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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 OSTI2014

A neural network clustering algorithm for the ATLAS silicon pixel detector

A novel technique to identify and split clusters created by multiple charged particles in the ATLAS pixel detector using a set of artificial neural networks is presented. Such merged clusters are a common feature of tracks originating from highly energetic objects, such as jets. Neural networks are trained using Monte Carlo samples produced with a detailed detector simulation. This technique replaces the former clustering approach based on a connected component analysis and charge interpolation. The performance of the neural network splitting technique is quantified using data from proton-proton collisions at the LHC collected by the ATLAS detector in 2011 and from Monte Carlo simulations. This technique reduces the number of clusters shared between tracks in highly energetic jets by up to a factor of three. It also provides more precise position and error estimates of the clusters in both the transverse and longitudinal impact parameter resolution.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Metastable Metallic Phase of a Bilayer Blue Phosphorene Induced by Interlayer Bonding and Intralayer Charge Redistributions

We have carried out diffusion Monte Carlo calculations for an A 1 B -1 -stacked bilayer blue phosphorene to find that it undergoes a semiconductor-metal transition as the interlayer distance decreases. While the most stable bilayer structure is a semiconducting one with two monolayers coupled through weak van der Waals interaction, the metallic bilayer at a shorter interlayer distance is found to be only metastable. This is in contrast to a recent theoretical prediction based on random phase approximation that the metallic phase would be the most stable bilayer configuration of blue phosphorene. Our analysis of charge density distributions reveals that the metastable metallic phase is induced by interlayer chemical bonding and intralayer charge redistributions. This study enriches our understanding of interlayer binding of a blue phosphorene and contributes to establishment of correct energetic order between its different phases, which will be essential in devising an experimental pathway for a metallic phosphorene.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Measurement of charge state distributions using a scintillation screen

Absolute cross sections measured using electromagnetic devices to separate and detect heavy recoiling ions need to be corrected for charge state fractions. Accurate prediction of charge state distributions using theoretical models is not always a possibility, especially in energy and mass regions where data is sparse. As such, it is often necessary to measure charge state fractions directly. In this paper we present a novel method of using a scintillation screen along with a CMOS camera to image the charge dispersed beam after a set of magnetic dipoles. A measurement of the charge state distribution for 88 Sr passing through a natural carbon foil is performed. Using a Bayesian model to extract statistically meaningful uncertainties from these images, we find agreement between the new method and a more traditional method using Faraday cups. Additional future work is need to better understand systematic uncertainties. Our technique offers a viable method to measure charge state distributions.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Real-Time Analysis and Signal Optimization for Charge Detection Mass Spectrometry

Charge detection mass spectrometry (CDMS) is an important tool for measuring mass distributions for high mass samples and heterogeneous mixtures. In CDMS, single ions are trapped and their m/z and charge are measured simultaneously. As a single particle technique, the average signal must be optimized to maximize the number of single ion trapping events. If the average signal is too small, most of the trapping events will be empty, and if the average signal is too large, most of the trapping events will contain multiple ions. In recent embodiments, the time domain signal from the trapped ion is analyzed by fast Fourier transforms. The analysis time is much longer that the data collection time which precludes real-time optimization of the experimental conditions. In this paper, we describe the implementation of CDMS with real-time analysis. Processing the data in real time allows the average signal intensities to be dynamically optimized to maximize the number of single ion trapping events. Real-time analysis also allows the experimental settings to be optimized in a timely manner to target specific mass regimes to maximize the useful information content of the measurements. .

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

Evaluation of electronic state of Cs-adsorbed clay minerals by NEXAFS analysis using DFT calculations

In this work, a combined analytical method of NEXAFS measurement and DFT-calculation was employed for the evaluation of Cs states in clay minerals. The measured Cs M 4,5 NEXAFS spectra of Cs halides were analyzed using the DFT-calculations in order to establish the analytical methods. The NEXAFS spectra of the Cs halides were well reproduced by incorporating the core-hole strength. The Cs M 4,5 NEXAFS spectrum of the clay minerals was well reproduced by the DFT-calculations including the major transitions and tail structures with the established method. Further evaluation of this spectrum by charge density analysis suggested that these major transitions and the tail structures likely reflect the bonding state and the local environment around the Cs atoms. Comparison of electronic states of Cs in the clay mineral with those in the Cs halides by DFT-calculations has shown that the interaction between Cs and the nearest-neighbor atom is largest in the clay mineral, which differs from those of Cs halides. This happened due to the energy level of Cs-5s and 5p, which was closer to that of O-2s and 2p than the s and p orbitals of other alkali metal and alkali earth metal elements.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Enhanced electrochemical performances of PANI using redox additive of K{sub 4}[Fe(CN){sub 6}] in aqueous electrolyte for symmetric supercapacitors

Highlights: • Effect of K{sub 4}[Fe(CN){sub 6}] in H{sub 2}SO{sub 4} studied on the electrochemical properties of PANI. • The polaron band – π* transition reveals the emeraldine salt (conductive) form. • CV curves exhibit quasi-reversible redox behavior. • Symmetric PANI SC shows 228 F g{sup −1} at 1 mA cm{sup −2} in K{sub 4}[Fe (CN){sub 6}] added 1 M H{sub 2}SO{sub 4}. • PANI-1 symmetric supercapacitor shows almost 100% of capacity retention. - Abstract: Polyaniline (PANI) particles were prepared by reflux assisted chemical oxidative polymerization method with the aid of ammonium per sulfate/ferric chloride as oxidants and HCl/H{sub 2}SO{sub 4} as the medium. Amorphous nature and the emeraldine state of PANI were revealed from X-ray diffraction and Fourier transform infrared analysis. Moreover, ultra violet–visible spectra attributes to the polaron band – π* transition of polyaniline. The scanning electron microscopic image shows that the particle size is in the range of 0.2–2 μm. The electrochemical performances of the material were investigated in 1 M H{sub 2}SO{sub 4} and 0.08 M K{sub 4}[Fe(CN){sub 6}] added 1 M H{sub 2}SO{sub 4} aqueous electrolytes. Cyclic voltammetry and galvanostatic charge–discharge studies were carried out to find its suitability as a supercapacitor electrode material. The charge discharge analysis of the fabricated symmetric supercapacitors revealed the fact that the electrolyte containing redox additive (0.08 M K{sub 4}[Fe(CN){sub 6}]) delivered an enhanced specific capacitance of 228 F g{sup −1} (∼912 F g{sup −1} for single electrode) than that of 1 M H{sub 2}SO{sub 4} (100 F g{sup −1}) at 1 mA cm{sup −2}. Further cycling stability is performed at 5 mA cm{sup −2} ensures the durability of the supercapacitor.

36 MATERIALS SCIENCE↗
NASA NTRS1976

Analysis of LEAM experiment response to charged particles

The objectives of the Lunar Ejecta and Meteorites Experiment (LEAM) were to measure the long-term variations in cosmic dust influx rates and the extent and nature of the lunar ejecta. While analyzing these characteristics in the data, it was discovered that a majority of the events could not be associated with hypervelocity particle impacts of the type usually identified with cosmic dust, but could only be correlated with the lunar surface and local sun angle. The possibility that charged particles could be incident on the sensors led to an analysis of the electronics to determine if such signals could cause the large pulse height analysis (PHA) signals. A qualitative analysis of the PHA circuit showed that an alternative mode of operation existed if the input signal were composed of pulses with pulse durations very long compared to the durations for which it was designed. This alternative mode would give large PHA outputs even though the actual input amplitudes were small. This revelation led to the examination of the sensor and its response to charged particles to determine the type of signals that could be expected.

Perkins, D.↗
DOE OSTI2014

Supercapacitive properties of hydrothermally synthesized sphere like MoS{sub 2} nanostructures

Highlights: • MoS{sub 2} nanostructures were synthesized by hydrothermal method. • Randomly stacked MoS{sub 2} was obtained. • FE-SEM studies show the sphere like morphology of MoS{sub 2}. • Specific capacitance of 92.85 F/g was achieved using charge–discharge analysis. • MoS{sub 2} electrode shows capacitance retention of about 93.8% after 1000 cycles. - Abstract: In this communication, we have investigated the supercapacitive behaviour of MoS{sub 2} nanostructures prepared by a facile one-pot hydrothermal approach using ammonium heptamolybdate and thiourea as starting materials. The X-ray diffraction study revealed the formation of randomly stacked layers of MoS{sub 2}. The field-emission scanning electron microscope studies suggested the formation of sphere like MoS{sub 2} nanostructures and a plausible mechanism for the formation of the obtained structure is discussed. The cyclic voltammetry study shows the typical rectangular shaped curves with a specific capacitance of 106 F/g at a scan rate of 5 mV/s. Galvanostatic charge–discharge measurements suggested the maximum specific capacitance of about 92.85 F/g at discharge current density of 0.5 mA/cm{sup 2}. Cyclic stability tests revealed the capacitance retention of about 93.8% after 1000 cycles suggesting a good cyclic capacity of the prepared MoS{sub 2}. The electrochemical impedance spectroscopic results such as Nyquist and Bode phase angle plots suggested that the hydrothermally synthesized MoS{sub 2} nanostructures will be a suitable candidate for electrochemical supercapacitor applications.

36 MATERIALS SCIENCE↗
DOE OSTI2014

High spatial and temporal resolution charge exchange recombination spectroscopy on the HL-2A tokamak

A 32/64-channel charge exchange recombination spectroscopy (CXRS) diagnostic system is developed on the HL-2A tokamak (R = 1.65 m, a = 0.4 m), monitoring plasma ion temperature and toroidal rotation velocity simultaneously. A high throughput spectrometer (F/2.8) and a pitch-controlled fiber bundle enable the temporal resolution of the system up to 400 Hz. The observation geometry and an optimized optic system enable the highest radial resolution up to ~1 cm at the plasma edge. The CXRS system monitors the carbon line emission (C VI, n = 8–7, 529.06 nm) whose Doppler broadening and Doppler shift provide ion temperature and plasma rotation velocity during the neutral beam injection. The composite CX spectral data are analyzed by the atomic data and analysis structure charge exchange spectroscopy fitting (ADAS CXSFIT) code. First experimental results are shown for the case of HL-2A plasmas with sawtooth oscillations, electron cyclotron resonance heating, and edge transport barrier during the high-confinement mode (H-mode)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

Reconstruction and Analysis for the DUNE 35-ton Liquid Argon Prototype

Neutrino physics is approaching the precision era, with current and future experiments aiming to perform highly accurate measurements of the parameters which govern the phenomenon of neutrino oscillations. The ultimate ambition with these results is to search for evidence of CP-violation in the lepton sector, currently hinted at in the world-leading analyses from present experiments, which may explain the dominance of matter over antimatter in the Universe. The Deep Underground Neutrino Experiment (DUNE) is a future long-baseline experiment based at Fermi National Accelerator Laboratory (FNAL), with a far detector at the Sanford Underground Research Facility (SURF) and a baseline of 1300 km. In order to make the required precision measurements, the far detector will consist of 40 kton liquid argon and an embedded time projection chamber. This promising technology is still in development and, since each detector module is around a factor 15 larger than any previous experiment employing this design, prototyping the detector and design choices is critical to the success of the experiment. The 35-ton experiment was constructed for this purpose and will be described in detail in this thesis. The outcomes of the 35-ton prototype are already influencing DUNE and, following the successes and lessons learned from the experiment, confidence can be taken forward to the next stage of the DUNE programme. The main oscillation signal at DUNE will be electron neutrino appearance from the muon neutrino beam. High-precision studies of these νe interactions requires advanced processing and event reconstruction techniques, particularly in the handling of showering particles such as electrons and photons. Novel methods developed for the purposes of shower reconstruction in liquid argon are presented with an aim to successfully develop a selection to use in a νe charged-current analysis, and a first-generation selection using the new techniques is presented.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Ultrasensitive single-cell proteomics workflow identifies >1000 protein groups per mammalian cell

Here, we report on the combination of nanodroplet sample preparation, ultra-low-flow nanoLC, high-field asymmetric ion mobility spectrometry (FAIMS), and the latest-generation Orbitrap Eclipse Tribrid mass spectrometer for greatly improved single-cell proteome profiling. FAIMS effectively filtered out singly charged ions for more effective MS analysis of multiply charged peptides, resulting in an average of 1056 protein groups identified from single HeLa cells without MS1-level feature matching. This is 2.3 times more identifications than without FAIMS and a far greater level of proteome coverage for single mammalian cells than has been previously reported for a label-free study. Differential analysis of single microdissected motor neurons and interneurons from human spinal tissue indicated a similar level of proteome coverage, and the two subpopulations of cells were readily differentiated based on single-cell label-free quantification.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Building Blocks for High-Efficiency Organic Photovoltaics: Interplay of Molecular, Crystal, and Electronic Properties in Post-Fullerene ITIC Ensembles

Accurate single-crystal X-ray diffraction data offer a unique opportunity to compare and contrast the atomistic details of bulk heterojunction photovoltaic small-molecule acceptor structure and packing, as well as provide an essential starting point for computational electronic structure and charge transport analysis. Herein, we report diffraction-derived crystal structures and computational analyses on the n-type semiconductors which enable some of the highest efficiency organic solar cells produced to date, 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2',3'-d']-s-indaceno[1,2-b:5,6-b']dithiophene (ITIC) and seven derivatives (including three new crystal structures: 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-propylphenyl)-dithieno[2,3-d:2',3'-d']-s-indaceno[1,2-b:5,6-b']dithiophene (ITIC-C3), 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(3-hexylphenyl)-dithieno[2,3-d:2',3'-d']-s-indaceno[1,2-b:5,6-b']dithiophene (m-ITIC-C6), and 3,9-bis(2-methylene-((3-(1,1-dicyanomethylene)-6,7-difluoro)-indanone))-5,5,11,11-tetrakis(4-butylphenyl)-dithieno[2,3-d:2',3'-d']-s-indaceno[1,2-b:5,6-b']dithiophene (ITIC-C4-4F). IDTT acceptors typically pack in a face-to-face fashion with π–π distances ranging from 3.28–3.95 Å. Additionally, edge-to-face packing is observed with S...π interactions as short as 3.21–3.24 Å. Moreover, ITIC end group identities and side chain substituents influence the nature and strength of noncovalent interactions (e.g. H-bonding, π–π) and thus correlate with the observed packing motif, electronic structure, and charge transport properties of the crystals. Furthermore, density functional theory (DFT) calculations reveal relatively large nearest-neighbor intermolecular π-π electronic couplings (5.85–56.8 meV) and correlate the nature of the band structure with the dispersion interactions in the single crystals and core–end group polarization effects. Overall, this combined experimental and theoretical work reveals key insights into crystal engineering strategies for indacenodithienothiophene (IDTT) acceptors, as well as general design rules for high-efficiency post-fullerene small molecule acceptors.

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

Bottom‐Up Synthesized Nanoporous Graphene Transistors

Abstract Nanoporous graphene (NPG) can exhibit a uniform electronic band gap and rationally‐engineered emergent electronic properties, promising for electronic devices such as field‐effect transistors (FETs), when synthesized with atomic precision. Bottom‐up, on‐surface synthetic approaches developed for graphene nanoribbons (GNRs) now provide the necessary atomic precision in NPG formation to access these desirable properties. However, the potential of bottom‐up synthesized NPG for electronic devices has remained largely unexplored to date. Here, FETs based on bottom‐up synthesized chevron‐type NPG (C‐NPG), consisting of ordered arrays of nanopores defined by laterally connected chevron GNRs, are demonstrated. C‐NPG FETs show excellent switching performance with on–off ratios exceeding 10 4 , which are tightly linked to the structural quality of C‐NPG. The devices operate as p‐type transistors in the air, while n‐type transport is observed when measured under vacuum, which is associated with reversible adsorption of gases or moisture. Theoretical analysis of charge transport in C‐NPG is also performed through electronic structure and transport calculations, which reveal strong conductance anisotropy effects in C‐NPG. The present study provides important insights into the design of high‐performance graphene‐based electronic devices where ballistic conductance and conduction anisotropy are achieved, which could be used in logic applications, and ultra‐sensitive sensors for chemical or biological detection.

Mutlu, Zafer↗
DOE OSTI2018

Geometric constraints on the space of N = 2 SCFTs. Part I: physical constraints on relevant deformations

We initiate a systematic study of four dimensional N = 2 superconformal field theories (SCFTs) based on the analysis of their Coulomb branch geometries. Because these SCFTs are not uniquely characterized by their scale-invariant Coulomb branch geometries we also need information on their deformations. We construct all inequivalent such deformations preserving N = 2 supersymmetry and additional physical consistency conditions in the rank 1 case. These not only include all the ones previously predicted by S-duality, but also 16 additional deformations satisfying all the known N = 2 low energy consistency conditions. All but two of these additonal deformations have recently been identified with new rank 1 SCFTs; these identifications are briefly reviewed. Some novel ingredients which are important for this study include: a discussion of RG-flows in the presence of a moduli space of vacua; a classification of local N = 2 supersymmetry-preserving deformations of unitary N = 2 SCFTs; and an analysis of charge normalizations and the Dirac quantization condition on Coulomb branches. With this being said, this paper is the first in a series of three. The second paper [1] gives the details of the explicit construction of the Coulomb branch geometries discussed here, while the third [2] discusses the computation of central charges of the associated SCFTs.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Defect Thermodynamics and Transport Properties of Proton Conducting Oxide BaZr 1–x Y x O 3–δ (x ≤ 0.1) Guided by Density Functional Theory Modeling

Density functional theory-based thermodynamic modeling was performed to determine the effect of humidity and H 2 /O 2 gas pressure on the defect chemistry and transport properties of proton conducting oxide BaZr 1-x Y x O 3-δ (x ≤ 0.1) in the temperature range of 800–1200K, relevant for solid oxide fuel/electrolysis cell applications. The first-principles charge defect analysis was carried out to obtain the defect energetic ensembles as a function of Fermi level as well as the dependence of the hydration and oxidation reaction energies on complex defect-dopant configurations. It is shown that oxygen vacancies introduced to compensate for the extra Ba vacancies may cause a slight increase in the concentration of hydroxyl and proton species upon hydration of Ba deficient BaZr 1-x Y x O 3-δ , while the overall proton diffusivity is predicted to decrease with increased proton hopping barriers upon trapping near the Ba vacancies. The developed defect model is further demonstrated to be able to describe the bulk defect chemistry and transport properties of BaZr 0.9 Y 0.1 O 3-δ under the solid oxide cell operating conditions. Finally, the theoretical framework developed in this work further allows the inclusion of configurational, energetic and electronic characteristics of the defects that can be used as a complementary tool to experimental measurements for testing various mechanistic pathways or to provide essential mechanistic data.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Top-Down Analysis of Proteins in Low Charge States

The impact of charging methods on the dissociation behavior of intact proteins in low charge states is investigated using HCD and 193 nm UVPD. Low charge states are produced for seven different proteins using the following four different methods: (1) proton transfer reactions of ions in high charge states generated from conventional denaturing solutions; (2) ESI of proteins in solutions of high ionic strength to enhance retention of folded native-like conformations; (3) ESI of proteins in high pH solutions to limit protonation; and (4) ESI of carbamylated proteins. Comparison of sequence coverages, degree of preferential cleavages, and types and distribution of fragment ions reveals a number of differences in the fragmentation patterns depending on the method used to generate the ions. More notable differences in these metrics are observed upon HCD than upon UVPD. The fragmentation caused by HCD is influenced more significantly by the presence/absence of mobile protons, a factor that modulates the degree of preferential cleavages and net sequence coverages. Carbamylation of the lysines and the N-terminus of the proteins alters the proton mobility by reducing the number of proton-sequestering, highly basic sites as evidenced by decreased preferential fragmentation C-terminal to Asp or N-terminal to Pro upon HCD. UVPD is less dependent on the method used to generate the low charge states and favors non-specific fragmentation, an outcome which is important for obtaining high sequence coverage of intact proteins. .

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2016

Electronic and optical properties of novel carbon allotropes

The vibrational properties, electronic structures and optical properties of novel carbon allotropes, such as monolayer penta-graphene (PG), double-layer PG and T12-carbon, were studied by first-principles calculations. Results of phonon calculations demonstrate that these exotic carbon allotropes are dynamically stable. The bulk T12 phase is an indirect-gap semiconductor having a quasiparticle (QP) bandgap of ~5.19 eV. When the bulk material transforms to a two-dimensional (2D) phase, the monolayer and double-layer PG become quasi-direct gap semiconductors with smaller QP bandgaps of ~4.48 eV and ~3.67 eV, respectively. Furthermore, the partial charge density analysis indicates that the 2D phases retain part of the electronic characteristics of the T12 phase. The linear photon energy-dependent dielectric functions and related optical properties including refractive index, extinction coefficient, absorption spectrum, reflectivity, and energy-loss spectrum were also computed and discussed. Additionally, the chemical stability of monolayer PG and the electronic and optical properties of double-side hydrogenated monolayer PG were also investigated. Furthermore, the results obtained from our calculations are beneficial to practical applications of these exotic carbon allotropes in optoelectronics and electronics.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Tuning discharge voltage by Schottky electron barrier in P2-Na 2/3 Mg 0.205 Ni 0.1 Fe 0.05 Mn 0.645 O 2

Recently, Mg doped Na metal oxide layered cathode compounds have attracted strong interest for Na-ion battery applications. We report a new type of asymmetric phase evolution between charge and discharge is found to show much-enhanced discharge voltage in P2-Na 2/3 Mg 0.205 Ni 0.1 Fe 0.05 Mn 0.645 O 2 over the parent cathode compound. P2 solid solution is found to show an abnormal coexistence with O2-P2 two-phase reaction during discharge with simultaneous reduction of O, Ni, and Fe redoxes, distinct from the conventional P2-O2 two-phase reaction in the charge. Our analysis suggests that the P2 and O2 two-phase boundary forms a novel unidirectional Schottky barrier to impede electron and Na diffusions in discharge only, thus making the kinetically preferred P2 solid solution phase abnormally coexist with the two-phase region for high discharge voltage and low polarization. Our work demonstrates tuning dynamic evolution of electronic Schottky barrier as a new dimension for advanced kinetic design of high-performance battery cathode materials.

25 ENERGY STORAGE↗