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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 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Determination of air-kerma strength for the {sup 192}Ir GammaMedplus iX pulsed-dose-rate brachytherapy source

Purpose: Pulsed-dose-rate (PDR) brachytherapy was originally proposed to combine the therapeutic advantages of high-dose-rate (HDR) and low-dose-rate brachytherapy. Though uncommon in the United States, several facilities employ pulsed-dose-rate brachytherapy in Europe and Canada. Currently, there is no air-kerma strength standard for PDR brachytherapy {sup 192}Ir sources traceable to the National Institute of Standards and Technology. Discrepancies in clinical measurements of the air-kerma strength of the PDR brachytherapy sources using HDR source-calibrated well chambers warrant further investigation.Methods: In this research, the air-kerma strength for an {sup 192}Ir PDR brachytherapy source was compared with the University of Wisconsin Accredited Dosimetry Calibration Laboratory transfer standard well chambers, the seven-distance technique [B. E. Rasmussen et al., 'The air-kerma strength standard for 192Ir HDR sources,' Med. Phys. 38, 6721-6729 (2011)], and the manufacturer's stated value. Radiochromic film and Monte Carlo techniques were also employed for comparison to the results of the measurements.Results: While the measurements using the seven-distance technique were within + 0.44% from the manufacturer's determination, there was a + 3.10% difference between the transfer standard well chamber measurements and the manufacturer's stated value. Results showed that the PDR brachytherapy source has geometric and thus radiological qualities that exhibit behaviors similar to a point source model in contrast to a conventional line source model.Conclusions: The resulting effect of the pointlike characteristics of the PDR brachytherapy source likely account for the differences observed between well chamber and in-air measurements.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2015

HDR {sup 192}Ir source speed measurements using a high speed video camera

Purpose: The dose delivered with a HDR {sup 192}Ir afterloader can be separated into a dwell component, and a transit component resulting from the source movement. The transit component is directly dependent on the source speed profile and it is the goal of this study to measure accurate source speed profiles. Methods: A high speed video camera was used to record the movement of a {sup 192}Ir source (Nucletron, an Elekta company, Stockholm, Sweden) for interdwell distances of 0.25–5 cm with dwell times of 0.1, 1, and 2 s. Transit dose distributions were calculated using a Monte Carlo code simulating the source movement. Results: The source stops at each dwell position oscillating around the desired position for a duration up to (0.026 ± 0.005) s. The source speed profile shows variations between 0 and 81 cm/s with average speed of ∼33 cm/s for most of the interdwell distances. The source stops for up to (0.005 ± 0.001) s at nonprogrammed positions in between two programmed dwell positions. The dwell time correction applied by the manufacturer compensates the transit dose between the dwell positions leading to a maximum overdose of 41 mGy for the considered cases and assuming an air-kerma strength of 48 000 U. The transit dose component is not uniformly distributed leading to over and underdoses, which is within 1.4% for commonly prescribed doses (3–10 Gy). Conclusions: The source maintains its speed even for the short interdwell distances. Dose variations due to the transit dose component are much lower than the prescribed treatment doses for brachytherapy, although transit dose component should be evaluated individually for clinical cases.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2019

Remote detection of radioactive material using mid-IR laser–driven electron avalanche

Remote detection of a distant, shielded sample of radioactive material is an important goal, but it is made difficult by the finite spatial range of the decay products. Here, we present a proof-of-principle demonstration of a remote detection scheme using mid-infrared (mid-IR) (λ = 3.9 μm) laser–induced avalanche breakdown of air. In the scheme’s most basic version, we observe on-off breakdown sensitivity to the presence of an external radioactive source. In another realization of the technique, we correlate the shift of the temporal onset of avalanche to the degree of seed ionization from the source. We present scaling of the interaction with laser intensity, verify observed trends with numerical simulations, and discuss the use of mid-IR laser–driven electron avalanche breakdown to detect radioactive material at range.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Synthesis, Structure, IR-Spectroscopic Characterization, and Ionic Conductivity of Mg{sub 0.5}Zr{sub 2}(AsO{sub 4}){sub x}(PO{sub 4}){sub 3−x}

Mg{sub 0.5}Zr{sub 2}(AsO{sub 4}){sub x}(PO{sub 4}){sub 3−x} arsenate phosphates have been prepared by a sol–gel process and characterized by X-ray diffraction, IR spectroscopy, and impedance spectroscopy. The results indicate the formation of a continuous series of solid solutions with the Sc{sub 2}(WO{sub 4}){sub 3} structure (sp. gr. P2{sub 1/n}) in the composition range 0 < x < 3. The unit-cell parameters of the solid solutions increase linearly with composition, as a consequence of arsenic substitution for phosphorus, which has a smaller ionic radius. The number of observed stretching and bending bands of the AsO{sub 4}{sup 3-} and PO{sub 4}{sup 3-} ions in the IR spectra of the solid solutions agrees with that predicted by factor group analysis for space group P2{sub 1/n}. The observed gradual shift of the absorption bands of the AsO{sub 4} tetrahedra to lower frequencies with increasing arsenic content on the tetrahedral site supports the X-ray diffraction evidence of the formation of substitutional solid solutions. The cation conductivity of Mg{sub 0.5}Zr{sub 2}(AsO{sub 4}){sub x}(PO{sub 4}){sub 3−x} with 0 ≤ х ≤ 1 has been shown to exceed the conductivity of the parent magnesium zirconium arsenate.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Investigation of Deuterium Substitution Effects in a Polymer Membrane Using IR Fourier Spectrometry

Experiments on IR Fourier spectrometry of a Nafion polymer membrane swollen in water are described. The dynamics of Nafion swelling is studied in relation to the deuterium content in water. It has turned out that, if the polymer swells in waters with different deuterium contents, a considerable confinement effect is observed, which, in this case, manifests itself in that the transmittance of IR radiation of water that is enclosed within a region with a size of ~100 μm differs from that of water that is inside nanometer pores of the polymer membrane. In addition, the transmittance of Nafion swollen in water measured at a wavelength of λ = 1.92 μm (spectral minimum) experiences a local minimum in the deuterium concentration range 10{sup 2} < C < 10{sup 3} ppm, irrespective of the soaking time of the polymer in deuterated water. Finally, the effect of the deuterium substitution of the residual water present in the volume of the membrane has been revealed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Control of the clustering process in molecular beams using IR lasers

The control of clustering in molecular beams with the help of IR lasers is experimentally studied. Studies were performed with a molecular CF{sub 3}I gas diluted with argon or xenon using a cw CO{sub 2} laser. The control of clustering is based on the resonance vibrational excitation of molecules or clusters by the IR laser radiation near the nozzle exit. Depending on the distance from the excitation region to the nozzle cut, the irradiation of the molecular beam either suppresses the clustering of resonantly excited molecules (when the beam is irradiated near the nozzle exit where clustering occurs) or causes the dissociation of small clusters (when the beam is irradiated away from the nozzle where clustering is at the growth stage). The suppression of molecular clustering and the dissociation of clusters in beams were studied by measuring and analyzing the integrated intensities of ion peaks of cluster fragments with a time-of-flight spectrometer. The efficiencies of clustering suppression and cluster dissociation were studied as functions of exciting laser radiation parameters, the beam irradiation geometry, gas parameters over the nozzle, and the nozzle construction. It is shown that the efficiencies of clustering suppression and cluster dissociation strongly depend on the exciting laser radiation intensity, the nozzle construction, and the distance from the irradiation region to the nozzle cut. Parameters providing the most efficient control of clustering suppression and cluster dissociation are found.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

IR Laser Control of the Clustering of CF{sub 3}Br Molecules during the Gas-Dynamic Expansion of a CF{sub 3}Br/Ar Mixture: Bromine Isotope Selectivity

The infrared (IR) laser radiation control of the clustering of CF3Br molecules during the gas-dynamic expansion of a CF{sub 3}Br/Ar mixture at the exit from a nozzle is investigated. Prominence is given to studying the possibility of bromine-isotope-selective suppression of the clustering of CF{sub 3}Br molecules due to their resonance vibrational excitation in the gas-dynamic expansion zone near the nozzle. A continuous CO{sub 2} laser is used in experiments to excite molecules and clusters in a beam, and a quadrupole mass spectrometer is used to detect them. The experimental setup and the experimental technique are described. The dependences of the efficiency of molecule clustering suppression on the exciting laser radiation parameters, the gas parameters (composition, pressure) above the nozzle, and the distance from the nozzle exit section to a molecule irradiation zone are obtained. Bromine-isotope-selective suppression of molecule clustering is shown to occur at the exit from the nozzle due to the resonance vibrational excitation of gas-dynamically cooled CF{sub 3}Br molecules. When CF{sub 3}Br/Ar mixtures are used at pressure ratios p(CF{sub 3}Br): p(Ar) = 1: 10 and 1: 30, the enrichment of a cluster beam by bromine isotopes are K{sub enr}({sup 81}Br) ≈ 1.18 ± 0.09 and 1.12 ± 0.07 during the 9R(30) laser line (1084.635 cm{sup –1}) irradiation of a jet. The clustering suppression selectivity is α ≈ 1.18 when the mixture at the pressure ratio p(CF{sub 3}Br): p(Ar) = 1: 10 is used. These results suggest that the proposed method can selectively control the clustering of the molecules containing the heavy element isotopes that have a small isotope shift in IR absorption spectra (OsO{sub 4}, WF{sub 6}, UF{sub 6}).

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Experimental investigation of neutronic characteristics of the IR-8 reactor to confirm the results of calculations by MCU-PTR code

A comparison of measured and calculated neutronic characteristics (fast neutron flux and fission rate of {sup 235}U) in the core and reflector of the IR-8 reactor is presented. The irradiation devices equipped with neutron activation detectors were prepared. The determination of fast neutron flux was performed using the {sup 54}Fe (n, p) and {sup 58}Ni (n, p) reactions. The {sup 235}U fission rate was measured using uranium dioxide with 10% enrichment in {sup 235}U. The determination of specific activities of detectors was carried out by measuring the intensity of characteristic gamma peaks using the ORTEC gamma spectrometer. Neutron fields in the core and reflector of the IR-8 reactor were calculated using the MCU-PTR code.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2013

Photonic crystals and Bragg gratings for the mid-IR and terahertz spectral ranges

A method for the fabrication of 2D periodic structures by contact optical photolithography with image inversion is reported. The optical properties of photonic crystals and Bragg gratings for mid-IR and terahertz emitters are considered. The possibility of raising the integral emission intensity of light-emitting diodes for the mid-IR spectral range is demonstrated. The requirements to gratings for the output of terahertz emission generated by surface plasmons excited in layers of narrow-gap degenerate semiconductors with an accumulation layer are determined.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Investigation of the Far-IR Reflection Spectra of SmS Single Crystals and Polycrystals in the Homogeneity Range

The far- and mid-IR reflection spectra of Sm{sub 1+} {sub x}S (x = 0–0.17) samples are recorded and analyzed, as well as their electrical and structural parameters at a temperature of T = 300 K. The bond ionicity in SmS is shown to fall with a decrease in the area of the X-ray coherent scattering region and an increase in the concentration of donor impurities and, consequently, conduction electron concentration. The electrical conductivity of stoichiometric SmS single crystals and polycrystals can be determined with an error of 10% from the IR reflection spectra. Due to the low structural quality of the samples, the electrical conductivity cannot be determined in the case of deviation from stoichiometry.

36 MATERIALS SCIENCE↗
DOE OSTI2018

IR Spectroscopy for Precision Monitoring of Iron and Chromium Impurity Diffusion Profiles in Zinc Chalcogenides

A technique for precision rapid nondestructive monitoring of the dopant behavior in zinc chalcogenide–based laser media is reported. Results suggest that it is possible to determine the concentration profiles of Fe{sup 2+} and Cr{sup 2+} dopant ions in zinc chalcogenide by IR spectroscopy combined with an IR microscope in the concentration rage 5 × 10{sup 17}–2.5 × 10{sup 20} atoms/cm{sup 3} with a spatial resolution of several micrometers. The diffusion profiles of dopants have been taken for zinc chalcogenide codoped by several impurities.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Adsorptive interaction of bisphenol A with mesoporous titanosilicate/reduced graphene oxide nanocomposite materials: FT-IR and Raman analyses

Nanocomposite materials containing graphene oxide have attracted tremendous interest as catalysts and adsorbents for water purification. In this study, mesoporous titanosilicate/reduced graphene oxide composite materials with different Ti contents were employed as adsorbents for removing bisphenol A (BPA) from water systems. The adsorptive interaction between BPA and adsorption sites on the composite materials was investigated by Fourier transform infrared (FT-IR) and Raman spectroscopy. Adsorption capacities of BPA at equilibrium, qe (mg/g), decreased with increasing Ti contents, proportional to the surface area of the composite materials. FT-IR observations for fresh and spent adsorbents indicated that BPA adsorbed onto the composite materials by the electrostatic interaction between OH functional groups contained in BPA and on the adsorbents. The electrostatic adsorption sites on the adsorbents were categorized into three hydroxyl groups: Si-OH, Ti-OH, and graphene-OH. In Raman spectra, the intensity ratios of D to G band were decreased after the adsorption of BPA, implying adsorptive interaction of benzene rings of BPA with the sp 2 hybrid structure of the reduced graphene oxide.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Measurement of ultralow radiation-induced charge densities using picosecond mid-IR laser-induced breakdown

We demonstrate that avalanche ionization breakdown of air with picosecond mid-infrared (mid-IR) laser pulses is an exceptionally sensitive and quantitative probe of extremely low concentrations of charged species. By exponentially increasing the electron density in the vicinity of a single seed atom or molecule to detectable levels, mid-IR electron avalanche is an analogue of single photon detection in photomultiplier tubes and can be useful in a range of applications. We apply the technique to meter-scale standoff detection of a radioactive source, sensitive to extremely low concentrations of radiation-induced negative ions down to ~ 10 3 cm - 3 , limited only by background. By imaging the location of spatially isolated avalanche breakdown sites, we directly measure these low densities and benchmark the performance of standoff detection diagnostics. We discuss implementation of this radiation detection scheme at ranges of 10–100 m and adapting the avalanche probe to detection of other low-density plasmas.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2013

Structural analysis of an ancient pottery by using FT-IR technique

Pottery artifacts are one of the most abundant findings among archaeological artifacts and their analysis can reveal information regarding daily life of that society. The composition of the artifact can be correlated to the age in which it was created. The authenticity of the artifact is also important. Forgers can “touch up” artifacts to make them appear original. FT-IR is a useful method to investigate the structure, bonding and chemical properties of materials and is used for the analysis of art and historical objects in support of efforts to conserve, restore, and validate authenticity of these rare objects. Generally, the minerals found in the pottery can be classified into primary minerals, firing minerals, and secondary minerals. The identification of firing minerals is essential requirement for the clarification of firing temperature which provides understanding of the civilization that created the potteries. Qualitative and also quantitative techniques such as XRD and bench top FTIR spectrometers are often not destructive but require a small amount of the sample to be separated from the material, in this case artifact. On the other hand, hand held FT-IR offers a method that is not invasive. The piece of the pottery used in the present study is shown in fig.1. The pot contains black, white, and brown decorations. The areas analyzed were mapped over the different colored decorations. This was done to determine the consistency of the composition of the pot. This can ultimately be used to determine if the pot was made at the same time.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Low Dose IR Creates an Oncogenic Microenvironment by Inducing Premature

Much of the work addressing ionizing radiation-induced cellular response has been carried out mainly with the traditional cell culture technique involving only one cell type, how cellular response to IR is influenced by the tissue microenvironment remains elusive. By use of a three-dimensional (3D) co-culture system to model critical interactions of different cell types with their neighbors and with their environment, we recently showed that low-dose IR-induced extracellular signaling via the tissue environment affects profoundly cellular responses. This proposal aims at determining the response of mammary epithelial cells in a tissue-like setting.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2014

Accelerated Aging of BKC 44306-10 Rigid Polyurethane Foam: FT-IR Spectroscopy, Dimensional Analysis, and Micro Computed Tomography

An accelerated aging study of BKC 44306-10 rigid polyurethane foam was carried out. Foam samples were aged in a nitrogen atmosphere at three different temperatures: 50 °C, 65 °C, and 80 °C. Foam samples were periodically removed from the aging canisters at 1, 3, 6, 9, 12, and 15 month intervals when FT-IR spectroscopy, dimensional analysis, and mechanical testing experiments were performed. Micro Computed Tomography imaging was also employed to study the morphology of the foams. Over the course of the aging study the foams the decreased in size by a magnitude of 0.001 inches per inch of foam. Micro CT showed the heterogeneous nature of the foam structure likely resulting from flow effects during the molding process. The effect of aging on the compression and tensile strength of the foam was minor and no cause for concern. FT-IR spectroscopy was used to follow the foam chemistry. However, it was difficult to draw definitive conclusions about the changes in chemical nature of the materials due to large variability throughout the samples.

36 MATERIALS SCIENCE↗
DOE OSTI2015

XPS and IR Characterization of Ultra-High Molecular Weight Polyethylene

We used x-ray photoelectron spectroscopy (XPS) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) to characterize samples of 3-mil thick rolled sheets of ultrahigh molecular weight polyethylene (UHMWPE). The purpose of the XPS work was to determine the surface composition of the UHMWPE and determine if any impurities (particularly halogens) were consistently present of the surface of the sheet. XPS results indicate as-received UHMWPE is reasonably clean, but somewhat inhomogeneous. Some as-received samples contain small amounts of silicon, chlorine, and sodium, while others only contain carbon and oxygen (as expected for ambient exposed plastic). Both ethanol wiping and ethanol sonication effectively remove the Si, Cl, and Na impurities. Additionally, these impurities are not detected by XPS after the top 20nm of material is ablated from as-received sample surfaces. These results suggest the impurities are surface contaminants arising from sample handling and/or ambient exposure. The purpose of the IR work was to collect baseline spectra of the UHMWPE for match factor comparison against known polyethylene materials. The IR spectra for all UHMWPE samples are similar to one another and to known polyethylene materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Multimodal Instrument Platform for High-Pressure MAS-NMR and IR Spectroscopic Interrogation

This project developed and tested a high-pressure (HP) flow-through instrument platform that combines HP- magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy for interrogating reactivity at interfaces between solid materials and HP fluids with HP- infrared (IR) spectroscopy for measuring fluid composition. Solid-fluid interfacial reactivity is usually dependent on concentrations of species within the fluid; thus, knowledge of the fluid composition measured by IR is critical to understanding solid-fluid interfacial reactivity probed by NMR. This new system adds to PNNL’s core capabilities in Chemical and Material Sciences to support fundamental programs in catalysis, interfacial molecular science, and geosciences, as well as in Earth and Biological Sciences to support energy production and storage, efforts to mitigate the impacts energy production systems, attenuation of contaminant plumes, and design of subsurface engineered systems for energy production and waste disposal.

36 MATERIALS SCIENCE↗