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  • 1
    Digitale Medien
    Digitale Medien
    Effect of cylindrical curvature on nonlocal electron transport in a plasma (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 3518-3519 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Following earlier analyses for the planar and spherical cases, nonlocal electron radial transport is treated for cylindrical high-Z plasmas. Comparison of the result with earlier ones shows that, for the same parameters, the magnitude of the nonlocal heat flux for the cylindrical case is intermediate between the planar and spherical cases, and somewhat closer to the spherical case. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.871503
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  • 2
    Digitale Medien
    Digitale Medien
    Electron kinetic simulations of solid density Al plasmas produced by intense subpicosecond laser pulses. I. Ionization dynamics in 30 femtosecond pulses (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 1650-1658 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The interaction of a 1018 W/cm2, 30 fs laser pulse with solid Al was simulated with the electron kinetic code "FPI" [J. P. Matte et al., Phys. Rev. Lett. 72, 1208 (1994)] in which an improved average ion module was fully coupled to the electron kinetics. It includes electron impact ionization and excitation and their inverse processes: collisional recombination and de-excitation; as well as radiative decay and pressure ionization. We compare to runs without the inverse processes, and also without atomic physics (with 〈Z〉 set to 11). Atomic physics strongly affects the energy balance and the shape of the distribution function. Line radiation is mostly due to three body recombination into excited states after the peak of the pulse, as the plasma cools down. Despite the atomic processes and the high density, strongly non-Maxwellian distribution functions were obtained due to very steep temperature gradients and strong collisional heating, at the peak of the pulse. However, after the pulse, there is a very rapid thermalization of the electron distribution to which inverse processes strongly contribute. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1357221
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  • 3
    Digitale Medien
    Digitale Medien
    Nonlocal electron transport in spherical plasmas (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 1280-1283 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The influence of spherical geometry on nonlocal radial electron heat transport has been studied using perturbation analysis . The nonlocal expression for the radial heat flux is obtained in the limit of large ion charge. The deviation of the spherical nonlocal heat transport from the planar theory has been investigated and it has been found that the space curvature can significantly modify the heat flux compared to the planar result when the delocalization length (that associated with the faster electrons which dominate energy transport) is comparable to the radius. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.871752
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  • 4
    Digitale Medien
    Digitale Medien
    Modeling and effects of nonlocal electron heat flow in planar shock waves (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 1412-1420 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Electron heat flow was computed in the context of a steadily propagating shock wave. Two problems were studied: a Mach 8 shock in hydrogen, simulated with an ion kinetic code, and a Mach 5 shock in lithium, simulated with an Eulerian hydrodynamic code. The electron heat flow was calculated with Spitzer–Härm classical conductivity, with and without a flux limit, and several nonlocal electron heat flow formulas published in the literature. To evaluate these, the shock's density, velocity, and ion temperature profiles were fixed, and the electron temperature and heat flow were compared to those computed by an electron kinetic code. There were quantitative differences between the electron temperature profiles calculated with the various formulas. For the Mach 8 shock in hydrogen, the best agreement with the kinetic simulation was obtained with the Epperlein–Short delocalization formula [Phys. Fluids B 4, 2211 and 4190 (1992)], and the Luciani–Mora–Bendib formula [Phys. Rev. Lett. 55, 2421 (1985)] gave good agreement. For the Mach 5 shock in lithium, both of these gave good agreement. The earlier Luciani–Mora–Virmont formula [Phys. Rev. Lett. 51, 1664 (1983)] gave fair agreement, while that of San Martin et al. [Phys. Fluids B 4, 3579 (1992); 5, 1485 (1993)] was even further off than the classical Spitzer–Härm [Phys. Rev. 89, 977 (1953)] formula for thermal conduction. To assess the effect of nonlocal electron heat flow on the shock's hydrodynamics and ion kinetics, each of the two problems was done with two different electron heat flow models: the classical Spitzer–Härm local heat conductivity, and the Epperlein–Short nonlocal electron heat-flow formula. In spite of the somewhat different electron temperature profiles, the effect on the shock dynamics was not important. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.871357
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  • 5
    Digitale Medien
    Digitale Medien
    X-ray spectroscopy of hot solid density plasmas produced by subpicosecond high contrast laser pulses at 1018–1019 W/cm2 (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 1702-1711 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Analysis is presented of K-shell spectra obtained from solid density plasmas produced by a high contrast (1010:1) subpicosecond laser pulse (0.5 μm) at 1018–1019 W/cm2. Stark broadening measurements of He-like and Li-like lines are used to infer the mean electron density at which emission takes place. The measurements indicate that there is an optimum condition to produce x-ray emission at solid density for a given isoelectronic sequence, and that the window of optimum conditions to obtain simultaneously the shortest and the brightest x-ray pulse at a given wavelength is relatively narrow. Lower intensity produces a short x-ray pulse but low brightness. The x-ray yield (and also the energy fraction in hot electrons) increases with the laser intensity, but above some laser intensity (1018 W/cm2 for Al) the plasma is overdriven: during the expansion, the plasma is still hot enough to emit, so that emission occurs at lower density and lasts much longer. Energy transport measurements indicate that approximately 6% of the laser energy is coupled to the target at 1018 W/cm2 (1% in thermal electrons with Te≈0.6 keV and 5% in suprathermal electrons with Th≈25 keV). At Iλ2=1018 W μm2/cm2 (no prepulse) around 1010 photons are emitted per laser shot, in 2π srd in cold Kα radiation (2–9 A(ring), depending on the target material) and up to 2×1011 photons are obtained in 2π srd with the unresolved transition array (UTA) emission from the Ta target. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.871318
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  • 6
    Digitale Medien
    Digitale Medien
    Electron heat transport with non-Maxwellian distributions (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 3570-3576 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Measurements are presented of electron heat transport with non-Maxwellian (flattopped) distributions due to inverse bremsstrahlung absorption of intense microwaves in the University of California at Davis Aurora II device [Rogers et al., Phys. Fluids B 1, 741 (1989)]. The plasma is created by pulsed discharge in a cylindrical vacuum chamber with surface magnets arranged to create a density gradient. The ionization fraction (∼1%) is high enough that charged particle collisions are strongly dominant in the afterglow plasma. A short microwave pulse (∼2 μs) heats a region of the afterglow plasma (ne/ncr≤0.5) creating a steep axial (LT∼1–10λei) temperature gradient. Langmuir probes are used to measure the relaxation of the heat front after the microwave pulse. Time and space resolved measurements show that the isotropic component of the electron velocity distribution is flat topped (∼exp[−(v/vm)m], m(approximately-greater-than)2) in agreement with Fokker–Planck calculations using the measured density profile. Classical heat transport theory is not valid both because the isotropic component of the electron velocity distribution is flattopped and the temperature gradients are very steep.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.870892
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  • 7
    Digitale Medien
    Digitale Medien
    Modeling nonlocal heat flow in laser-produced plasmas (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 2296-2300 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Nonlocal heat transport is investigated under conditions relevant to laser-driven fusion. Results from the nonlocal transport model of Luciani and Mora are compared with results from Fokker–Planck codes and from local flux-limited diffusion simulations. No significant nonlocal effects are found in hydrodynamic simulations for irradiation with either 1.06 or 0.35 μm laser light. Over a large range of conditions, the transport is well modeled with a harmonic averaged flux-limiter between 0.1 and 0.2.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.337191
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  • 8
    Digitale Medien
    Digitale Medien
    Non-Maxwellian electron distributions in ionizing plasmas (1991)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 485-491 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Electron kinetics is considered in a plasma in which the distribution of ion charge stages is far from the coronal equilibrium. In rapidly ionizing plasmas, radiative cooling and ionization are found to cause the electron distribution to deviate significantly from a Maxwellian. The relevance of such distribution functions to divertor plasmas near the neutralizer plate is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.859892
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  • 9
    Digitale Medien
    Digitale Medien
    Nonlocal fluxes at a plasma sheath (1990)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 1247-1251 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The particle and energy fluxes of electrons at the boundary of a plasma in contact with a perfectly absorbing plate are considered. In general, the fluxes are shown not to be determined by the plasma temperature and density at the plate but rather by a convolution of the plasma profiles in the vicinity of the plate. A simple empirical expression is proposed for the nonlocal fluxes, which approximately reproduces the results of a full kinetic calculation. The implications of this, to divertor plasmas near the neutralizer plate, are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.859264
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  • 10
    Digitale Medien
    Digitale Medien
    Ultrafast x-ray sourcesf| (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 2676-2681 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Time-resolved spectroscopy (with a 2 psec temporal resolution) of plasmas produced by the interaction between solid targets and a high contrast subpicosecond table top terawatt (T3) laser at 1016 W/cm2, is used to study the basic processes which control the x-ray pulse duration. Short x-ray pulses have been obtained by spectral selection or by plasma gradient scalelength control. Time-dependent calculations of the atomic physics [Phys. Fluids B 4, 2007, 1992] coupled to a Fokker–Planck code [Phys. Rev. Lett. 53, 1461, 1984] indicate that it is essential to take into account the non-Maxwellian character of the electron distribution for a quantitative analysis of the experimental results.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.860705
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