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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Grazing-Incidence Texture Tomography and Diffuse Reflectivity Tomography of an Organic Semiconductor Device Array

The use of grazing-incidence scattering methods for the characterization of 2D patterned organic thin films is limited due to the elongated 1D footprint of the X-ray beam on the sample. However, this characteristic feature can be turned into an advantage, when combined with tomographic reconstruction. In this pilot study we show, how the use of a chosen texture reflection and a diffuse reflectivity signal can each provide 2D images of the deposits, simultaneously revealing the organic film's crystal orientation and the location of the metal electrodes in a field-effect transistor structure from a single sequence of diffraction images.

36 MATERIALS SCIENCE↗
NASA NTRS2008

Grazing-Incidence Neutron Optics based on Wolter Geometries

The feasibility of grazing-incidence neutron imaging optics based on the Wolter geometries have been successfully demonstrated. Biological microscopy, neutron radiography, medical imaging, neutron crystallography and boron neutron capture therapy would benefit from high resolution focusing neutron optics. Two bounce optics can also be used to focus neutrons in SANS experiments. Here, the use of the optics would result in lower values of obtainable scattering angles. The high efficiency of the optics permits a decrease in the minimum scattering vector without lowering the neutron intensity on sample. In this application, a significant advantage of the reflective optics over refractive optics is that the focus is independent of wavelength, so that the technique can be applied to polychromatic beams at pulsed neutron sources.

Gubarev, M. V.↗
NASA NTRS2010

Computer-Controlled Cylindrical Polishing Process for Development of Grazing Incidence Optics for Hard X-Ray Region

The presentation includes grazing incidence X-ray optics, motivation and challenges, mid spatial frequency generation in cylindrical polishing, design considerations for polishing lap, simulation studies and experimental results, future scope, and summary. Topics include current status of replication optics technology, cylindrical polishing process using large size polishing lap, non-conformance of polishin lap to the optics, development of software and polishing machine, deterministic prediction of polishing, polishing experiment under optimum conditions, and polishing experiment based on known error profile. Future plans include determination of non-uniformity in the polishing lap compliance, development of a polishing sequence based on a known error profile of the specimen, software for generating a mandrel polishing sequence, design an development of a flexible polishing lap, and computer controlled localized polishing process.

Khan, Gufran Sayeed↗
NASA NTRSDate not supplied

The Next Generation Marshall Grazing Incidence X-Ray Spectrometer (MaGIXS) Sounding Rocket Experiments

The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) is a sounding rocket experiment that carries an X-ray slitless imaging spectrograph to observe spectrally dispersed soft X-ray (SXR) images of the solar corona over a wide field-of-view. The first flight of MaGIXS occurred on 30 July 2021, during which several emission lines from coronal structures including X-ray bright points were observed. Analysis of MaGIXS-1 data demonstrated the application of new inversion techniques and opened a new arena of inverting complex spectroheliogram data, which has spatial-spectral information overlapped. The second flight of MaGIXS, with a simplified optical design, is scheduled for 2024. The goal of MaGIXS-2 is to observe high temperature diagnostic emission lines within an active region core. MaGIXS-1 discovered dominant missing emission lines near 15Å wavelength region, which hosts several closely spaced satellite lines of Fe XVII, Fe XVI, and Fe XV ions, arising from relatively cool plasma that peaks near 2MK. These lines are expected to be enhanced at lower temperatures and offers one of the most unique diagnostics to measure electron temperature, as well as signatures of equilibrium state of the plasma in active regions, which has not been studied so far. The science goal of the third sounding rocket flight of MaGIXS is to determine coronal heating parameters, such as the spatial and temporal properties of coronal heating events, by measuring discriminating observations, such as electron temperature, effective temperature, density, abundance, and departures from thermal equilibrium of the plasma, by observing the Sun in the SXR wavelength range. For this, the MaGIXS instrument will be upgraded with a new X-ray telescope mirror that will provide higher spatial and spectral resolution and throughput, allowing for spectral lines to be observed at the relevant spatial and temporal scales. In addition, MaGIXS-3 will also carry The Resolving Inversion Context X-ray Spectrometer (TRICXS), a high dispersion Bragg crystal spectrometer to spectrally resolve the lines near 15Å, critical to unlock the full diagnostic potential of this wavelength range. Here we will present the preliminary concept design of MaGIXS-3 and discuss the potential observations.

X-ray Imaging↗
DOE OSTI2023

Using Grazing-Incidence Small-Angle Neutron Scattering to Study the Orientation of Block Copolymer Morphologies in Thin Films

Here, we used grazing-incidence small-angle neutron scattering (GISANS) to probe the depth-dependent orientation of self-assembled morphologies of block copolymers. A hydrophobic–hydrophobic block copolymer, poly(solketal methacrylate)-block-polystyrene (PSM-b-PS), was synthesized and spin-coated into films tens of nanometers in thickness where the polymers adopted a disordered state. PSM-b-PS was then hydrolyzed by exposing the polymer thin film to trifluoroacetic acid vapor or embedding a photoacid generator in the film during spin coating, followed by exposure to UV light. The hydrolysis converted the block copolymer into a hydrophilic–hydrophobic block copolymer, poly(glycerol monomethacrylate)-block-polystyrene (PGM-b-PS), significantly increasing the segmental interaction parameter (χ) and causing microphase separation of the copolymers. GISANS was used to study the depth-dependent structure of the films and revealed that the orientation of the microphase-separated structure differed at the polymer–air and polymer–substrate interfaces. In the regions where the lamellae were parallel to the interfaces, the orientation propagated into the film from the interfaces. However, in the areas where the lamellae were perpendicular to the interfaces, the orientation did not persist with increasing distance from the interfaces.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1979

Astronomical applications of grazing incidence telescopes with polynomial surfaces

The report has examined the claim that grazing incidence telescopes having surfaces described by generalized equations have image characteristics superior to those of the paraboloid-hyperboloid and Wolter-Schwarzschild configurations. With emphasis on specific applications in solar and cosmic X-ray/EUV astronomy, raytracing has shown that in many cases there is no advantage in the polynomial design, and in those cases where advantages are theoretically to be expected, the advantages are outweighed by practical considerations.

Cash, W.↗
NASA NTRS2019

Marshall Grazing Incidence X-Ray Spectrometer (MaGIXS)

Outline: Scientific motivation for MaGIXS (Marshall Grazing Incidence X-ray Spectrometer) - Demonstrate sensitivity of MaGIXS to determine high temperature plasma; Instrument design - Challenges involved; Instrument status - alignment and calibration.

Athiray, P. S.↗
NASA NTRS2019

Design, Testing, and Implementation of the Marshall Grazing Incidence X-ray Spectrometer Slit-Jaw Context Imaging System

The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) is a NASA sounding rocket payload providing a 0.6 – 2.5 nm spectrum with unprecedented spatial and spectral resolution. The instrument is comprised of a novel optical design, featuring a Wolter 1 grazing mirror in the telescope module focusing the solar image on a slit plate; two corrective optics, a diffraction grating and a low-noise detector make up the spectrometer module. When MaGIXS flies on a suborbital launch in 2020, a slit-jaw camera system will image the sun in extreme ultraviolet (EUV) to soft x-ray wavelengths, providing a reference for pointing the telescope and aligning the data to supporting observations from satellites.

Phillip Wilkerson↗
NASA NTRS1984

Near anastigmatic grazing incidence telescope

A performance capability assessment is presently conducted for short versus long grazing incidence telescope designs, in view of the observation that the field curvature and astigmatism that are the primary residual aberrations of a Wolter-type incidence telescope can be substantially reduced through mirror length reduction. A major advantage of the short element telescope is that, if sufficiently short, both the paraboloid and hyperboloid surfaces may be fabricated as a single piece; this significantly facilitates the task of alignment.

Korsch, D.↗
DOE OSTI2021

A refraction correction for buried interfaces applied to in situ grazing-incidence X-ray diffraction studies on Pd electrodes

In situ characterization of electrochemical systems can provide deep insights into the structure of electrodes under applied potential. Grazing-incidence X-ray diffraction (GIXRD) is a particularly valuable tool owing to its ability to characterize the near-surface structure of electrodes through a layer of electrolyte, which is of paramount importance in surface-mediated processes such as catalysis and adsorption. Corrections for the refraction that occurs as an X-ray passes through an interface have been derived for a vacuum–material interface. In this work, a more general form of the refraction correction was developed which can be applied to buried interfaces, including liquid–solid interfaces. Furthermore, the correction is largest at incidence angles near the critical angle for the interface and decreases at angles larger and smaller than the critical angle. Effective optical constants are also introduced which can be used to calculate the critical angle for total external reflection at the interface. This correction is applied to GIXRD measurements of an aqueous electrolyte–Pd interface, demonstrating that the correction allows for the comparison of GIXRD measurements at multiple incidence angles. This work improves quantitative analysis of d-spacing values from GIXRD measurements of liquid–solid systems, facilitating the connection between electrochemical behavior and structure under in situ conditions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1973

Design of grazing-incidence X-ray telescopes. I.

The theoretical and practical constraints on designs of grazing-incidence X-ray telescopes are discussed. It is shown that there is a maximum useful diameter for an X-ray telescope. It is further shown that when practical constraints are considered, the maximum reflecting area is not necessarily achieved by utilizing the largest available area within this diameter. Equations are derived that allow rapid calculation of the effective area of an X-ray telescope before one proceeds to detailed studies utilizing Monte Carlo techniques.

Weisskopf, M. C.↗
NASA NTRS1988

Grazing incidence reflectance of SiC films produced by plasma-assisted chemical vapor deposition

The grazing incidence reflectance of silicon carbide films produced by plasma-assisted chemical vapor deposition has been evaluated in the spectral region from 256 to 1216 A. The results show that reflectivities higher than conventional coatings can be obtained on coatings deposited both on silicon wafers and quartz substrates. Potential application of silicon carbide films for EUV astronomical instruments will be discussed.

Keski-Kuha, Ritva A. M.↗
DOE OSTI2023

Development of a versatile electrochemical cell for in situ grazing-incidence X-ray diffraction during non-aqueous electrochemical nitrogen reduction

In situ techniques are essential to understanding the behavior of electrocatalysts under operating conditions. When employed, in situ synchrotron grazing-incidence X-ray diffraction (GI-XRD) can provide time-resolved structural information of materials formed at the electrode surface. In situ cells, however, often require epoxy resins to secure electrodes, do not enable electrolyte flow, or exhibit limited chemical compatibility, hindering the study of non-aqueous electrochemical systems. Here, a versatile electrochemical cell for air-free in situ synchrotron GI-XRD during non-aqueous Li-mediated electrochemical N 2 reduction (Li-N 2 R) has been designed. This cell not only fulfills the stringent material requirements necessary to study this system but is also readily extendable to other electrochemical systems. Under conditions relevant to non-aqueous Li-N 2 R, the formation of Li metal, LiOH and Li 2 O as well as a peak consistent with the α-phase of Li 3 N was observed, thus demonstrating the functionality of this cell toward developing a mechanistic understanding of complicated electrochemical systems.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1977

Measuring concave diffraction grating efficiencies at grazing incidence

The efficiency of a concave diffraction grating in a given order is obtained by measuring the intensities of the diffracted and incident beams and taking their ratio. A valid measurement requires that both the incident and diffracted beams be collected by the detector. At grazing incidence, however, the diffracted beam may spread beyond the detector due to aberrations. In addition, the diffracted beams of consecutive orders may overlap so that unambiguous efficiency measurements cannot be made. The effect of aberrations on efficiency measurements has been studied, using ray tracing, for the geometry of the measuring instrument in use at the Naval Research Laboratory. This instrument is attached to a VUV monochromator which furnishes a diverging beam. The main effect of aberrations for this instrument is a spread of the diffracted beam in the direction of dispersion. The width of the diffracted beam is wavelength dependent and is minimal at the horizontal focus, spreading to longer and shorter wavelengths. Reducing the divergence of the incident beam reduces the spread but, for small radius gratings, not always sufficiently so that the entire diffracted beam can be collected by the detector. The distance from the detector to the grating can also be adjusted to aid in collecting all the diffracted beam.

Hunter, W. R.↗
NASA NTRS1986

Analysis of a new class of grazing incidence spectroscopic telescope

The throughput and imaging properties of one of a new class of grazing incidence spectroscopic telescope are examined with a Monte Carlo ray tracing technique. The results are compared with Wolter Schwarzschild type II telescopes of similar size. The image quality of this telescope is comparable, and the control of the off-axis light is superior to the Wolter Schwarzschild design.

Green, J. C.↗