@misc{oai:repo.qst.go.jp:00076656,
 author = {Fukuda, Yuji and A. Pikuz, Sergey and Fukuda, Yuuji},
 month = {Oct},
 note = {Combined with X-ray spectral plasma diagnostics, studies on the interaction of intense laser pulses with cluster targets provide essential information for the basic properties of matter under extreme conditions. The X-ray radiation spectra of high-temperature plasmas are formed primarily due to atomic processes occurring in it, like electron–ion collisions and the radiative or autoionization decay of ion levels. Therefore, X-ray diagnostics are employed primarily for evaluating the electron density and the temperature of the transient nonequilibrium plasmas, as well as the nonlinear processes occurring in the relativistic laser plasmas. One practical outcome is the capability to estimate the effect of laser prepulses: Without the accurate knowledge of the temporal structure of a laser pulse, theoretical calculations based on atomic and kinetic models can give a rough estimation of the cluster evolution under the influence of the laser prepulses and the main pulse by comparing the profiles of the resonance spectral lines and the hollow ion spectra. 
Here we propose to introduce the focusing spectrometer with spatial resolution (FSSR) equipped with spherically bent crystals and the micron-scale cluster target, both of which have been successfully applied simultaneously in several HEDP experiments with high-intensity lasers at QST-KPSI and CEA Saclay. The introduction of these two devices promises to give absolutely unique research environment if combined with the ELI-NP 10 PW laser facility: We will start with Argon clusters to know how well the laser system performs at laser intensity of around 10^18 W/cm^2. With the increase of intensity for 1-2 orders of magnitude (around 10^20 W/cm^2), there will be a lot of H-like Argons, never observed before. With the higher laser contrasts, the spectral lines of hollow ions could be clearly identified. An observation of hollow ion spectra suggests the existence of a dense core at the moment of arrival of the main pulse, i.e. the laser contrast is extremely high enough. For the unexplored laser intensities over 10^22 W/cm^2, we try to look on Krypton K-shell spectra from Krypton clusters to examine the higher temperature and density plasmas, and try to find a way to define laser intensity from X ray spectroscopy., 1st ELI-NP User Workshop},
 title = {X ray diagnostics of hot dense plasma created by the action of 10 PW ultra-intense laser pulses on micron-scale cluster targets},
 year = {2019}
}