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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

A New Concept for Kilotonne Scale Liquid Argon Time Projection Chambers

We develop a novel Time Projection Chamber (TPC) concept suitable for deployment in kilotonne-scale detectors, with a charge-readout system free from reconstruction ambiguities, and a robust TPC design that reduces high-voltage risks while increasing the coverage of the light-collection system and maximizing the active volume. This novel concept could be used as a far detector module in the Deep Underground Neutrino Experiment (DUNE). For the charge-readout system, we used the charge-collection pixels and associated application-specific integrated circuits currently being developed for the liquid argon (LAr) component of the DUNE Near Detector design, ArgonCube. In addition, we divided the TPC into a number of shorter drift volumes, reducing the total voltage used to drift the ionization electrons, and minimizing the stored energy per TPC. Segmenting the TPC also contains scintillation light, allowing for precise trigger localization and a more expansive light-readout system. Furthermore, the design opens the possibility of replacing or upgrading components. These augmentations could substantially improve the reliability and the sensitivity, particularly for low-energy signals, in comparison to traditional monolithic LArTPCs with projective-wire charge readouts.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1983

Time dependence of solid-particle impingement erosion of an aluminum alloy

Erosion studies were conducted on 6061-T6511 aluminum alloy by using jet impingement of glass beads and crushed glass particles to investigate the influence of exposure time on volume loss rate at different pressures. The results indicate a direct relationship between erosion-versus-time curves and pitmorphology (width, depth, and width-depth ratio)-versus-time curves for both glass forms. Extensive erosion data from the literature were analyzed to find the variations of erosion-rate-versus-time curves with respect to the type of device, the size and shape of erodent particles, the abrasive charge, the impact velocity, etc. Analysis of the experimental data, obtained with two forms of glass, resulted in three types of erosion-rate-versus-time curves: (1) curves with incubation, acceleration, and steadystate periods (type 1); (2) curves with incubation, acceleration, decleration, and steady-state periods (type 3); and (3) curves with incubation, acceleration, peak rate, and deceleration periods (type 4). The type 4 curve is a less frequently seen curve and was not reported in the literature. Analysis of extensive literature data generally indicated three types of erosion-rate-versus-time curves. Two types (types 1 and 3) were observed in the present study; the third type involves incubation (and deposition), acceleration, and steady-state periods (type 2). Examination of the extensive literature data indicated that it is absolutely necessary to consider the corresponding stages or periods of erosion in correlating and characterizing erosion resistance of a wide spectrum of ductile materials.

Veerabhadrarao, P.↗
NASA NTRS1991

Electrostatic Stabilization Of Growing Protein Crystals

Proposed technique produces large crystals in compact, economical apparatus. Report presents concept for supporting protein crystals during growth in microgravity. Yields crystals larger and more-nearly perfect than those grown on Earth. Combines best features of sandwich-drop and electrostatic-levitation methods of support. Drop of protein solution inserted between pair of glass or plastic plates, as in sandwich-drop-support method. Electrostatically charged ring confines drop laterally and shapes it, as in electrostatic technique. Apparatus also made to accommodate several drops simultaneously between same pair of supporting plates. Drops can be inserted and crystals removed through ducts in plates.

Shlichta, Paul J.↗
NASA NTRS1994

Compound chondrules: An experimental investigation

Compound chondrules are considered to be the product of collisions between molten chondrules during chondrule formation Wasson, J. T. et al. (1994) have argued that some compound chondrules are formed when a chondrule with an accretional rim experienced a flash-melting event similar to a chondrule-forming event. We have designed experiments to investigate the formation of compound chondrules by both methods. Experiments were performed on a Deltech vertical muffle tube furnace to form synthetic chondrules to use as accretion rim material. For our experimental conditions, it is clear that compound chondrules can only be made by a collisional event. Our changes maintain their spherical shape and produce distinct boundaries between charges that are similar to natural compound chondrules. Furthermore, collision event(s) between chondrules will cause nucleation if they are molten and undercooled, thus producing chondrule textures. Flash melting chondrules with accretionary rims will not produce compound chondrules but will produce new chondrules with new textures.

Connolly, H. C., Jr.↗
NASA NTRS1995

Structural, dynamical and electronic properties of CaCuO2

The scalar relativistic version of an accurate first principles full potential self-consistent linearized muffin tin orbital (LMTO) method has been employed for describing the physical properties of the parent system of the high-T(sub c) oxide superconductors, i.e., CaCuO2. The presently employed modified version of the LMTO method is quite fast and goes beyond the usual LMTO ASA method in the sense that it permits a completely general shape of the potential and the charge density. Also, in contrast to LMTO ASA, the present method is also capable of treating distorted lattice structures accurately. The calculated values of the lattice parameters of pure CaCuO2 lie within 3% of the experimentally measured values for the Sr-doped system Ca(0.86)Sr(0.14)CuO(2). The computed electronic structures and the density of states is quite similar to those of the other oxide superconductors, except of their three- dimensional character because of the presence of strong coupling between the closely spaced CuO2 layers. The van Hove singularity peak appears slightly below the Fermi level and a small concentration of oxygenation /or/ substitutional doping may pin it at the Fermi level. The calculated frequencies for some symmetric frozen phonons for undoped CaCuO2 are quite near to the measured data for the Sr-doped CaCuO2.

Agrawal, Bal K.↗
NASA NTRS2006

The Zero-Degree Detector System

We will report on a detector system used for accelerator measurement of nuclear fragmentation cross sections. This system consists of two detector planes, each carrying a ring of 8 detectors. Each detector has 64 pads. These two detector planes are arranged facing each other so that the matching detector pads on each plane form a two element charged particle telescope. Each of these telescopes is capable of determining the elemental identity of nuclear fragments passing through it. The system is used to measure light fragment production in the presence of heavier fragments. We will present a detailed discussion of the 64-pad detector design, the substrate design. The front-end electronics used to read out the signals is based on a custom VLSI chip developed for the Advanced Thin Ionization Calorimeter experiment which has been flown successfully twice in Antarctica. Each of these chips has 16 channels and each channel consists of a charge-sensitive preamplifier followed by a shaping amplifier and a track-and-hold circuit. The track-and-hold circuits are connected via a multiplexer to an output line driver. This allows the held signals to be presented, one-by-one via a common data line to a analog-to-digital converter. Because the output line driver can be placed in a high input impedance state when not in use, it is possible to daisy-change many chips on the same common data line. The front-end electronics and data readout scheme will be discussed in detail. The Zero Degree Detector has been used in several accelerator experiments conducted at the NASA Space Radiation Laboratory and the Alternating Gradient Synchrotron at Brookhaven National Laboratory as well as at the HIMAC accelerator in Japan. We will show examples of data taken at these accelerator runs to demonstrate how the system works.

Adams, James H.↗
NASA NTRS1987

Anomalous transport in discrete arcs and simulation of double layers in a model auroral circuit

The evolution and long-time stability of a double layer (DL) in a discrete auroral arc requires that the parallel current in the arc, which may be considered uniform at the source, be diverted within the arc to charge the flanks of the U-shaped double layer potential structure. A simple model is presented in which this current redistribution is effected by anomalous transport based on electrostatic lower hybrid waves driven by the flank structure itself. This process provides the limiting constraint on the double layer potential. The flank charging may be represented as that of a nonlinear transmission line. A simplified model circuit, in which the transmission line is represented by a nonlinear impedance in parallel with a variable resistor, is incorporated in a one-dimensional simulation model to give the current density at the DL boundaries. Results are presented for the scaling of the DL potential as a function of the width of the arc and the saturation efficiency of the lower hybrid instability mechanism.

Smith, Robert A.↗
NASA NTRS2001

An Analytical Model for Non-Uniform Magnetic Field Effects on Two-Dimensional Laminar Jet Diffusion Flames

In 1846, Michael Faraday found that permanent magnets could cause candle flames to deform into equatorial disks. He believed that the change in flame shape was caused by the presence of charged particles within the flames interacting with the magnetic fields. Later researchers found that the interaction between the flame ions and the magnetic fields were much too small to cause the flame deflection. Through a force analysis, von Engel and Cozens showed that the change in the flame shape could be attributed to the diamagnetic flame gases in the paramagnetic atmosphere. Paramagnetism occurs in materials composed of atoms with permanent magnetic dipole moments. In the presence of magnetic field gradients, the atoms align with the magnetic field and are drawn into the direction of increasing magnetic field. Diamagnetism occurs when atoms have no net magnetic dipole moment. In the presence of magnetic gradient fields, diamagnetic substances are repelled towards areas of decreasing magnetism. Oxygen is an example of a paramagnetic substance. Nitrogen, carbon monoxide and dioxide, and most hydrocarbon fuels are examples of diamagnetic substances. In order to evaluate the usefulness of these magnets in altering flame behavior, a study has been undertaken to develop an analytical model to describe the change in the flame length of a laminar diffusion jet in the presence of a nonuniform magnetic field.

Calvert, M. E.↗
DOE OSTI2020

Passivating Nucleobases Bring Charge Transfer Character to Optically Active Transitions in Small Silver Nanoclusters

DNA-wrapped silver nanoclusters (DNA–AgNCs) are known for their efficient luminescence. However, their emission is highly sensitive to the DNA sequence, the cluster size, and its charge state. To get better insights into photophysics of these hybrid systems, simulations based on density functional theory (DFT) are performed. Our calculations elucidate the effect of the structural conformations, charges, solvent polarity, and passivating bases on optical spectra of DNA–AgNCs containing five and six Ag atoms. It is found that inclusion of water in calculations as a polar solvent media results in stabilization of nonplanar conformations of base-passivated clusters, while their planar conformations are more stable in vacuum, similar to the bare Ag5 and Ag6 clusters. Cytosines and guanines interact with the cluster twice stronger than thymines, due to their larger dipole moments. In addition to the base–cluster interactions, hydrogen bonds between bases notably contribute to the structure stabilization. While the relative intensity, line width, and the energy of absorption peaks are slightly changing depending on the cluster charge, conformations, and base types, the overall spectral shape with five well-resolved bands at 2.5–5.5 eV is consistent for all structures. Independent of the passivating bases and the cluster size and charge, the low energy optical transitions at 2.5–3.5 eV exhibit a metal to ligand charge transfer (MLCT) character with the main contribution emerging from Ag-core to the bases. Cytosines facilitate the MLCT character to a larger degree comparing to the other bases. However, the doublet transitions in clusters with the open shell electronic structure (Ag5 and Ag6 + ) result in appearance of additional red-shifted (<2.5 eV) and optically weak band with negligible MLCT character. The passivated clusters with the closed shell electronic structure (Ag5 + and Ag6) exhibit higher optical intensity of their lowest transitions with much higher MLCT contribution, thus having better potential for emission, than their open shell counterparts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1987

Anomalous transport in discrete arcs and simulation of double layers in a model auroral circuit

The evolution and long-time stability of a double layer in a discrete auroral arc requires that the parallel current in the arc, which may be considered uniform at the source, be diverted within the arc to charge the flanks of the U-shaped double-layer potential structure. A simple model is presented in which this current re-distribution is effected by anomalous transport based on electrostatic lower hybrid waves driven by the flank structure itself. This process provides the limiting constraint on the double-layer potential. The flank charging may be represented as that of a nonlinear transmission. A simplified model circuit, in which the transmission line is represented by a nonlinear impedance in parallel with a variable resistor, is incorporated in a 1-d simulation model to give the current density at the DL boundaries. Results are presented for the scaling of the DL potential as a function of the width of the arc and the saturation efficiency of the lower hybrid instability mechanism.

Smith, Robert A.↗
DOE OSTI2022

Strong-field ionization of plasmonic nanoparticles

We modeled strong-field ionization of metal nanoparticles by intense infrared laser pulses, accounting for and distinguishing in photoelectron (PE) momentum distributions the effects of PE correlation, PE–residual-charge interactions, PE rescattering and recombination, and transient laser-induced plasmonic fields. Our numerical results for 5-, 30-, and 70-nm-diameter gold nanospheres and peak laser-pulse intensities of 8.0×10 12 and 1.2×10 13 W/cm 2 show how PE velocity-map images are distinctly shaped by PE Coulomb repulsion, residual-charge accumulations, and plasmonic near fields. In contrast to gaseous atomic targets and dielectric nanoparticles, we find very large PE cutoff energies, for both directly emitted and rescattered PEs, that exceed the incident laser-pulse ponderomotive energy by two orders of magnitude.

74 ATOMIC AND MOLECULAR PHYSICS↗
NASA NTRS1987

High spacecraft potentials on ISEE-1 in sunlight

Data from two electric field experiments and from the plasma composition experiment on ISEE-1 show that the spacecraft charged to close to -70 V in sunlight at about 0700 UT on March 17, 1978. Data from the electron spectrometer experiment show that there was a potential barrier of some -10 to -20 V about the spacecraft during this event. The potential barrier was effective in turning back emitted photoelectrons to the spacecraft. Potential barriers can be formed by differential charging on the spacecraft or by the presence of space charge. The stringent electrostatic cleanliness specifications imposed on ISEE made the presence of differential charging seem unlikely, if these precautions were effective. Modeling of the event to determine if the barrier was produced by the presence of space charge suggested that this could not explain the observed barrier. The angular shape of the distribution could be successfully modeled as a product of differential charging on the solar arrays. This implies that the conductive coating was not completely effective in preventing differential charging, and that differential charging did occur.

Whipple, E. C., Jr.↗
NASA NTRS2008

Particle-Charge Spectrometer

An instrument for rapidly measuring the electric charges and sizes (from approximately 1 to approximately 100 micrometers) of airborne particles is undergoing development. Conceived for monitoring atmospheric dust particles on Mars, instruments like this one could also be used on Earth to monitor natural and artificial aerosols in diverse indoor and outdoor settings for example, volcanic regions, clean rooms, powder-processing machinery, and spray-coating facilities. The instrument incorporates a commercially available, low-noise, ultrasensitive charge-sensing preamplifier circuit. The input terminal of this circuit--the gate of a field-effect transistor--is connected to a Faraday-cage cylindrical electrode. The charged particles of interest are suspended in air or other suitable gas that is made to flow along the axis of the cylindrical electrode without touching the electrode. The flow can be channeled and generated by any of several alternative means; in the prototype of this instrument, the gas is drawn along a glass capillary tube (see upper part of figure) coaxial with the electrode. The size of a particle affects its rate of acceleration in the flow and thus affects the timing and shape of the corresponding signal peak generated by the charge-sensing amplifier. The charge affects the magnitude (and thus also the shape) of the signal peak. Thus, the signal peak (see figure) conveys information on both the size and electric charge of a sensed particle. In experiments thus far, the instrument has been found to be capable of measuring individual aerosol particle charges of magnitude greater than 350 e (where e is the fundamental unit of electric charge) with a precision of +/- 150 e. The instrument can sample particles at a rate as high as several thousand per second.

Fuerstenau, Stephen↗
DOE OSTI2023

Light- and Chemical-Doping-Induced Magnetic Behavior of Eu Molecular Systems

Variable temperature electron paramagnetic resonance (VT-EPR) was used to investigate the role of the environment and oxidation states of several coordinated Eu compounds. We find that while Eu(III) chelating complexes are diamagnetic, simple chemical reduction results in the formation of paramagnetic species. In agreement with the distorted D 3h symmetry of Eu molecular complexes investigated in this study, the EPR spectrum of reduced complexes showed axially symmetric signals (g ⊥ = 2.001 and g ∥ = 1.994) that were successfully simulated with two Eu isotopes with nuclear spin 5/2 ( 151 Eu and 153 Eu with 48% and 52% natural abundance, respectively) and nuclear g-factors 151 Eu/ 153 Eu = 2.27. Illumination of water-soluble complex Eu(dipic) 3 at 4 K led to the ligand-to-metal charge transfer (LMCT) that resulted in the formation of Eu(II) in a rhombic environment (g x = 2.006, g y = 1.995, g z = 1.988). The existence of LMCT affects the luminescence of Eu(dipic) 3 , and pre-reduction of the complex to Eu(II)(dipic) 3 reversibly reduces red luminescence with the appearance of a weak CT blue luminescence. Furthermore, encapsulation of a large portion of the dipic ligand with Cucurbit[7]uril, a pumpkin-shaped macrocycle, inhibited ligand-to-metal charge transfer, preventing the formation of Eu(II) upon illumination.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Measurement of b jet shapes in proton-proton collisions at $\sqrt{s} =$ 5.02 TeV

We present the first study of charged-hadron production associated with jets originating from b quarks in proton-proton collisions at a center-of-mass energy of 5.02 TeV. The data sample used in this study was collected with the CMS detector at the CERN LHC and corresponds to an integrated luminosity of 27.4 pb$^{−1}$. To characterize the jet substructure, the differential jet shapes, defined as the normalized transverse momentum distribution of charged hadrons as a function of angular distance from the jet axis, are measured for b jets. In addition to the jet shapes, the per-jet yields of charged particles associated with b jets are also quantified, again as a function of the angular distance with respect to the jet axis. Extracted jet shape and particle yield distributions for b jets are compared with results for inclusive jets, as well as with the predictions from the pythia and herwig++ event generators.[graphic not available: see fulltext]

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

In-Plane Anisotropy of Charge Density Wave Fluctuations in 1⁢𝑇−TiSe 2

We report measurements of anisotropic triple-𝑞 charge density wave (CDW) fluctuations in the transition metal dichalcogenide 1⁢𝑇−TiSe 2 over a large volume of reciprocal space with x-ray diffuse scattering. Above the transition temperature, 𝑇 CDW , the in-plane diffuse scattering is marked by ellipses which reveal that the in-plane fluctuations are anisotropic. In addition, the out-of-plane diffuse scattering is characterized by rodlike structures which indicate that the CDW fluctuations in neighboring layers are largely decoupled. Furthermore, our analysis of the diffuse scattering line shapes and orientations suggests that the three charge density wave components contain independent phase fluctuations with a hierarchy of length scales, leading to intricate fluctuation patterns that go beyond the conventional 2D-to-3D crossover picture.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗