Temperature determination usingKαspectra fromM-shell Ti ions

The compact multipulse terawatt (COMET) laser facility at LLNL was used to irradiate Al-coated $2–50\mu \mathrm{m}$ Ti foils with $\approx {10}^{19}\mathrm{W}{\mathrm{cm}}^{-2}$, 500 fs, 3–6 J laser pulses. Laser-plasma interactions on the front side of the target generate hot electrons with sufficient energy to excite inner-shell electrons in Ti, creating $K\alpha$ emission which has been measured using a focusing spectrometer with spatial resolution aimed at the back surface of the targets. The spatial extent of the emission varies with target thickness. The high spectral resolution $(\lambda ∕\Delta \lambda \approx 3800)$ is sufficient to measure broadening of the $K\alpha$ emission feature due to the emergence of blueshifted satellites from ionized Ti in a heated region of the target. A self-consistent-field model is used to spectroscopically diagnose thermal electron temperatures up to 40 eV in the strongly coupled Ti plasmas.