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Biener, M. M.

Publications and source records attributed to Biener, M. M..

13 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Laser transport and backscatter in low-density SiO 2 and Ta2O 5 foams

Experiments using a single 527 nm wavelength beam interacting with sub- and supercritical density SiO 2 and Ta 2 O 5 foams examined laser propagation and backscatter from laser–plasma instabilities such as Stimulated Brillouin Scattering (SBS). Two densities of each material were examined, and multiple diagnostics were used to characterize the propagation and backscatter. For 5 mg/cc SiO 2 (n e /n c = 0.375), the laser propagation distance was well approximated by treating the foam as a gas. However, for the 2 mg/cc SiO 2 foam (n e /n c = 0.15), the same model over-predicts the propagation distance by ~40%. Furthermore, existing analytical theories on propagation through subcritical foams were able to account for this difference. The laser heat wave propagated ~1/2 as far in Ta 2 O 5 than SiO 2 foams with similar electron density. We showed that this difference is due to the increased radiation losses in the higher Z foam. The fraction of backscattered light scales linearly with incident laser intensity for the range of intensities examined. Ta 2 O 5 foams had significantly lower levels of backscatter (1–3%) than the SiO 2 (4–8%), which is consistent with estimates of large Landau damping due to the presence of the oxygen atoms. The measured fraction of SBS backscattered laser energy for a 2 mg/cc SiO 2 foam shot was ~4 times lower than predicted by simulations assuming a gas-like foam. We found that we needed to assume increased ion heating such that T i /T e ~1.2–1.5 in the plasma to agree with the measured SBS reflectivity. Analytical models of laser-heated foams predict preferential heating of the ions as has been observed in previous experiments.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2019

Fullerene-grafted 3D graphene as electrical energy storage material

In this project we developed a concept that allows the integration of the characteristic properties of Carbon sixty (C-60) fullerene in three-dimensional (3D) graphene networks. In these composite materials, the graphene network provides high electrical conductivity and surface area while fullerenes add high electron affinity thus boosting the electrical energy storage performance of the material. Guided by theory, we developed C-60 monoadduct derivatives to optimize the graphene-fullerene interaction, specifically in the context of stability and charge transfer performance in an electrochemical environment. We demonstrated that the electrical energy storage capacity of the 3D graphene network is significantly improved upon the addition of C-60 and C-60 monoadducts by providing additional acceptor states in the form of the low lying Lowest Unoccupied Molecular Orbitals (LUMOs) of C-60 and its derivative. Using first-principles calculations we studied the key factors that determine the electrical energy storage performance.

25 ENERGY STORAGE↗
DOE OSTI2019

Progress of indirect drive inertial confinement fusion in the United States

Abstract Indirect drive converts high power laser light into x-rays using small high- Z cavities called hohlraums. X-rays generated at the hohlraum walls drive a capsule filled with deuterium–tritium (DT) fuel to fusion conditions. Recent experiments have produced fusion yields exceeding 50 kJ where alpha heating provides ~3× increase in yield over PdV work. Closing the gaps toward ignition is challenging, requiring optimization of the target/implosions and the laser to extract maximum energy. The US program has a three-pronged approach to maximize target performance, each closing some portion of the gap. The first item is optimizing the hohlraum to couple more energy to the capsule while maintaining symmetry control. Novel hohlraum designs are being pursued that enable a larger capsule to be driven symmetrically to both reduce 3D effects and increase energy coupled to the capsule. The second issue being addressed is capsule stability. Seeding of instabilities by the hardware used to mount the capsule and fill it with DT fuel remains a concern. Work reducing the impact of the DT fill tubes and novel capsule mounts is being pursed to reduce the effect of mix on the capsule implosions. There is also growing evidence native capsule seeds such as a micro-structure may be playing a role on limiting capsule performance and dedicated experiments are being developed to better understand the phenomenon. The last area of emphasis is the laser. As technology progresses and understanding of laser damage/mitigation advances, increasing the laser energy seems possible. This would increase the amount of energy available to couple to the capsule, and allow larger capsules, potentially increasing the hot spot pressure and confinement time. The combination of each of these focus areas has the potential to produce conditions to initiate thermo-nuclear ignition.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Optical properties of nanoporous gold foams

We fabricated and experimentally studied Au nano-foams and Al 2 O 3 scaffolds filled with Au nanoparticles (NPs). We found that while the reflectance spectra of Au nano-foams depended very little on the 8-10 nm Al 2 O 3 ALD coating, the spectra were highly sensitive to annealing, which increased the sizes of voids and ligaments from 50-100 nm to ~300 nm. The effective dielectric permittivities of the Au nano-foams and Al 2 O 3 scaffolds with Au NPs were extremely high, ~50. At the same time, Au nano-foams covered with a dielectric (MgF 2 ) featured bright structural colors, calling for the model, which extends beyond the effective medium approximation.

36 MATERIALS SCIENCE↗
DOE OSTI2016

First Liquid Layer Inertial Confinement Fusion Implosions at the National Ignition Facility

The first cryogenic deuterium and deuterium-tritium liquid layer implosions at the National Ignition Facility (NIF) demonstrate D 2 and DT layer Inertial Confinement Fusion (ICF) implosions that can access low-to-moderate hot spot convergence ratio (12 30) DT ice layer implosions. Although high CR is desirable in an idealized 1D sense, it amplifies the deleterious effects of asymmetries. To date, these asymmetries prevented the achievement of ignition at the NIF and are the major cause of simulation-experiment disagreement. In the initial liquid layer experiments, high neutron yields were achieved with CR’s of 12-17, and the hot spot formation is well understood, demonstrated by good agreement between the experimental data and the radiation hydrodynamic simulations. These initial experiments open a new NIF experimental capability that provides an opportunity to explore the relationship between hot-spot convergence ratio and the robustness of hot-spot formation during ICF implosions.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Spatially resolved density and ionization measurements of shocked foams using x-ray fluorescence

We present experiments at the Trident laser facility demonstrating the use of x-ray fluorescence (XRF) to simultaneously measure density, ionization state populations, and electron temperature in shocked foams. An imaging x-ray spectrometer obtained spatially resolved measurements of Ti K-α emission. Density profiles were measured from K-α intensity. Ti ionization state distributions and electron temperatures were inferred by fitting K-α spectra to spectra from CRETIN simulations. This work shows that XRF provides a powerful tool to complement other diagnostics to make equation of state measurements of shocked materials containing a suitable tracer element.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Wetted foam liquid fuel ICF target experiments

We are developing a new NIF experimental platform that employs wetted foam liquid fuel layer ICF capsules. We will use the liquid fuel layer capsules in a NIF sub-scale experimental campaign to explore the relationship between hot spot convergence ratio (CR) and the predictability of hot spot formation. DT liquid layer ICF capsules allow for flexibility in hot spot CR via the adjustment of the initial cryogenic capsule temperature and, hence, DT vapor density. Our hypothesis is that the predictive capability of hot spot formation is robust and 1D-like for a relatively low CR hot spot (CR~15), but will become less reliable as hot spot CR is increased to CR>20. Simulations indicate that backing off on hot spot CR is an excellent way to reduce capsule instability growth and to improve robustness to low-mode x-ray flux asymmetries. In the initial experiments, we will test our hypothesis by measuring hot spot size, neutron yield, ion temperature, and burn width to infer hot spot pressure and compare to predictions for implosions with hot spot CR's in the range of 12 to 25. Larger scale experiments are also being designed, and we will advance from sub-scale to full-scale NIF experiments to determine if 1D-like behavior at low CR is retained as the scale-size is increased. The long-term objective is to develop a liquid fuel layer ICF capsule platform with robust thermonuclear burn, modest CR, and significant α-heating with burn propagation.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

Pore architecture of nanoporous gold and titania by hydrogen thermoporometry

Nanoporous gold (NPG) and materials derived from it by templating have complex pore architecture that determines their technologically relevant physical properties. Here, we apply high-resolution hydrogen thermoporometry to study the pore structure of NPG and NPG-derived titania nanofoam (TNF). Results reveal complex multimodal pore size distributions for NPG and TNF. The freezing–melting hysteresis is pronounced, with freezing and melting scans having entirely different shapes. Experiments involving partial freeze–melt cycles reveal the lack of direct correlation between individual freezing and melting peaks, pointing to phenomena that are beyond the Gibbs-Thomson formalism. The depression of the average freezing temperature scales linearly with the ratio of the internal surface area (measured by gas sorption) and the total pore volume derived from the density of monoliths. In conclusion, thermoporometry yields total pore volumes in good agreement with those derived from monolith densities for both NPG and TNF.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Demonstration of x-ray fluorescence imaging of a high-energy-density plasma

Experiments at the Trident Laser Facility have successfully demonstrated the use of x-ray fluorescence imaging (XRFI) to diagnose shocked carbonized resorcinol formaldehyde (CRF) foams doped with Ti. One laser beam created a shock wave in the doped foam. A second laser beam produced a flux of vanadium He-α x-rays, which in turn induced Ti K-shell fluorescence within the foam. Spectrally resolved 1D imaging of the x-ray fluorescence provided shock location and compression measurements. Additionally, experiments using a collimator demonstrated that one can probe specific regions within a target. These results show that XRFI is a capable alternative to path-integrated measurements for diagnosing hydrodynamic experiments at high energy density.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Incipient plasticity of single-crystal tantalum as a function of temperature and orientation

The nanocontact plastic behavior of single-crystalline Ta (1 0 0), Ta (1 1 0) and Ta (1 1 1) was studied as a function of temperature and indentation rate. Tantalum, a representative body centred cubic (BCC) metal, reveals a unique deformation behavior dominated by twinning and the generation of stacking faults. Experiments performed at room temperature exhibit a single pop-in event, while at 200 °C, above the critical temperature, a transition to multiple pop-ins was observed. The experimental results are discussed with respect to the orientation as well as temperature and correlated to the defect structures using both anisotropic finite element and MD simulations. In addition, the serrated flow observed at 200 °C is related to differences in the quasi-elastic reloading originating from changes in the defect mechanism.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Bright x-ray sources from laser irradiation of foams with high concentration of Ti

Low-density foams irradiated by a 20 kJ laser at the Omega laser facility (Laboratory for Laser Energetics, Rochester, NY, USA) are shown to convert more than 5% of the laser energy into 4.6 to 6.0 keV x rays. This record efficiency with foam targets is due to novel fabrication techniques based on atomic-layer-deposition of Ti atoms on an aerogel scaffold. A Ti concentration of 33 at. % was obtained in a foam with a total density of 5 mg/cm{sup 3}. The dynamics of the ionization front through these foams were investigated at the 1 kJ laser of the Gekko XII facility (Institute for Laser Engineering, Osaka, Japan). Hydrodynamic simulations can reproduce the average electron temperature but fail to predict accurately the heat front velocity in the foam. This discrepancy is shown to be unrelated to the possible water adsorbed in the foam but could be attributed to effects of the foam micro-structure.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2010

Fusion Application Targets

Complex target structures are necessary to take full advantage of the unique laboratory environment created by inertial confinement fusion experiments. For example, uses-ofignition targets that contain a thin layer of a low density nanoporous material inside a spherical ablator shell allow placing dopants in direct contact with the DT fuel. The ideal foam for this application is a low-density hydrocarbon foam that is strong enough to survive wetting with cryogenic hydrogen, and low enough in density (density less than ~30 mg/cc) to not reduce the yield of the target. Here, we discuss the fabrication foamlined uses-of-ignition targets, and the development of low-density foams that can be used for this application.

36 MATERIALS SCIENCE↗