@misc{oai:repo.qst.go.jp:00082794,
 author = {Pikuz, T. and A. Alkhimova, M. and N. Ryazantsev, S. and Yu. Skobelev, I. and Pikuz, S. and S. Martynenko, A. and V. Sedov, M. and N. Shatokhin, A. and A. Vishnyakov, E. and Akito, Sagisaka and Koichi, Ogura and Gonzalez Izquierdo, B. and Kotaro, Kondo and Yasuhiro, Miyasaka and Akira, Kon and Masahiko, Ishino and Masaharu, Nishikino and Timur, Esirkepov and Kevin Koga, James and Masaki, Kando and Hiromitsu, Kiriyama and Kiminori, Kondo and Kodama, R. and Tetsuya, Kawachi and Yuji, Fukuda and Pirozhkov, Alexander and Sakawa, Y. and Akito, Sagisaka and Koichi, Ogura and Kotaro, Kondo and Yasuhiro, Miyasaka and Akira, Kon and Masahiko, Ishino and Masaharu, Nishikino and Timur, Esirkepov and Kevin Koga, James and Masaki, Kando and Hiromitsu, Kiriyama and Kiminori, Kondo and Tetsuya, Kawachi and Yuuji, Fukuda and Pirozhkov, Alexander},
 month = {Apr},
 note = {After recent upgrade of the Petawatt-class J-KEREN-P laser system the experiments with on-target relativistic intensity up to 10^22 W/cm^2 (pulse energy ~10 J, pulse length ~40 fs, focal spot down to 1.5 um) are routinely carried out at KPSI, QST. In general, for solid targets the plasma formation threshold is of ~10^10-10^12 W/cm^2, therefore the long ASE prepulse, short and ultrashort pedestal intensity crucially impact the formation of plasma conditions and the observed phenomena. It was demonstrated that there exists a strong dependence of the degree of Fe ionization on a laser prepulse, and that an effective generation of energetic, multiply-charged moderate- and high-Z ions can be driven only with laser pulses of ultra-high contrast.
Here we report on the new experiments performed at J-KAREN-P laser with the tailored plasma density profile created by specially incorporated prepulse. For the prepulse the ~1/100 of the main pulse power was picked up and delivered to the target with controlled sub-nanosecond time interval prior to the main pulse. The prepulse was focused: (1) on the front of a stainless steel foil for the formation of downstream preplasma with conditions aiming the efficient generation of x-ray flare and high-order harmonics (experiment led by A.S. Pirozhkov); and (2) on the rear-side of a 4-Chlorosterene foil mimicking upstream preplasma, which has the necessary density profile for collisionless shock ion acceleration, when the main pulse is irradiated (experiment led by Y. Fukuda and Y. Sakawa). For both experiments, we present the detailed analysis of plasma parameters provided by means of high-resolution x-ray spectroscopic methods, based on emission characteristics of plasma in the spectral range of Ne-like Fe and H-like Cl ionization states, respectively., International Conference on High Energy Density Sciences (HEDS2021)},
 title = {X-ray spectroscopy of relativistic plasma with controlled preplasma formation at J-KAREN-P experiments},
 year = {2021}
}