Satellite formation in high intensity laser-solid interactions due to the presence of non-thermal electrons

The COMET laser in LLNL was used to study the energy distribution between thermal and non-thermal electrons created by short-pulse laser interacting with soild-density matter. The aluminum-coated titanium targets were illuminated by the ultrashort laser pulses with variable intensities of 10$^{17}$-10$^{19}$ W/cm$^{2}$. We have measured the time-dependent x-ray spectra of titanium K$_{\alpha }$ and the aluminum He-like 1s2p-1s$^{2}$ and Li-like satellites for tens of picoseconds. Data show that the titanium K$_{\alpha }$ line is broadened and shifted to higher energies and the Li-like satellites of aluminum He$_{\alpha }$ vary with time. Time-dependent collisional-radiative calculations were preformed to generate the time-resolved x-ray spectra of aluminum and titanium in the presence of a small fraction of non-thermal electrons in solid-density bulk electrons. We present the spectroscopic analysis to determine the plasma conditions of the front aluminum layer as a function of laser intensity, which will improve the understanding of the dynamics of non-thermal electrons and the heating of the thermal electrons.