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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Electroluminescence Yield Measurements in Xenon Gas with the NEXT-DEMO++ Detector

The NEXT-DEMO++ detector, a high-pressure xenon gas time projection chamber serving as a prototype for the NEXT-100 experiment, was used to measure the electroluminescence (EL) yield as a function of reduced electric field ($E/p$) across pressures from 2.0 to 9.4 bar, utilizing the 41.5 keV de-excitation peak of $^{83m}$Kr. These measurements were made to examine the pressure dependence of the slope of the reduced EL yield $Y/p$, which has shown inconsistencies in the literature. The reduced yield was fitted with a linear model, revealing a modest ($\sim$5%) change in slope, beginning around 5 bar and increasing with pressure up to 9.4 bar.

Renner, J. [Valencia U., IFIC]↗
DOE OSTI2017

A Global Data Analysis for Representing Sediment and Particulate Organic Carbon Yield in Earth System Models

Although sediment yield (SY) from water erosion is ubiquitous and its environmental consequences are well recognized, its impacts on the global carbon cycle remain largely uncertain. This knowledge gap is partly due to the lack of soil erosion modeling in Earth System Models (ESMs), which are important tools used to understand the global carbon cycle and explore its changes. As such, this study analyzed sediment and particulate organic carbon yield (CY) data from 1081 and 38 small catchments (0.1-200 km 2 ), respectively, in different environments across the globe. Using multiple statistical analysis techniques, we explored environmental factors and hydrological processes important for SY and CY modeling in ESMs. Our results show clear correlations of high SY with traditional agriculture, seismicity and heavy storms, as well as strong correlations between SY and annual peak runoff. These highlight the potential limitation of SY models that represent only interrill and rill erosion because shallow overland flow and rill flow have limited transport capacity due to their hydraulic geometry to produce high SY. Further, our results suggest that SY modeling in ESMs should be implemented at the event scale to produce the catastrophic mass transport during episodic events. Several environmental factors such as seismicity and land management that are often not considered in current catchment-scale SY models can be important in controlling global SY. Our analyses show that SY is likely the primary control on CY in small catchments and a statistically significant empirical relationship is established to calculate SY and CY jointly in ESMs.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2015

19 F(α,n) thick target yield from 3.5 to 10.0 MeV

Using a target of PbF 2 , the thick-target yield from the 19 F(α,n) reaction was measured from E α =3.5–10 MeV. From these results, we infer the thick-target neutron yields from targets of F 2 and UF 6 over this same alpha-particle energy range.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Microstructure, mechanical properties and microtexture of friction stir welded S690QL high yield steel

Two try-out campaigns of friction stir welding (FSW) were performed with different friction parameters to join S690QL high yield strength steel. The welds were investigated at macroscopic and microscopic scales using optical and electronic microscopy and microhardness mapping. Welds of the second campaign exhibit microstructures and mechanical properties in accordance with requirements for service use. Microtexture measurements were carried out in different zones of welds by electron backscattered diffraction (EBSD). It is shown that that texture of the bottom of the weld is similar to that of the base metal, suggesting a diffusion bonding mechanism. Finally, the mechanical properties (tensile strength, resilience, bending) were established on the most promising welds. It is shown that it is possible to weld this high yield strength steel using FSW process with satisfactory geometric, microstructural and mechanical properties. - Highlights: •1000 mm ∗ 400 mm ∗ 8 mm S690QL steel plates are joined by friction stir welding (FSW). •Maximum hardness is reduced by optimization of process parameters. •Various microstructures are formed but no martensite after process optimization. •Texture is modified in mechanically affected zones of the weld. •Texture in the bottom of the weld is preserved, suggesting diffusion bonding.

36 MATERIALS SCIENCE↗
DOE OSTI2019

A method for smoothing multiple yield functions

A method is presented that produces a single C 2 differentiable and convex yield function from a plastic model that contains multiple yield surfaces that are individually C 2 differentiable and convex. The method is suitable for implementation in numerical computer codes. Here, the error incurred through the smoothing procedure is quantified. The method is illustrated through a number of examples. Two simple finite-element models are solved to compare this method with existing approaches.

42 ENGINEERING↗
DOE OSTI2015

Reducing uncertainties for short lived cumulative fission product yields

Uncertainties associated with short lived (halflives less than 1 day) fission product yields listed in databases such as the National Nuclear Data Center’s ENDF/B-VII are large enough for certain isotopes to provide an opportunity for new precision measurements to offer significant uncertainty reductions. A series of experiments has begun where small samples of 235 U are irradiated with a pulsed, fission neutron spectrum at the Nevada National Security Site and placed between two broad-energy germanium detectors. The amount of various isotopes present immediately following the irradiation can be determined given the total counts and the calibrated properties of the detector system. The uncertainty on the fission yields for multiple isotopes has been reduced by nearly an order of magnitude.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Contradictory Feature Size Effects in the Tensile Yield Strength of Cu Sheets Produced Using Different Sequences Involving Annealing, Rolling, and Grinding

The feature size effect is significant research interest in the field of microforming. It is assumed that the size effect is influenced by the material preparation process. To verify this, the feature size effects associated with the tensile yield strength of Cu sheets with thicknesses ranging from 100 to 200 μm, produced using different sequences involving annealing, rolling, and grinding, were studied. Differing feature size effects were observed in the Cu specimens, and it was confirmed that the size effect was indeed influenced by the specimen preparation sequence. The tensile yield strengths of the annealed–ground–rolled and annealed–rolled specimens increased as the specimen thicknesses decreased. However, an opposing size effect was observed in the case of the annealed–rolled–annealed, annealed–ground, and annealed–rolled–ground specimens. The reduction ratio did not alter the trend associated with the size effect, but influenced the intensity of the size effect. It is believed that the reinforcement and erosion of the surface-hardened layer introduced during rolling resulted in the contradictory results.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Numerical simulations of yield-based sooting tendencies of aromatic fuels using ReaxFF molecular dynamics

In this work, we present the first ReaxFF Molecular Dynamics (MD) simulations to quantitatively predict the sooting tendencies of various fuels. The specific sooting tendency metric used in this work is the Yield Sooting Index (YSI), which quantifies the effects of fuel molecular structure on soot yield. YSI has been experimentally measured and numerically simulated using computational fluid dynamics for a large range of fuels, but there is no existing reactive MD framework for YSI simulations. To adopt the experimental YSI concept, a multi-stage simulation procedure is designed using ReaxFF. As a proof-of-concept, toluene and phenol are selected as test fuels, since both have relatively well-understood reaction pathways. The ReaxFF YSI simulations are shown to capture key reaction events for both fuels selected that are consistent with existing chemical kinetic understanding. Toluene is shown to mostly retain its original aromatic ring structure and directly grow to larger aromatic compounds with multiple rings. On the other hand, the aromatic growth process from phenol is accompanied by carbon-loss reactions with CO release. In addition, a quantitative YSI formulation is also derived in ReaxFF and the ReaxFF-predicted YSI values are compared with measurement data and reasonably good agreement is achieved. The results reported in this work demonstrates that the ReaxFF-based framework can potentially be used to quantitatively predict the relative sooting tendencies, especially for fuels with unknown or poorly-known chemistry, to understand their sooting properties and in search for soot relevant reaction pathways from these fuels.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Dependence of the yield stress of Fe3Al on heat treatment

The room-temperature yield strength of quenched FeAl-based iron aluminides depends strongly on the temperature from which the quench occurs. There is evidence that Fe{sub 3}Al-based iron aluminides show similar behavior, albeit not as pronounced. The purpose of this work was to carry out quenching and annealing experiments to clearly demonstrate this effect, as well as to study its kinetics. Room-temperature compression tests were performed using cast Fe-28at%Al and Fe-30at%Al after quenching from temperatures in the range 300-1000 C. Kinetic studies were carried out to assess the reduction of the yield stress by subsequent annealing for various times at relatively low temperatures. Results from the present study are compared with data available in the literature and explanations for the dependence of room-temperature mechanical behavior on annealing history are evaluated. It is concluded that room-temperature strengthening in Fe{sub 3}Al-based iron aluminides is consistent with behavior expected for quenched-in thermal vacancies and this could be an important strengthening mechanism in Fe{sub 3}Al.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Data-driven reduced order models for effective yield strength and partitioning of strain in multiphase materials

There is a critical need for the development and verification of practically useful multiscale modeling strategies for simulating the mechanical response of multiphase metallic materials with heterogeneous microstructures. In this contribution, we present data-driven reduced order models for effective yield strength and strain partitioning in such microstructures. These models are built employing the recently developed framework of Materials Knowledge Systems that employ 2-point spatial correlations (or 2-point statistics) for the quantification of the heterostructures and principal component analyses for their low-dimensional representation. The models are calibrated to a large collection of finite element (FE) results obtained for a diverse range of microstructures with various sizes, shapes, and volume fractions of the phases. The performance of the models is evaluated by comparing the predictions of yield strength and strain partitioning in two-phase materials with the corresponding predictions from a classical self-consistent model as well as results of full-field FE simulations. The reduced-order models developed in this work show an excellent combination of accuracy and computational efficiency, and therefore present an important advance towards computationally efficient microstructure-sensitive multiscale modeling frameworks. - Graphical abstract:.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Neutron spectroscopy by thermalization light yield measurement in a composite heterogeneous scintillator

An exothermic neutron capture reaction can be used to uniquely identify neutrons in particle detectors. With the use of a capture-gated coincidence technique, the sequence of scatter events that lead to neutron thermalization prior to the neutron capture can also be used to measure neutron energy. We report on the measurement of thermalization light yield via a time-of-flight technique in a polyvinyl toluene-based scintillator EJ-290 within a heterogeneous composite detector that also includes 6Li-doped glass scintillator. The thermalization light output exhibits a strong correlation with neutron energy because of the preference for near-complete energy deposition prior to the 6Li(n,t)4He neutron capture reaction. The nonproportionality of the light yield from nuclear recoils contributes to the observed broadening of the distribution of thermalization light output. The nonproportional dependence of the scintillation light output in the EJ-290 scintillator as a function of proton recoil energy has been characterized in the range of 0.3–14.1 MeV via the Birks parametrization through a combination of time-of-flight measurement and previously conducted measurements with Monoenergetic neutron sources.

6Li-doped scintillator↗
DOE OSTI2020

Differential electron yield imaging with STXM

In this report total electron yield (TEY) imaging is an established scanning transmission X-ray microscopy (STXM) technique that gives varying contrast based on a sample's geometry, elemental composition, and electrical conductivity. However, the TEY-STXM signal is determined solely by the electrons that the beam ejects from the sample. A related technique, X-ray beam-induced current (XBIC) imaging, is sensitive to electrons and holes independently, but requires electric fields in the sample. Here we report that multi-electrode devices can be wired to produce differential electron yield (DEY) contrast, which is also independently sensitive to electrons and holes, but does not require an electric field. Depending on whether the region illuminated by the focused STXM beam is better connected to one electrode or another, the DEY-TXM contrast changes sign. DEY-STXM images thus provide a vivid map of a device's connectivity landscape, which can be key to understanding device function and failure. To demonstrate an application in the area of failure analysis, we image a 100 nm, lithographically-defined aluminum nanowire that has failed after being stressed with a large current density.

47 OTHER INSTRUMENTATION↗
DOE OSTI2017

Probing Linewidths and Biexciton Quantum Yields of Single Cesium Lead Halide Nanocrystals in Solution

Cesium lead halide (CsPbX 3 , X = Cl, Br, I) perovskite nanocrystals (PNCs) have recently become a promising material for optoelectronic applications due to their high emission quantum yields and facile band gap tunability via both halide composition and size. The spectroscopy of single PNCs enhances our understanding of the effect of confinement on excitations in PNCs in the absence of obfuscating ensemble averaging and can also inform synthetic efforts. However, single PNC studies have been hampered by poor PNC photostability under confocal excitation, precluding interrogation of all but the most stable PNCs, and leading to a lack of understanding of PNCs in the regime of high confinement. Here, we report the first comprehensive spectroscopic investigation of single PNC properties using solution-phase photon-correlation methods, including both highly confined and blue-emitting PNCs, previously inaccessible to single NC techniques. With minimally perturbative solution-phase photon-correlation Fourier spectroscopy (s-PCFS), we establish that the ensemble emission linewidth of PNCs of all sizes and compositions is predominantly determined by the intrinsic single PNC linewidth (homogeneous broadening). The single PNC linewidth, in turn, dramatically increases with increasing confinement, consistent with what has been found for II–VI semiconductor nanocrystals. With solution-phase photon antibunching measurements, we survey the biexciton-to-exciton quantum yield ratio (BX/X QY) in the absence of user-selection bias or photodegradation. Remarkably, the BX/X QY ratio depends both on the PNC size and halide composition, with values between ~2% for highly confined bromide PNCs and ~50% for intermediately confined iodide PNCs. Our results suggest a wide range of underlying Auger rates, likely due to transitory charge carrier separation in PNCs with relaxed confinement.

single nanocrystal spectroscopy↗
DOE OSTI2017

Purcell-enhanced quantum yield from carbon nanotube excitons coupled to plasmonic nanocavities

Single-walled carbon nanotubes (SWCNTs) are promising absorbers and emitters to enable novel photonic applications and devices but are also known to suffer from low optical quantum yields. Here we demonstrate SWCNT excitons coupled to plasmonic nanocavity arrays reaching deeply into the Purcell regime with Purcell factors (F P ) up to F P = 180 (average F P = 57), Purcell-enhanced quantum yields of 62% (average 42%), and a photon emission rate of 15 MHz into the first lens. The cavity coupling is quasi-deterministic since the photophysical properties of every SWCNT are enhanced by at least one order of magnitude. Furthermore, the measured ultra-narrow exciton linewidth (18 ueV) reaches the radiative lifetime limit, which is promising towards generation of transform-limited single photons. Furthermore, to demonstrate utility beyond quantum light sources we show that nanocavity-coupled SWCNTs perform as single-molecule thermometers detecting plasmonically induced heat at cryogenic temperatures in a unique interplay of excitons, phonons, and plasmons at the nanoscale.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2011

Precise Measurement of the Absolute Fluorescence Yield

We present preliminary results of the absolute yield of fluorescence emission in atmospheric gases. Measurements were performed at the Fermilab Test Beam Facility with a variety of beam particles and gases. Absolute calibration of the fluorescence yield to 5% level was achieved by comparison with two known light sources - the Cherenkov light emitted by the beam particles, and a calibrated nitrogen laser. The uncertainty of the energy scale of current Ultra-High Energy Cosmic Rays experiments will be significantly improved by the AIRFLY measurement.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2013

High yield neutron generators using the DD reaction

A product line of high yield neutron generators has been developed at Adelphi technology inc. The generators use the D-D fusion reaction and are driven by an ion beam supplied by a microwave ion source. Yields of up to 5 Multiplication-Sign 10{sup 9} n/s have been achieved, which are comparable to those obtained using the more efficient D-T reaction. The microwave-driven plasma uses the electron cyclotron resonance (ECR) to produce a high plasma density for high current and high atomic ion species. These generators have an actively pumped vacuum system that allows operation at reduced pressure in the target chamber, increasing the overall system reliability. Since no radioactive tritium is used, the generators can be easily serviced, and components can be easily replaced, providing essentially an unlimited lifetime. Fast neutron source size can be adjusted by selecting the aperture and target geometries according to customer specifications. Pulsed and continuous operation has been demonstrated. Minimum pulse lengths of 50 {mu}s have been achieved. Since the generators are easily serviceable, they offer a long lifetime neutron generator for laboratories and commercial systems requiring continuous operation. Several of the generators have been enclosed in radiation shielding/moderator structures designed for customer specifications. These generators have been proven to be useful for prompt gamma neutron activation analysis (PGNAA), neutron activation analysis (NAA) and fast neutron radiography. Thus these generators make excellent fast, epithermal and thermal neutron sources for laboratories and industrial applications that require neutrons with safe operation, small footprint, low cost and small regulatory burden.

43 PARTICLE ACCELERATORS↗
DOE OSTI2013

Measurement of the muon-induced neutron yield in liquid scintillator and stainless steel at LNGS with the LVD experiment

We describe the measurement of the muon-induced neutron yield in liquid scintillator and stainless steel (SS) at the Gran Sasso National Laboratory (LNGS), with the LVD experiment. The Large Volume Detector (LVD) is located in Hall A of the LNGS and is made of 1000 t of liquid scintillator and 1000 t of SS. Using an independent measurement to evaluate the background and with the support of a full Monte Carlo simulation based on Geant4, we measured a neutron yield of (2.9±0.6)×10{sup −4} and (1.5±0.3)×10{sup −3} in liquid scintillator and in stainless steel, respectively.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Calibration methodology for proportional counters applied to yield measurements of a neutron burst

This paper introduces a methodology for the yield measurement of a neutron burst using neutron proportional counters. This methodology is to be applied when single neutron events cannot be resolved in time by nuclear standard electronics, or when a continuous current cannot be measured at the output of the counter. The methodology is based on the calibration of the counter in pulse mode, and the use of a statistical model to estimate the number of detected events from the accumulated charge resulting from the detection of the burst of neutrons. The model is developed and presented in full detail. For the measurement of fast neutron yields generated from plasma focus experiments using a moderated proportional counter, the implementation of the methodology is herein discussed. An experimental verification of the accuracy of the methodology is presented. An improvement of more than one order of magnitude in the accuracy of the detection system is obtained by using this methodology with respect to previous calibration methods.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗