Engineering Papers⌕ Search

Engineering topics

Byvank, Tom

Publications and source records attributed to Byvank, Tom.

17 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

WDM-SP-25A: Development of a stopping power platform using secondary nuclear reactions in Warm Dense Matter (Director’s Post-Doc Shot Request) [Slides]

Motivation: Recent theoretical modeling at LANL has demonstrated that the ignition criteria is a strong function of the temperature of the DT ice that surrounds the hot spot [Daughton et al. PoP 2023]. Alpha heating of the DT shell can raise the ignition threshold. Critical to modeling the alpha-particle deposition in the shell is understanding charged particle stopping in warm dense matter.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2024

XFOL FY25 Omega 3 pager [Slides]

The XFOL campaign is continuing to study radiation flow in stochastic media. Purpose: Simultaneously measure the ionization state of the background and inclusions of a binary stochastic media using the COAX/OUTI diagnostic. Motivation: Radflow is stochastic media is of wide, growing interest and COAX is a new powerful diagnostic that can characterize the radflow physics and validate codes, models, and their underlying assumptions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Roadmap for the exposé of radiation flows (Xflows) experiment on $\mathrm{NIF}$

Here, the goal of the Xflows experimental campaign is to study the radiation flow on the National Ignition Facility (NIF) reproducing the sensitivity of the temperature (±8 eV, ±23 μm) and density (±11 mg/cc) measurements of the COAX platform. This new platform will enable future astrophysical experiments involving supernova shock breakout, such as Radishock on OMEGA-60, and stochastic media (such as XFOL on OMEGA). Greater energy and larger physical scale on NIF will enable a greater travel distance of radiation flow, higher density, and more manufacturable foams and enable exploration of a greater range of radiation behavior than achievable in the prior OMEGA experiments. This publication will describe the baseline configuration for the Xflows experimental campaign and the roadmap to achieve its primary objectives.

47 OTHER INSTRUMENTATION↗
DOE OSTI2022

Monte Carlo N-Particle forward modeling for density reconstruction of double shell capsule radiographs

In the Double Shell Inertial Confinement Fusion concept, characterizing the shape asymmetry of imploding metal shells is vital for understanding energy-efficient compression and radiative losses of the thermonuclear fuel. The Monte Carlo N-Particle MCNP® code forward models radiography of Double Shell capsule implosions using the Advanced Radiographic Capability at the National Ignition Facility. A procedure is developed for using MCNP to reconstruct density profiles from the radiograph image intensity. For a given Double Shell imploding target geometry, MCNP radiographs predict image contrast, which can help guide experimental design. Finally, in future work, the calculated MCNP synthetic radiographs will be compared with experimental radiographs to determine the radial and azimuthal density profiles of the Double Shell capsules.

47 OTHER INSTRUMENTATION↗
DOE OSTI2022

Detailed temperature diagnostic studies for Radishock and COAX experiments

Spectral diagnostics provide a powerful probe of high energy-density physics experiments. By shining an x-ray source on a target, absorption features can be used to determine accurate temperature profiles of that target material. Many studies produce a single temperature/density measurement by fitting these observed spectra. This paper demonstrates how, by leveraging detailed simulations, we can not only measure the average temperature and density, but the full density and temperature profiles. To do so, we must conduct a careful analysis of the uncertainties in the diagnostic measurement. Here we discuss the characteristics and associated uncertainties of the spectral diagnostic used in the COAX, Radishock and OuTi experiments, ultimately demonstrating how these detailed studies increase the potential of this powerful probe.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

“Complete Arc development for Double/Multi-Shell target designs" (Level 2 Milestone Report)

The goal of the Double Shell platform is to determine the efficacy of the shell platforms to provide a robust burn platform. One critical aspect of this is to understand the physics associated with the inner shell. In this report, we will discuss the motivation, development and results from the experimental platform to study the physics of the inner shell of a double (or multi-) shell capsule.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

High command fidelity electromagnetically driven calorimeter

An example apparatus can comprise an emitter to emit radio frequency radiation, an absorber that changes temperature based on emissions from the emitter, and one or more sensors to measure a temperature difference between a sample and a reference coupled to the absorber.

42 ENGINEERING↗
DOE OSTI2020

Observation of shock-front separation in multi-ion-species collisional plasma shocks

We observe shock-front separation and species-dependent shock widths in multi-ion-species collisional plasma shocks, which are produced by obliquely merging plasma jets of a He/Ar mixture (97% He and 3% Ar by initial number density) on the plasma liner experiment. Visible plasma emission near the He-I 587.6-nm and Ar-II 476.5–514.5-nm lines is simultaneously recorded by splitting a single visible image of the shock into two different fast-framing cameras with different narrow bandpass filters (589 ± 5 nm for observing the He-I line and 500 ± 25 nm for the Ar-II lines). For conditions in these experiments (pre-shock ion and electron densities ≈5×10 14 cm –3 , ion and electron temperatures of ≈2.2 eV, and relative plasma-merging speed of 22 km/s), the observationally inferred magnitude of He/Ar shock-front separation and the shock widths themselves are <1 cm, which correspond to ~50 post-shock thermal ion–ion mean free paths. These experimental length scales are in reasonable qualitative and quantitative agreement with results from 1D multi-fluid simulations using the CHICAGO code. However, we note there are differences between the experimentally inferred and simulation-predicted ionization states and line emission intensities, particularly in the post-shock region. Overall, the experimental and simulation results are consistent with theoretical predictions that the lighter He ions diffuse farther ahead within the overall shock front than the heavier Ar ions.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

w18_plxa Final Report Viewgraphs [Slides]

For our fusion concept, we want to look at the influence of: 1) Density perturbations of the liner [shell that pushes on the target to get the target to fusion conditions] and 2) Magnetic field and anisotropic conductivity effects. On the compression of the target (final ion temperatures, without nuclear reaction calculations)

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2019

Plasma Jet Formation Disruption From a Critical Applied Uniform Axial Magnetic Field

We examine the effects of varying the magnitude of an applied, uniform, axial magnetic field (Bz) on the formation of laboratory plasma jets produced by a 1-MA 100-ns rise time pulsed power generator in a radial foil configuration. A Helmholtz coil applies the external magnetic field (0 to 2 T). With a small-enough applied field, the foil surface ablation is relatively azimuthally uniform, and J×B forces drive the ablated plasma inward and upward to form a well-defined azimuthally symmetric jet. Using applied field strengths larger than a critical Bz = 1.1±0.1 T with aluminum foils, the plasma ablation is not azimuthally uniform, discrete bursts of plasma initiate from the foil surface, and the formation of a well-defined jet is disrupted. The critical Bz for this plasma jet formation disruption correlates with the foil material’s electrical resistivity and equation of state (EOS). To better understand the material-dependent phenomenon, we compare the experimental results with 3-D extended magnetohydrodynamics simulations of ablation of a 2 mm × 2 mm by 25-μm slab that represents a section of the radial foil. The simulations initialize the slab in the solid state and include the material resistivity and EOS from the solid to plasma phases. As is observed in the experimental disruption, these simulations show enhanced nonuniform plasma ablation with an applied Bz, which can inhibit the azimuthal uniformity necessary to produce a well-defined plasma jet. Furthermore, the simulations also show a material and resistivity dependence on the ablation process similar to the trend shown by the experiments. These results demonstrate the necessity of accurate, detailed modeling of material properties during the transition from solid to plasma phases.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

External Magnetic Field Effects on Ablation of Current-Driven Foils Using an Extended Magnetohydrodynamics Simulation

We numerically model the ablation process of a 25-μm-thick aluminum foil driven by a pulsed-power machine that provides a 1-MA peak current in a 100-ns zero-to-peak rise time. The extended magnetohydrodynamics simulation is a discontinuous Galerkin code with Cartesian coordinates in 3-D and with 25-μm spatial resolution. We investigate here the influence of an external magnetic field normal to the foil surface, B z . During the foil ablation, B z = 1 T causes more nonuniform distributions of density and current compared to B z = 0 T. B z = 4 T delays the generation of surface plasma relative to the 0- and 1-T cases. The understanding of a material's ablation as it undergoes transition from the solid to plasma phases requires detailed knowledge of a material's equation of state and conductivity. This paper of warm dense matter and how instabilities propagate from a solid material to plasma motivates improvements to both numerical simulations and experimental diagnostics.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗