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All sources NASA NTRS DOE OSTI

DOE OSTI2015

Laser beam centering and pointing system

An optical instrument aligns an optical beam without the need for physical intervention of the instrument within the apparatus or platforms from which the trajectory of the beam to be ascertained. The alignment apparatus and method enable the desired function to be realized without the placement of physical apertures or sensors directly in the path of the beam through the system whose spatial position and slope is to be sought. An image plane provides the observer with a pair of well-defined images that are indicative of the beam centering and pointing alignment parameters. The optical alignment can be realized without the need for referencing to an external or fixed set of coordinates or fiducials. The instrument can therefore service situations where adverse environments would otherwise prohibit the use of such instruments, including regions of high radiation, high temperature, vacuum and/or cryogenic atmospheres.

42 ENGINEERING↗

DOE OSTI2023

CIEL ∗ Ch color map for visualization and analysis of sea ice motion

The International Commission on Illumination (CIE) designed its color space to be perceptually uniform so that a given numerical change in the color code corresponds to perceived change in color. This color encoding is demon- strated to be advantageous in scientific visualization and analysis of vector fields. The specific application is analysis of ice motion in the Arctic where patterns in smooth monthly-averaged ice motion are seen. Furthermore, fractures occurring in the ice cover result in discontinuities in the ice motion. This vector jump in displacement can also be visualized. We then analyze modeled and observed fractures through the use of a metric on the color space, and image amplitude and phase metrics. Amplitude and phase met- rics arise from image registration that is accomplished by sampling images using space filling curves, thus reducing the image registration problem to the more reliable functional alignment problem. We demonstrate this through an exploration of the metrics to compare model runs to an observed ice crack.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2020

LoTToR: An Algorithm for Missing-Wedge Correction of the Low-Tilt Tomographic 3D Reconstruction of a Single-Molecule Structure

A single-molecule three-dimensional (3D) structure is essential for understanding the thermal vibrations and dynamics as well as the conformational changes during the chemical reaction of macromolecules. Individual-particle electron tomography (IPET) is an approach for obtaining a snap-shot 3D structure of an individual macromolecule particle by aligning the tilt series of electron tomographic (ET) images of a targeted particle through a focused iterative 3D reconstruction method. The method can reduce the influence on the 3D reconstruction from large-scale image distortion and deformation. Due to the mechanical tilt limitation, 3D reconstruction often contains missing-wedge artifacts, presented as elongation and an anisotropic resolution. Here, we report a post-processing method to correct the missing-wedge artifact. This low-tilt tomographic reconstruction (LoTToR) method contains a model-free iteration process under a set of constraints in real and reciprocal spaces. A proof of concept is conducted by using the LoTToR on a phantom, i.e., a simulated 3D reconstruction from a low-tilt series of images, including that within a tilt range of ±15°. The method is validated by using both negative-staining (NS) and cryo-electron tomography (cryo-ET) experimental data. A significantly reduced missing-wedge artifact verifies the capability of LoTToR, suggesting a new tool to support the future study of macromolecular dynamics, fluctuation and chemical activity from the viewpoint of single-molecule 3D structure determination.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2014

Smooth cubic commensurate oxides on gallium nitride

Smooth, commensurate alloys of 〈111〉-oriented Mg{sub 0.52}Ca{sub 0.48}O (MCO) thin films are demonstrated on Ga-polar, c+ [0001]-oriented GaN by surfactant-assisted molecular beam epitaxy and pulsed laser deposition. These are unique examples of coherent cubic oxide|nitride interfaces with structural and morphological perfection. Metal-insulator-semiconductor capacitor structures were fabricated on n-type GaN. A comparison of leakage current density for conventional and surfactant-assisted growth reveals a nearly 100× reduction in leakage current density for the surfactant-assisted samples. HAADF-STEM images of the MCO|GaN interface show commensurate alignment of atomic planes with minimal defects due to lattice mismatch. STEM and DFT calculations show that GaN c/2 steps create incoherent boundaries in MCO over layers which manifest as two in-plane rotations and determine consequently the density of structural defects in otherwise coherent MCO. This new understanding of interfacial steps between HCP and FCC crystals identifies the steps needed to create globally defect-free heterostructures.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2020

Nanoscale Conductivity Imaging of Correlated Electronic States in WSe 2 /WS 2 Moiré Superlattices

We report the nanoscale conductivity imaging of correlated electronic states in angle-aligned WSe 2 /WS 2 heterostructures using microwave impedance microscopy. Here, the noncontact microwave probe allows us to observe the Mott insulating state with one hole per moiré unit cell that persists for temperatures up to 150 K, consistent with other characterization techniques. In addition, we identify for the first time a Mott insulating state at one electron per moiré unit cell. Appreciable inhomogeneity of the correlated states is directly visualized in the hetero-bilayer region, indicative of local disorders in the moiré superlattice potential or electrostatic doping. Our work provides important insights on 2D moiré systems down to the microscopic level.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2019

Digital Time-Resolved Spot Diagnostic

The digital time-resolved spot diagnostic (D-TRSD) is intended to be a fast-response, time-dependent beam diagnostic for measuring the spot size emitted from radiographic x-ray sources. It will measure spot sizes from submillimeters up to several millimeters for photon energies in the range of 150 keV to 20 MeV with doses as low as 0.03 rad up to 500 rad. The D-TRSD performs fast data acquisition as radiographic x-ray sources typically produce pulses in the tens of nanosecond ranges. The system will be optimized to capture multiple individual pulses in time within the same data record. The data collected will be used to support beam tuning and source optimization with on-the-fly evaluation of radiographic source performance. The diagnostic is based on penumbral imaging techniques. A scintillating fiber array of parallel aligned fibers is positioned in the beam path with a high-Z rolled edge inserted between the source and the array, thereby creating the penumbral x-ray signal that is captured by the D-TRSD system. The light from the scintillation conversion is recorded by individual avalanche photodiode detectors integrated into custom digitizer electronics. The penumbra is used to calculate the spot of the beam on the axis orthogonal to the fiber array based on the magnification from the rolled edge, the resolution of the spaced fibers, and the rotation of the array normal to the beam path. Many arrays can be used to capture additional spot widths about different rotations. The D-TRSD system is modular, software-driven, and easier to use than legacy TRSD systems.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2021

Imaging orbital ferromagnetism in a moiré Chern insulator

Capturing exotic magnetism Ferromagnetism is associated with the breaking of time-reversal symmetry, most frequently by the spin degree of freedom. Although the orbital motion of electrons can also contribute to ferromagnetism, in most materials, it is small relative to the spin contribution. Tschirhart et al. showed that the reverse is true in an unusual magnetic state hosted by twisted bilayer graphene. Their scanning magnetometry measurements were consistent with ferromagnetism of predominantly orbital origin. Science , abd3190, this issue p. 1323

Science & Technology - Other Topics↗

DOE OSTI2025

A Region-Growing Segmentation Approach to Delineating Timberline from Satellite-Derived Tree Fractional Cover Products

Timberline marks the transitions from continuous forests to sparse forests and tundra landscapes. As the spatial distribution and dynamics of timberline are closely associated with regional energy and carbon balance, mapping timberline is important to a wide range of environmental and ecological studies. However, current timberline delineation approaches remain under-developed. We proposed an automatic timberline delineation method based on a seeded region-growing segmentation technique and satellite-derived products of tree fractional cover. We applied our approach to the West Siberian Plain and Alaska treeline regions as defined by the Circumpolar Arctic Vegetation Map. The results demonstrate the effectiveness of the proposed method for the accurate delineation of the timberlines that spatially align well with very-high-resolution satellite images. Based on the delineated timberlines, we find regional-scale tree encroachment to be not as substantial as previously reported. The proposed approach can be applied to understanding climate-induced forest responses and inform forest management practices.

Circumpolar Arctic Vegetation Map↗

DOE OSTI2016

THE SUBARCSECOND MID-INFRARED VIEW OF LOCAL ACTIVE GALACTIC NUCLEI. III. POLAR DUST EMISSION

Recent mid-infrared (MIR) interferometric observations have shown that in a few active galactic nuclei (AGNs) the bulk of the infrared emission originates from the polar region above the putative torus, where only a little dust should be present. Here, we investigate whether such strong polar dust emission is common in AGNs. Out of 149 Seyferts in the MIR atlas of local AGNs, 21 show extended MIR emission on single-dish images. In 18 objects, the extended MIR emission aligns with the position angle (PA) of the system axis, established by [O iii], radio, polarization, and maser-based PA measurements. The relative amount of resolved MIR emission is at least 40% and scales with the [O iv] fluxes, implying a strong connection between the extended continuum and [O iv] emitters. These results together with the radio-quiet nature of the Seyferts support the scenario that the bulk of MIR emission is emitted by dust in the polar region and not by the torus, which would demand a new paradigm for the infrared emission structure in AGNs. The current low detection rate of polar dust in the AGNs of the MIR atlas is explained by the lack of sufficient high-quality MIR data and the requirements on the orientation, strength of narrow-line region, and distance of the AGNs. The James Webb Space Telescope will enable much deeper nuclear MIR studies with comparable angular resolution, allowing us to resolve the polar emission and surroundings in most of the nearby AGNs.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2017

The size evolution of star-forming galaxies since z ∼ 7 using ZFOURGE

For the first time, we present the size evolution of a mass-complete (log(M{sub *}/M{sub ⊙}) > 10) sample of star-forming galaxies over redshifts z = 1–7, selected from the FourStar Galaxy Evolution Survey. Observed H-band sizes are measured from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) Hubble Space Telescope (HST)/F160W imaging. Distributions of individual galaxy masses and sizes illustrate that a clear mass−size relation exists up to z ∼ 7. At z ∼ 7, we find that the average galaxy size from the mass−size relation is more compact at a fixed mass of log(M{sub *}/M{sub ⊙}) = 10.1, with r{sub 1/2,maj}=1.02±0.29 kpc, than at lower redshifts. This is consistent with our results from stacking the same CANDELS HST/F160W imaging, when we correct for galaxy position angle alignment. We find that the size evolution of star-forming galaxies is well fit by a power law of the form r{sub e}=7.07(1+z){sup −0.89} kpc, which is consistent with previous works for normal star-formers at 1 < z < 4. In order to compare our slope with those derived Lyman break galaxy studies, we correct for different IMFs and methodology and find a slope of −0.97 ± 0.02, which is shallower than that reported for the evolution of Lyman break galaxies (LBGs) at z > 4 (r{sub e}∝(1+z){sup −1.2±0.06}). Therefore, we conclude the LBGs likely represent a subset of highly star-forming galaxies that exhibit rapid size growth at z > 4.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS1992

Simple Schlieren Light Meter

Simple light-meter circuit used to position knife edge of schlieren optical system to block exactly half light. Enables operator to check quickly position of knife edge between tunnel runs to ascertain whether or not in alignment. Permanent measuring system made part of each schlieren system. If placed in unused area of image plane, or in monitoring beam from mirror knife edge, provides real-time assessment of alignment of schlieren system.

Rhodes, David B.↗

NASA NTRS1994

Electric currents and coronal heating in NOAA active region 6952

We examine the spatial and temporal relationship between coronal structures observed with the soft X-ray telescope (SXT) on board the Yohkoh spacecraft and the vertical electric current density derived from photospheric vector magnetograms obtained using the Stokes Polarimeter at the Mees Solar Observatory. We focus on a single active region: AR 6952 which we observed on 7 days during 1991 December. For 11 independent maps of the vertical electric current density co-aligned with non-flaring X-ray images, we search for a morphological relationship between sites of high vertical current density in the photosphere and enhanced X-ray emission in the overlying corona. We find no compelling spatial or temporal correlation between the sites of vertical current and the bright X-ray structures in this active region.

Metcalf, T. R.↗

NASA NTRSDate not supplied

Fluid-Thermal-Structural Interactions Induced by an Asymmetric Shock-Wave/Boundary-Layer Interaction in a Mach-6 Compression Corner

An experimental study is conducted of the fluid-thermal-structural interaction of a clamped compliant panel exposed to a three dimensional shock-wave/boundary-layer interaction (SWBLI) induced by a Mach-6 compression ramp with a spanwise nonuniform incoming boundary layer. The nonuniform boundary layer was produced by placing trips on one side of the upstream flat plate, resulting in largely turbulent flow on the tripped side and transitional flow on the untripped side. Measurements of the flowfield confirmed that the tripped boundary layer contained elevated levels of unsteadiness, and the SWBLI was observed to vary from attached to fully separated as the ramp angle was increased from 10◦ to 38◦; the separation region on the tripped side of the panel was noticeably smaller, showing the elevated turbulence levels of the tripped-side flow to remain relatively localized rather than diffusing across the whole model. Full-field, time-resolved panel deformations were measured using high-speed photogrammetry and the vibrational response at each compression angle was characterized. Although the measured modes conformed largely to those from classical clamped-plate theory, some skewing of the mode shapes was observed. IR thermography highlighted regions of the compliant region where elevated temperatures were likely to promote thermal softening effects to the transient panel response. The quasi-static deformation and stress field was used to characterize the internal stress factor of each mode and showed a meaningful relationship between transient panel response and stress contained within each mode: modes with antinodes lying in high-stress areas of the plate tended to exhibit increases in vibrational frequency and decreases in vibrational power, whereas the opposite was true for modes with antinodes in low-stress areas.

Spectral Proper Orthogonal Decomposition↗

DOE OSTI2023

Neutron Capture and Transmission Measurements and Evaluation of 54 Fe at the RPI LINAC [Slides]

This presentation covers neutron capture and transmission measurements and evaluation of 54 Fe (Iron) at the Rensselaer Polytechnic Insitute (RPI) Linear Accelerator (LINAC). Presentation conclusions find that 54 Fe is near its conclusion, covariance matrix generation is needed for both experiments before data is made available and released (Completion by April 2023). RPI will be conducting a full Resolved Resonance Region (RRR) evaluation following release of data (Completion by September 2023). Additionally, the neutron beam imager shows promise in providing an easy way to align samples in the most intense part of the neutron beam and there will be a new evaluation that will offer improvements in crit safety, shielding, and stellar applications.

07 ISOTOPE AND RADIATION SOURCES↗

NASA NTRS2004

Optical Metrology for the Segmented Optics on the Constellation-X Spectroscopy X-Ray Telescope

We present the metrology requirements and metrology implementation necessary to prove out the reflector technology for the Constellation X(C-X) spectroscopy X-ray telescope (SXT). This segmented, 1.6m diameter highly nested Wolter-1 telescope presents many metrology and alignment challenges. In particular, these mirrors have a stringent imaging error budget as compared to their intrinsic stiffness; This is required for Constellation-X to have sufficient effective area with the weight requirement. This has implications for the metrology that can be used. A variety of contract and noncontact optical profiling and interferometric methods are combined to test the formed glass substrates before replication and the replicated reflector segments.The reflectors are tested both stand-alone and in-situ in an alignment tower.Some of these methods have not been used on prior X-ray telescopes and some are feasible only because of the segmented approach used on the SXT. Methods discussed include high precision coordinate measurement machines using very low force or optical probe axial interferometric profiling azimuthal circularity profiling and use of advanced null optics such as conical computer generated hologram (CGHs).

Content, David↗

DOE OSTI2016

Design of the polar neutron-imaging aperture for use at the National Ignition Facility

The installation of a neutron imaging diagnostic with a polar view at the National Ignition Facility (NIF) required design of a new aperture, an extended pinhole array (PHA). This PHA is different from the pinhole array for the existing equatorial system due to significant changes in the alignment and recording systems. The complex set of component requirements, as well as significant space constraints in its intended location, makes the design of this aperture challenging. In addition, lessons learned from development of prior apertures mandate careful aperture metrology prior to first use. This paper discusses the PHA requirements, constraints, and the final design. The PHA design is complex due to size constraints, machining precision, assembly tolerances, and design requirements. When fully assembled, the aperture is a 15 mm × 15 mm × 200 mm tungsten and gold assembly. The PHA body is made from 2 layers of tungsten and 11 layers of gold. The gold layers include 4 layers containing penumbral openings, 4 layers containing pinholes and 3 spacer layers. In total, there are 64 individual, triangular pinholes with a field of view (FOV) of 200 μm and 6 penumbral apertures. Each pinhole is pointed to a slightly different location in the target plane, making the effective FOV of this PHA a 700 μm square in the target plane. The large FOV of the PHA reduces the alignment requirements both for the PHA and the target, allowing for alignment with a laser tracking system at NIF.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2016

Anisotropic seismic-waveform inversion: Application to a seismic velocity model from Eleven-Mile Canyon in Nevada

Accurate imaging and characterization of fracture zones is crucial for geothermal energy exploration. Aligned fractures within fracture zones behave as anisotropic media for seismic-wave propagation. The anisotropic properties in fracture zones introduce extra difficulties for seismic imaging and waveform inversion. We have recently developed a new anisotropic elastic-waveform inversion method using a modified total-variation regularization scheme and a wave-energy-base preconditioning technique. Our new inversion method uses the parameterization of elasticity constants to describe anisotropic media, and hence it can properly handle arbitrary anisotropy. We apply our new inversion method to a seismic velocity model along a 2D-line seismic data acquired at Eleven-Mile Canyon located at the Southern Dixie Valley in Nevada for geothermal energy exploration. Our inversion results show that anisotropic elastic-waveform inversion has potential to reconstruct subsurface anisotropic elastic parameters for imaging and characterization of fracture zones.

15 GEOTHERMAL ENERGY↗

DOE OSTI2016

Influence of orbital symmetry on diffraction imaging with rescattering electron wave packets

The ability to directly follow and time-resolve the rearrangement of the nuclei within molecules is a frontier of science that requires atomic spatial and few-femtosecond temporal resolutions. While laser-induced electron diffraction can meet these requirements, it was recently concluded that molecules with particular orbital symmetries (such as pg) cannot be imaged using purely backscattering electron wave packets without molecular alignment. Here, we demonstrate, in direct contradiction to these findings, that the orientation and shape of molecular orbitals presents no impediment for retrieving molecular structure with adequate sampling of the momentum transfer space. We overcome previous issues by showcasing retrieval of the structure of randomly oriented O 2 and C 2 H 2 molecules, with π g and π u symmetries, respectively, and where their ionization probabilities do not maximize along their molecular axes. As a result, while this removes a serious bottleneck for laser-induced diffraction imaging, we find unexpectedly strong backscattering contributions from low-Z atoms.

74 ATOMIC AND MOLECULAR PHYSICS↗