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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 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

The energy spectrum of cosmic ray electrons between 9 and 300 GeV

The high-energy cosmic-ray electron spectrum between 9 and 300 GeV has been measured using an instrument consisting of a combination of a transition-radiation detector and a shower detector. The instrument has been calibrated at accelerators over the energy range 5-300 GeV and has been exposed in a balloon flight for 9.3 sq m sr hr. The design of the instrument and the data analysis procedures are described. It is found that the electron spectrum is significantly steeper than the proton spectrum. If the spectrum is fitted to a single power law, a spectral index of 3.35 is obtained. This suggests the influence of radiative energy losses on galactic electrons at low energies. The results are interpreted in the context of the homogeneous model for galactic cosmic rays.

Prince, T. A.↗
DOE OSTI2017

TREAT HODOSCOPE – A Predictive Simulation Model

The Transient Reactor Test Facility (TREAT) reactor is being restarted after over two decades of standby operation. TREAT is designed to test the time-dependent behavior of nuclear fuel during simulated reactor accidents. One of the principle data collection systems of TREAT is the fast neutron hodoscope which is used to observe the motion of the fuel test specimen as it is being damaged, deformed, or melted over the course of the power transient. The hodoscope is a grid of ex-core collimator channels paired with a bank of fast neutron sensitive radiation detectors. These detectors have historically been calibrated using empirical methods utilizing measurement data from smaller power pulses. Given modern computational capabilities this work sets out to establish a predictive computational capability of the fast neutron flux field exiting the hodoscope to support these calibrations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

A Search for Sterile Neutrino Dark Matter (Final Report)

Decades of dark matter searches with increasingly higher sensitivity have so far not been able to detect the most-favored hypothetical dark matter particles. This has increased interest in sterile neutrinos with masses in the kilo-electronvolt (keV) range as possible dark matter candidates. We have established a and new and world-leading approach to search for keV-scale sterile neutrinos with superconducting radiation detectors. For this, we have implanted radioactive beryllium-7 (Be-7) nuclei into our superconducting tunnel junction (STJ) detectors and measured the recoil energy of the lithium-7 (Li-7) daughter nucleus with high accuracy. If the associated electron neutrino wave function contains some admixture of a keV sterile flavor, the Li-7 recoil energy will be shifted and produce an additional peak in the spectrum whose energy depends on the sterile neutrino mass. While we have not observed any evidence for sterile neutrinos in these precision decay experiments, the experiment has increased the sensitivity of sterile neutrino searches by a factor of ~10 over competing approaches in the mass range from ~10 to ~800 keV. The next generation of STJ detectors that we have developed as part of this project will be able further increase the sensitivity of the sterile neutrino search by at least another two orders of magnitude.

42 ENGINEERING↗
DOE OSTI2017

Measurement and Analysis of the Extreme Physical Shock Environment Experienced by Crane-Mounted Radiation Detection Systems.

Potentially, radiation detectors at ports of entry could be mounted on container gantry crane spreaders to monitor cargo containers entering and leaving the country. These detectors would have to withstand the extreme physical environment experienced by these spreaders during normal operations. Physical shock data from the gable ends of a spreader were recorded during the loading and unloading of a cargo ship with two Lansmont SAVER 9X30 units (with padding) and two PCB Piezotronics model 340A50 accelerometers (hard mounted). Physical shocks in the form of rapid acceleration were observed in all accelerometer units with values ranging from 0.20 g’s to 199.99 g’s. The majority of the shocks for all the Lansmont and PCB accelerometers were below 50 g’s. The Lansmont recorded mean shocks of 21.83 ± 13.62 g’s and 24.78 ± 11.49 g’s while the PCB accelerometers experienced mean shocks of 34.39 ± 25.51 g’s and 41.77 ± 22.68 g’s for the landside and waterside units, respectively. Encased detector units with external padding should be designed to withstand at least 200 g’s of acceleration without padding and typical shocks of 30 g’s with padding for mounting on a spreader.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2023

Utilization of ACE nuclear data file toolkit ACEtk to calculate relative sensitivity coefficients of point-kinetics parameters

Sensitivity and uncertainty methods are quintessential for nuclear criticality safety and experiment design. This type of analysis relies on calculations of sensitivity coefficients; sensitivity coefficients of the effective neutron multiplication factor with respect to some nuclear data are predominantly calculated and used. As a part of the Laboratory Directed Research & Development project EUCLID (Experiments Underpinned by Computational Learning for Improvements in nuclear Data) at Los Alamos National Laboratory, sensitivity coefficients of many radiation detector measurement responses with respect to nuclear data were investigated. Specifically, this paper outlines a method to calculate point-kinetics parameters relative sensitivity coefficients with respect to nuclear data. Point-kinetics parameters such as the prompt neutron decay constant, effective delayed neutron fraction, and neutron generation time are especially important to experimenters and reactor operators designing systems with dynamic neutron populations. This method couples capabilities of the ACE (A Compact ENDF) nuclear data file toolkit, ACEtk, with the ability to load cross sections into the radiation transport code Monte Carlo N-Particle (MCNP). In conclusion, key aspects of optimizing this method for a particular application and sensitivity profiles of the Jezebel criticality experiment are examined and discussed.

98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL P↗
DOE OSTI2015

Gamma and proton irradiation effects and thermal stability of electrical characteristics of metal-oxide-silicon capacitors with atomic layer deposited Al 2 O 3 dielectric

The radiation hardness and thermal stability of the electrical characteristics of atomic layer deposited Al 2 O 3 layers to be used as passivation films for silicon radiation detectors with slim edges are investigated. To directly measure the interface charge and to evaluate its change with the ionizing dose, metal-oxide-silicon (MOS) capacitors implementing differently processed Al 2 O 3 layers were fabricated on p-type silicon substrates. Qualitatively similar results are obtained for degradation of capacitance–voltage and current–voltage characteristics under gamma and proton irradiations up to equivalent doses of 30 Mrad and 21.07 Mrad, respectively. While similar negative charge densities are initially extracted for all non-irradiated capacitors, superior radiation hardness is obtained for MOS structures with alumina layers grown with H 2 O instead of O 3 as oxidant precursor. Competing effects between radiation-induced positive charge trapping and hydrogen release from the H 2 O-grown Al 2 O 3 layers may explain their higher radiation resistance. Finally, irradiated and non-irradiated MOS capacitors with differently processed Al 2 O 3 layers have been subjected to thermal treatments in air at temperatures ranging between 100 °C and 200 °C and the thermal stability of their electrical characteristics has been evaluated. Partial recovery of the gamma-induced degradation has been noticed for O 3 -grown MOS structures. Lastly, this can be explained by a trapped holes emission process, for which an activation energy of 1.38 ± 0.15 eV has been extracted.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2025

Development of a military-specific mesh-type computational phantom library and its application to internal dosimetry and in-field radiological triage screening

Estimates of organ-absorbed and committed doses to individuals exposed to radioactive materials via acute inhalation often rely on internal dose coefficients and detector responses from reference human computational models. To achieve more accurate dose assessments to United States Armed Forces service members exposed in-field, computational models with varying morphometric parameters representative of this population are necessary. The International Commission on Radiological Protection (ICRP) Publication 145 provides detailed mesh reference computational phantoms (MRCPs) for adult males and females, with morphometric parameters matched to the 50th percentile. Previously, these phantoms were 2D and 3D scaled to match desired height, mass, and secondary anthropomorphic parameters in the creation of the University of Florida / Memorial Sloan Kettering (UF/MSK) computational phantom library. To achieve body fat percentage targets required for accession into the US Armed Forces, muscle and fat volumes were adjusted accordingly, thus, creating the UF/Department of Defence computational phantom library presented in this study. A comprehensive library of mesh-type computational human phantoms was created, including 57 adult males and 49 adult females with morphometric parameters aligned with United States Armed Forces service members. Phantoms were restricted to a body mass index between 19 and 27.5, with body fat percentages below 26% for males and 36% for females. Specific absorbed fractions were computed for selected source and target combinations, demonstrating how variations in height and body mass influence energy absorption in target regions relative to the ICRP MRCPs. Radiation detector responses were also computed, revealing that higher body masses resulted in decreased registered counts in the detection volume. These findings highlight the importance of incorporating morphometric variability in computational phantoms to achieve more accurate dose assessments and radiation detection responses for United States Armed Forces service members who inhale radioactive materials in-field.

computational phantoms↗
DOE OSTI2014

Comparison of Atomic and Electronic Structures of Silica and Sodium Silicate Glasses

Glass scintillators may hold great promise for low-cost, large-volume, shapeable radiation detectors. However, the light yield and energy resolution of glass scintillators to-date have been more than an order of magnitude worse than for crystalline scintillators and far from the theoretical limits. Glass scintillators are fabricated by dissolving rare-earth dopants into a glass matrix. Their operation relies on gamma ray absorption in the glass generating electrons and holes that must migrate to a rare-earth activator atom to emit light. The transport of carriers in the glass limits the performance, particularly in glasses where the solubility limit of activator is low, since carriers may recombine non-radiatively before reaching an activator atom. In this work, we aim to use atomistic simulations to discover the nature of electron transport in specific glass materials and how it may be enhanced by tuning the composition or forming process. The analysis proceeds in two steps: generation of a computational model of a given glass’s atomic structure, then extraction of the electronic structure to correlate electronic structure with carrier transport. Here we report results for two glasses: silica (SiO 2 ) and sodium silicate (Na 2 O:SiO 2 ). Multiple compositions of the latter are studied, namely Na 2 O:SiO 2 ratios of of 1:2, 1:3, and 3:7, with most results focused on the 3:7 composition. The overall goal is to establish a computational framework that can mimic a range of experimental glass structures by tuning computational parameters in the construction of the glass model, and enable studies of the correlation between atomic structure and electronic transport properties of the glass materials. These correlations would direct synthesis parameters for a given glass to optimize its transport properties.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Three-colour digital holographic microscopy based on a Mach – Zender interferometer and a solid-state RGB laser

We have developed a facility for recording colour digital holograms involving a Mach – Zender interferometer and a pulsed solid-state RGB laser, which radiates simultaneously at three wavelengths: 451, 532, and 634 nm. These wavelengths are obtained in the conversion of the radiation of a pulsed Nd{sup 3+} : YAG laser (1064 nm), which operates in the regime of intracavity parametric oscillation at a wavelength of 1570 nm, with the subsequent conversion of its frequencies to the red, green, and blue spectral regions in nonlinear KTP-crystal elements. The combination of this three-wavelength pulsed light source with the Mach – Zender interferometer provides the simultaneous recording of three spectral digital holograms with one matrix RGB radiation detector. Pulsed three-colour digital holography shows promise for the analysis of fast processes and rapidly varying colour phase objects. (paper)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

Accurate measurement of the first excited nuclear state in U 235

In this paper, we have used superconducting high-resolution radiation detectors to measure the energy level of metastable $^{235m}\mathrm{U}$ as 76.737 ± 0.018 eV. The $^{235m}\mathrm{U}$ isomer is created from the α decay of $^{239}\mathrm{Pu}$ and embedded directly into the detector. When the $^{235m}\mathrm{U}$ subsequently decays, the energy is fully contained within the detector and is independent of the decay mode or the chemical state of the uranium. The detector is calibrated using an energy comb from a pulsed UV laser. Finally, a comparable measurement of the metastable $^{229m}\mathrm{Th}$ nucleus would enable a laser search for the exact transition energy in $^{229}\mathrm{Th}{-}^{229m}\mathrm{Th}$ as a step towards developing the first ever nuclear (baryonic) clock.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1983

Skeletal and body composition evaluation

Research on radiation detectors for absorptiometry; analysis of errors affective single photon absorptiometry and development of instrumentation; analysis of errors affecting dual photon absorptiometry and development of instrumentation; comparison of skeletal measurements with other techniques; cooperation with NASA projects for skeletal evaluation in spaceflight (Experiment MO-78) and in laboratory studies with immobilized animals; studies of postmenopausal osteoporosis; organization of scientific meetings and workshops on absorptiometric measurement; and development of instrumentation for measurement of fluid shifts in the human body were performed. Instrumentation was developed that allows accurate and precise (2% error) measurements of mineral content in compact and trabecular bone and of the total skeleton. Instrumentation was also developed to measure fluid shifts in the extremities. Radiation exposure with those procedures is low (2-10 MREM). One hundred seventy three technical reports and one hundred and four published papers of studies from the University of Wisconsin Bone Mineral Lab are listed.

Mazess, R. B.↗
DOE OSTI2018

Cryogenic scintillation properties of n -type GaAs for the direct detection of MeV/c 2 dark matter

This paper is the first report of n-type GaAs as a cryogenic scintillation radiation detector for the detection of electron recoils from interacting dark matter (DM) particles in the poorly explored MeV/c 2 mass range. Seven GaAs samples from two commercial suppliers and with different silicon and boron concentrations were studied for their low temperature optical and scintillation properties. All samples are n -type even at low temperatures and exhibit emission between silicon donors and boron acceptors that peaks at 1.33 eV (930 nm). The lowest excitation band peaks at 1.44 eV (860 nm), and the overlap between the emission and excitation bands is small. The X-ray excited luminosities range from 7 to 43 photons/keV. Thermally stimulated luminescence measurements show that n -type GaAs does not accumulate metastable radiative states that could cause afterglow. Further development and use with cryogenic photodetectors promises a remarkable combination of large target size, ultra-low backgrounds, and a sensitivity to electron recoils of a few eV that would be produced by DM particles as light as a few MeV/c 2 .

36 MATERIALS SCIENCE↗
DOE OSTI2016

TU-E-TOUR-I-00: Exhibit Hall Guided Tours-Dosimters for QC in Diagnostic Imaging (Tuesday)

Tour Leader: Xia Jiang, Ohio State University, Columbus, OH Tour Guides: Xia Jiang, Ohio State University, Columbus, OH Kevin Little, The University of Chicago, Chicago, IL Christina Sammet, Lurie Children’s Hospital of Chicago, Chicago, IL Participating Vendors: IBA PTW - New York Radcal Corporation RTI Electronics, Inc. Exhibit Hall Guided Tours is a new program launching this year at the Annual Meeting. The Guided Tours are designed to enhance the interaction between meeting attendees and exhibitors. This year’s Imaging Guided Tours are organized around the theme of dosimeters for quality control in diagnostic imaging. Tours will begin with an introduction and background given by Dr. Xia Jiang, the Tour Leader. The introduction will cover the types and properties of different radiation dosimeters used for quality assurance in clinical radiology. Attendees will then break into smaller groups, each lead by an AAPM-member Tour Guide. The tour groups will visit the exhibit booths of vendors who provide appropriate dosimeters, and a vendor representative will give a presentation to the group about their particular product(s). The vendor representatives as well as the Tour Guides will be available to answer questions. Outline: Types and properties of radiation detectors and dosimeters Ionization chamber dosimeters Solid state dosimeters Dosimeter calibration: Primary and secondary standards dosimetry laboratories Instruments for measuring tube voltage and exposure time Vendor presentations will likely cover features and innovations of different dosimeter systems, as well as their practical use. Learning Objectives: Understand the types and properties of different instrumentations used for quality control in diagnostic imaging. Understand the process of dosimeter calibration. Gain familiarity with the latest commercial dosimeter systems from different vendors.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2016

WE-C-TOUR-I-00: Exhibit Hall Guided Tours-Dosimters for QC in Diagnostic Imaging (Wednesday)

Tour Leader: Xia Jiang, Ohio State University, Columbus, OH Tour Guides: Xia Jiang, Ohio State University, Columbus, OH Kevin Little, The University of Chicago, Chicago, IL Adrien Sanchez, University of Chicago, Chicago, IL Participating Vendors: IBA PTW - New York Radcal Corporation RTI Electronics, Inc. Exhibit Hall Guided Tours is a new program launching this year at the Annual Meeting. The Guided Tours are designed to enhance the interaction between meeting attendees and exhibitors. This year’s Imaging Guided Tours are organized around the theme of dosimeters for quality control in diagnostic imaging. Tours will begin with an introduction and background given by Dr. Xia Jiang, the Tour Leader. The introduction will cover the types and properties of different radiation dosimeters used for quality assurance in clinical radiology. Attendees will then break into smaller groups, each lead by an AAPM-member Tour Guide. The tour groups will visit the exhibit booths of vendors who provide appropriate dosimeters, and a vendor representative will give a presentation to the group about their particular product(s). The vendor representatives as well as the Tour Guides will be available to answer questions. Outline: Types and properties of radiation detectors and dosimeters Ionization chamber dosimeters Solid state dosimeters Dosimeter calibration: Primary and secondary standards dosimetry laboratories Instruments for measuring tube voltage and exposure time Vendor presentations will likely cover features and innovations of different dosimeter systems, as well as their practical use. Learning Objectives: Understand the types and properties of different instrumentations used for quality control in diagnostic imaging. Understand the process of dosimeter calibration. Gain familiarity with the latest commercial dosimeter systems from different vendors.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2016

WE-C-TOUR-I-01: Dosimters for QC in Diagnostic Imaging

Tour Leader: Xia Jiang, Ohio State University, Columbus, OH Tour Guides: Xia Jiang, Ohio State University, Columbus, OH Kevin Little, The University of Chicago, Chicago, IL Adrien Sanchez, University of Chicago, Chicago, IL Participating Vendors: IBA PTW - New York Radcal Corporation RTI Electronics, Inc. Exhibit Hall Guided Tours is a new program launching this year at the Annual Meeting. The Guided Tours are designed to enhance the interaction between meeting attendees and exhibitors. This year’s Imaging Guided Tours are organized around the theme of dosimeters for quality control in diagnostic imaging. Tours will begin with an introduction and background given by Dr. Xia Jiang, the Tour Leader. The introduction will cover the types and properties of different radiation dosimeters used for quality assurance in clinical radiology. Attendees will then break into smaller groups, each lead by an AAPM-member Tour Guide. The tour groups will visit the exhibit booths of vendors who provide appropriate dosimeters, and a vendor representative will give a presentation to the group about their particular product(s). The vendor representatives as well as the Tour Guides will be available to answer questions. Outline: Types and properties of radiation detectors and dosimeters Ionization chamber dosimeters Solid state dosimeters Dosimeter calibration: Primary and secondary standards dosimetry laboratories Instruments for measuring tube voltage and exposure time Vendor presentations will likely cover features and innovations of different dosimeter systems, as well as their practical use. Learning Objectives: Understand the types and properties of different instrumentations used for quality control in diagnostic imaging. Understand the process of dosimeter calibration. Gain familiarity with the latest commercial dosimeter systems from different vendors.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2024

OSCAR-Mike: Why not ATAK?

The Office of Nuclear Smuggling Detection and Deterrence (NSDD) is evaluating methods to increase the probability that international partners will detect radioactive materials. One proposed method to accomplish this goal is to improve communications within teams operating in challenging environments. The goal of these improvements would be to enable remote monitoring of detection equipment, share data among end users in the field and subject matter experts, and integrate data from radiation detectors with other types of sensors and camera systems. Accomplishing this goal has the potential to improve the capabilities of currently deployed NSDD equipment. During FY 2021, Oak Ridge National Laboratory demonstrated some core and expanded capabilities of the Android Team Awareness Kit (ATAK), a situational awareness application developed by the US Department of Defense, to enable precision targeting, navigation, and data sharing. During FY 2022, Oak Ridge National Laboratory developed software requirements for an NSDD team awareness kit–based system. The requirements were developed by liaising with NSDD management and subject matter experts to determine NSDD’s needs and by reviewing available software and hardware solutions with US Department of Defense team awareness kit program managers and developers and radiation detection equipment vendors.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2017

An analysis of point defects induced by In, Al, Ni, and Sn dopants in Bridgman-grown CdZnTe detectors and their influence on trapping of charge carriers

In this paper, we studied point defects induced in Bridgman-grown CdZnTe detectors doped with Indium (In), Aluminium (Al), Nickel (Ni), and Tin (Sn). Point defects associated with different dopants were observed, and these defects were analyzed in detail for their contributions to electron/hole (e/h) trapping. We also explored the correlations between the nature and abundance of the point defects with their influence on the resistivity, electron mobility-lifetime (μτ e ) product, and electron trapping time. We used current-deep level transient spectroscopy to determine the energy, capture cross-section, and concentration of each trap. Furthermore, we used the data to determine the trapping and de-trapping times for the charge carriers. In In-doped CdZnTe detectors, uncompensated Cd vacancies (V Cd - ) were identified as a dominant trap. The V Cd - were almost compensated in detectors doped with Al, Ni, and Sn, in addition to co-doping with In. Dominant traps related to the dopant were found at E v + 0.36 eV and E v + 1.1 eV, E c + 76 meV and E v + 0.61 eV, E v + 36 meV and E v + 0.86 eV, E v + 0.52 eV and E c + 0.83 eV in CZT:In, CZT:In + Al, CZT:In + Ni, and CZT:In + Sn, respectively. Results indicate that the addition of other dopants with In affects the type, nature, concentration (N t ), and capture cross-section (σ) and hence trapping (t t ) and de-trapping (t dt ) times. Finally, the dopant-induced traps, their corresponding concentrations, and charge capture cross-section play an important role in the performance of radiation detectors, especially for devices that rely solely on electron transport.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Pulse shape discrimination of Cs 2 LiYCl 6 :Ce 3+ detectors at high count rate based on triangular and trapezoidal filters

Cs 2 LiYCl 6 :Ce 3+ (CLYC) detectors have demonstrated the capability to simultaneously detect γ-rays and thermal and fast neutrons with medium energy resolution, reasonable detection efficiency, and substantially high pulse shape discrimination performance. In this work, a disadvantage of CLYC detectors is the long scintillation decay times, which causes pulse pile-up at moderate input count rate. Pulse processing algorithms were developed based on triangular and trapezoidal filters to discriminate between neutrons and γ-rays at high count rate. The algorithms were first tested using low-rate data. They exhibit a pulse-shape discrimination performance comparable to that of the charge comparison method, at low rate. Then, they were evaluated at high count rate. Neutrons and γ-rays were adequately identified with high throughput at rates of up to 375 kcps. The algorithm developed using the triangular filter exhibits discrimination capability marginally higher than that of the trapezoidal filter based algorithm irrespective of low or high rate. The algorithms exhibit low computational complexity and are executable on an FPGA in real-time. Finally, they are also suitable for application to other radiation detectors whose pulses are piled-up at high rate owing to long scintillation decay times.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗