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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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At least 1,657 records · Page 92
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Consistent solutions of the radiation diffusion equation in spherical and cylindrical geometries

We have extended the radiation diffusion model of Hammer and Rosen [Phys. Plasmas 10, 1829 (2003)] to diverging spherical and cylindrical geometries. The effect of curvilinear geometry on the supersonic, expanding wavefront increases as the internal radius of a spherical or cylindrical shell approaches zero. Small spherical geometries are important for modeling systems at the size scale of inertial confinement fusion capsules, at these scales existing quasi-analytic models for planar geometry significantly disagree with the results of simulation. With this method, the benefits of rapid iteration can be applied to common spherical systems at much smaller length scales. We present comparisons between numerical diffusion solutions and the analytic model to give ranges of applicability for the model.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Impurity transport in ion- and electron-root confinement scenarios at Wendelstein 7-X

This paper reports on the observation of enhanced Ar impurity confinement in high density, turbulence reduced ion-root confinement (IRC) scenarios in Wendelstein 7-X (W7-X). Compared to the central electron-root confinement (CERC), Ar densities are substantially increased up to one order of magnitude and Ar flux profiles switch from slightly positive to pronounced negative fluxes all along the plasma radius in IRC. Estimations of the diffusive D and convective V transport parameter profiles using the STRAHL impurity transport code suggest a fundamentally different behavior in CERC and IRC with, compared to neoclassical values, high diffusive D and typical V profiles in CERC versus strongly reduced D and pronounced negative V profiles in IRC.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

Modeling pulse characteristics in Xenon with NEST

In this paper, a comprehensive model for describing the characteristics of pulsed signals, generated by particle interactions in xenon detectors, is presented. An emphasis is laid on two-phase time projection chambers, but the models presented are also applicable to single phase detectors. In order to simulate the pulse shape due to primary scintillation light, the effects of the ratio of singlet and triplet dimer state populations, as well as their corresponding decay times, and the recombination time are incorporated into the model. In a two phase time projection chamber, when simulating the pulse caused by electroluminescence light, the ionization electron mean free path in gas, the drift velocity, singlet and triplet decay times, diffusion constants, and the electron trapping time, have been implemented. Finally, this modeling has been incorporated into a complete software package, which realistically simulates the expected pulse shapes for these types of detectors.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2024

Assessment of the literature about Be-W mixed material layer formation in the fusion reactor environment

Abstract All plasma facing surfaces in a fusion reactor, whether initially pure or an alloy, will rapidly evolve into a mixed material due to plasma-induced erosion, migration and redeposition. Beryllium (Be) erosion from the main chamber, and its transport and deposition on to a tungsten (W) divertor results in the growth of mixed Be-W layers, which can evolve to form beryllides. These Be-W mixed materials exhibit generally less desirable properties than pure tungsten or pure beryllium, such as lower melting points. In order to better understand the parameter space for growth of these alloys, this paper reviews the literature on Be-W mixed material formation experiments—in magnetically confined fusion reactors, in linear plasma test stands, and during thin-film deposition—and on computational modeling of Be-W interactions, as well as briefly assesses the Be-W growth kinetics. We conclude that the following kinetic steps drive the material mixing: adsorption of the implanted/deposited ion on the metal surface; diffusion of the implanted/deposited ion from surface into the bulk, which is accelerated by defects; and loss of deposited material through erosion. Adsorption dominates (or prevents) material mixing in thin-film deposition experiments, whereas diffusion drives material mixing in plasma exposures due to the energetic ion implantation.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2017

Modeling and Preparation for Experimental Testing of Heat Fluxes on W7-X Divertor Scraper Elements

Simulations of heat fluxes to the plasma facing components in the Wendelstein 7-X stellarator will be tested in its next operational phase. The simulations consist of core transport calculations that determine the evolution of the kinetic profiles and the toroidal current, which modifies the fluxes to the divertor, as the magnetic geometry changes. An additional divertor component, the scraper element, was designed to protect the edges of the primary divertor throughout this evolution during certain high-power long-pulse operational scenarios. The effect of unknown parameters of the heat flux calculations, namely, the cross-field thermal diffusivity and the magnetic field structure, is explored. The predicted scaling of the heat flux widths and magnitudes is presented, along with a new method of calculating the 3-D magnetic field structure required to perform the flux calculations.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2026

Altered morphology and diffusivity of water confined in MXenes: Machine learning–accelerated computations combined with experiments

Nanoconfined water exhibits unique properties compared to bulk water due to limited quantities, frustrated hydrogen bonding, and surface interactions, which are fundamental for energy storage and transport applications. We integrate machine learning–accelerated ab initio molecular dynamics with x-ray diffraction (XRD) and inelastic neutron scattering (INS) to systematically analyze the thermodynamic and dynamic behavior of water confined between functionalized (-F, -O, and -OH) two-dimensional (2D) Ti 3 C 2 T x MXene layers. As water intercalates between layers, the interlayer spacing exhibits layer-dependent staging characteristics. The water polarization can be flipped by the count and morphology of intercalated molecules interacting with MXene surface groups, resulting in varying electrostatic potential profiles. On the basis of interfacial electrostatic potential, hydrogen bond lifetime, and molecular orientation, we establish a linear combination of exponential model describing water diffusivity. These computational insights align well with experimental x-ray and neutron measurements, suggesting strategies for tuning water morphology and transport by tailoring MXene surface chemistry and water content for electrochemical energy storage and nanofluidic applications.

Tang, Jiawei [Southeast Univ., Nanjing (China)] (O↗
DOE OSTI2017

Study of Diffuse Supernova Neutrino Background with Modern and Future Detectors

Basic properties of the diffuse supernova neutrino background (DSNB) are reviewed. Current DSNB studies and the limits already set on the DSNB flow by the operating detectors Super-Kamiokande, SNO, and KamLAND are discussed. Prospects of DSNB studies with future high-mass neutrino detectors, such as JUNO and Hyper-Kamiokande, are considered.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

Physical Parameters of a Reactor-Stellarator with Small Ripples of the Helical Magnetic Field

The paper describes the calculation data on the physical parameters of a reactor-stellarator, where the nonuniformities of the helical field are smaller than the toroidal magnetic field nonuniformities: ε{sub h} < ε{sub t}. Unlike the previous studies, where the ion-component transport coefficients had the collision frequency dependence proportional to ν{sup 1/2}, this being equivalent to the ε{sub h} > ε{sub t} case, in the present calculations, these coefficients were assumed to be in proportion to the first power of the collision frequency, D{sub i} ∝ ν for ν{sub eff} < 2ω{sub E}, and to D{sub i} ∝ ν{sup −1} for the inverse inequality. Here, ω{sub E} is the rotation frequency of plasma in the radial electric field. As before, the plasma electrons corresponded to the mode of D{sub e} ∝ ν{sup −1}. As initial parameters for numerical calculations, a reactor with R = 8 m, r{sub p} = 2 m, and B{sub 0} = 5 Т was taken. A numerical code was used to solve the set of equations that describes the plasma space−time behavior in the reactor-stellarator under the conditions of equal diffusion fluxes. The start of reactor operation in the mode of thermonuclear burning was provided by heating sources with a power of several tens of megawatts. Steady-state operating conditions of a self-sustained thermonuclear reaction were attained by maintaining the plasma density through DT fuel pellet injection into the plasma.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Validation of the Mach Stem Triple Point

Among the more complex characteristics of an explosion’s shock front is the creation of the Mach stem and its triple point. The scientific footage of the US Atmospheric Nuclear Weapons Testing Program has a film that may show the locus of points formed by the triple point, allowing us to visually investigate the trajectory of these shockwaves. During a nuclear blast, once the X-ray diffusion process ends, an incident shockwave forms in all directions. When the incident shockwave contacts the ground, a reflected shockwave is created. The overall magnitude and impact of these two shockwaves are proportional to the increasing total pressure and temperature, allowing the disturbances to move faster than the local speed of sound.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2021

Tools for Assessing Performance Project: FY2021 Quarter 4 Report

The rotatable building located at Texas Tech’s Reese Technology Center is approximately 14 m wide (width being defined as more normal to the wind than parallel), 9 m long (aligned more with the wind than perpendicular), and 4 m tall. By placing 29 sonic anemometers downwind of the building, see Fig. 1, this facility provided a chance to collect data concerning both the wake velocity deficit distribution in the downstream and crosssteam directions (relative to the mean wind) behind an isolated building. A preliminary comparison between this data and the recently- developed fast-running diffusive wake model, which was developed based on wind tunnel and LES (performed with JOULES) simulations, for the purpose of either validating this model of understanding potential persistent differences between the idealized wind tunnel or LES conditions and those of full-scale real world phenomena. For this preliminary exploration, we utilized the diffusive wake model implemented in the QUIC model.

42 ENGINEERING↗
DOE OSTI2022

Technical Guidance on Use of the Netzsch LFA 447 Nanoflash for Measurement of Ceramic-Metallic (Cermet) Pellet Specimen

The Netzsch LFA 447 Nanoflash Instrument uses the laser flash method to measure thermal diffusivity of a material. Thermal conductivity can be determined if specific heat and density are known for that material. The 238 Pu Supply Program is interested in re-establishing the capability to determine thermal diffusivity and thermal conductivity of various 237Np Al/cermet samples during heating. The bottom side of a plane parallel sample is heated by an energy pulse from a light source (in this case a xenon lamp). An infrared (IR) detector is on the top side of the sample which detects the time dependent temperature rise of the sample due to the energy input from the xenon lamp. The LFA 447 Nanoflash is user-friendly, simple to operate, and has minor sample preparation which will allow technicians to be trained easily on its use. When using the multi-property measurement option, the LFA 447 Nanoflash can determine both thermal diffusivity and specific heat which means only density is needed to identify the thermal conductivity of a sample. This equipment is recognized for being highly accurate and having fast test times, replacing steady-state methods which have proven to be difficult and much slower.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2026

Highlight of IC project: w25_dreamxd

(left) The Earth’s radiation belts are donut-shaped regions containing MeV electrons (color contour for density) trapped by the magnetic field (white curves). We use DREAMxD code to model their dynamics. (right) We develop a new method to accelerate a key piece of the code – diffusion coefficient calculation. Comparing the compute time in node hours required by the standard approach to the compute time required for the fast method, it shows that the new method can be 100x faster for a large problem size.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Aerosol Microphysics and Chemical Measurements at Mt. Soledad and Scripps Pier during the Eastern Pacific Cloud Aerosol Precipitation Experiment (EPCAPE) from February 2023 to February 2024 UCSD Library Collection

This dataset includes guest instrument measurements and other PI products for aerosol microphysics and chemical measurements collected at Mt. Soledad and Scripps Pier during the Eastern Pacific Cloud Aerosol Precipitation Experiment (EPCAPE) from February 2023 to February 2024. The measurements include the following instruments at Mt. Soledad: High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS, Aerodyne), Scanning Electrical Mobility Spectrometer (SEMS, Brechtel Manufacturing Inc.), Aerodynamic Particle Sizer (APS, Droplet Measurements Technologies), Single Particle Soot Photometer (SP2, Drople Measurements Technologies), Meteorological Station (WXT520, Vaisala), Ozone (Teco), and trace gas proxies (Teledyne). In addition, the analyses of particle filters collected at Mt. Soledad for three dry-diameter size cuts (<1 micron, <0.5 micron, <0.18 micron) and at Scripps Pier for one dry-diameter size cut (<1 micron) by Fourier Transform Infrared (FTIR) and X-ray Fluorescence (XRF) are reported. A differential mobility analyzer operated as a scanning mobility particle sizer (SMPS, TSI Inc.), a printed particle optical spectrometer (POPS, Grimm), and a continuous flow diffusion cloud condensation nuclei (CCN, DMT) counter provide the mobility aerosol size distribution (30-360 nm), optical size distribution (150 - 6000 nm), size-resolved CCN distribution (30-360 nm) at 0.2, 0.4, 0.6, 0.8, and 1.0% supersaturation. Measurements are reported for both sampling from an isokinetic aerosol inlet and from a Counterflow Virtual Impactor (CVI, Brechtel Manufacturing Inc.). The data are available at the following link: https://library.ucsd.edu/dc/collection/bb0898306q

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Two species drag/diffusion model for energetic particle driven modes

A nonlinear bump-on-tail model for the growth and saturation of energetic particle driven plasma waves has been extended to include two populations of fast particles—one dominated by dynamical friction at the resonance and the other by velocity space diffusion. The resulting temporal evolution of the wave amplitude and frequency depends on the relative weight of the two populations. The two species model is applied to burning plasma with drag-dominated alpha particles and diffusion-dominated ICRH accelerated minority ions, showing the stabilization of bursting modes. The model also suggests an explanation for the recent observations on the TJ-II stellarator, where Alfv'en Eigenmodes transition between steady state and bursting as the magnetic configuration varied.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Data-Driven First-Principles Methods for the Study and Design of Alkali Superionic Conductors

We present a detailed exposition of how first-principles methods can be used to guide alkali superionic conductor (ASIC) study and design. Using the argyrodite Li 6 PS 5 Cl as a case study, we demonstrate how modern information technology (IT) infrastructure and software tools can facilitate the assessment of alkali superionic conductors in terms of various critical properties of interest such as phase and electrochemical stability and ionic conductivity. The emphasis is on well-documented, reproducible analysis code that can be readily generalized to other material systems and design problems. For our chosen Li 6 PS 5 Cl case study material, we show that Li excess is crucial to enhancing its conductivity by increasing the occupancy of interstitial sites that promote long-range Li + diffusion between cage-like frameworks. The predicted room-temperature conductivities and activation barriers are in reasonably good agreement with experimental values.

42 ENGINEERING↗
DOE OSTI2026

How Silica Surface Chemistry Modulates Interfacial Water: Insights from Machine Learning Molecular Dynamics

Controlling water structure and dynamics at silica interfaces are central to a wide range of technologies, including protective oxide layers for solar water splitting and nanoporous membranes. In this work, we develop a machine learning interatomic potential, trained via active learning, to achieve ab initio accuracy for water confined between hydroxylated silica surfaces over a range of silanol coverages and slit widths. We find that partially hydroxylated surfaces (50 and 75% OH) support stronger water−surface hydrogen bonding and more extended interfacial density profiles than fully hydroxylated (100% OH) surfaces, indicating that increasing OH coverage does not necessarily strengthen interfacial hydrogenbond networks. Translational diffusion decreases approximately linearly with slit width and OH coverage, whereas rotational dynamics respond nonlinearly. In particular, at the smallest slit width of 5 Å, 75% OH coverage produces an enhanced local tetrahedral ordered interfacial network that strongly suppresses reorientation, while 100% coverage yields a crowded, disordered interfacial layer that also hinders rotation. In contrast, the 50% OH coverage is sufficiently sparse that it does not markedly alter water structure or dynamics under confinement. These results show that coupled control of pore size and surface chemistry enables nonlinear tuning of interfacial water structure and transport, providing a design strategy for optimizing porous silica for either enhanced interfacial stability and controlled reactivity or rapid and selective transport.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗