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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 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

An Atom Probe Tomography Study of the Through Wall Attenuation Effect on Cu-rich Precipitate Formation in a Reactor Pressure Vessel Steel

In this study, high-Cu weld material harvested from an ex service reactor pressure vessel (RPV) steel from Unit 1 of the decommissioned Zion Nuclear Generating Station has been characterized using atom probe tomography. Samples taken from 4 different positions through the thicknesses of the pressure vessel wall from the water-side to the air-side were characterized, along with an unirradiated baseline material. In the baseline material, no precipitates were found and the Cu was observed to be fully in solid solution; however, scanning transmission electron microscopy combined with energy dispersive spectroscopy (STEM-EDS) revealed the presence of ϵ -Cu that form during processing of the material and results in the concomitant decrease of matrix Cu. Following irradiation, a high number density of nano-scale Cu-rich precipitates (CRPs) were observed, uniformly distributed throughout the matrix. The Cu content within the CRPs was found to be ~30-35 at.% regardless of location in the wall. No statistically significant variation in the compositions, mean radius, number density, or volume fraction as a function of location within the wall was observed. The measured matrix Cu level excluding CRPs contribution was found to be ~90 appm higher than the solubility limit suggesting that further nucleation and growth of the CRPs under continued operations would have occurred. These results clearly demonstrate that the neutron energy attenuation has no significant effect on the precipitation kinetics of CRPs regardless of location in the wall in high-Cu RPV steels under irradiation.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Energy transfer and tunable emission of Ca14Al10Zn6O35:Bi3+,Sm3+ phosphor

Highlights: • We have firstly synthesized a single-phased Ca{sub 14}Al{sub 10}Zn{sub 6}O{sub 35}:Bi{sup 3+},Sm{sup 3+} phosphor. • Different measurement support the energy transfer from Bi{sup 3+} to Sm{sup 3+}. • Based on the energy transfer, tunable emission were realized. - Abstract: A series of Bi{sup 3+}, Sm{sup 3+}-codoped Ca{sub 14}Al{sub 10}Zn{sub 6}O{sub 35} phosphors were synthesized via conventional high temperature solid-state method. The crystal structure, morphology, photoluminescence and energy transfer mechanism from Bi{sup 3+} to Sm{sup 3+} were investigated in detail. A broad blue emission band due to {sup 3}P{sub 1} → {sup 1}S{sub 0} transition of Bi{sup 3+} was observed in the Bi{sup 3+} single-doped Ca{sub 14}Al{sub 10}Zn{sub 6}O{sub 35} sample, the Ca{sup 2+} position are verified to be replaced by Bi{sup 3+} and the corresponding concentration quenching mechanism was dipole-dipole interaction. The considerable spectral overlap between the broad emission band of Bi{sup 3+} around 350–550 nm and the excitation band of Sm{sup 3+} supports the energy transfer from Bi{sup 3+} to Sm{sup 3+}. This investigation will contribute to the comprehension of interactions between Bi{sup 3+} and Sm{sup 3+}. These results reveal the potential application of Bi{sup 3+}, Sm{sup 3+} co-doped phosphor in UV light-emitting diodes and artificial light in plant.

36 MATERIALS SCIENCE↗
DOE OSTI2014

A highly miniaturized electron and ion energy spectrometer prototype for the rapid analysis of space plasmas

MEMS (Micro Electro-Mechanical Systems) plasma analyzers are a promising possibility for future space missions but conventional instrument designs are not necessarily well suited to micro-fabrication. Here, a candidate design for a MEMS-based instrument has been prototyped using electron-discharge machining. The device features 10 electrostatic analyzers that, with a single voltage applied to it, allow five different energies of electron and five different energies of positive ion to be simultaneously sampled. It has been simulated using SIMION and the electron response characteristics tested in an instrument calibration chamber. Small deviations found in the electrode spacing of the as-built prototype were found to have some effect on the electron response characteristics but do not significantly impede its performance.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Investigation of trap properties in high-k/metal gate p-type metal-oxide-semiconductor field-effect-transistors with aluminum ion implantation using random telegraph noise analysis

In this study, the impact of aluminum ion implantation (Al I/I) on random telegraph noise (RTN) in high-k/metal gate (HK/MG) p-type metal-oxide-semiconductor field-effect-transistors (pMOSFETs) was investigated. The trap parameters of HK/MG pMOSFETs with Al I/I, such as trap energy level, capture time and emission time, activation energies for capture and emission, and trap location in the gate dielectric, were determined. The configuration coordinate diagram was also established. It was observed that the implanted Al could fill defects and form a thin Al{sub 2}O{sub 3} layer and thus increase the tunneling barrier height for holes. It was also observed that the trap position in the Al I/I samples was lower due to the Al I/I-induced dipole at the HfO{sub 2}/SiO{sub 2} interface.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Preparation of Ag Schottky contacts on n-type GaN bulk crystals grown in nitrogen rich atmosphere by the hydride vapor phase epitaxy technique

Electrical properties of Schottky contacts on n-type GaN grown in nitrogen rich atmosphere with different N/Ga ratios by hydride vapor phase epitaxy were investigated. We show that tunneling of electrons from the conduction band of GaN to the metal is dominant in our samples. The quality of Schottky contacts does not only depend on surface preparation but also on the growth conditions of the crystals. Schottky contacts on these crystals show an increasing deterioration when higher N/Ga growth ratios are used. We correlate our results with the presence of negatively charged gallium vacancies in the samples. These charges compensate the positively charged donors and lead to a significant increase in series resistance.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Compact turnkey focussing neutron guide system for inelastic scattering investigations

We demonstrate the performance of a compact neutron guide module which boosts the intensity in inelastic neutron scattering experiments by approximately a factor of 40. The module consists of two housings containing truly curved elliptic focussing guide elements, positioned before and after the sample. The advantage of the module lies in the ease with which it may be reproducibly mounted on a spectrometer within a few hours, on the same timescale as conventional sample environments. It is particularly well suited for samples with a volume of a few mm{sup 3}, thus enabling the investigation of materials which to date would have been considered prohibitively small or samples exposed to extreme environments, where there are space constraints. We benchmark the excellent performance of the module by measurements of the structural and magnetic excitations in single crystals of model systems. In particular, we report the phonon dispersion in the simple element lead. We also determine the magnon dispersion in the spinel ZnCr{sub 2}Se{sub 4} (V = 12.5 mm{sup 3}), where strong magnetic diffuse scattering at low temperatures evolves into distinct helical order.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Global biogeography of microbial nitrogen-cycling traits in soil

Microorganisms drive much of the Earth’s nitrogen (N) cycle, but we still lack a global overview of the abundance and composition of the microorganisms carrying out soil N processes. To address this gap, we characterized the biogeography of microbial N traits, defined as eight N-cycling pathways, using publically available soil metagenomes. The relative frequency of N pathways varied consistently across soils, such that the frequencies of the individual N pathways were positively correlated across the soil samples. Habitat type, soil carbon, and soil N largely explained the total N pathway frequency in a sample. In contrast, we could not identify major drivers of the taxonomic composition of the N functional groups. Further, the dominant genera encoding a pathway were generally similar among habitat types. The soil samples also revealed an unexpectedly high frequency of bacteria carrying the pathways required for dissimilatory nitrate reduction to ammonium, a little-studied N process in soil. Finally, phylogenetic analysis showed that some microbial groups seem to be N-cycling specialists or generalists. For instance, taxa within the Deltaproteobacteria encoded all eight N pathways, whereas those within the Cyanobacteria primarily encoded three pathways. Overall, this trait-based approach provides a baseline for investigating the relationship between microbial diversity and N cycling across global soils.

Nelson, Michaeline B.↗
DOE OSTI2015

BANYAN. V. A SYSTEMATIC ALL-SKY SURVEY FOR NEW VERY LATE-TYPE LOW-MASS STARS AND BROWN DWARFS IN NEARBY YOUNG MOVING GROUPS

We present the BANYAN All-Sky Survey (BASS) catalog, consisting of 228 new late-type (M4-L6) candidate members of nearby young moving groups (YMGs) with an expected false-positive rate of ∼13%. This sample includes 79 new candidate young brown dwarfs and 22 planetary-mass objects. These candidates were identified through the first systematic all-sky survey for late-type low-mass stars and brown dwarfs in YMGs. We cross-matched the Two Micron All Sky Survey and AllWISE catalogs outside of the galactic plane to build a sample of 98,970 potential ≥M5 dwarfs in the solar neighborhood and calculated their proper motions with typical precisions of 5-15 mas yr{sup –1}. We selected highly probable candidate members of several YMGs from this sample using the Bayesian Analysis for Nearby Young AssociatioNs II tool (BANYAN II). We used the most probable statistical distances inferred from BANYAN II to estimate the spectral type and mass of these candidate YMG members. We used this unique sample to show tentative signs of mass segregation in the AB Doradus moving group and the Tucana-Horologium and Columba associations. The BASS sample has already been successful in identifying several new young brown dwarfs in earlier publications, and will be of great interest in studying the initial mass function of YMGs and for the search of exoplanets by direct imaging; the input sample of potential close-by ≥M5 dwarfs will be useful to study the kinematics of low-mass stars and brown dwarfs and search for new proper motion pairs.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

MULTIPLICITY AMONG F-TYPE STARS. II

In continuation of our previous study we present an updated census of new companions and model atmosphere analyses for some 50 southern dwarfs, mostly in the mass range 0.90⩽M⩽1.10 M{sub ⊙}. For the common-proper-motion companions μ Vir B, HR 2225 B, HD 67199 B, and HD 114853 B, we confirm their physical association from their radial velocities. We report the discovery of the F-type visual binary α For as a field blue straggler and confirm (ζ Ret, HR 5864) or identify (HD 67199, HR 4013, HR 8843) another five mass transfer systems or candidates. For the F stars τ{sup 1} Eri and 111 Tau, we present 10σ and 7σ cases for astrometric binaries by virtue of the very accurate van Leeuwen Hipparcos parallaxes. Following the work of Shaya and Olling, we suggest the F-type star ι Vir to be a wide (0.37 pc) hierarchical quadruple system. We confirm the visual binary NLTT 23781/2 as a common-proper-motion object to the very wide (0.54 pc) F star 40 Leo, but discard the G star HD 128987 as an ultra-wide (1.01 pc) physical companion to the α Lib quadruple system on account of a diverse metallicity. The improved statistics of our sample establishes the previously discovered positive correlation of stellar multiplicities with primary mass. For the F star multiplicity census in the mass range 1.10⩽M⩽1.70 M{sub ⊙}, we find that at least a quarter consists of triple or higher level systems and at least two out of three F stars are non-single.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Probing plasma physics with spectral index maps of accreting black holes on event horizon scales

The Event Horizon Telescope (EHT) collaboration has produced the first resolved images of the supermassive black holes at the centre of our galaxy and at the centre of the elliptical galaxy M87. As both technology and analysis pipelines improve, it will soon become possible to produce spectral index maps of black hole accretion flows on event horizon scales. Here, in this work, we predict spectral index maps of both M87* and Sgr A* by applying the general relativistic radiative transfer (GRRT) code IPOLE to a suite of general relativistic magnetohydrodynamic (GRMHD) simulations. We analytically show that the spectral index increases with increasing magnetic field strength, electron temperature, and optical depth. Consequently, spectral index maps grow more negative with increasing radius in almost all models, since all of these quantities tend to be maximized near the event horizon. Additionally, photon ring geodesics exhibit more positive spectral indices, since they sample the innermost regions of the accretion flow with the most extreme plasma conditions. Spectral index maps are sensitive to highly uncertain plasma heating prescriptions (the electron temperature and distribution function). However, if our understanding of these aspects of plasma physics can be tightened, even the spatially unresolved spectral index around 230 GHz can be used to discriminate between models. In particular, Standard and Normal Evolution (SANE) flows tend to exhibit more negative spectral indices than Magnetically Arrested Disc (MAD) flows due to differences in the characteristic magnetic field strength and temperature of emitting plasma.

(magnetohydrodynamics) MHD↗
DOE OSTI2015

Phonon spectroscopy with sub-meV resolution by femtosecond x-ray diffuse scattering

We present a reconstruction of the transverse acoustic phonon dispersion of germanium from femtosecond time-resolved x-ray diffuse scattering measurements at the Linac Coherent Light Source. We demonstrate an energy resolution of 0.3 meV with a momentum resolution of 0.01 nm -1 using 10-keV x rays with a bandwidth of ~ 1 eV. This high resolution was achieved simultaneously for a large section of reciprocal space including regions closely following three of the principal symmetry directions. The phonon dispersion was reconstructed with less than 3 h of measurement time, during which neither the x-ray energy, the sample orientation, nor the detector position were scanned. In conclusion, these results demonstrate how time-domain measurements can complement conventional frequency domain inelastic-scattering techniques.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2012

Optimizing charge neutralization for a magnetic sector SIMS instrument in negative mode

Successful self-adjusted charge compensation was demonstrated for a CAMECA magnetic-sector secondary ion mass spectrometer applied in negative mode. Operation with the normal-incidence electron gun (NEG) potential positively biased relative to a sample potential enables substantial broadening of the Cs primary-ion-current density range available for analysis of insulators. The decrease of the negative NEG potential by 30 V allows the highest value of primary current density used for the analysis of a silica sample to increase by a factor of more than 6. By applying the improved charge neutralization technique, accurate Na depth profiles for SiO{sub 2} samples were obtained within detection limits of {approx}3 Multiplication-Sign 10{sup 15} atoms/cm{sup 3}.

42 ENGINEERING↗
DOE OSTI2014

Mounting a thermocouple of type E onto a Cu single crystal for use in a magnetically sensitive environment below 77 K

Type E thermocouples show magnetic effects at liquid nitrogen temperature and below. This may cause trouble in experiments that are sensitive to magnetic stray fields like nuclear magnetic resonance, photoemission or high resolution electron energy loss spectroscopy. Here, a solution for the temperature measurement of a single crystal is presented. The authors weld a copper rod onto the back side of the single crystal, thereby relocating the sensitive sample from the thermocouple attachment position. They show that it is possible to measure the crystal temperature at the end of the rod while significantly reducing the ferromagnetic influence due to the increased distance.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Measurement of the radiative decay of polarized muons in the MEG experiment

Here, we studied the radiative muon decay μ + → e + νν¯γ by using for the first time an almost fully polarized muon source. We identified a large sample (~13,000) of these decays in a total sample of 1.8×10 14 positive muon decays collected in the MEG experiment in the years 2009–2010 and measured the branching ratio B(μ → eνν¯γ)=(6.03 ± 0.14(stat.) ± 0.53(sys.))×10 –8 for E e > 45 MeV and E γ > 40 MeV, consistent with the Standard Model prediction. The precise measurement of this decay mode provides a basic tool for the timing calibration, a normalization channel, and a strong quality check of the complete MEG experiment in the search for μ+→e+γ process.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

A software package for modeling and simulating fault graphs

This report describes a novel fault graph modeling language and a simulation tool for executing models specified in the language. The modeling language has three primary features that distinguish it from similar reliability analysis tools. These are (1) a random variable modeling several distinct outcomes of a single fault; (2) chains of faults in which one fault triggers another; and (3) time to fail sampled from probability distributions including positive normal, exponential, Weibull with a minimum, or immediate. These features are motivated by their use in a historical analysis of centrifuge reliability.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2022

Improving Fission Products at CARIBU: Near Field Detection (Q2/FY22 Quarterly Progress Report)

We continued our work on preparation for the upcoming branching ratio measurements. The CARIBU facility has not been delivering radioactive beams since January this year due to an issue with the magnet that is used for mass separation. The parts needed to be replaced to fix the issue has been since ordered, shipped from Germany, and installed at CARIBU. The CARIBU is now operational and the first experiments that are ran will be those that had to be cancelled in January due to the facility complications, and we are in a position to schedule our next sample collection. In the meantime, we have been continuing work on data analysis of fission product mass measurements in the Canadian Penning Trap. This analysis is now complete. We continue our outreach to recruit a graduate student who would be interested in working with us on this project. In the past month, we have a conversation with a potential student at UC Berkeley and Texas A&M. There students are still to decide if they would accept the offer to these graduate schools.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Vehicle Powertrain Simulation Accuracy for Various Drive Cycle Frequencies and Upsampling Techniques

As connected and automated vehicle technologies emerge and proliferate, lower frequency vehicle trajectory data is becoming more widely available. In some cases, entire fleets are streaming position, speed, and telemetry at sample rates of less than 10 seconds. This presents opportunities to apply powertrain simulators such as the National Renewable Energy Laboratory's Future Automotive Systems Technology Simulator to model how advanced powertrain technologies would perform in the real world. However, connected vehicle data tends to be available at lower temporal frequencies than the 1-10 Hz trajectories that have typically been used for powertrain simulation. Higher frequency data, typically used for simulation, is costly to collect and store and therefore is often limited in density and geography. This paper explores the suitability of lower frequency, high availability, connected vehicle data for detailed powertrain simulation. A large data set of 1 Hz trajectories is used to quantify the accuracy loss when simulating energy consumption for conventional, hybrid, and battery electric powertrains using less than 1 Hz data. Techniques to upsample lower frequency drive cycle data in order to increase accuracy are also explored. Median energy consumption errors when simulating energy consumption for a 1/10 Hz trajectory are found to be 3-6% when compared to 1 Hz trajectories. Applying upsampling and interpolation techniques are shown to reduce the simulation errors by roughly 50%. The findings in this work can guide connected vehicle data collection specifications and processing techniques applied when using collected data for powertrain simulation.

ADVANCED PROPULSION SYSTEMS↗
NASA NTRS1979

Gas phase oxidation downstream of a catalytic combustor

Effect of the length available for gas-phase reactions downstream of the catalytic reactor on the emission of CO and unburned hydrocarbons was investigated. A premixed, prevaporized propane/air feed to a 12/cm/diameter catalytic/reactor test section was used. The catalytic reactor was made of four 2.5 cm long monolithic catalyst elements. Four water cooled gas sampling probes were located at positions between 0 and 22 cm downstream of the catalytic reactor. Measurements of unburned hydrocarbon, CO, and CO2 were made. Tests were performed with an inlet air temperature of 800 K, a reference velocity of 10 m/s, pressures of 3 and 600,000 Pa, and fuel air equivalence ratios of 0.14 to 0.24. For very lean mixtures, hydrocarbon emissions were high and CO continued to be formed downstream of the catalytic reactor. At the highest equivalence ratios tested, hydrocarbon levels were much lower and CO was oxidized to CO2 in the gas phase downstream. To achieve acceptable emissions, a downstream region several times longer than the catalytic reactor could be required.

Tien, J. S.↗