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We report a significant enhancement in both the energy and the flux of relativistic electrons accelerated by ultra-intense laser pulse irradiation (>1 10 21 W cm-2) of near solid density aligned CD2 nanowire arrays in comparison to those from solid CD2 foils irradiated with the same laser pulses. Ultrahigh contrast femtosecond laser pulses penetrate deep into the nanowire array creating a large interaction volume. Detailed three dimensional relativistic particle-in-cell simulations show that electrons originating anywhere along the nanowire length are first driven towards the laser to reach a lower density plasma region near the tip of the nanowires, where they are accelerated to the highest energies. Electrons that reach the lower density plasma experience direct laser acceleration up to the dephasing length, where they outrun the laser pulse. This yields an electron beam characterized by a 3 higher electron temperature and an integrated flux 22.4 larger respect to foil targets. Additionally, the generation of >1 MeV photons were observed to increase up to 4.5. Fil: Moreau, A.. State University of Colorado - Fort Collins; Estados Unidos Fil: Hollinger, R.. State University of Colorado - Fort Collins; Estados Unidos Fil: Calvi, C.. State University of Colorado - Fort Collins; Estados Unidos Fil: Wang, S.. State University of Colorado - Fort Collins; Estados Unidos Fil: Wang, Y.. State University of Colorado - Fort Collins; Estados Unidos Fil: Capeluto, Maria Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina Fil: Rockwood, A.. State University of Colorado - Fort Collins; Estados Unidos Fil: Curtis, A.. State University of Colorado - Fort Collins; Estados Unidos Fil: Kasdorf, S.. State University of Colorado - Fort Collins; Estados Unidos Fil: Shlyaptsev, V.N.. State University of Colorado - Fort Collins; Estados Unidos Fil: Kaymak, V.. Universitat Dusseldorf; Alemania Fil: Pukhov, A.. Universitat Dusseldorf; Alemania Fil: Rocca, J.J.. State University of Colorado - Fort Collins; Estados Unidos

The jets driven by magnetic reconnection in laser-plasma interactions are investigated experimentally. The diagnostics in the optical and X-ray ranges provide detailed information about the jet characteristics. The plasma jets perpendicular to and along the target surface are observed clearly, which is evident signatures of laser driven magnetic reconnection. The jet formation is also investigated for different experimental parameters.

We investigated numerically the broadening mechanisms of the energy spectrum of ions accelerated by electrostatic shocks in over dense plasmas irradiated by intense ultra-short laser pulses. It was found that the width of the shock-accelerated ion spectrum could be ineluctably broadened by two mechanisms, which are the continuously decreasing speed of the shock front due to the energy dissipation into ions, and the further acceleration by the sheath field at target rears when energetic ions arrive there. Other effects, such like that of driving laser pulse duration, were also studied.

The Collisinal-Radiative (CR) model with fine atomic data included in the hydrodynamic code MED103 is used for the soft x-ray spectra analysis of laser-produced molybdenum plasmas. The charge distribution drawn from the soft x-ray spectra can be used to determine the pre-plasma conditions for the plasma-based molybdenum soft x-ray lasers (SXRLs).

Photo-ionized silicon plasma was studied using 500-eV Planckian radiation from implosion core plasma generated with Gekko-XII laser to simulate a astrophysical photo-ionized plasma. Three major features were observed in an energy range from 1.80 to 1.88 keV and origins of the features were replicated with a time-dependent collisional-radiative model including photo-ionization processes: The line at 1.865 keV is the resonance line by inner-shell photo-ionization of Li-like Si ions and that at 1.840 keV is the sum of satellite lines attributed to the inner-shell photo-ionization of Be-like ions. Emission lines in the soft x-ray/extreme ultra-violet (EUV) region (i.e., 140 to 300 eV) from the low-temperature Si plasma in prior to the photo-ionization were also identified to extract the intial temperature and density of the pre-formed Si.

Photoionized plasmas are encountered in astrophysics wherever low-temperature gas/plasma is bathed in a strong radiation field. X-ray line emissions in the several kiloelectronvolts spectral range were observed from accreting clouds of binary systems, such as CYGNUS X-3 and VELA X-1, in which high-intensity x-ray continua from compact objects (neutron stars, black holes or white dwarfs) irradiate the cold and rarefied clouds. X-ray continuum- induced line emission accurately describes the accreting clouds, but experimental verification of this photoionized plasma model is scarce. Here we report the generation of photoionized plasmas in the laboratory under well-characterized conditions using a high-power laser. A blackbody radiator at a temperature of 500 eV, corresponding to a compact object, was created by means of a laser-driven implosion. The emerging x-rays irradiate a low-density (n(e) < 10(20) cm(-3)) and low- temperature (T(e) < 30 eV) silicon plasma. Line emissions from lithium- and helium-like silicon ions were observed from a thermally cold silicon plasma in the 1.8-1.9 keV spectral region, far from equilibrium conditions. This result reveals the laboratory generation of a photoionizing plasma. Atomic kinetic calculations imply the importance of direct K-shell photoionization by incoming hard x-rays.

We propose that most of the collisionless shocks in the Universe, for example, supernova remnant shocks, are produced because of the magnetic field generated by Weibel instability and its nonlinear process. In order to verify and validate the computational result confirming this theory, we are carrying out model experiments with intense lasers. We are going to make a collisionless counter-streaming plasma with intense laser ablation based on the scaling law to laser plasma with the particle-in-cell simulation resulting in Weibel-mediated shock formation. Preliminary experimental data are shown. The photo-ionization and resultant non-LTE plasma physics are also very important subjects in astrophysics related to mainly compact objects, for example, black hole, neutron star and white dwarf. Planckian radiation with its temperature 80–100 eV has been produced in gold cavity with irradiation of intense lasers inside the cavity. The sample materials are irradiated by the radiation inside the cavity and absorption and self-emission spectra are observed and analyzed theoretically. It is demonstrated how the effect of non-LTE is essential to reproduce the experimental spectra with the use of a precision computational code.