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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 1,495 records · Page 83
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

3D localization of electrophysiology catheters from a single x-ray cone-beam projection

Purpose: X-ray images allow the visualization of percutaneous devices such as catheters in real time but inherently lack depth information. The provision of 3D localization of these devices from cone beam x-ray projections would be advantageous for interventions such as electrophysiology (EP), whereby the operator needs to return a device to the same anatomical locations during the procedure. A method to achieve real-time 3D single view localization (SVL) of an object of known geometry from a single x-ray image is presented. SVL exploits the change in the magnification of an object as its distance from the x-ray source is varied. The x-ray projection of an object of interest is compared to a synthetic x-ray projection of a model of said object as its pose is varied. Methods: SVL was tested with a 3 mm spherical marker and an electrophysiology catheter. The effect of x-ray acquisition parameters on SVL was investigated. An independent reference localization method was developed to compare results when imaging a catheter translated via a computer controlled three-axes stage. SVL was also performed on clinical fluoroscopy image sequences. A commercial navigation system was used in some clinical image sequences for comparison. Results: SVL estimates exhibited little change as x-ray acquisition parameters were varied. The reproducibility of catheter position estimates in phantoms denoted by the standard deviations, (σ{sub x}, σ{sub y}, σ{sub z}) = (0.099 mm, 0.093 mm, 2.2 mm), where x and y are parallel to the detector plane and z is the distance from the x-ray source. Position estimates (x, y, z) exhibited a 4% systematic error (underestimation) when compared to the reference method. The authors demonstrated that EP catheters can be tracked in clinical fluoroscopic images. Conclusions: It has been shown that EP catheters can be localized in real time in phantoms and clinical images at fluoroscopic exposure rates. Further work is required to characterize performance in clinical images as well as the sensitivity to clinical image quality.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

High-Intensity Linear Accelerator with Ribbon Beam

We propose a solution of the fundamental problem in accelerator physics: significant increase of peak beam power in linear accelerator with conservation of beam brightness. It is of primary importance for operation of existing high-power accelerators (LANSCE, Spallation Neutron Source), for development of the next generation of high-power accelerators for basic scientific research and Accelerator-Driven Systems applications (Transmutation of Waste, Nuclear Reactor-Driver), and national security applications, which are all $1B-class facilities. The concept utilizes acceleration of beam with ribbon geometry instead of traditional circular beam. High value of beam current is reached using large width of the beam. Acceleration and focusing is achieved using alternative-focusing principle, which does not require traditional focusing elements (quadrupoles, solenoids). The concept utilizes advantage of 2D plane geometry which excludes beam distortion along beam width and results in conservation of high-value of beam brightness.

43 PARTICLE ACCELERATORS↗
DOE OSTI2025

Modeling hydraulic fracture opening and closure with proppant transport and settlement

Hydraulic fracturing is a widely used reservoir stimulation technique for improving fluid circulation in rock formations with extremely low permeability, particularly in enhanced geothermal systems (EGS). To better understand the complex processes involved and improve hydraulic stimulation performance, we have developed ELK (ELectrical fracKing), a MOOSE-based 3D finite element application designed to model the behavior of proppant-fluid mixtures in propagating fractures. ELK integrates both the fluid and proppant components, incorporating particle-driven processes such as gravity settling, particle-particle interactions, and strong density and viscosity contracts, in addition to conventional fluid-driven fracture propagation. In this contribution, we extend ELK to model propped fracture closure, which occurs after the injection phase due to a dramatic drop in the effective stress on the fracture plane. During the shut-in, flowback, and production periods, the fracture width decreases, with the closure behavior depending on proppant concentration.. At low concentrations, closure follows a nonlinear joint law linked to the stiffness of asperities in the fracture walls. While at high concentrations, it is controlled by the properties of packed proppant bed. The extended ELK application is validated against several benchmark examples, including the propagation of an inclined frictional crack, fracture opening and sliding in response to fluid injection, and flowback analysis. We believe that ELK’s enhanced capabilities can serve as a valuable tool for the design and optimization of EGS deployment.

15 - GEOTHERMAL ENERGY↗
DOE OSTI2017

Coexistence of Low Damping and Strong Magnetoelastic Coupling in Epitaxial Spinel Ferrite Thin Films

Low‐loss magnetization dynamics and strong magnetoelastic coupling are generally mutually exclusive properties due to opposing dependencies on spin–orbit interactions. So far, the lack of low‐damping, magnetostrictive ferrite films has hindered the development of power‐efficient magnetoelectric and acoustic spintronic devices. Here, magnetically soft epitaxial spinel NiZnAl‐ferrite thin films with an unusually low Gilbert damping parameter (<3 × 10 −3 ), as well as strong magnetoelastic coupling evidenced by a giant strain‐induced anisotropy field (≈1 T) and a sizable magnetostriction coefficient (≈10 ppm), are reported. This exceptional combination of low intrinsic damping and substantial magnetostriction arises from the cation chemistry of NiZnAl‐ferrite. At the same time, the coherently strained film structure suppresses extrinsic damping, enables soft magnetic behavior, and generates large easy‐plane magnetoelastic anisotropy. These findings provide a foundation for a new class of low‐loss, magnetoelastic thin film materials that are promising for spin‐mechanical devices.

Emori, Satoru↗
DOE OSTI2022

Atomically Resolved Electrically Active Intragrain Interfaces in Perovskite Semiconductors

Deciphering the atomic and electronic structures of interfaces is key to developing state-of-the-art perovskite semiconductors. However, conventional characterization techniques have limited previous studies mainly to grain-boundary interfaces, whereas the intragrain-interface microstructures and their electronic properties have been much less revealed. Herein using scanning transmission electron microscopy, we resolved the atomic-scale structural information on three prototypical intragrain interfaces, unraveling intriguing features clearly different from those from previous observations based on standalone films or nanomaterial samples. These intragrain interfaces include composition boundaries formed by heterogeneous ion distribution, stacking faults resulted from wrongly stacked crystal planes, and symmetrical twinning boundaries. The atomic-scale imaging of these intragrain interfaces enables us to build unequivocal models for the ab initio calculation of electronic properties. Our results suggest that these structure interfaces are generally electronically benign, whereas their dynamic interaction with point defects can still evoke detrimental effects. This work paves the way toward a more complete fundamental understanding of the microscopic structure-property-performance relationship in metal halide perovskites.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Strong interplay between stripe spin fluctuations, nematicity and superconductivity in FeSe

In iron-based superconductors the interactions driving the nematic order (that breaks four-fold rotational symmetry in the iron plane) may also mediate the Cooper pairing. The experimental determination of these interactions, which are believed to depend on the orbital or the spin degrees of freedom, is challenging because nematic order occurs at, or slightly above, the ordering temperature of a stripe magnetic phase. In this paper, we study FeSe—which exhibits a nematic (orthorhombic) phase transition at T s = 90 K without antiferromagnetic ordering—by neutron scattering, finding substantial stripe spin fluctuations coupled with the nematicity that are enhanced abruptly on cooling through T s . A sharp spin resonance develops in the superconducting state, whose energy (~4 meV) is consistent with an electron–boson coupling mode revealed by scanning tunnelling spectroscopy. The magnetic spectral weight in FeSe is found to be comparable to that of the iron arsenides. Finally, our results support recent theoretical proposals that both nematicity and superconductivity are driven by spin fluctuations.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Hydrogen-Assisted Fracture of Stainless Steel

Symmetric four-point bending (S4PB) and anti-symmetric four-point bending (AS4PB) were applied to assess the effect of hydrogen on crack initiation and propagation in a stable, nitrogen-strengthened austenitic stainless steel (21Cr-6Ni-9Mn). Specimens of a high strength aluminum alloy (AA2219-T851), which has also been identified as hydrogen-compatible, were used for test method development prior to completing the stainless steel test matrix. Single edge notched bend (SEN(B)) specimens were extracted from forged 21Cr-6Ni-9Mn bar and AA2219 plate. The 21Cr-6Ni-9Mn specimens were then hydrogen charged with ~200 wt. ppm hydrogen; AA2219 specimens were not charged. Aluminum specimens were tested in S4PB to induced mode I (pure bending), and AS4PB to attain varying levels of mode I/II mixity and mode II (pure shear), where the ratio of mode I to mode II varies with the position of the crack plane relative to the load line. After test method troubleshooting and validation, hydrogen charged stainless steel specimens were then subjected to mode I and two ratios of mixed mode I/II. Mode II loading was not achieved due to high load limitations. Analyses of fracture profiles for both materials reveal a marked effect of loading mode mixity on initial crack propagation orientation, however a specific contribution of hydrogen was not readily identifiable. Fracture initiation toughness in the presence of hydrogen, J IH , was calculated following the J-integral approach; the mode I J IH calculated for stainless steel samples fractured in S4PB were consistent with published values determined from compact tension specimens. The peak loads required to initiate fracture during AS4PB far exceeded those required during S4PB. This is attributed to the increasing shear force applied to the specimens as the degree of mode mixity increases. Ultimately, understanding the fracture response of hydrogen exposed stainless steels subjected to mixed mode I/II loading is critical for designing hydrogen containment vessels or gas transfer systems (GTS).

36 MATERIALS SCIENCE↗
DOE OSTI2019

Charging the Johannsen–Psaltis spacetime

In this paper we develop the charged version of the spacetime proposed by Johannsen and Psaltis. Rotation is introduced in the deformed Reissner–Nordström spacetime by complex coordinate transformation. The event horizon and Killing horizon are studied. Killing horizons are represented graphically also. The analysis of the determinant of the metric shows that the spacetime does not have Lorentz violating regions. Similarly, from the study of the closed time-like curves, we see that no such curves exist outside the central body. Expressions for the energy and angular momentum for a particle on the equatorial plane are determined. Location of the circular photon orbits and innermost stable circular orbits is also computed.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

Analysis of strain in ion implanted 4H-SiC by fringes observed in synchrotron X-ray topography

A novel high energy implantation system has been successfully developed to fabricate 4H-SiC superjunction devices for medium and high voltage via implantation of dopant atoms with multi-energies ranging from 13 to 66 MeV. The significantly higher levels of energy used compared to conventional implantation processes, necessitates detailed characterization of the lattice damage caused by implantation. To achieve this by employing the novel high energy system, 4H-SiC wafer with 12 μm epilayers were blanket implanted by 13.8–65.7 MeV Al atoms. The lattice damages induced by the implantation were primarily characterized by Synchrotron X-ray Plane Wave Topography (SXPWT) and Reciprocal Space Mapping (RSM). Topographs reveal fringe contrast akin to multiple asymmetric diffraction peaks with an angular separation of only 2″ (arcseconds) observed on rocking curves, indicating inhomogeneous strain distribution across the implanted layer. The strain profile of the implanted layer was extracted from the fringe contrast by applying Rocking-curve Analysis by Dynamical Simulation (RADS). In conclusion, the maximum strain value is similar to that measured on the RSM.

A1. Characterization↗
DOE OSTI2018

Source complexity of the 2015 Mw 7.9 Bonin earthquake

The 30 May 2015 Mw 7.9 Bonin earthquake, one of the largest and deepest earthquakes ever recorded by modern seismology, provides a unique opportunity to study the source process and physical mechanisms of deep-focus earthquakes. We develop a novel back-projection technique that allows source imaging in full three-dimensional space with high depth resolution. Our results indicate an initial SW-NE bilateral source propagation followed by a northwest source extension. The multiple-source inversion reveals a two-step source process with propagating directions near-perpendicular to each other, consistent with the 3D back-projection result. The spatial distribution and focal mechanisms of the sub-events cannot be modeled by a single planar rupture, which may display a curved rupture plane or sub-events crossing multiple fault interfaces. Thus, the complex source process can be best explained by stress or structure heterogeneity within the deep slab.

58 GEOSCIENCES↗
DOE OSTI2021

Decay and renormalization of a longitudinal mode in a quasi-two-dimensional antiferromagnet

Abstract An ongoing challenge in the study of quantum materials, is to reveal and explain collective quantum effects in spin systems where interactions between different modes types are important. Here we approach this problem through a combined experimental and theoretical study of interacting transverse and longitudinal modes in an easy-plane quantum magnet near a continuous quantum phase transition. Our inelastic neutron scattering measurements of Ba 2 FeSi 2 O 7 reveal the emergence, decay, and renormalization of a longitudinal mode throughout the Brillouin zone. The decay of the longitudinal mode is particularly pronounced at the zone center. To account for the many-body effects of the interacting low-energy modes in anisotropic magnets, we generalize the standard spin-wave theory. The measured mode decay and renormalization is reproduced by including all one-loop corrections. The theoretical framework developed here is broadly applicable to quantum magnets with more than one type of low energy mode.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Observation of plaid-like spin splitting in a noncoplanar antiferromagnet

Spatial, momentum and energy separation of electronic spins in condensed matter systems guides the development of novel devices where spin-polarized current is generated and manipulated. Recent attention on a set of previously overlooked symmetry operations in magnetic materials leads to the emergence of a new type of spin splitting, enabling giant and momentum-dependent spin polarization of energy bands on selected antiferromagnets. Despite the ever-growing theoretical predictions, the direct spectroscopic proof of such spin splitting is still lacking. Here, we provide solid spectroscopic and computational evidence for the existence of such materials. In the noncoplanar antiferromagnet MnTe 2 , the in-plane components of spin are found to be antisymmetric about the high-symmetry planes of the Brillouin zone, comprising a plaid-like spin texture in the antiferromagnetic (AFM) ground state. Such an unconventional spin pattern, further found to diminish at the high- temperature paramagnetic state, stems from the intrinsic AFM order instead of spin- orbit coupling (SOC). Furthermore, our finding demonstrates a new type of quadratic spin texture induced by time-reversal breaking, placing AFM spintronics on a firm basis and paving the way for studying exotic quantum phenomena in related materials.

Electronic devices↗
DOE OSTI2013

Quantization maps, algebra representation, and non-commutative Fourier transform for Lie groups

The phase space given by the cotangent bundle of a Lie group appears in the context of several models for physical systems. A representation for the quantum system in terms of non-commutative functions on the (dual) Lie algebra, and a generalized notion of (non-commutative) Fourier transform, different from standard harmonic analysis, has been recently developed, and found several applications, especially in the quantum gravity literature. We show that this algebra representation can be defined on the sole basis of a quantization map of the classical Poisson algebra, and identify the conditions for its existence. In particular, the corresponding non-commutative star-product carried by this representation is obtained directly from the quantization map via deformation quantization. We then clarify under which conditions a unitary intertwiner between such algebra representation and the usual group representation can be constructed giving rise to the non-commutative plane waves and consequently, the non-commutative Fourier transform. The compact groups U(1) and SU(2) are considered for different choices of quantization maps, such as the symmetric and the Duflo map, and we exhibit the corresponding star-products, algebra representations, and non-commutative plane waves.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Atomic-scale investigation of point defects and hydrogen-solute atmospheres on the edge dislocation mobility in alpha iron

In this study, we present atomistic mechanisms of 1/2 [111](11{sup ¯}0) edge dislocation interactions with point defects (hydrogen and vacancies) and hydrogen solute atmospheres in body centered cubic (bcc) iron. In metals such as iron, increases in hydrogen concentration can increase dislocation mobility and/or cleavage-type decohesion. Here, we first investigate the dislocation mobility in the presence of various point defects, i.e., change in the frictional stress as the edge dislocation interacts with (a) vacancy, (b) substitutional hydrogen, (c) one substitutional and one interstitial hydrogen, (d) interstitial hydrogen, (e) vacancy and interstitial hydrogen, and (f) two interstitial hydrogen. Second, we examine the role of a hydrogen-solute atmosphere on the rate of local dislocation velocity. The edge dislocation simulation with a vacancy in the compression side of the dislocation and an interstitial hydrogen atom at the tension side exhibit the strongest mechanical response, suggesting a higher potential barrier and hence, the higher frictional stress (i.e., ∼83% higher than the pure iron Peierls stress). In the case of a dislocation interacting with a vacancy on the compressive side, the vacancy binds with the edge dislocation, resulting in an increase in the friction stress of about 28% when compared with the Peierls stress of an edge dislocation in pure iron. Furthermore, as the applied strain increases, the vacancy migrates through a dislocation transportation mechanism by attaining a velocity of the same order as the dislocation velocity. For the case of the edge dislocation interacting with interstitial hydrogen on the tension side, the hydrogen atom jumps through one layer perpendicular to the glide plane during the pinning-unpinning process. Finally, our simulation of dislocation interactions with hydrogen show first an increase in the local dislocation velocity followed by a pinning of the dislocation core in the atmosphere, resulting in resistance to dislocation motion as the dislocation moves though the hydrogen-solute atmospheres. With this systematic, atomistic study of the edge dislocation with various point defects, we show significant increase in obstacle strengths in addition to an increase in the local dislocation velocity during interaction with solute atmospheres. The results have implications for constitutive development and modeling of the hydrogen effect on dislocation mobility and deformation in metals.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Predicting Hugoniot equation of state in erythritol with ab initio and reactive molecular dynamics

Erythritol has been proposed as an inert surrogate for developing theoretical and computational models to study aging in energetic materials. In this work, we present a comparison of mechanical and shock properties of erythritol computed using the ReaxFF reactive force field and from ab initio calculations employing density functional theory (DFT). We screened eight different ReaxFF parameterizations, of which the CHO parameters developed for hydrocarbon oxidation provide the most accurate predictions of mechanical properties and the crystal structure of erythritol. Further validation of the applicability of this ReaxFF parameterization for modeling erythritol is demonstrated by comparing predictions of the elastic constants, crystal structure, vibrational density of states, and Hugoniot curves against DFT calculations. The ReaxFF predictions are in close agreement with the DFT simulations for the elastic constants and shock Hugoniot when the crystal is loaded along its c axis but show as much as 30% disagreement in the elastic constants in the ab plane and 12% difference in shock pressures when shocked along the a or b crystal axes. Last, we compare thermomechanical properties predicted from classical molecular dynamics with those calculated using the quasi-harmonic approximation and show that quantum mechanical effects produce large discrepancies in the computed values of heat capacity and thermal expansion coefficients compared with classical assumptions. Combining classical molecular dynamics predictions of mechanical behavior with phonon-based calculations of thermal behaviors, we show that predicted shock-induced temperatures for pressures up to 6.5 GPa do not exceed the pressure-dependent melting point of erythritol.

Hu, Jing↗
DOE OSTI2023

Flow field characteristics of a 127-pin rod bundle with hexagonal spacer grids

A determination of nominal flow phenomena in liquid metal fast reactor (LMFR) fuel assemblies is critical toward generation-IV reactor development. Axially positioned spacer grids are used to maintain the geometry of hexagonal rod bundles and simultaneously introduce perturbations in the flow. Three-dimensional (3D) printed asymmetric honeycomb spacer grids were installed in a prototypical 127-pin LMFR fuel assembly model to study complex fluid dynamics interactions induced by the spacer grid and rods. To characterize flow dynamics in this intricate geometry, time-resolved particle image velocimetry (TR-PIV) using the matched-index-of-refraction method was employed to obtain non-intrusive velocity measurements for three axial planes (one near-wall and two interior planes) at a Reynolds number of 6000. The statistical TR-PIV results compared sub-channel-dependent normalized time-averaged velocity, velocity fluctuations, Reynolds stress, vorticity, and turbulence kinetic energy distributions. TR-PIV line profiles characterized downstream spacer grid flow dynamics. Two-point spatial and spatial–temporal cross-correlation fields revealed local coherent structures and quantified convection velocities of traveling vortices. Spatial–temporal decomposition using dynamic mode decomposition (DMD) applied to the near-wall vorticity fields extracted turbulent structures and flow instabilities in the wake region of the spacer grid, along with their decay and frequency rates. Reduced-order velocity fields from DMD reconstructions identified the most energy-containing coherent structures persistent in the near-wall region. This research provides experimental data sets and analyses of flow behavior in rod bundles with hexagonal spacer grids. In conclusion, the results are critical toward LMFR design and geometry optimization, crucial for the validation of computational fluid dynamics and reduced-order flow models.

42 ENGINEERING↗
DOE OSTI2023

Symmetry-driven persistent spin texture for the two-dimensional nonsymmorphic CdTe and ZnTe crystal structures

In this paper, two nonsymmorphic two-dimensional structures of CdTe and ZnTe are modeled, and using state-of-the-art density functional theory with the group theory of solids, their symmetry-enforced electronic properties are studied. The in-plane ferroelectricity coupled with strong spin-orbit coupling induces a unidirectional out-of-plane Rashba spin-orbit field that can host a momentum-independent uniform spin configuration known as persistent spin texture (PST) at the Brillouin zone center. PST in these structures is found to be robust against external perturbations such as strain, structural distortion, and independent of layer thickness. These unprecedented intrinsic spin transport properties hold utmost importance in spintronics, as the experimental stringent condition of equal Rashba and Dresselhaus constants [Phys. Rev. Lett. 90, 146801 (2003)] is eliminated. The calculated persistent spin helix wavelength of <~5 nm paves the way for developing next-generation nanosized nonballistic spin field-effect transistors compared with micrometer-sized GaAs/AlGaAs quantum wells. Further, these materials exhibit finite spin Hall conductivity at the band edges and hence can be used in ferromagnet-free spin Hall transistors. Although CdTe and ZnTe systems have been widely studied for photocatalysis and solar cell applications over the past few decades, their potential application in spintronic devices has not been explored. Mono/few layers of CdTe and ZnTe synthesized from (110) facets of bulk zinc-blende crystals [Nat. Commun. 3, 1057 (2012)] satisfy all symmetry operations of the nonsymmorphic space group and hence can be considered ideal materials to verify our theoretical results experimentally.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2013

RF Gap Transformation in PARMILA

The PARMILA (Phase And Radial Motion in Ion Linear Accelerators) code is used to design ion linacs and simulate the beam dynamics therein. The original code was developed in the 1960’s and later the Los Alamos Accelerator Code Group developed a PC version that has been used worldwide. Recently, in an effort to modernize the code and use it as the basis for a high-performance beam dynamics simulator with the LANSCE linac, the details of the code have come under additional scrutiny. PARMILA is a “z code” that uses various transformations to approximately represent the effect of the beam line element on the beam. In the case of the RF gap, it treats the particle dynamics inside the gap as a combination of drift + kick at the mid-plane + drift. Recently, we uncovered an undocumented keyword “off-exact” in PARMILA that enables the code to use the full modified-Bessel functions instead of low-order approximations in the RF gap transformation. This change improved the accuracy of the transformation for off-axis particles. However, a discrepancy between the analytical formula and the code was found for the transformation of the transverse coordinates. The purpose of this tech note is to document the derivation of the gap transformation and the related DTL cell length calculation used in the PARMILA code.

43 PARTICLE ACCELERATORS↗