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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 1,693 records · Page 94
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

Structure determination of thin CoFe films by anomalous x-ray diffraction

This work reports on the investigation of structure-property relationships in thin CoFe films grown on MgO. Because of the very similar scattering factors of Fe and Co, it is not possible to distinguish the random A2 (W-type) structure from the ordered B2 (CsCl-type) structure with commonly used x-ray sources. Synchrotron radiation based anomalous x-ray diffraction overcomes this problem. It is shown that as grown thin films and 300 K post annealed films exhibit the A2 structure with a random distribution of Co and Fe. In contrast, films annealed at 400 K adopt the ordered B2 structure.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2012

A von Hamos x-ray spectrometer based on a segmented-type diffraction crystal for single-shot x-ray emission spectroscopy and time-resolved resonant inelastic x-ray scattering studies

We report on the design and performance of a wavelength-dispersive type spectrometer based on the von Hamos geometry. The spectrometer is equipped with a segmented-type crystal for x-ray diffraction and provides an energy resolution in the order of 0.25 eV and 1 eV over an energy range of 8000 eV-9600 eV. The use of a segmented crystal results in a simple and straightforward crystal preparation that allows to preserve the spectrometer resolution and spectrometer efficiency. Application of the spectrometer for time-resolved resonant inelastic x-ray scattering and single-shot x-ray emission spectroscopy is demonstrated.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

Diffractive Higgs production at LHC: A case study

We discuss the case of the diffractive Higgs production at LHC. Aim of this talk is to propose the method of using Fracture Functions as an alternative to the ones already present in the literature. We discuss some of the questions involved and the main related issues.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

ATLAS measurements of soft particle production and diffraction

The ATLAS Collaboration has measured a wide range of properties of soft particle production in {radical}(s) = 900GeV and {radical}(s) = 7TeV proton-proton collisions at the Large Hadron Collider (LHC). These include forward-backward and azimuthal correlations, azimuthal ordering of hadron production, underlying event properties and their dependence on aspects of the hard scattering process. The inelastic and diffractive cross sections have also been measured, using particle forward flow and rapidity gaps. Many of these measurements are used to develop and tune models for soft particle production.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Integration of a broad beam ion source with a high-temperature x-ray diffraction vacuum chamber

Here, the integration of a low energy, linearly variable ion beam current density, mechanically in situ adjustable broad beam ion source with a high-temperature x-ray diffraction (XRD) vacuum chamber is reported. This allows in situ XRD investigation of phase formation and evolution processes induced by low energy ion implantation. Special care has been taken to an independent adjustment of the ion beam for geometrical directing towards the substrate, a 15 mm small ion source exit aperture to avoid a secondary sputter process of the chamber walls, linearly variable ion current density by using a pulse length modulation (PLM) for the accelerating voltages without changing the ion beam density profile, nearly homogeneous ion beam distribution over the x-ray footprint, together with easily replaceable Kapton{sup Registered-Sign} windows for x-rays entry and exit. By combining a position sensitive x-ray detector with this PLM-modulated ion beam, a fast and efficient time resolved investigation of low energy implantation processes is obtained in a compact experimental setup.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

Experimental investigations of the TE{sub 11} mode radiation from a relativistic magnetron with diffraction output

Directly radiating microwaves at TE{sub 11} mode, a relativistic magnetron with diffraction output (MDO) is experimentally investigated. Two important factors, transition section and working condition, significantly affecting the microwave powers, efficiencies, and pulse durations are analyzed. The experimental results on our designed MDO show that the optimized transition section with the parameters, 46 mm in height and 70 mm in length, is beneficial for producing high power TE{sub 11} mode microwaves. Under the low applied voltage condition (less than 650 kV), the power conversion efficiency will be higher than that obtained from the high applied voltage condition. {approx}24 ns of the microwave duration is a typical value under the voltage duration of 56 ns. Pulse shortens will happen if the applied voltage is higher than 650 kV. When the applied voltage reaches 880 kV, the microwave duration is only just {approx}12 ns. Impendence mismatch between the accelerator and the diode is the chief reason causing the pulse shortens.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

Coherent femtosecond low-energy single-electron pulses for time-resolved diffraction and imaging: A numerical study

We numerically investigate the properties of coherent femtosecond single electron wave packets photoemitted from nanotips in view of their application in ultrafast electron diffraction and non-destructive imaging with low-energy electrons. For two different geometries, we analyze the temporal and spatial broadening during propagation from the needle emitter to an anode, identifying the experimental parameters and challenges for realizing femtosecond time resolution. The simple tip-anode geometry is most versatile and allows for electron pulses of several ten of femtosecond duration using a very compact experimental design, however, providing very limited control over the electron beam collimation. A more sophisticated geometry comprising a suppressor-extractor electrostatic unit and a lens, similar to typical field emission electron microscope optics, is also investigated, allowing full control over the beam parameters. Using such a design, we find {approx}230 fs pulses feasible in a focused electron beam. The main limitation to achieve sub-hundred femtosecond time resolution is the typical size of such a device, and we suggest the implementation of more compact electron optics for optimal performance.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

Three-dimensional imaging of dislocations by X-ray diffraction laminography

Synchrotron radiation laminography with X-ray diffraction contrast enables three-dimensional imaging of dislocations in monocrystalline wafers. We outline the principle of the technique, the required experimental conditions, and the reconstruction procedure. The feasibility and the potential of the method are demonstrated by three-dimensional imaging of dislocation loops in an indent-damaged and annealed silicon wafer.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2013

X-ray diffraction and extended X-ray absorption fine structure study of epitaxial mixed ternary bixbyite Pr{sub x}Y{sub 2-x}O{sub 3} (x = 0-2) films on Si (111)

Ternary single crystalline bixbyite Pr{sub x}Y{sub 2-x}O{sub 3} films over the full stoichiometry range (x = 0-2) have been epitaxially grown on Si (111) with tailored electronic and crystallographic structure. In this work, we present a detailed study of their local atomic environment by extended X-ray absorption fine structure at both Y K and Pr L{sub III} edges, in combination with complementary high resolution x-ray diffraction measurements. The local structure exhibits systematic variations as a function of the film composition. The cation coordination in the second and third coordination shells changes with composition and is equal to the average concentration, implying that the Pr{sub x}Y{sub 2-x}O{sub 3} films are indeed fully mixed and have a local bixbyite structure with random atomic-scale ordering. A clear deviation from the virtual crystal approximation for the cation-oxygen bond lengths is detected. This demonstrates that the observed Vegard's law for the lattice variation as a function of composition is based microscopically on a more complex scheme related to local structural distortions which accommodate the different cation-oxygen bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Investigation of the near-surface structures of polar InN films by chemical-state-discriminated hard X-ray photoelectron diffraction

Near-surface structures of polar InN films were investigated by laboratory-based hard X-ray photoelectron diffraction (HXPD) with chemical-state-discrimination. HXPD patterns from In 3d{sub 5/2} and N 1s core levels of the In-polar and N-polar InN films were different from each other and compared with the simulation results using a multiple-scattering cluster model. It was found that the near-surface structure of the In-polar InN film was close to the ideal wurtzite structure. On the other hand, on the N-polar InN film, defects-rich surface was formed. In addition, the existence of the In-polar domains was observed in the HXPD patterns.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2013

An in situ diffraction study of domain wall motion contributions to the frequency dispersion of the piezoelectric coefficient in lead zirconate titanate

The contribution of non-180 Degree-Sign domain wall displacement to the frequency dependence of the longitudinal piezoelectric coefficient has been determined experimentally in lead zirconate titanate using time-resolved, in situ neutron diffraction. Under subcoercive electric fields of low frequencies, approximately 3% to 4% of the volume fraction of non-180 Degree-Sign domains parallel to the field experienced polarization reorientation. This subtle non-180 Degree-Sign domain wall motion directly contributes to 64% to 75% of the magnitude of the piezoelectric coefficient. Moreover, part of the 33 pm/V decrease in piezoelectric coefficient across 2 orders of magnitude in frequency is quantitatively attributed to non-180 Degree-Sign domain wall motion effects.

36 MATERIALS SCIENCE↗
DOE OSTI2013

In-situ study of the growth of CuO nanowires by energy dispersive X-ray diffraction

Growth of CuO nanowires by annealing method has been studied in-situ by grazing incidence Energy Dispersive X-ray Diffraction (EDXRD) technique on Indus-2. It was observed that Cu slowly oxidized to Cu{sub 2}O and finally to CuO. The data was taken as a function of time at two annealing temperatures 500 Degree-Sign C where nanowires form and 300 Degree-Sign C where nanowires don't form. We found that the strain in the CuO layer may be a principal factor for the spontaneous growth of nanowires in annealing method.

36 MATERIALS SCIENCE↗
DOE OSTI2013

An experimental system for high temperature X-ray diffraction studies with in situ mechanical loading

An experimental system with in situ thermomechanical loading has been developed to enable high energy synchrotron x-ray diffraction studies of crystalline materials. The system applies and maintains loads of up to 2250 N in uniaxial tension or compression at a frequency of up to 100 Hz. The furnace heats the specimen uniformly up to a maximum temperature of 1200 Degree-Sign C in a variety of atmospheres (oxidizing, inert, reducing) that, combined with in situ mechanical loading, can be used to mimic processing and operating conditions of engineering components. The loaded specimen is reoriented with respect to the incident beam of x-rays using two rotational axes to increase the number of crystal orientations interrogated. The system was used at the Cornell High Energy Synchrotron Source to conduct experiments on single crystal silicon and polycrystalline Low Solvus High Refractory nickel-based superalloy. The data from these experiments provide new insights into how stresses evolve at the crystal scale during thermomechanical loading and complement the development of high-fidelity material models.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Millimeter wave scattering and diffraction in 110 GHz air breakdown plasma

We present measurements of the scattering, reflection, absorption, and transmission of a 1.5 MW, 110 GHz quasioptical gyrotron beam by a self-induced air breakdown plasma. The breakdown forms a periodic array of plasma filaments, oriented parallel to the incident electric field polarization that propagates toward the microwave source. For incident intensity of 3 MW/cm{sup 2}, calorimetric measurements show that as much as 45% of the full beam power is absorbed by the plasma, averaged over the pulse, 1% is reflected backward, and the remainder is transmitted and also scattered into a wide angular spread. We observe that approximately 10 times more power is scattered in the direction perpendicular to the filaments than parallel. The far-field angular distribution of transmitted power exhibits a diffraction pattern that changes throughout the 2-{mu}s life of the plasma.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Diffractive {rho} production with an AdS/QCD holographic wavefunction for the {rho} meson

We report on the results of our recent research published in [1] that shows that AdS/QCD generates predictions for the rate of diffractive {rho}-meson electroproduction that are in agreement with data collected at the HERA electron-proton collider [2, 3]. Preliminary results of this research were presented in [4].

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗