in a laser produced plasma*

We present measurements characterizing a laser generated, highly ionized microplasma suitable to extend the cut-off energy of High Harmonic Generation (HHG) to energies up to 5 keV. The HHG process occurs when a strong ultrafast laser hits a gaseous target producing coherent radiation with a much higher photon energy than the driving laser. Commonly, noble gases are used and typical photon energies of several 100 eV are obtained. We plan to use Cr$^{5+}$ species as the target for HHG as generated by a double pulse method: the first pulse creates the plasma, the second pulse is used to obtain the temperature required for Cr$^{5+}$. Here, we present results on the optimization of plasma parameters such as the plasma temperature, the number density and the dynamics of Cr$^{5+}$ by means of spectroscopic techniques in the optical and the XUV regime.