参加報告：ルーマニア ELI-NP研究所の共同実験（大阪大学先導的学際研究機構・PIKUZ, Tatiana）

The joint team from ILE (T. Pikuz) and KPSI (F. Fukuda, K. Kondo) participated in ELI-NP commissioning experiment in May-June 2023.

The x-ray spectroscopic diagnostics was implemented to measure parameters of the plasma produced in the interaction of 1PW-10PW laser system with the solid target at the different regimes of laser energy and laser contrast. For the first time, the emission from H-like Ni ions was observed experimentally. Such high ionization states of the element with Z = 28 indicate that laser intensity on the target exceeded 1022 W/cm2 is achieved. The spectral line shapes are characterized by a great broadening and large intensity ratio H-like Lya / He-like Hea lines. That suggested that the close-to-solid-density plasma with an electron density above 3 keV was created by laser pulses with high contrast. The spectra measured on the dependence of laser contrast show a significant (probably dominant) role of tunneling ionization on plasma formation. The detailed atomic-kinetic modeling of the obtained spectra is started.