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  • 1
    Electronic Resource
    Electronic Resource
    Interaction of an ultra-intense laser pulse with a nonuniform preformed plasma (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 3009-3016 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The propagation of an ultra-intense laser pulse in a preformed plasma channel was investigated experimentally. Different regimes of propagation were observed when the pulse duration was varied. For a long pulse and powers lower than the critical power for self-focusing, PL/PC〈1 (I0=2×1017 W/cm2), the laser pulse was guided by the preformed plasma channel over three Rayleigh lengths (4 mm) and a longitudinal plasma wave was generated by envelope self-modulation of the pulse. For a short pulse and PL/PC(very-much-greater-than)1, the interaction was dominated by self-focusing and Raman instabilities. Numerical simulations were run for the latter case, giving results comparable to the experiment. The simulations were also used to investigate the dynamics of the instabilities at high power. They showed that strong Raman side scattering first occurs at the beginning of the interaction and is then followed by self-focusing and envelope self-modulation. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.874153
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  • 2
    Electronic Resource
    Electronic Resource
    Acceleration of injected electrons in a laser wakefield experiment (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 2903-2913 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An electron plasma wave (EPW) has been excited by a short laser pulse (5 J, 400 fs) via the laser wakefield (LWF) mechanism. At the LWF quasi-resonance condition, the 3 MeV injected electrons have been accelerated with a maximum energy gain of 1.5 MeV. The maximum longitudinal electric field is estimated to be 1.5 GV/m. It has been observed that electrons deflected during the interaction, can scatter on the walls of the experimental chamber and fake a high energy signal. A special effort has been given in the electron detection to separate the accelerated electrons signal from the background noise. The experimental data are confirmed with numerical simulations, demonstrating that the energy gain is affected by the EPW radial electric field. The duration of the EPW inferred by the number of accelerated electrons and by the numerical simulations is of the order of 1–10 ps. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873248
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  • 3
    Electronic Resource
    Electronic Resource
    Laser wakefield: Experimental study of nonlinear radial electron oscillations (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 1162-1177 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The plasma electron density oscillation produced in the wake of a narrow (beam waist(very-much-less-than)plasma wavelength) ultrashort laser pulse is measured by frequency-domain interferometry with a temporal resolution much better than the electron plasma period, and a spatial resolution across the laser focal spot. The absolute density perturbation is observed to be maximum when the pulse duration equals half the plasma period. The relative density perturbation varies from a few percent at high density to 100% at low density. For nonlinear oscillations we measure the increase of the electron plasma frequency predicted for radial oscillations [J. M. Dawson, Phys. Rev. 113, 383 (1959)]. The damping of the oscillations is observed. It is very rapid (a few periods) when the oscillation is nonlinear. Comparison with the code WAKE [P. Mora and T. M. Antonsen, Jr., Phys. Rev. E 53, R2068 (1996)] indicates that the gas ionization creates a steep radial density gradient near the edge of the focus and that the electrons oscillating near this density gradient are responsible for the damping. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873001
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  • 4
    Electronic Resource
    Electronic Resource
    Coupling between electron and ion waves in Nd-laser beat-wave experiments (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 1318-1327 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The beating between two colinear Nd-YLF and Nd-YAG lasers in a homogeneous plasma generates intense relativistic plasma waves associated with a high longitudinal electric field of the order of 1 GV/m. It is shown that these electron waves couple with ion waves in the regime of modulational instability. Electric field amplitude and saturation time obtained by Thomson scattering are in agreement with theoretical predictions taking this mechanism into account.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870730
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  • 5
    Electronic Resource
    Electronic Resource
    Stimulated Raman backscattering instability in short pulse laser interaction with helium gas (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 1682-1688 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experimental and theoretical results on the stimulated Raman backscattering (SRS) reflectivity of a short laser pulse (120 fs) interaction with an optically ionized helium gas are presented. The reflectivity is measured as a function of the gas pressure from 1 to 100 Torr. A monodimensional (1-D) theoretical model, including the refraction induced during the ionization process, describes the dependence of the SRS reflectivity with the gas pressure and explains its maximum at around 35 Torr. In the very low pressure case (〈15 Torr), the radial ponderomotive force expels the electrons out of the propagation region before the laser pulse reaches its peak intensity and significantly reduces the observed reflectivity. A 1-D hydrodynamic calculation, included in the model, describes this density depletion and a good agreement is obtained between theory and experiments in the whole range of pressures. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871688
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  • 6
    Electronic Resource
    Electronic Resource
    Characterization of plasmas produced by laser–gas jet interaction (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 3467-3472 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An experiment has been performed with one of the six nanosecond beams of the Laboratoire pour l'Utilisation des Lasers Intenses laser facility in order to create long scale uniform plasmas over a wide range of electron density (1×1019–1.6×1020 cm−3) and electron temperature (0.5–1.3 keV). Electron density and temperature evolution have been measured using Thomson scattering. Numerical simulations obtained by using a simple model are presented. Scaling law related electron density and electron temperature have been established in agreement with experimental data. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1379587
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  • 7
    Electronic Resource
    Electronic Resource
    Characterization of electron beams produced by ultrashort (30 fs) laser pulses (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 2605-2608 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Detailed measurements of electron spectra and charges from the interaction of 10 Hz, 600 mJ laser pulses in the relativistic regime with a gas jet have been done over a wide range of intensities (1018–2×1019 W/cm2) and electron densities (1.5×1018–1.5×1020 cm−3), from the "classical laser wakefield regime" to the "self-modulated laser wakefield" regime. In the best case the maximum electron energy reaches 70 MeV. It increases at lower electron densities and higher laser intensities. A total charge of 8 nC was measured. The presented simulation results indicate that the electrons are accelerated mainly by relativistic plasma waves, and, to some extent, by direct laser acceleration. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1374584
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  • 8
    Electronic Resource
    Electronic Resource
    Suprathermal and relativistic electrons produced in laser–plasma interaction at 0.26, 0.53, and 1.05 μm laser wavelength (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 2589-2595 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Very energetic electrons produced in laser–plasma interactions at 0.26, 0.53, and 1.05 μm laser wavelength have been measured. The targets were 1.5 μm plastic foils and the laser intensity was around 1015 W/cm2. Detailed measurements of the electron distribution performed at a 0.26 μm laser wavelength exhibit an angular distribution strongly peaked along the laser axis at the highest energies (above 200 keV). Electrons up to 1.3 MeV have been observed in the 1.05 μm experiments. The hot temperatures inferred from the measured energy distributions are of the order of 100 keV in the 1.05 μm experiments, and 50 keV in the 0.53 μm/0.26 μm experiments. The experimental electron emission features are discussed with a special focus on the relation between the linear as well as the nonlinear electron plasma wave generation mechanisms and the maximum energy reached by an electron trapped in this wave.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860174
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  • 9
    Electronic Resource
    Electronic Resource
    Plasma production by multiphoton ionization: Density inhomogeneities due to ponderomotive effects (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 597-604 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The generation of long and homogeneous plasmas by multiphoton ionization of low-pressure gases—H2, D2, and N2 at pressures of a few Torr—with a high-power laser at λ=0.53 μm and intensities of the order of 1015 W/cm2 has been studied. The temperature and density of the plasma are measured by Thomson thermal scattering. After the initial full ionization the hydrodynamic density evolution with time is observed. The comparison with a simple model shows that this evolution is mainly due to the ponderomotive force of the laser beam itself. Typical density variations range from 1% to 5% per 100 psec.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860491
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  • 10
    Electronic Resource
    Electronic Resource
    Three-halves harmonic measurements on 0.53 μm laser produced plasmas (1987)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 30 (1987), S. 2221-2225 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Three-halves harmonic spectra measured at three different observation angles from 0.53 μm laser produced plasmas are presented. The results are compared with existing models. On plastic targets a very good fit is obtained with Barr's model with Te(approximately-equal-to)1.6 keV and a plasma velocity at nc/4 of v(approximately-equal-to)8.107 cm/sec. For higher Z material, the electron temperature seems to increase and Landau damping may become significant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866156
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