Search NASA⌕ Search

SEARCH · Search NASA

Results for “MONOCHROMATIC RADIATION”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

A Paris-Edinburgh Cell for High-Pressure and High-Temperature Structure Studies on Silicate Liquids Using Monochromatic Synchrotron Radiation

A Paris-Edinburgh press combined with a multi-channel collimator assembly has been commissioned at the GeoSoilEnviro Center for Advanced Radiation Sources (GSECARS) beamline for monochromatic X-ray scattering, with an emphasis on studying low-Z liquids, especially silicate liquids at high pressure. The Paris-Edinburgh press is mounted on a general-purpose diffractometer, with a pixel array detector mounted on the detector arm. The incident monochromatic undulator beam with energies up to 60 keV is focused both horizontally and vertically to a beam size about 30 × 30 µm. With this setup, background scattering from the surrounding pressure media is completely removed at 2θ angles above 10° for samples larger than 1.05 mm in diameter. Thirty minutes is typically sufficient to collect robust X-ray scattering signals from a 1.6 mm diameter amorphous silicate sample. Cell assemblies for the standard Paris-Edinburgh anvils have been developed and pressures and temperatures up to 7 GPa and 2300 K, respectively, have been maintained steadily over hours. We have also developed a cupped-toroidal Drickamer anvil to further increase pressure and temperature capabilities. The cupped-toroidal Drickamer anvil combines features of a modified Drickamer anvil and the traditional Paris-Edinburgh anvil. Pressures up to 12 GPa have been generated at temperatures up to 2100 K.

58 GEOSCIENCES↗
DOE OSTI2018

Attenuation of Scattered Monochromatic Synchrotron Radiation in Iron and Lead

Attenuation curves have been calculated with STAC8 for photon radiation scattered by silicon target. Monochromatic beam with energies from 20 keV to 150 keV has been considered. The materials studies were those typical of hutch shielding (iron or lead). Three examples, showing how to use these curves for shielding design are included.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Phase transition in two-dimensional monolayer (1L)-molybdenum disulfide induced by atomic S-basal plane gliding via synchrotron X-ray monochromatic beam radiation for superior electronic performance

Here, in this work, we report a novel approach to reduce the channel resistance by inducing a phase transition behavior from 2H to 1T in a monolayer MoS 2 (1L-MoS 2 ) by a synchrotron X-ray monochromatic beam (mono-beam) radiation. The effects of the biphase structure by the mono-beam on the 1L-MoS2 film were investigated using Raman spectra, photoluminescence (PL) spectra, scanning tunneling microscopy, and scanning tunneling spectroscopy, respectively. Through material characterization, we identified that the lateral sliding of S-vacancies along the S-plane in the 1L-MoS 2 is the key reason for the origin of unidirectional phase transition. The precise phase engineering triggered by the mono-beam radiation process allows the realization of field-effect transistors (FET) with 2X improvement in mobility toward a high on/off ratio (~10 8 ) and a near-ideal subthreshold swing of ~88 mV per decade. The validity of the phase engineering could be further extended for its application as a memory device, exhibiting a gate tunable conduction modulation behavior and a high resistance ratio of ~10 2 at a gate bias of 5 V with endurance of ~100 cycles. Furthermore, an artificial neural network using the synaptic weight update with accuracy of ~93 % was achieved.

36 MATERIALS SCIENCE↗
DOE OSTI2017

On contrast of biological X-ray nanomicroscopy

We analyse the absorption contrast of histological and cytological preparations, which can be achieved in nanomicroscopic studies using monochromatic radiation in the spectral range of 90 – 600 eV (14 – 2 nm). Two types of unstained biological objects are considered: untreated and fixed in paraffin, and optimum wavelengths are determined for the study of samples with a thickness of 0.5 – 10 μm with a spatial resolution of 100 – 20 nm. Taking into account the efficiency of X-ray optics, the number of source photons required to produce a single image is estimated. It is shown that the greatest interest for the study of fixed objects represents the spectral region of 7 – 14 nm, for which, on the basis of rapidly developing compact sources of incoherent and coherent radiation and effective optics, microscopes for scientific and clinical research can be designed. (paper)

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Photovoltaic Characteristics of AlGaAs-Based LEDs

Photovoltaic characteristics of more than 20 types of AlGaAs-based light-emitting diodes operating in the 830- to 970-nm wavelength range have been considered. It is established that Al{sub x}Ga{sub 1–} {sub x}As semiconductor structures employed in these devices can also be used for manufacturing photovoltaic converters of monochromatic radiation with quite high efficiency.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Anomalous scattering, transport, and spatial distribution of X-ray fluorescence at the exit of polycapillary structures

The angular distribution of the X-ray intensity at the exit of microchannel plates at grazing incidence of monochromatic radiation on the walls of microcapillaries has been investigated. The angles and energies of the primary radiation quanta at which the synchrotron beam excites X-ray fluorescence propagating inside polycapillary structures have been determined. The angular dependences of the intensity distribution of X-rays transmitted through the microcapillaries have been studied theoretically and experimentally for energies corresponding to the region of anomalous dispersion near the L{sub 2,3} absorption edges of silicon. The propagation of waves in hollow polycapillary waveguides, the excitation of X-ray fluorescence, and the X-ray diffraction at the exit of microchannel plates have been modeled mathematically. The mathematical model takes into account the presence of a transition layer on the microchannel surface.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Phase Identification in Synchrotron X-ray Diffraction Patterns of Ti–6Al–4V Using Computer Vision and Deep Learning

X-ray diffraction patterns contain information about the atomistic structure and microstructure (defect population) of materials, extracting detailed information from diffraction patterns is complex, demanding and relies on prior knowledge. Here, we hypothesize that deep-learning techniques can help to perform an effective and accurate analysis with high throughput rates. To demonstrate this concept, we applied a novel deep learning framework to determine the evolution of the β-phase volume fraction in a Ti–6Al–4V alloy during heat-treatment from video sequences of 2D diffraction patterns recorded in transmission and with highly monochromatic radiation in a synchrotron beamline. In particular, we studied the impact of network design on prediction reliability and computational performance. Networks of different architectures were trained using 3008 experimental 2D patterns. A well-tuned model was found to reproduce the phase fractions of another experimental data set, consisting of 1100 diffraction patterns, with a mean-square error as small as 2.6 x 10 -4 . The average prediction error of β-phase volume fraction was within 1.6 x 10 -2 (in each diffraction pattern) of the values obtained by conventional methods. Our work demonstrates that convolutional neural networks can evaluate high energy X-ray diffraction patterns with a remarkable level of reliability. Furthermore, it demonstrates the significance of network design on the reliability of predictions and computational performance. The most complex models do not necessarily result in highest accuracy and may even fail to learn from the data.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Pink-beam serial crystallography

Serial X-ray crystallography allows macromolecular structure determination at both X-ray free electron lasers (XFELs) and, more recently, synchrotron sources. The time resolution for serial synchrotron crystallography experiments has been limited to millisecond timescales with monochromatic beams. The polychromatic, “pink”, beam provides a more than two orders of magnitude increased photon flux and hence allows accessing much shorter timescales in diffraction experiments at synchrotron sources. Here we report the structure determination of two different protein samples by merging pink-beam diffraction patterns from many crystals, each collected with a single 100 ps X-ray pulse exposure per crystal using a setup optimized for very low scattering background. In contrast to experiments with monochromatic radiation, data from only 50 crystals were required to obtain complete datasets. The high quality of the diffraction data highlights the potential of this method for studying irreversible reactions at sub-microsecond timescales using high-brightness X-ray facilities.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

Energy scale calibration of the KEDR tagging system

The KEDR detector tagging system is a symmetric focusing magnetic spectrometer of small-angle electrons born in the interaction region of the VEPP-4M collider. Using this system, which is designed for studying the two-photon processes, the scattered electrons and positrons energy is measured with a resolution of ΔE/E{sub 0}= 0.03–0.6% where E{sub 0} is the beam energy. Two different methods are employed for calibrating the tagging system energy scale: the first one involves the electron/positron tagging by the energy of the singlebremsstrahlung photon measured in the BGO calorimeter, and the second one is based on the determination of the recoil electrons spectrum edge in the Compton backscattering of monochromatic laser radiation. The technical implementation and the present status of the calibration system are discussed in this paper.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

X-RAY IRRADIATION OF H{sub 2}O + CO ICE MIXTURES WITH SYNCHROTRON LIGHT

We irradiated a (4:1) mixture of water and carbon monoxide with soft X-rays of energies up to 1.2 keV. The experiments were performed using the spherical grating monochromator beamline at National Synchrotron Radiation Research Center in Taiwan. Both monochromatic (300 and 900 eV) and broader energy fluxes (250–1200 eV) were employed. During the irradiation, the H{sub 2}O + CO mixture was ionized, excited, and fragmented, producing a number of reactive species. The composition of the ice has been monitored throughout both the irradiation and warm-up phases. We identified several products, which can be related through a plausible chemical reaction scheme. Such chemistry is initiated by the injection of energetic photoelectrons that produce multiple ionization events generating a secondary electron cascade. The results have been discussed in light of a model for protoplanetary disks around young solar-type stars.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2020

Production of two-colour radiation with polarisations of components rotating in opposite directions

A method is proposed for the production of two-colour radiation with monochromatic components, the polarisation vectors of which rotate in opposite directions, and the rotation speed is controlled by the sound frequency. The method is based on acousto-optic (AO) interaction upon double passage of two-colour radiation through an AO cell made of a gyrotropic crystal; the method efficiency is demonstrated by the example of radiation from an Ar laser generating at wavelengths of 0.488 and 0.514 μm and an AO cell made of TeO{sub 2}, operating at a sound frequency of 60 MHz. (paper)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

CHEMICAL EVOLUTION OF A CO ICE INDUCED BY SOFT X-RAYS

We irradiated a pure carbon monoxide ice with soft X-rays of energies up to 1.2 keV. The experiments were performed using the spherical grating monochromator beamline at the National Synchrotron Radiation Research Center in Taiwan, exploiting both monochromatic (at 0.3 and 0.55 keV) and broader energy (0.25–1.2 keV) fluxes. The infrared spectra of the irradiated ices showed the formation of a number of products such as polycarbon mono- and dioxides C{sub n}O{sub m}, and chains containing up to 10 carbon atoms. While a gentle increase in the energy absorbed by the ice sample is reflected by an increase in the column densities of newly born species, such correlation breaks down at very high fluxes. In this regime the production yield falls down sharply by about a factor of 100. The refractory residue obtained in the broad energy irradiation is a “compromise” between those obtained with proton irradiation of C{sub 3}O{sub 2} and CO ices in previous experiments. Finally, we discuss the possible implications for space chemistry.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Self-Generation of Chaotic Microwave Signal in Spin Wave Optoelectronic Generator

Abstract—The self-generation of a chaotic microwave signal in a spin-wave optoelectronic generator has been experimentally investigated for the first time. The generator was a ring circuit, in the microwave path of which there was a spin-wave delay line on the film of an yttrium iron garnet (YIG) and a microwave amplifier. The optical path contained a fiber optic delay line. The nonlinear element of the generator was a film of YIG, which worked under the conditions of four-wave parametric interaction of spin waves. It has been shown that it is possible to generate monochromatic, periodic, quasi-periodic, and chaotic microwave signals by controlling the gain coefficient of the ring. The parameters characterizing the chaotic signal that are generated by the ring have been determined.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

High-Current Light-Ion Cyclotron for Applications in Nuclear Security and Radioisotope Production

In this article, we propose the conceptual design, with supporting beam dynamics results, of a normal conducting, separated-sector cyclotron with a strong-focusing field gradient designed to accelerate light ions with a charge-to-mass ratio of 1/2 up to 15–20 MeV/u. The design can support a host of applications for therapy, radiobiology, material science, and instrumentation development. The light-ion species, which can include a mixed ion beam, can be dynamically chosen to provide a range of characteristic signals appropriate for specific material identification such as special nuclear materials. A conservative baseline concept is presented which has been optimized for radioisotope production of alpha emitters and theranostic radiopharmaceuticals. The modular design is also demonstrated to be scalable in gross physical parameters by a factor of 2–3, thereby reducing the size, weight, and power requirements (SWaP) and enabling near-term security applications.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2018

Spectrometer of Synchrotron Radiation Based on Diffraction Focusing a Divergent Beam Formed by a Compound Refractive Lens

The results of the first experimental realization of a spectrometer based on the effect of diffraction focusing of X rays by a flat single crystal are discussed. A secondary X-ray source with a relatively high angular divergence and small sizes was formed at the focus of a compound refractive lens having 50 beryllium biconcave elements with a curvature radius of 50 μm. The silicon spectrometer crystal was cut in the form of a wedge of variable thickness, oriented perpendicular to the diffraction plane. The reflection 111 was used for energies of 8.3 and 12 keV. To simulate the experiment, a computer program was developed, which takes into account accurately and for the first time the focusing of radiation by the lens and its subsequent diffraction in the crystal. A calculated curve for a monochromatic beam has made it possible to determine the monochromator spectrum with high resolution from experimental data for a polychromatic beam. It is shown that monochromator resolution increases with an increase in the distance from the compound refractive lens to the crystal.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

AN INTEGRATED MODEL FOR THE PRODUCTION OF X-RAY TIME LAGS AND QUIESCENT SPECTRA FROM HOMOGENEOUS AND INHOMOGENEOUS BLACK HOLE ACCRETION CORONAE

Many accreting black holes manifest time lags during outbursts, in which the hard Fourier component typically lags behind the soft component. Despite decades of observations of this phenomenon, the underlying physical explanation for the time lags has remained elusive, although there are suggestions that Compton reverberation plays an important role. However, the lack of analytical solutions has hindered the interpretation of the available data. In this paper, we investigate the generation of X-ray time lags in Compton scattering coronae using a new mathematical approach based on analysis of the Fourier-transformed transport equation. By solving this equation, we obtain the Fourier transform of the radiation Green’s function, which allows us to calculate the exact dependence of the time lags on the Fourier frequency, for both homogeneous and inhomogeneous coronal clouds. We use the new formalism to explore a variety of injection scenarios, including both monochromatic and broadband (bremsstrahlung) seed photon injection. We show that our model can successfully reproduce both the observed time lags and the time-averaged (quiescent) X-ray spectra for Cyg X-1 and GX 339-04, using a single set of coronal parameters for each source. The time lags are the result of impulsive bremsstrahlung injection occurring near the outer edge of the corona, while the time-averaged spectra are the result of continual distributed injection of soft photons throughout the cloud.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Nanosized Particles of Tantalum, Hafnium, and Cerium Oxides Used with Monochromatic Photon Beams and Brachytherapy Sources

High-Z nanoparticles can increase the absorbed radiation dose if they are accumulated in tumor cells. The quantitative measure of this radiosensitization effect is the dose enhancement factor (DEF), that is, the ratio of the doses absorbed in the presence and in the absence of nanoparticles. In the present work, the values of the dose enhancement factors of Ta{sub 2}O{sub 5}, HfO{sub 2}, and CeO{sub 2} ceramic nanoparticles were calculated analytically for monochromatic radiation of the X-ray energy range (1–180 keV) and for low-energy sources for brachytherapy: {sup 103}Pd (mean energy, 20.6 keV), {sup 125}I (26.7 keV), and {sup 131}Cs (30.4 keV). For all types of nanoparticles in the concentration of 5 mg/mL, the values of the dose enhancement factor were high both for monochromatic radiation and for brachytherapy sources. The highest DEF values of ~1.7 were obtained for nanoparticles of tantalum oxide. For brachytherapy sources, the highest dose enhancement factors (1.48 to 1.67) were obtained for Ta{sub 2}O{sub 5} and HfO{sub 2} nanoparticles. These results confirm that ceramic nanoparticles are promising dose modifying agents for radiotherapy.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2017

Cosmological implications of primordial black holes

The possibility that a relevant fraction of the dark matter might be comprised of Primordial Black Holes (PBHs) has been seriously reconsidered after LIGO's detection of a ∼ 30 M {sub ⊙} binary black holes merger. Despite the strong interest in the model, there is a lack of studies on possible cosmological implications and effects on cosmological parameters inference. We investigate correlations with the other standard cosmological parameters using cosmic microwave background observations, finding significant degeneracies, especially with the tilt of the primordial power spectrum and the sound horizon at radiation drag. However, these degeneracies can be greatly reduced with the inclusion of small scale polarization data. We also explore if PBHs as dark matter in simple extensions of the standard ΛCDM cosmological model induces extra degeneracies, especially between the additional parameters and the PBH's ones. Finally, we present cosmic microwave background constraints on the fraction of dark matter in PBHs, not only for monochromatic PBH mass distributions but also for popular extended mass distributions. Our results show that extended mass distribution's constraints are tighter, but also that a considerable amount of constraining power comes from the high-ℓ polarization data. Moreover, we constrain the shape of such mass distributions in terms of the correspondent constraints on the PBH mass fraction.

79 ASTRONOMY AND ASTROPHYSICS↗