R.E. Reinovsky’s research while affiliated with Los Alamos National Laboratory and other places

Three continuum compaction models are calibrated to planar impact data for CeO2 powder and used to predict the shock compaction behavior of CeO2 powder under cylindrically converging shock wave loading. All experiments and computations are performed on powder compacts with an initial pressed density of 4.0 g/cm³ (56% TMD). A magnetically-driven, cylindrically-converging shock compaction experiment is computationally designed using the calibrated compaction models in the multi-physics code FLAG. Magnetohydrodynamic (MHD) calculations of impact conditions are performed using a calibrated circuit model in FLAG. The first cylindrical shock compaction experiment is executed using the mobile pulsed power driver PHELIX. In situ areal density measurements of the CeO2 target assembly are performed during the compaction event with proton radiography. Calculations of the late time compaction response of the CeO2 powder under PHELIX compression are greater than 90% accurate using the P-α compaction models calibrated under planar loading.

This report investigates the validity of the P-alpha and Bi-linear Ramp continuum compaction models to predict the densification response of CeO2 powder to complex, nonplanar shock wave loading using a combined experimental and computational approach. Compaction models are calibrated to planar impact Hugoniot data for CeO2 powder, then used to design a nonplanar complex loading experiment, applying the pulsed power driver PHELIX to compress the CeO2 powder. Two compaction experiments are fielded on PHELIX, using proton radiography to measure the densification response. Comparison of the simulated and experimental data reveal that the P-alpha models more accurately describe densification response than the Bi-linear Ramp model. Preliminary investigations into coupled compaction and strength modeling suggest that incorporating a strength model for porous CeO2 will further increase model accuracy.

The LANL PHELIX pulsed-power driven liner implosion apparatus is fielded to measure the growth of Richtmyer-Meshkov instabilities (RMIs) in a cylindrical geometry under the conditions of liquid (Cren-1), mixed-state (Cren-2), and solid (Cren-3) release. 2D Lagrangian hydrocode simulations of this imploding geometry are compared against 800-MeV proton radiography data of the RMI growth. The liquid release (>35 GPa) was achieved with a liner velocity of 3 km s⁻¹, and demonstrates a linear, continuous spike growth that agrees with the model. The mixed release (20 - 35 GPa) was achieved with a liner velocity of 1.4 km s⁻¹ and demonstrates growth stagnation with time, due to increased transit time effects. The solid release (<20 GPa), achieved with a liner velocity of 0.8 km s⁻¹, also demonstrates growth stagnation, while also showing an effect not predicted by the model, in that some peaks, at late time, disappear completely, while other, central, peaks, grow disproportionately large, due to RMI bubble merger behavior. These experiments demonstrate a broad parameter space in which to study RMIs in a cylindrical geometry, and a rich dataset against which to validate and inform future iterations of the simulation.

Warm Dense Matter (WDM) is the state of matter in the range between condensed matter and ideal plasma, which has higher temperature than condensed matter, but lower temperature and higher density than the traditional ideal plasma. In this range, which is often characterized by temperatures of 1 0 0 (ρ 0 is solid density), matter cannot be described by theories applicable to ideal plasma or condensed (solid) matter. Understanding WDM properties is a challenging physical problem, because this state of matter is hard to simulate theoretically or produce/measure experimentally under laboratory conditions. WDM occurs in the core of gas-giant planets and in engineering and physical applications it forms in systems with fast solid-to-plasma transition, such as exploding wires or quickly heated (by laser or high magnetic fields) materials. This paper investigates a WDM generation system by electric explosion of a thin cylindrical metal foil enclosed in an insulator. This experimental setup provides the homogeneity of the WDM and present availability of WDM for the diagnostics. The electric explosion of the metal foil can be realized by currents of such current sources as the helical explosive magnetic flux compression generator (EMG) with an opening switch and stationary facility PHELIX of LANL. A diameter 200 mm EMG with an explosive opening switch can deliver a current of ∼5 MA with a characteristic rise time of 0.3 μs. It is shown that in such the WDM generation system driven by the EMG with the opening switch one can obtain a large volume of matter with density on the order of (0.01–1) of solid density and temperature about 2–3 eV. The PHELIX facility is a small-size capacitor bank coupled to the current transformer; it allows to reach load currents 3–5 MA with characteristic times ∼10 μs. The paper shows that in a system with using of this facility significant volumes of uniform WDM with the density of ∼ 0.1–1 g/cm 3 and temperature of 3–4 eV can be obtained with good accessibility for measurements. A way to recover the WDM parameters based on electrotechnical measurements and exploded foil boundary velocimetry is described.

When a sufficiently strong shock emerges from the free surface of a solid, micron-sized particles may be “ejected” from the tiny defects, grain boundaries or surface inclusions characteristic of real surfaces. If the solid surface bounds a gas or plasma such as an MTF or ICF target, the introduction of surface (perhaps high-Z) material into the gas or plasma may significantly alter its properties and behavior. The formation of ejecta particles has been the subject of both experimental measurements and computational modeling. Simple hydrodynamic drag models have been less than completely adequate, and recent work has explored hydrodynamic (such as Richtmyer-Meshkov) explanations. Less experimental work has been devoted to exploring ejecta particle transport in gas (or plasmas), and most of that work has been done in planar geometries. A new high precision, experiment, called the Damaged Surface Hydrodynamics Experiment, has been developed to explore transport of ejecta particles into gas (or plasma) in converging geometries, diagnosed by high resolution, fast, multi-frame imaging by proton radiography to inform the continuing development of transport models and validate current and future simulations.