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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Micro-tensile Properties of Fueled Irradiated AGR-2 TRISO-coated Particle Buffer, IPyC, and SiC Interlayer Regions

Tristructural isotropic (TRISO) coated nuclear fuel particles are proving to be a versatile fuel form for new reactor designs. Understanding the bounding strength and failure mode of each coating interface is important to both fuel quality evaluation and failure prediction. A mechanism of key significance is failure of the silicon carbide (SiC) layer to retain fission products due to incomplete tearing of the buffer layer. This is a two-step mechanism involving both mechanical failure in the buffer and inner pyrolytic carbon (IPyC) layers and degradation of the SiC layer through palladium silicides at the IPyC-SiC interface. However, the mechanical properties of TRISO particle coating layers have yet to be fully characterized due to the small dimension of TRISO fuel particles and high radioactivity. To investigate this mechanism, in situ micro-tensile properties of the buffer, IPyC, SiC, buffer-IPyC, and IPyC-SiC interlayer regions of fueled TRISO particles have been tested at both as-fabricated and irradiated conditions. Determination of the mechanical properties of these TRISO particle regions will lead to a better understanding of the SiC layer failure mechanism and enable progress towards TRISO fuel qualification.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2024

AI-Driven Detector Design for the EIC (Final Technical Report)

We developed an optimization workflow based on DNN-based fast-simulation and reconstruction algorithms. We used these methods to advance the design of calorimeter systems for the Electron-Ion Collider (EIC). This DNN-driven optimization provides a blueprint for integrating gradient-based methods into detector-design workflows. All software pipelines and methods have been released publicly and incorporated into the EIC collaboration’s physics studies, broadening their impact. Three journal articles detailing the methods developed here serve as a reference for the design and optimal use of next generation high-granularity calorimeter systems in nuclear and particle physics.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Modeling Solids in Nuclear Astrophysics with Smoothed Particle Hydrodynamics

Abstract Smoothed particle hydrodynamics (SPH) is a frequently applied tool in computational astrophysics to solve the fluid dynamics equations governing the systems under study. For some problems, for example when involving asteroids and asteroid impacts, the additional inclusion of material strength is necessary in order to accurately describe the dynamics. In compact stars, that is white dwarfs and neutron stars, solid components are also present. Neutron stars have a solid crust, which is the strongest material known in nature. However, their dynamical evolution, when modeled via SPH or other computational fluid dynamics codes, is usually described as a purely fluid dynamics problem. Here, we present the first 3D simulations of neutron star crustal toroidal oscillations including material strength with the Los Alamos National Laboratory SPH code FleCSPH. In the first half of the paper, we present the numerical implementation of solid material modeling together with standard tests. The second half is on the simulation of crustal oscillations in the fundamental toroidal mode. Here, we dedicate a large fraction of the paper to approaches that can suppress numerical noise in the solid. If not minimized, the latter can dominate the crustal motion in the simulations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

The MicroBooNE Single-Photon Low-Energy Excess Search (Public Note 1087)

MicroBooNE is a short baseline neutrino experiment at Fermilab designed to address the low energy excess observed by the MiniBooNE experiment. This note describes and presents preliminary results for the MicroBooNE analysis developed to address this excess as a single photon plus one or zero protons in the final state. The analysis assumes neutrino neutral current Δ resonance production followed by Δ radiative decay on argon (NC Δ → Nγ ) as the "signal model"; event reconstruction and selection have been developed and optimized in order to maximize efficiency and reduce cosmogenic and other beam-related backgrounds to the NC Δ → Nγ signal. We present the analysis methodology and validation checks performed on limited-statistics open data sets, corresponding to 5 x10 19 protons on target (POT), following a blind analysis, as well as the projected sensitivities for testing the Standard Model (SM) predicted rate for the NC Δ → Nγ process and for testing the interpretation of the previously observed MiniBooNE low energy excess as NC Δ → Nγ events, using the full anticipated MicroBooNE data set of 12.25 x 10 20 POT.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Deep Underground Neutrino Experiment (DUNE), Far Detector Technical Design Report (Volume II: DUNE Physics)

The Physics volume of the DUNE far detector (FD) Technical Design Report (TDR) presents the science program of DUNE. Within, we describe the array of identified scientific opportunities and key goals. Crucially, we also report our best current understanding of the capability of DUNE to realize these goals, along with the detailed arguments and investigations on which this understanding is based. In the context of the complete set of DUNE TDR volumes, a central role for this volume is to document the scientific basis underlying the conception and design of the LBNF/DUNE experimental configurations. As a result, it is the description of DUNE’s experimental capabilities that constitutes the bulk of the document. Key linkages between requirements for successful execution of the physics program and primary specifications of the experimental configurations are drawn and summarized. This document also serves a wider purpose as a statement on the scientific potential of DUNE as a central component within a global program of frontier theoretical and experimental particle physics research. Thus, the presentation also aims to serve as a resource for the particle physics community at large. In this chapter, the scientific goals, the methodologies utilized to obtain sensitivity projections, the corresponding results for selected elements of the scientific program, and the demands placed on the experiment design and performance are presented in summary form. Together with the two chapters that follow, this summary establishes the context for the detailed descriptions specific to each area of research that comprise the remaining chapters.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1974

Variations in the nuclear abundances in solar particle events

Measurements of the flux of helium nuclei in the 24 January 1971 event and of helium and (C, N, O) nuclei in the 1 September 1971 event are combined with previous measurements to obtain the relative abundances of helium, (C, N, O), and Fe-group nuclei in these events. These data are then summarized together with previously reported results to show that, even when the same detector system using a dE/dx plus range technique is used, differences in the He/(C, N, O) value in the same energy/nucleon interval are observed in solar cosmic ray events. Further, when the He/(C, N, O) value is lower the He/(Fe-group nuclei) value is also systematically lower in these large events.

Bertsch, D. L.↗
DOE OSTI2021

MeV Scale Physics in MicroBooNE

This thesis presents the reconstruction and measurement of low-energy electromagnetic activity with beam neutrino interactions within the MicroBooNE Liquid Argon Time Projection Chamber (LArTPC). LArTPCs have proven to be excellent detectors to measure neutrino interaction cross sections and are being used to perform precision measurements of neutrino oscillation parameters. The work presented in this thesis has demonstrated unprecedentedly low, sub-MeV energy thresholds that have increased sensitivity of LArTPCs to detect neutrino interactions from core collapse supernovae and Muon Decay at Rest (µDAR). In addition, such low thresholds have also increased measurement sensitivity for interactions from Beyond the Standard Model (BSM) candidates such as millicharged particles and nuclear and electron recoils from dark matter candidate particles. On the reconstruction side, this work has established an energy resolution of 6.3% for electromagnetic activity i the 0-5 MeV energy range within the MicroBooNE LArTPC. Additionally this work presents the quantitative analysis of the low-energy activity emanating from G-10 support ribs in MicroBooNE and discusses how such activity could be a problematic source of background for low-energy physics analyses in future neutrino detectors such as the Deep Underground Neutrino Experiment (DUNE).

Bhat, Avinay↗
DOE OSTI2022

Two bright, optically clear, intrinsic fast-neutron and charged-particle detector materials for neutron imaging and other applications

Two optically clear, bright, scintillating ZnS materials have been identified that, like previous opaque ZnS scintillators, are excellent charged particle detectors. We show that ZnS is a good fast-neutron-to charged-particle converter making optically clear ZnS an intrinsic fast-neutron detector that does not require layering or mixing of converter materials and scintillator materials, and removes the limitations imposed by opaque ZnS scintillator materials used for more than a century. Thermal neutron detection using optically clear 6 LiF or 10 BN and clear ZnS may benefit from improved spatial resolution and light transmission. Properties and tests of clear scintillating ZnS are described. Fast-neutron imaging applications benefit from increased efficiency of these scintillators, minimal scattering in the scintillator, and increased useful detector volume. Charged particle and fast-neutron detectors have numerous applications in nuclear non-proliferation and security, nuclear and particle physics, and non-destructive testing and environmental measurements.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

Reexamining the variational two-particle reduced density matrix for nuclear systems

We report that in most nuclear many-body methods, observables are calculated using many-body wave functions explicitly. The variational two-particle reduced density matrix method is one of the few exceptions to the rule. Ground-state energies of both closed-shell and open-shell nuclear systems can indeed be evaluated by minimizing a constrained linear functional of the two-particle reduced density matrix. However, it has virtually never been used in nuclear theory, because nuclear ground states were found to be well overbound, contrary to those of atoms and molecules. Consequently, we introduced new constraints in the nuclear variational two-particle reduced density matrix method, developed recently for atomic and molecular systems. Our calculations then show that this approach can provide a proper description of nuclear systems where only valence neutrons are included. For the nuclear systems where both neutrons and protons are active, however, the energies obtained with the variational two-particle reduced density matrix method are still overbound. The possible reasons for the noticed discrepancies and solutions to this problem will be discussed.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1995

Charge, energy and LET spectra of high LET primary and secondary particles in CR-39 plastic nuclear track detectors of the P0006 experiment

We have measured the charge, energy and linear energy transfer (LET) spectra of about 800 high LET (LET(sub infinity) H2O greater than 50 keV/micron) particles in CR-39 plastic nuclear track detectors in the P0006 experiment of LDEF. Primary particles with residual range at the reference surface greater than about 2 microns and secondary particles produced in the detector material with total range greater than about 4 microns were measured. We have used a multi-etch technique and an internal calibration to identify and measure the energy of the particles at the reference surface. The LET spectrum was obtained from the charge and energy distribution of the particles.

Csige, I.↗