[en] Hugoniot measurements of liquid molecular deuterium were made using laser-driven shocks. The equation-of-state data are in agreement with the dissociation model

[en] The authors present their calculations of fragmentation functions for quark and gluon breakup into two mesons within the jet calculus framework. The momentum fraction and Q/sup 2/ dependence of such two particle functions are presented and studied. The dependence on these variables is compared with the calculation by Willen who appends phenomenological fragmentation functions to the two parton jet calculus diagrams. Their approach requires all four parton diagrams. The Q/sup 2/ dependence of meson-meson correlations found by Willen are quite different from that in our approach and the two should be experimentally differentiated

[en] The behavior of laser-driven shock waves in impedance-match, multilayered targets has been explored in hydrodynamic simulations as well as experimental measurements, taking aluminum-gold as the sample target. To achieve maximum pressure enhancement in the gold layer, one needs to consider not only the aluminum layer thickness but also the thickness of the gold layer. Such optimization was demonstrated in the numerical calculations which showed good agreement with observations. 13 references

[en] Solids heated by femtosecond lasers at moderate irradiances (up to 10¹⁵ W/cm²) yield readily plasmas with near-solid densities and relatively low temperatures. Such strongly coupled plasmas have been the focus of many experimental investigations, the objective of which is to determine the plasma transport properties. In particular, the reflectivity measurement of Milchberg et al suggested strong disagreements between observations and existing electrical conductivity models. This has stimulated further experimental and theoretical studies. More recently, a possible means of probing the plasma thermal conductivity via Doppler shift measurements on the reflected light from a heat front was reported. Using numerical simulations which treat self-consistently laser absorption and plasma hydrodynamics, the author has examined the absorption of femtosecond laser light and the formation and propagation of a laser-driven heat front in a solid. In this paper, he reviews two important findings: (i) the reconciliation between the earlier reflectivity measurements and plasma electrical conductivity models and (ii) heat front propagation as a probe of both electrical and thermal conductivities

[en] Efficient absorption of long-pulse CO₂ laser radiation is observed to follow a transient phase of stimulated backscatter (SBS) in critical density, laminar oxygen gas target irradiation experiments. Backscatter is found to peak at 5x10¹²W.cm^-2 ( v²₀/v²sub(e) approximately 1) and decrease with higher incident intensity. Maximum total ''reflectance'' of 30% is measured, decreasing to 18% at 10¹³W.cm^-2, roughly divided between specular and stimulated backscatter. The level of backscatter is consistent with predictions of convective gain for highly damped ion waves, i.e. Compton scattering. X-ray measurements and spatial hot spots in the backscatter indicate filamentation similar to that observed in underdense hydrogen plasma. Nearly complete energy absorption occurs for <10ns following SBS after which target burn-through and refraction dominate. Inverse bremsstrahlung and resonance absorption cannot account for the high absorption in the critical density plasma with scale length <100μm at early time or subsequently underdense plasma at later time. Anomalous collisions of electrons with strong ion turbulence induced by the incident laser radiation are postulated to account for the efficient absorption. Ion charge measurements indicate that approximately 8% of the particles carry 60% of the ion energy (average particle energy approximately 6keV). These energetic ions may be generated either through flux inhibition (f approximately equal to 0.04) due to strong ion fluctuations or directly through laser-induced decays. (author)

[en] Substantially reduced Brillouin reflection has been found for CO₂ laser irradiated high density gas targets. In contrast to high reflectivity (60%) previously observed for underdense hydrogen plasma, total backscatter (stimulated plus specular) is found to peak at 30% for incident intensity 5 x 10¹² W/cm² and decrease thereafter to 18% at 10¹³ W/cm². Ponderomotive effects are postulated to account for these observations. (orig.)

[en] This paper describes a novel diagnostic technique which may provide a new means for studying the physical properties of a dense, degenerate plasma. This is based on the measurement of the reflectivity of the shock-compressed, free surface of a solid when the shock emerges. By comparing the observed temporal evolution of the reflectivity of the unloading surface with results of numerical simulations, one can examine theoretical models of equations of state as well as transport coefficients. In particular, the electrical conductivity of a dense plasma is found to exhibit a strong effect on its reflectivity. A schematic of the experimental set-up is shown which incorporates a Nd-glass laser

[en] This paper presents a detailed review of the often misunderstood theoretical approach to the design and construction of covers for uranium tailings. The purpose of the cover is to mitigate the adverse effects of uranium tailings on the public health and safety. Topics considered include radon emanation reduction, long-term stability, and radon attenuation. Uranium mill operators are required to prepare detailed reclamation plans to reclaim inactive uranium tailings ponds. The design, implementation and performance of a cover for uranium tailings is the most costly and controversial aspect of uranium mill tailings reclamation. Several methods are offered to stabilize tailings prior to cover placement. It is concluded that coupling the practical knowledge of cover implementation with realistic theoretical assessments can provide optimum covers which meet the goal of public health and safety

[en] Strong backscatter (> approximately 20%) has been observed in the interaction of focused CO₂ laser radiation (I approximately 10¹² W/cm²) with a hydrogen gas target plasma. Spectral measurements show it to arise from stimulated ion Compton scattering (SCS) at later times when the electron-ion temperature ratio is not large. The scattering growth rate γ was determined experimentally to be 3.4 x 10¹² s^-1, in good agreement with theoretical predictions for our plasma parameters. Temporal modulation of the backscatter clearly shows build-up and decay of SCS durng the interaction time. It may be anticipated that such scattering will be important in laser-pellet fusion experiments. (author)

[en] The effects of thermal conduction are examined for the expansion of a plasma from a vacuum interface using an analytic model based on well-known self-similar models of rarefaction waves. Conventional analysis of shock-unloading experiments uses an isotropic expansion model. However, thermal conduction introduces a characteristic time scale during which the flow is not self-similar. The significance of this time scale for experimental measurements is also discussed. The characteristic time is calculated for an aluminum plasma using theoretical equation-of-state and conductivity models. (Author) 19 refs., 5 figs