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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Z-Pinch and Laser-Ablation–Driven High-Yield Neutron Source, LO-005-20, Year 1. Presentation to be given a the FY 2020 SDRD Annual Meeting, to be held Sept. 23-24, on WebEx.
The goal of this exploratory express LDRD is to demonstrate a reproducible laser activated doping diagnostic for eventual use on the Z machine by producing consistent spectral line emission with radiances above 10 5 W sr -1 nm -1 111 -2 from a variety of dopant materials. Here we show that while such radiances are achieved, the line emission is from regions with high electron densities, and close to the laser ablation surface. Therefore, it would be more ideal to improve current optical spectroscopy capabilities on Z to view radiances around 10 4 W sr -l nm -l m -2 . We also discuss the viability of a modular beam path that can be remotely aligned and used on the Z machine. This technique can be used to make spatially resolved measurements of electric and magnetic field strengths and electron densities within the Z power flow and load regions. The measurements can also be used to inform theory and simulation efforts needed to design the next generation of pulsed power capabilities. This was funded as an exploratory LDRD project, number: 214278
The Rayleigh-Taylor Instability (RTI) is a ubiquitous flow phenomenon occurring in a multitude of natural and engineered systems in which buoyancy forces exist. RTI is primarily a limiting process in many HED applications and there are significant efforts within the NNSA-ICF program to account for its effect in large scale simulations of ICF implosions both in two- and three-dimensions. The goal of the proposed research is to develop a fundamental understanding of the evolution and role of magnetic fields in the ablative Rayleigh–Taylor instability (aRTI) in the deeply nonlinear stage.
The goal of this project was to conduct dynamic compression experiments and predictive simulations to reveal the fundamental high-energy-density (HED) physics of amorphous carbon. These results are essential for assessing amorphous carbon as a potential ablator material for next generation of inertial confinement fusion (ICF) capsules. We made significant progress in exploring the HED properties of amorphous carbon through experiments at Omega EP Laser and the European XFEL, in addition to billion-atom, quantum-accurate molecular dynamics (MD) simulations. Through our joint experimental and simulation program, we mapped the phase diagram of amorphous carbon, uncovering its range of metastability and identifying phase transitions to diamond and liquid carbon along the Hugoniot and at higher pressures using double shock compression pathways. Our findings indicate that amorphous carbon melts at significantly lower shock pressures than high-density carbon (diamond). However, nanocrystalline diamond nucleates across a broad range of pressures and temperatures. This emergence of the nanocrystalline microstructure during compression can negatively impact the planarity of the shock front and potentially trigger ablator/fuel mixing during Inertial Fusion Energy (IFE) applications.
A conference presentation (oral talk for ablation workshop) of LDRD results
Recent progress has seen multiple Ta 2 O 5 polymorphs generated by different synthesis techniques. However, discrepancies arise when these polymorphs are produced in widely varying thermodynamic conditions and characterized using different techniques. This work aimed to characterize and compare Ta 2 O 5 particles formed at high and low temperatures using nanosecond pulsed laser ablation (PLA) and continuous wave (CW) laser heating of a local area of tantalum in either air or an 18 O 2 atmosphere. Scanning electron microscopy (SEM) and Raman spectroscopy of the micrometer-sized particles generated by PLA were consistent with either a localized amorphous Ta 2 O 5 phase or a similar, but not identical, crystalline β-Ta 2 O 5 phase. The Raman spectrum of the material formed at the point of CW laser impingement was in good agreement with the previously established ceramic “H-Ta 2 O 5 ” phase. TEM and electron diffraction analysis of these particles indicated the phase structure matched an oxygen-vacated superstructure of monoclinic H-Ta 2 O 5 . Further from the point of laser impingement, CW heating produced particles with a Raman spectrum that matched β-Ta 2 O 5 . We confirmed that the high-temperature ceramic phase characterized in previous work by Raman spectroscopy was the same monoclinic phase characterized in different work by TEM and could be produced by direct laser heating of metal in air.
Comparison of foamed radiating materials with composite charring materials to evaluate their ablation and radiation properties for application to thermal protection for manned space vehicles
Free flight tests of subliming ablators and transpiration cooling as thermal protection at hypersonic speeds
Effect of simulated ablation gas injection on shock layer of blunt bodies at Mach 3 and 5
Viscoelastic analysis of structural integrity of accelerated ablating rocket
Radioisotopic continuous measurement techniques for determination of heat shield ablation and sublimation
Passive temperature control coatings for Apollo spacecraft ablative thermal protection system
Attached and separated boundary layers on highly cooled, ablating and nonablating models at Mach 13.8
Hypersonic trim angle of attack of lifting entry vehicles, correlating stagnation point values obtained from heat shield ablation and pressure distribution measurements
Event recorder for in-flight measurements of missile heat-shield ablation
Ablative material degradation in liquid propellant rocket engine environment of nitrogen tetroxide-aerozine
Performance evaluation of low density phenolic nylon, and elastomeric ablative composites
Trajectory optimization and ablation parameters of ballistic models made of eutectic alloys