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Willey, T. M.

Publications and source records attributed to Willey, T. M..

13 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

X-ray Transparent Barrels for Exploding Foil Initiators

Little is known about the shape and curvature of exploding foil initiator (EFI) flyers, especially as they are forming within a finite barrel. This is because the typical barrel materials, such as stainless-steel, hinder observation of the flyer material during flight. Here we report a new capability for imaging EFI flyers within X-ray transparent barrels by using thin-walled aluminum or polycarbonate. We show that the change in confining material to aluminum does not perturb the flyer produced by the EFI through image comparison and velocity calculations. We found that polycarbonate barrels changed the flyer shape but did not affect the flyer velocity. This highlights the importance of imaging for understanding the spatial characteristics of an EFI. These results provide unprecedented fidelity and resolution for in situ X-ray profile imaging of EFI flyers as they form within a barrel.

42 ENGINEERING↗
DOE OSTI2017

Probing He bubbles in naturally aged and annealed δ-Pu alloys using ultra-small-angle x-ray scattering

We report the self-irradiation of Pu alloys generates He that is trapped within the metal matrix in the form of He bubbles. The distribution of these He bubbles in δ-phase Pu-Ga alloys exhibits a peak near a radius of 0.7 nm, and this size is remarkably stable as function of time. When annealed, the He bubbles in δ-Pu alloys grow, coarsening the distribution. However, the magnitude of this coarsening is uncertain, as different experimental methods reveal bubbles that differ by at least one order of magnitude. Small-angle x-ray scattering results, which can probe a wide range of bubble sizes, imply only a mild coarsening of the He bubble distribution for an annealing treatment of 425 °C for 24 h, and analysis of the He bubble content suggests that He is actually lost from the bubbles with annealing.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Use of small-angle X-ray scattering to resolve intracellular structure changes of Escherichia coli cells induced by antibiotic treatment

The application of small-angle X-ray scattering (SAXS) to whole Escherichia coli cells is challenging owing to the variety of internal constituents. To resolve their contributions, the outer shape was captured by ultra-small-angle X-ray scattering and combined with the internal structure resolved by SAXS. Building on these data, a model for the major structural components of E. coli was developed. It was thus possible to deduce information on the occupied volume, occurrence and average size of the most important intracellular constituents: ribosomes, DNA and proteins. E. coli was studied after treatment with three different antibiotic agents (chloramphenicol, tetracycline and rifampicin) and the impact on the intracellular constituents was monitored.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Measurement of carbon condensates using small-angle x-ray scattering during detonation of the high explosive hexanitrostilbene

The dynamics of carbon condensation in detonating high explosives remains controversial. Detonation model validation requires data for processes occurring at nanometer length scales on time scales ranging from nanoseconds to microseconds. A new detonation endstation has been commissioned to acquire and provide time-resolved small-angle x-ray scattering (SAXS) from detonating explosives. Hexanitrostilbene (HNS) was selected as the first to investigate due to its ease of initiation using exploding foils and flyers, vacuum compatibility, high thermal stability, and stoichiometric carbon abundance that produces high carbon condensate yields. The SAXS data during detonation, collected with 300 ns time resolution, provide unprecedented signal fidelity over a broad q-range. This fidelity permits the first analysis of both the Guinier and Porod/power-law regions of the scattering profile during detonation, which contains information about the size and morphology of the resultant carbon condensate nanoparticles. To bolster confidence in these data, the scattering angle and intensity were additionally cross-referenced with a separate, highly calibrated SAXS beamline. The data show that HNS produces carbon particles with a radius of gyration of 2.7 nm in less than 400 ns after the detonation front has passed, and this size and morphology are constant over the next several microseconds. These data directly contradict previous pioneering work on RDX/TNT mixtures and TATB, where observations indicate significant particle growth (50% or more) continues over several microseconds. The power-law slope is about −3, which is consistent with a complex disordered, irregular, or folded sp{sup 2} sub-arrangement within a relatively monodisperse structure possessing radius of gyration of 2.7 nm after the detonation of HNS.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Nanoporous Cu-C composites based on carbon-nanotube aerogels

Current synthesis methods of nanoporous Cu–C composites offer limited control of the material composition, structure, and properties, particularly for large Cu loadings of ≳20 wt%. Here, we describe two related approaches to realize novel nanoporous Cu–C composites based on the templating of recently developed carbon-nanotube aerogels (CNT-CAs). Our first approach involves the trapping of Cu nanoparticles while CNT-CAs undergo gelation. This method yields nanofoams with relatively high densities of ≳65 mg cm -3 for Cu loadings of ≳10 wt%. Our second approach overcomes this limitation by filling the pores of undoped CNT-CA monoliths with an aqueous solution of CuSO 4 followed by (i) freeze-drying to remove water and (ii) thermal decomposition of CuSO 4 . With this approach, we demonstrate Cu–C composites with a C matrix density of -25 mg cm -3 and Cu loadings of up to 70 wt%. These versatile methods could be extended to fabricate other nanoporous metal–carbon composite materials geared for specific applications.

Charnvanichborikarn, S.↗
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↗