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Fukuda, Yuji; Kanasaki, Masato; Jinno, Satoshi*; Sakaki, Hironao; Nishiuchi, Mamiko; Faenov, A.*; Pikuz, T.*; Kiriyama, Hiromitsu; Kando, Masaki; Kondo, Kiminori; et al.
no journal, ,
In the laser-driven ion acceleration using cluster-gas target, the acceleration mechanism consists of different processes such as, (a) acceleration of ions due to Coulomb explosion of individual clusters, (b) compression and acceleration of background gas ions due to the Coulomb explosion of clusters, (c) magnetic vortex generation and associated pinching near the rear surface, and (d) sheath acceleration at the interface between the medium and vacuum. To understand the synergetic interplay between the Coulomb explosion of clusters and the background gas dynamics, we have conducted ion acceleration experiments using CO
clusters embedded in background H gas with the J-KAREN laser at JAEA-KPSI. By a careful analysis of CR-39, energy spectra for protons (from background gas) and carbon/oxygen ions (from clusters) are obtained separately for the first time. We found that the maximum energies of protons and carbon/oxygen ions are 
1.5 MeV and 1.1 MeV/u, respectively. Based on the experimental results, the acceleration mechanism of background gas ions induced by Coulomb explosion of clusters is discussed with the help from numerical simulations which employ a particle-in-cell (PIC) method including relaxation and ionization processes of plasma particles (EPIC3D).
Kiriyama, Hiromitsu; Mori, Michiaki; Kon, Akira; Nishiuchi, Mamiko; Sakaki, Hironao; Ogura, Koichi; Fukuda, Yuji; Pirozhkov, A. S.; Sagisaka, Akito; Esirkepov, T. Z.; et al.
no journal, ,
We present the on-going upgrade of our high intensity laser system (J-KAREN laser system) in JAEA for higher energy and higher repetition rate operation as an invited talk. We discuss the status and implementation of the upgrade, including system design, evaluation of the components in the system, and the expected performance and characterization of the laser.
Kiriyama, Hiromitsu; Mashiba, Yuji; Sasao, Hajime; Asakawa, Makoto*; Kondo, Kiminori; Bolton, P.
no journal, ,
The effect of the random phase noise on the contrast is analyzed using the experimental observation of the contrast in the J-KAREN laser. The random phase noise can be a good explanation for the pedestal observed in our contrast measurement. Thus, we concluded that the spectral phase noise generated in the grating in a compressor is the most probable factor causing the pedestal.
Kando, Masaki; Bolton, P.; Bulanov, S. V.; Esirkepov, T. Z.; Fukuda, Yuji; Hayashi, Yukio; Kanasaki, Masato; Kawachi, Tetsuya; Kiriyama, Hiromitsu; Koga, J. K.; et al.
no journal, ,