Search NASA⌕ Search

SEARCH · Search NASA

Results for “Conductance decay”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Proof of principle study: synchrotron X-ray fluorescence microscopy for identification of previously radioactive microparticles and elemental mapping of FFPE tissues

Biobanks containing formalin-fixed, paraffin-embedded (FFPE) tissues from animals and human atomic-bomb survivors exposed to radioactive particulates remain a vital resource for understanding the molecular effects of radiation exposure. These samples are often decades old and prepared using harsh fixation processes which limit sample imaging options. Optical imaging of hematoxylin and eosin (H&E) stained tissues may be the only feasible processing option, however, H&E images provide no information about radioactive microparticles or radioactive history. Synchrotron X-ray fluorescence microscopy (XFM) is a robust, non-destructive, semi-quantitative technique for elemental mapping and identifying candidate chemical element biomarkers in FFPE tissues. Still, XFM has never been used to uncover distribution of formerly radioactive micro-particulates in FFPE canine specimens collected more than 30 years ago. In this work, we demonstrate the first use of low-, medium-, and high-resolution XFM to generate 2D elemental maps of ~ 35-year-old, canine FFPE lung and lymph node specimens stored in the Northwestern University Radiobiology Archive documenting distribution of formerly radioactive micro-particulates. Additionally, we use XFM to identify individual microparticles and detect daughter products of radioactive decay. The results of this proof-of-principle study support the use of XFM to map chemical element composition in historic FFPE specimens and conduct radioactive micro-particulate forensics.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2025

Measured gain suppression in FBK LGADs with different active thicknesses

In recent years, the gain suppression mechanism has been studied for large localized charge deposits in Low-Gain Avalanche Detectors (LGADs). LGADs are a thin silicon detector with a highly doped gain layer that provides moderate internal signal amplification. Using the CENPA Tandem accelerator at the University of Washington, the response of LGADs with different thicknesses to MeV-range energy deposits from a proton beam were studied. Three LGAD prototypes of 50 μm, 100 μm, and 150 μm were characterized. The devices' gain was determined as a function of bias voltage, incidence beam angle, and proton energy. This study was conducted in the scope of the PIONEER experiment, an experiment proposed at the Paul Scherrer Institute to perform high-precision measurements of rare pion decays. LGADs are considered for the active target (ATAR), and energy linearity is an important property for particle ID capabilities.

Particle tracking detectors↗
DOE OSTI2021

Spin superfluidity in noncollinear antiferromagnets

We explore the spin superfluid transport in exchange interaction dominated three-sublattice antiferromagnets. The system in the long-wavelength regime is described by an $SO(3)$ invariant field theory. Additional corrections from Dzyaloshinskii-Moriya interactions or anisotropies can break the symmetry; however, the system still approximately holds a $U(1)$-rotation symmetry. Thus, the power-law spatial decay signature of spin superfluidity is identified in a nonlocal-measurement setup where the spin injection is described by the generalized spin-mixing conductance. Finally, we suggest iron jarosites as promising material candidates for realizing our proposal.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

In-beam $$\gamma $$-ray spectroscopy of $$^{94}$$Ag

Abstract A recoil-beta-tagging experiment has been performed to study the excited $$T=0$$ T = 0 and $$T=1$$ T = 1 states in the odd–odd $$N=Z$$ N = Z nucleus $$^{94}$$ 94 Ag, populated via the $$^{40}$$ 40 Ca( $$^{58}$$ 58 Ni,1p3n) $$^{94}$$ 94 Ag reaction. The experiment was conducted using the MARA recoil separator and JUROGAM3 array at the Accelerator Laboratory of the University of Jyväskylä. Through correlating fast, high-energy beta decays at the MARA focal plane with prompt $$\gamma $$ γ rays emitted at the reaction target, a number of transitions between excited states in $$^{94}$$ 94 Ag have been identified. The timing characteristics of these transitions confirm that they fall within decay sequences that feed the short-lived $$T=1$$ T = 1 ground state of $$^{94}$$ 94 Ag. The transitions are proposed to proceed within and between the sets of states with $$T=0$$ T = 0 and $$T=1$$ T = 1 . Possible correspondence between some of these transitions from analog states in $$^{94}$$ 94 Pd has been discussed, and shell-model calculations including multipole and monopole electromagnetic effects have been presented, in order to enable predictions of the decay patterns between the $$T=0$$ T = 0 and $$T=1$$ T = 1 states and to allow a theoretical set of Coulomb energy differences to be calculated for the $$A = 94$$ A = 94 $$T=1$$ T = 1 analog states.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Out-of-Pile Testing and Instrumentation Transient Water Irradiation System

Current initiatives to increase the burnup of conventional nuclear fuels past the approximate 62 GWd/t limit have been spurred on by direct savings to refueling and waste storage. The technical justification for a new license limit requires extensive qualification through experimental testing. Unlike beginning-of-life fuels, high-burnup fuels are more susceptible to fuel fragmentation, relocation, and dispersal (FFRD), therefore more data is needed to characterize fuels under key accident scenarios. The Transient Reactor Test Facility (TREAT) located at the Idaho National Laboratory has developed a testing apparatus architecture to test fuels and claddings at prototypic conditions. The Transient Water Irradiation System (TWIST) is the latest iteration of a testing device capable of conducting loss of coolant accidents (LOCAs) in TREAT. The Out-of-Pile Testing and Instrumentation TWIST (OPTI-TWIST) is an electrically heated device that is analogous to TWIST. OPTI-TWIST allows for detailed instrumentation and thermal-hydraulic characterization. TWIST ultimately aims to conduct the most advanced in-situ diagnostics to evaluate FFRD in a prototypic LOCA. Moreover, it will explore the phenomenological bifurcation of a decay-energy heat up driven LOCA and a stored-energy heat up driven LOCA. The instrumentation suite includes conventional thermocouples and pressure transducers in addition to an electro impedance sensor, an acoustic emission sensor, an optical pressure sensor, and an optical pyrometer. Characterizing these instruments in OPTI-TWIST eliminates complications of irradiation effects while preserving extreme thermal-hydraulic conditions. Finally, benchmarking both devices to a thermal-hydraulic code like the Reactor Excursion and Leak Analysis Program (RELAP)5-3D provides a unique opportunity for iteration. Pre-test predictions and post-test interpretations inform the physical designs, operational procedures, test conditions, and instrumentation types and positions.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2026

AutoSAC-Automated Sample Activation Calculation on VULCAN

AutoSAC is an automated python program to conduct sample activation calculation immediately after neutron scattering experiment on VULCAN. AutoSAC takes account of sample dimensions, compositions, forms, sample environments, neutron beam configurations, neutron scattering history, and proton charged resolved beam power etc., and uses a simplified method to rapidly estimate the radioactivity at end of beam or after. It generates a draft report per sample and repository of radioactivity per measurement and provides feedback of current radioactivity and decay time back to a neutron proposal Slack channel to inform users immediately on sample handling. It also utilizes either the sample note field in EPICS or sample composition or thickness correction and takes slack prompt or command to conduct post-beam SAC by demand. The program can be shared to be used in other beamlines at spallation neutron source with modified instrument configurations including instrument specific characteristic beam fluxes.

An, Ke [Oak Ridge National Laboratory (ORNL), Oak ↗
DOE OSTI2023

Experimental Evaluation of Refrigerant Leak Characteristics for Different HVAC&R Equipment Types–Phase 2

The US Department of Energy (DOE) Building Technology Office (BTO) and the Air-conditioning, Heating & Refrigeration Technology Institute (AHRTI) collaborated to sponsor an experimental study of refrigerant leak characteristics at Oak Ridge National Laboratory (ORNL); AHRTI project 9012. The project has been conducted in two phases with objectives to conduct refrigerant leak tests on several heating, ventilating, air-conditioning and refrigeration (HVAC&R) systems under operating conditions representative of actual applications to document the pressure decay rate and the mass flow rate of leaked refrigerant as a function of time. Phase 1 of the project ran from late 2017 to late 2018 with refrigerant leaks imposed on five systems and the collection of data to meet the project objectives. Systems chosen covered three air-conditioning (AC) applications (packaged terminal AC or PTAC, 3-ton residential split system AC, and 5-ton packaged rooftop AC) and two refrigeration applications (split system unit cooler, and standalone display case). AHRTI members donated the test systems used for the project. The systems were tested at two different leak rates (catastrophic high rate simulating full line break and a lower flow rate), two leak locations (high-pressure side and low-pressure side), and two operating conditions (compressor ON or OFF). Phase 1 results were summarized in a project report by Baxter, et al. (2019)1. The leak rates imposed in Phase 1 led to much more rapid charge releases than the more typical much slower rates seen in practice that would take days, weeks, or months to empty a system of its entire charge. For Phase 2, the project sponsors asked that the “higher” leak rate target a total charge release time of about 4 min. This was intended to represent a “reasonable” worst case release scenario to match the refrigerant leak rate assumption used in the International Electrotechnical Commission (IEC) standard IEC 60335-2-40 (2016 version [IEC 2016]. A charge release time of about 20–40 min (leak release rate 5 to 10 times lower than higher rate) was targeted for the “lower” leak rate. This report provides a summary of the Phase 2 effort. Two additional HVAC systems were selected for testing in this phase. First was a multi-split air-conditioning (MS-AC) system with one outdoor section and two indoor units and a nameplate refrigerant charge of 1.75 kg (3.86 lb.) of R-410A. The MS-AC was tested in cooling only or AC operation. Second was a split system heat pump coupled to two different representative supply duct systems (HP-duct) and a nameplate charge of 3.83 kg (8.44 lb.) of R-410A. This system was tested in both space heating and AC modes. As in Phase 1 of the project, all tests were conducted using R-410A.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2022

Large-Area (Ag,Cu)(In,Ga)Se 2 Thin-Film Solar Cells with Increased Bandgap and Reduced Voltage Losses Realized with Bulk Defect Reduction and Front-Grading of the Absorber Bandgap

The 1.24 eV bandgap, 18.8% power conversion efficiency Ag-alloyed chalcopyrite (Ag,Cu)(In,Ga)Se 2 (ACIGS) solar cells are characterized to relate voltage and efficiency improvements to electro-optical (EO) characteristics. Shockley-Read-Hall recombination center defect density, identified and characterized through deep level transient spectroscopy and time-resolved photoluminescence (TRPL), is reduced through potassium and copper treatment optimization. Concomitantly, longer minority carrier lifetimes are achieved, which increases open-circuit voltage (V OC ). Near-conduction band defects associated in earlier studies with light-induced current instability are also mitigated. Analysis of charge-carrier dynamics after single- and two-photon excitation is used to separate recombination at the front interface and in the absorber bulk. From TRPL decay simulations, the authors estimate ranges of key solar cell material characteristics: bulk carrier lifetime T bulk = 110-210 ns, charge-carrier mobility u = 110-160 cm 2 V -1 s -1 , and front interface recombination velocity S front = 700-1050 cm s -1 . This lowest-reported S front for ACIGS absorbers originates from the notched conduction band grading, which also makes the impact of the back interface recombination negligible. It is suggested in the results that solar cell performance enhancements can be made most readily with two distinct strategies: improving device architecture and reducing semiconductor defect densities. Using these approaches, power conversion efficiency in large-area solar cells is improved by 1.1% absolute.

14 SOLAR ENERGY↗
DOE OSTI2020

Strong constraints on the b → sγ photon polarisation from B0 → K*0e+e-decays

An angular analysis of the B 0 → K* 0 e + e - decay is performed using a data sample corresponding to an integrated luminosity of 9 fb - 1 of pp collisions collected with the LHCb experiment. The analysis is conducted in the very low dielectron mass squared ( q 2 ) interval between 0 . 0008 and 0 . 257 GeV 2 , where the rate is dominated by the B 0 → K * 0 γ transition with a virtual photon. The fraction of longitudinal polarisation of the K * 0 meson, F L , is measured to be F L = (4 . 4 ± 2 . 6 ± 1 . 4)%, where the first uncertainty is statistical and the second systematic. The \( {A}_{\mathrm{T}}^{\mathrm{Re}} \) observable, which is related to the lepton forward-backward asymmetry, is measured to be \( {A}_{\mathrm{T}}^{\mathrm{Re}} \) = - 0 . 06 ± 0 . 08 ± 0 . 02. The \( {A}_{\mathrm{T}}^{(2)} \) and \( {A}_{\mathrm{T}}^{\mathrm{Im}} \) transverse asymmetries, which are sensitive to the virtual photon polarisation, are found to be \( {A}_{\mathrm{T}}^{(2)} \) = 0 . 11 ± 0 . 10 ± 0 . 02 and \( {A}_{\mathrm{T}}^{\mathrm{Im}} \) = 0 . 02 ± 0 . 10 ± 0 . 01. The results are consistent with Standard Model predictions and provide the world’s best constraint on the b → sγ photon polarisation.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

ANOMALOUS SKIN EFFECT STUDY OF NORMAL CONDUCTING FILM

For the radiofrequency (RF) applications of normal conducting film with large mean free path at high frequency and low temperature, the anomalous skin effect differs considerably from the normal skin effect with field decaying exponentially in the film. Starting from the relationship be-tween the current and the electric field (E field) in the film, the amplitude of E field along the film depth is calculated and is found to be non-monotonic. The surface impedance is found to have a minimum value at certain film thickness.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

Mixing Cell Model: A One-Dimensional Numerical Model for Assessment of Water Flow and Contaminant Transport in the Unsaturated Zone

This report describes the Mixing Cell Model code, a one dimensional model for water flow and solute transport in the unsaturated zone under steady state or transient flow conditions. The model is based on the principles and assumptions underlying mixing-cell model formulations. The unsaturated zone is discretized into a series of independent mixing cells. Each cell may have unique hydrologic, lithologic, and sorptive properties. Ordinary differential equations describe the material (water and solute) balance within each cell. Water-flow equations are derived from the continuity equation, assuming that unit gradient conditions exist at all times in each cell. Pressure gradients are considered implicitly through model discretization. Unsaturated hydraulic conductivity and moisture contents are determined by the material specific moisture-characteristic curves. Solute-transport processes include explicit treatment of advective processes, first order chain decay, and linear sorption reactions. Dispersion is addressed through implicit and explicit dispersion. Implicit dispersion is an inherent feature of all mixing-cell models and originates from the formulation of the problem in terms of mass balance around fully mixed volume elements. Expressions are provided that relate implicit dispersion to the physical dispersion of the system. Two FORTRAN codes were developed to solve the water flow and solute-transport equations: (1) the Mixing Cell Model for Flow (MCMF) solves transient water-flow problems and (2) the Mixing Cell Model for Transport (MCMT) solves the solute-transport problem. The transient water-flow problem is typically solved first by estimating the water flux through each cell in the model domain as a function of time using the MCMF code. These data are stored in either ASCII or binary files that are later read by the solute transport code (MCMT). Code output includes solute pore water concentrations, water and solute inventories in each cell and at each specified output time, and water and solute fluxes through each cell and specified output time. Computer run times for coupled transient water flow and solute transport were typically several seconds on a 2 GHz Intel Pentium IV desktop computer. The model was benchmarked against analytical solutions and finite element approximations to the partial differential equations (PDE) describing unsaturated flow and transport. Differences between the maximum solute flux estimated by the mixing cell model and the PDE models were typically less than two percent. This revision includes an option for a fixed concentration lower boundary condition for diffusive fluxes for versions 020321 and later.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Search for CP violation in ${D}_{(s)}^{+}$ → K - K + K + decays

A search for direct CP violation in the Cabibbo-suppressed decay \( {D}_s^{+} \) → K - K + K + and in the doubly Cabibbo-suppressed decay D + → K - K + K + is reported. The analysis is performed with data collected by the LHCb experiment in proton-proton collisions at a centre-of-mass energy of 13 TeV corresponding to an integrated luminosity of 5.6 fb - 1 . The search is conducted by comparing the \( {D}_{(s)}^{+} \) and \( {D}_{(s)}^{-} \) Dalitz-plot distributions through a model-independent binned technique, based on fits to the K - K + K + invariant-mass distributions, with a total of 0.97 (1.27) million \( {D}_s^{+} \) ( D + ) signal candidates. The results are given as p -values for the hypothesis of CP conservation and are found to be 13.3% for the \( {D}_s^{+} \) → K - K + K + decay and 31.6% for the D + → K - K + K + decay. No evidence for CP violation is observed in these decays.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Electrical breakdown dynamics in an argon bubble submerged in conductive liquid for nanosecond pulsed discharges

Abstract This study delves into the dynamics of cold atmospheric plasma and their interaction within conductive solutions under the unique conditions of nanosecond pulsed discharges (22 kV peak voltage, 10 ns FWHM, 4.5 kV ns −1 rate-of-rise). The research focuses on the electrical response, breakdown, and discharge propagation in an argon bubble, submerged in a NaCl solution of varying conductivity. Full or partial discharges were observed at conductivities of 1.5 µ S cm −1 (deionized water) to 1.6 mS cm −1 , but no breakdown was observed at 11.0 mS cm −1 when reducing the electrode gap. It is demonstrated that at higher conductivity electric breakdown is observed only when the gas bubble comes into direct contact with the electrode and multiple emission nodes were observed at different timescales. These nodes expanded in the central region of the bubble over timescales longer than the initial high-voltage pulse. This work offers a temporal resolution of 2 ns exposure times over the first 30 ns of the initial voltage pulse, and insight into plasma formation over decaying reflected voltage oscillations over 200 ns.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Modeling injection-induced fault slip using long short-term memory networks

Stress changes due to changes in fluid pressure and temperature in a faulted formation may lead to the opening/shearing of the fault. This can be due to subsurface (geo)engineering activities such as fluid injections and geologic disposal of nuclear waste. Such activities are expected to rise in the future making it necessary to assess their short- and long-term safety. Here, a new machine learning (ML) approach to model pore pressure and fault displacements in response to high-pressure fluid injection cycles is developed. The focus is on fault behavior near the injection borehole. To capture the temporal dependencies in the data, long short-term memory (LSTM) networks are utilized. To prevent error accumulation within the forecast window, four critical measures to train a robust LSTM model for predicting fault response are highlighted: (i) setting an appropriate value of LSTM lag, (ii) calibrating the LSTM cell dimension, (iii) learning rate reduction during weight optimization, and (iv) not adopting an independent injection cycle as a validation set. Several numerical experiments were conducted, which demonstrated that the ML model can capture peaks in pressure and associated fault displacement that accompany an increase in fluid injection. The model also captured the decay in pressure and displacement during the injection shut-in period. Further, the ability of an ML model to highlight key changes in fault hydromechanical activation processes was investigated, which shows that ML can be used to monitor risk of fault activation and leakage during high pressure fluid injections.

58 GEOSCIENCES↗
DOE OSTI2025

Essential barrier height and a probabilistic approach in characterizing potential landscape

In this work we propose a probabilistic approach to investigate the shape of landscapes of multi-dimensional potential functions. Under a suitable coupling scheme, two copies of the overdamped Langevin dynamics associated with the potential function are coupled, and the coupling times are collected. Assuming a set of intuitive yet technically challenging conditions on the coupling scheme, it is shown that the tail distributions of the coupling times exhibit qualitatively different dependencies on the noise magnitude for single-well versus multi-well potential functions. More specifically, for convex single-well potentials, the negative tail exponent of the coupling time distribution is uniformly bounded away from zero by the convexity parameter and is independent of the noise magnitude. In contrast, for multi-well potentials, the negative tail exponent decreases exponentially as the noise vanishes, with the decay rate governed by the essential barrier height, a quantity introduced in this paper to characterize the non-convex nature of the potential function. Numerical investigations are conducted for a variety of examples, including the Rosenbrock function, interacting particle systems, and loss functions arising in artificial neural networks. These examples not only illustrate the theoretical results in various contexts but also provide crucial numerical validation of the conjectured assumptions, which are essential to the theoretical analysis yet lie beyond the reach of standard technical tools.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2026

Dynamic Evolution of Mass and Physical Properties of Atmospheric Organic Aerosol under Solar Irradiance

Organic aerosol (OA) particles constitute a substantial fraction of sub-micron particulate mass in the atmosphere and play a critical role in climate system. OA undergoes dynamic aging processes in the atmosphere, with photolytic aging induced by ultraviolet solar irradiance being an important yet poorly characterized mechanism. Knowledge gaps persist regarding the role of volatility transformations during photolytic aging on the OA mass decay kinetics and the evolution of climate-relevant properties, such as hygroscopicity, hindering the model evaluation of OA spatiotemporal distributions and atmospheric budgets. In this study, we conduct isothermal photolytic aging experiments on both laboratory-generated secondary organic aerosols and ambient-collected particles from urban Atlanta, utilizing a high-sensitivity Quartz Crystal Microbalance. Our results reveal that photolytic aging reduces 40–66% of the low-volatility OA mass with lifetimes ranging from 8 to 200 hours under solar irradiance, and 44–92% of the photolytic mass loss is through slow evaporation of semi- or intermediate-volatile products, kinetically limited by their volatility. We observe up to ±50% changes in OA hygroscopicity with the transformation of fresh OA to photo-recalcitrant low-volatility products, associated with changes in oxygen-to-carbon ratio and molecular weight. A kinetic model incorporating photolytic volatility transformation provides a cohesive explanation for the observed photolysis-induced changes in mass, volatility, and hygroscopicity. Our results can help constrain model representation of the dynamic evolutions of mass and climate-relevant properties during photolytic aging processes of the ambient OA, improving our understanding of OA atmospheric behavior and climate impact.

Bai, Bin↗
DOE OSTI2024

IER-580 CED-3b: Experiment Execution Summary for the Pulsed-Neutron Die-Away Experiments (PNDA) with H 2 O

This report summarizes new experiments performed with H 2 O for IER-580, a testbed for pulsed-neutron die-away (PNDA) experiments at Lawrence Livermore National Laboratory (LLNL). The experiments will become high-quality benchmarksthat serve to optimize and validate thermal neutron scattering laws (TSLs) of H 2 O, which are high-priority nuclear data for the Department of Energy’s Nuclear Criticality Safety Program (NCSP). The report presents the details of the measurements conducted in October of 2023, including the experimental set-up (PNDA equipment and H 2 O targets) and all experimentally measured data. The report gives the fitted decay constants for the die-away curves of each target sample. It also provides the tabulated data for the die-away curves in the appendices.

42 ENGINEERING↗
DOE OSTI2024

The persistence of memory in ionic conduction probed by nonlinear optics

Predicting practical rates of transport in condensed phases enables the rational design of materials, devices and processes. This is especially critical to developing low-carbon energy technologies such as rechargeable batteries. For ionic conduction, the collective mechanisms, variation of conductivity with timescales and confinement, and ambiguity in the phononic origin of translation, call for a direct probe of the fundamental steps of ionic diffusion: ion hops. However, such hops are rare-event large-amplitude translations, and are challenging to excite and detect. Here we use single-cycle terahertz pumps to impulsively trigger ionic hopping in battery solid electrolytes. This is visualized by an induced transient birefringence, enabling direct probing of anisotropy in ionic hopping on the picosecond timescale. The relaxation of the transient signal measures the decay of orientational memory, and the production of entropy in diffusion. We extend experimental results using in silico transient birefringence to identify vibrational attempt frequencies for ion hopping. Using nonlinear optical methods, we probe ion transport at its fastest limit, distinguish correlated conduction mechanisms from a true random walk at the atomic scale, and demonstrate the connection between activated transport and the thermodynamics of information.

25 ENERGY STORAGE↗