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Jun 1999

Volume 6, Issue 6, pp. 2319-2643

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back to top Inertially Confined Plasmas, Dense Plasmas, Equations of State

Experimental study of laser penetration in overdense plasmas at relativistic intensities. I: Hole boring through preformed plasmas layers

J. Fuchs, J. C. Adam, F. Amiranoff, S. D. Baton, N. Blanchot, P. Gallant, L. Gremillet, A. Héron, J. C. Kieffer, G. Laval, G. Malka, J. L. Miquel, P. Mora, H. Pépin, and C. Rousseaux

Phys. Plasmas 6, 2563 (1999); http://dx.doi.org/10.1063/1.873527 (6 pages)

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Propagation of a high-contrast subpicosecond (400–600 fs) relativistic (Iλ2 up to 2×1019 W⋅cm−2⋅μm2) laser pulse through long preformed overdense plasmas is experimentally studied. Transmission values up to 10% are measured in plasmas with initial peak densities above 10×nc. We compare these results with one-dimensional (1D) analytical calculations of the hole boring effect. It is shown that the ponderomotive force of the laser beam can push forward the overdense plasma, create a channel, and lead to transmission levels similar to the experimental ones. © 1999 American Institute of Physics.
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52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma
52.25.Kn Thermodynamics of plasmas
42.50.Hz Strong-field excitation of optical transitions in quantum systems; multiphoton processes; dynamic Stark shift
52.27.Ny Relativistic plasmas

Experimental study of laser penetration in overdense plasmas at relativistic intensities. II: Explosion of thin foils by laser driven fast electrons

J. Fuchs, J. C. Adam, F. Amiranoff, S. D. Baton, N. Blanchot, P. Gallant, L. Gremillet, A. Héron, J. C. Kieffer, G. Laval, G. Malka, J. Miquel, P. Mora, H. Pépin, and C. Rousseaux

Phys. Plasmas 6, 2569 (1999); http://dx.doi.org/10.1063/1.873528 (10 pages)

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Propagation of a high-contrast frequency-doubled subpicosecond (300 fs) relativistic (Iλ2 up to 5×1018 W⋅cm−2⋅μm2) laser pulse through thin and initially solid foils is studied. Transmission values up to 10% are measured through targets with initial near solid densities. The strong intensity threshold observed for the transmitted energy is correlated with clear modifications of the transmitted and reflected spectra, electron generation, and beam imaging. Two-dimensional Cartesian particle-in-cell (PIC) simulations that qualitatively reproduce the experimental results suggest specific rapid heating of the thin targets by fast electrons, plasma expansion, and density decrease to relativistically transmissive conditions during the pulse. © 1999 American Institute of Physics.
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52.38.-r Laser-plasma interactions
52.27.Ny Relativistic plasmas
52.65.-y Plasma simulation
52.80.Qj Explosions; exploding wires
52.25.Kn Thermodynamics of plasmas

Z-pinch discharges in aluminum and tungsten wires

J. Ruiz-Camacho, F. N. Beg, A. E. Dangor, M. G. Haines, E. L. Clark, and I. Ross

Phys. Plasmas 6, 2579 (1999); http://dx.doi.org/10.1063/1.873529 (9 pages)

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A series of experiments on Z-pinch plasmas, driven by a pulsed power generator that delivers 160 kA with a rise time (10%–90%) of 65 ns are reported. Tungsten wires of various diameters were used and results are compared with 15 μm diameter aluminum wire. The expansion of the pinch is studied as a function of wire diameter and material. Schlieren observations show that the coronal plasma of various diameters of tungsten wires expands with the velocity of (9.4±1.0)×103 m/s. The aluminum pinch expands at least a factor of 2 faster. The m = 0 perturbations appear at about 8 ns for the aluminum compared with 20 ns for the tungsten pinch. The wavelength and diameter of the perturbations increase with time for both types of wires, and relatively faster for the aluminum pinch. The short wavelength perturbations (∼200 μm) persist for a longer time for larger diameter tungsten wires. Bright spots are seen to appear after 60 ns from the current start for tungsten wires, whereas for aluminum wires, bright spots appear after 40 ns. The decay time of bright spots is 40 ns for the smallest diameter tungsten wire compared with only a few nanoseconds for larger diameter wires. Hard x-ray emission above 6 keV was observed from tungsten wire pinches, but it was not observed from either bright spots or the plasma column for the aluminum pinch. However, hard x-ray emission from the anode due to an electron beam was observed for wires of both materials. © 1999 American Institute of Physics.
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52.55.Ez Theta pinch
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
07.85.-m X- and γ-ray instruments
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