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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 1,243 records · Page 69
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Theoretical models for stellar X-ray polarization in compact objects

Degenerate stellar objects are expected to be strong sources of polarized X-ray emission. This is particularly true for strongly magnetized neutron stars, e.g. accretion or rotation powered pulsars, and gamma ray bursters. In these, linear polarization degrees well in excess of 30 percent are expected. Weaker magnetic field stellar sources, such as old neutron stars in low mass binary systems, white dwarfs and black holes are expected to have polarization degrees in the range 1-3 percent. A great interest attaches to the detection of polarization in these objects, since this would provide invaluable information concerning the geometry, radiation mechanism and magnetic field strength, necessary for testing and proving models of the structure and evolution of stars in their late stages. In this paper we review the theoretical models of the production of polarized radiation in compact stellar X-ray sources, and discuss the possibility of detecting these properties using currently planned detectors to be flown in space.

Meszaros, P.↗
NASA NTRSDate not supplied

Implications of Deep UV Raman Spectra of Gypsum and Fe-Bearing Dust Mixtures for Gypsum Detectability by the SHERLOC M2020 Instrument

Key science objectives of the Mars2020 Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals (SHERLOC) instrument suite include identification and characterization of inorganic and bio-logic phases and investigation of the past habitability of Jezero crater [1, 2]. To fully interpret in situ data received from SHERLOC, databases of deep ultraviolet (DUV) Raman spectra from a wide variety of martian analogue materials are being developed by us and others [e.g., 3]. Ferrous and ferric iron are abundant on the martian surface in bas-alt and, depending on alteration and transport processes, its alteration products. Fe-bearing phases are important to characterize with respect to detect-ability by DUV Raman spectroscopy because they strongly absorb DUV radiation, thereby decreasing Raman peak intensity [3, 4]. Ca-sulfates and Fe-bearing minerals have been commonly detected on the martian surface [5, 6]. In this analogue study, we collected Raman spectra of mechanical mixtures of powders of hematite HMS3 (~120 nm discrete particle diameter [7]), palagonite HWMK919 (<5 μm size fraction [8]) and gypsum WD163 (<150 μm size fraction) t o ex-amine the detectability of gypsum in the presence of relatively finer-grained, Fe bearing material. Be-cause of the difference in particle diameters, hematite and palagonite powders act as surrogates for martian dust, coating at small concentrations and then enveloping larger gypsum particles.

N C Haney↗
NASA NTRS2020

Fast Neutron Spectroscopy with Organic Scintillation Detectors in a High-Radiation Environment

Organic scintillators with pulse shape discrimination capability are widely used in both research and practical applications of neutron detection. The neutron and gamma-ray identification performance of the detector depends on the classification algorithms, noise filters and pileup rejection criteria in a high-flux bremsstrahlung radiation environment. In this paper, a technique has been developed and implemented for the neutron detection with multiple filter and discrimination steps, which to a high confidence level eliminates counting of gamma-ray pulses. Such a technique is merited when making measurements in a high flux bremsstrahlung and secondary fluorescence environment. The EJ-309 and stilbene detectors coupled to the digital data acquisition system were used for the calibration assessments with standard gamma-ray and neutron sources such as 137Cs, 60Co, 252Cf, and Am-Be. The MCNPX-PoliMi and GEANT4 toolkits were used to simulate the light output and the optical photon transport in the scintillators and create detector response functions for each type of detector. The neutron spectrum unfolding algorithm, GRAVELW, was used to recreate and calibrate with the Am-Be as final step before applying the neutron detection system to extract fusion neutron spectra generated in an intense bremsstrahlung radiation environment. This new technique described offers the user the ability to measure neutron spectra in a high-flux gamma-ray field and tune the parameters to meet required filtering needs.

Neutron Detector, Organic Scintillator, PulseShape↗
DOE OSTI2024

Spectroscopic Measurements and Models of Energy Deposition in the Substrate of Quantum Circuits by Natural Ionizing Radiation

Naturally occurring background radiation is a potential source of correlated decoherence events in superconducting qubits that will challenge error-correction schemes. In order to characterize the radiation environment in an unshielded laboratory representative of superconducting qubits’ environments, we performed broadband, spectroscopic measurements of background radiation events inside a millikelvin refrigerator. The spectrometer was designed to mimic the size and composition of a quantum circuit. Specifically, we measured the background radiation spectra in silicon substrates of two thicknesses, 500 and 1500 µm, and one area, 25 mm 2 . The observed spectra span energies from a few kilo-electron-volts up to nearly 10 MeV, are nearly featureless, and decrease in intensity by a factor of 40 000 between 100 keV and 3 MeV for the 500-µm substrate. We integrate the spectra to obtain the average event rates and deposited power levels. These quantities correspond to a rate of 0.023 events per second and a power of 4.9 keV s -1 , when counting events that deposit at least 40 keV for the 500-µm-thick substrate. We find that the cryogenic measurements are in good agreement with predictions based on simple measurements of the terrestrial gamma-ray flux outside the refrigerator, published models of cosmic-ray fluxes, a crude model of the cryostat, and radiation-transport simulations. This model requires no free parameters to predict the background radiation spectra in the silicon substrates. The agreement between measurements and predictions demonstrates that the model we present can be used to assess the relative contributions of terrestrial and cosmic-ray sources to background radiation interactions in silicon substrates of varying thickness. These spectroscopic measurements are performed with a novel combination of superconducting microresonators located on micromachined silicon islands that define the interaction volume with background radiation. The resonators transduce deposited energy to a readily detectable electrical signal. Microresonator readout closely resembles dispersive superconducting qubit readout, so similar devices—with or without micromachined islands—are suitable for integration with superconducting quantum circuits as detectors for background radiation events. For our specific laboratory conditions, we find that gamma-ray emissions from radioisotopes are responsible for the majority of events that deposit E < 1 ⁢Me⁢V. We present results demonstrating that the background radiation spectrum contains relevant contributions from cosmic-ray particles other than muons, particularly a tail of multi-mega-electron-volt events due to protons and neutrons. These observations suggest several paths to reducing the impact of background radiation on quantum circuits, supported by an empirically validated model for generating reliable predictions of radiation interactions with silicon substrates.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1986

Satellite interferometric measurements of auroral kilometric radiation

The first satellite interferometric measurements of auroral kilometric radiation were performed by cross-correlating the waveforms detected by the ISEE 1 and ISEE 2 spacecraft. High correlations were found for all projected baselines, with little or no tendency to decrease even for the longest baselines. For incoherent radiation, the correlation as a function of the baseline is the Fourier transform of the source brightness distribution, implying an average source region diameter for all of the bursts analyzed of less than about 10 km. For such small source diameters, the required growth rates are too large to be explained by existing incoherent theories, strongly indicating that the radiation must be coherent. For coherent radiation, an upper limit to the source region diameter can be inferred instead from the angular width of the radiation pattern. The angular width of the radiation pattern must be at least 2.5 deg, implying that the diameter of the source must be less than about 20 km.

Baumback, M. M.↗
NASA NTRS1990

Infrared response from metallic particles embedded in a single-crystal Si matrix - The layered internal photoemission sensor

Infrared radiation at wavelengths of 1-2 microns has been detected in a new device labeled the layered internal photoemission sensor. The device structure, which is grown by molecular beam epitaxy, incorporates epitaxial CoSi2 particles with dimensions of 10-50 nm. Radiation absorbed by these particles photoexcites carriers into a surrounding single-crystal silicon matrix. A peak quantum efficiency of 1.3 percent is measured, which is approximately six times higher than in planar CoSi2 Schottky diodes with 5-nm silicide thickness.

Fathauer, R. W.↗
DOE OSTI2025

Orchestrating Spontaneous Emission With Metasurfaces: Recent Advances in Engineering Thermal, Luminescent, and Quantum Emissions

Metasurfaces have emerged as powerful tools for controlling spontaneous emission, offering unprecedented control over light-matter interactions at sub-wavelength scales. While metasurfaces are traditionally utilized for shaping coherent electromagnetic waves, they have recently extended their capabilities to control incoherent or spontaneous emission. This examines review how metasurfaces can enhance and precisely control properties of thermal, luminescent, and quantum emission. In thermal emission, metasurfaces enable control over spatial, temporal, and spin coherence, offering new possibilities for applications such as energy harvesting, radiative cooling and heat assisted ranging and detection. For luminescent emission, metasurfaces significantly improve emission rates, quantum efficiency, and directionality, driving innovations in lighting and display technologies. For controlling quantized spontaneous emission, metasurfaces are instrumental in enhancing single-photon sources and enabling novel functionalities in quantum states through photon-pair generation, which is vital for quantum communication, meteorology, and computing. Here, despite these advancements several challenges to increase the operational bandwidths, accelerate and develop simulation strategies, and fabrication complexities persist. Emerging trends are also discussed, such as dynamic metasurfaces and their integration with nanophotonic platforms, which could further expand the capabilities of light-emitting metasurfaces.

Luminescence↗
DOE OSTI2023

Development and testing of a fission-like neutron field for dosimetry and instrument calibrations based on deuterium-tritium generator

For nearly five decades 252 Cf sources have been used for testing and calibration over a wide range of neutron detection devices used for nuclear safety and radiation protection. However, the vastly increased cost of 252 Cf sources, its short half-life, and concerns about future shortage have prompted nuclear facilities and radiological calibration laboratories that rely on high-intensity neutron sources to seek alternatives. There appear to be no other radionuclide neutron sources that would match “like-to-like” 252 Cf performance characteristics. Alternatives of producing a fission-like neutron spectrum based on commercially available deuterium-tritium (D-T) generators, and without any fissionable materials or beryllium, have been explored. This paper describes efforts of designing the spectrum shaping assembly, its construction and installation. The produced neutron field was evaluated both from the perspective of the neutron fluence spectrum and the resulting dosimetric outcome. Finally, it was tested for practical application by examining response of various health physics instruments and personal monitoring devices in comparison to the response of those devices when exposed to 252 Cf. In conclusion, the response of survey-type instruments tested within the prototype, surrogate fission, reference field are acceptably close to their response in the targeted 252 Cf field.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

Electron shelving of a superconducting artificial atom

Interfacing long-lived qubits with propagating photons is a fundamental challenge in quantum technology. Cavity and circuit quantum electrodynamics (cQED) architectures rely on an off-resonant cavity, which blocks the qubit emission and enables a quantum non-demolition (QND) dispersive readout. However, no such buffer mode is necessary for controlling a large class of three-level systems that combine a metastable qubit transition with a bright cycling transition, using the electron shelving effect. Here we demonstrate shelving of a circuit atom, fluxonium, placed inside a microwave waveguide. With no cavity modes in the setup, the qubit coherence time exceeds 50 μs, and the cycling transition’s radiative lifetime is under 100 ns. By detecting a homodyne fluorescence signal from the cycling transition, we implement a QND readout of the qubit and account for readout errors using a minimal optical pumping model. Our result establishes a resource-efficient (cavityless) alternative to cQED for controlling superconducting qubits.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Design of multilayer-based diagnostics for measurement of high energy x rays and gamma rays

We investigate several possible multilayer-based optic designs for future hard x-ray and gamma ray diagnostics, including the detection and measurement of the positron annihilation radiation at 511 keV. The focus is set on increasing the photon efficiency and signal-to-noise ratio, compared to a previous multilayer-based system that was successfully employed to measure spectra in the 55 keV–100 keV range. Several possible designs using multilayer coatings are discussed, including mirror-based optics and multilayer Laue lenses.

Burcklen, C. (ORCID:0000000271566357)↗
DOE OSTI2023

A Fission-like Neutron Spectrum Shaping Assembly based on D-T Generator

For nearly five decades, 252 Cf sources have been used for testing and calibration over a wide range of neutron detection devices used for nuclear safety and radiation protection. However, the vastly increased cost of 252 Cf sources, its short half-life, and concerns about future shortage have prompted nuclear facilities and radiological calibration laboratories that rely on high-intensity neutron sources to seek alternatives. While there appear to be no other radionuclide neutron sources that would match the 252 Cf performance characteristics, all of them, including 252 Cf, present similar concerns in terms of hazards, safety, and security. As a possible solution to this issue, the Pacific Northwest National Laboratory (PNNL) developed a low-risk, cost-efficient alternative to produce fission-like spectra based on commercially available deuterium-tritium (D-T) neutron generators. The alternative of producing a fission-like neutron spectrum without any fissionable materials or beryllium would enable the nuclear facilities across the entire complex to eliminate their reliance on high intensity 252 Cf sources for nuclear safety and radiation protection applications, substantially reducing risks and associated costs. This report describes efforts of designing the spectrum shaping assembly, its construction and characterization of the neutron field produced. Performance of this newly developed D-T generator based neutron field is demonstrated via calibration of a criticality detector, neutron survey instruments, and personal dosimeters verified against current standardized fields produced by 252 Cf spontaneous fission sources.

42 ENGINEERING↗
DOE OSTI2025

Evaluation of Neutron Detection Technology and Analysis Techniques to Support Fukushima Daiichi Decommissioning [Poster]

Decommissioning efforts and associated fuel debris retrieval from the damaged Units 1-3 require robust methods to monitor and assure subcriticality. These include adequate detection technologies capable to withstand high gamma radiation conditions within the units; as well as analysis methods capable to provide robust signatures to assure agile criticality monitoring in situation where material distribution is changing. This poster presents overview of experimental and analytical efforts focused on evaluation of neutronbased technologies and development of real-time analysis using state-of-the art capabilities available within the 1F Fuel Retrieval and Monitoring Experiments (1FRAME) project.

1FRAME↗
DOE OSTI2022

New insights on the prevalence of drizzle in marine stratocumulus clouds based on a machine learning algorithm applied to radar Doppler spectra

Abstract. The detection of the early growth of drizzle particles in marine stratocumulus clouds is important for studying the transition from cloud water to rainwater. Radar reflectivity is commonly used to detect drizzle; however, its utility is limited to larger drizzle particles. Alternatively, radar Doppler spectrum skewness has proven to be a more sensitive quantity for the detection of drizzle embryos. Here, a machine learning (ML)-based technique that uses radar reflectivity and skewness for detecting small drizzle particles is presented. Aircraft in situ measurements are used to develop and validate the ML algorithm. The drizzle detection algorithm is applied to three Atmospheric Radiation Measurement (ARM) observational campaigns to investigate the drizzle occurrence in marine boundary layer clouds. It is found that drizzle is far more ubiquitous than previously thought; the traditional radar-reflectivity-based approach significantly underestimates the drizzle occurrence, especially in thin clouds with liquid water paths lower than 50 g m−2. Furthermore, the drizzle occurrence in marine boundary layer clouds differs among the three ARM campaigns, indicating that the drizzle formation, which is controlled by the microphysical process, is regime dependent. A complete understanding of the drizzle distribution climatology in marine stratocumulus clouds calls for more observational campaigns and continuing investigations.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1968

Readout system for radiation detector

Improved electrical circuit determines the amount of light detected by a photomultiplier tube when its output signal is in the dark-current range of the tube. The low-intensity light to which the tube responds arises from a thermo-luminescent ionized dosimeter.

Baker, B. R.↗
NASA NTRS1976

Low fluxes of X-rays

Analytic and experimental investigations of the interactions of high-energy protons with spacecraft materials and light nucleus atoms were conducted. Irradiation of typical materials for scintillation detectors using accelerator-produced energetic protons and associated theoretical calculations indicate activity within detectors produced by this mechanism is significant to detection of low-level cosmic gamma radiation. Samples of several materials were flown aboard Skylab to obtain measures of the neutron and proton flux environment. Extremely weak activity was produced in the samples. Calculations of interactions of intermediate-energy protons with light nuclei were performed and a more complete theoretical model programmed for digital computation. Preliminary results appear promising for calculating products of such interactions.

Source record↗