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DOE OSTI2015

Experimental validation of a transformation optics based lens for beam steering

A transformation optics based lens for beam control is experimentally realized and measured at microwave frequencies. Laplace's equation is adopted to construct the mapping between the virtual and physical spaces. The metamaterial-based lens prototype is designed using electric LC resonators. A planar microstrip antenna source is used as transverse electric polarized wave launcher for the lens. Both the far field radiation patterns and the near-field distributions have been measured to experimentally demonstrate the beam steering properties. Measurements agree quantitatively and qualitatively with numerical simulations, and a non-narrow frequency bandwidth operation is observed.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2011

Experimental Mapping and Benchmarking of Magnetic Field Codes on the LHD Ion Accelerator

For the validation of the numerical models used for the design of the Neutral Beam Test Facility for ITER in Padua [1], an experimental benchmark against a full-size device has been sought. The LHD BL2 injector [2] has been chosen as a first benchmark, because the BL2 Negative Ion Source and Beam Accelerator are geometrically similar to SPIDER, even though BL2 does not include current bars and ferromagnetic materials. A comprehensive 3D magnetic field model of the LHD BL2 device has been developed based on the same assumptions used for SPIDER. In parallel, a detailed experimental magnetic map of the BL2 device has been obtained using a suitably designed 3D adjustable structure for the fine positioning of the magnetic sensors inside 27 of the 770 beamlet apertures. The calculated values have been compared to the experimental data. The work has confirmed the quality of the numerical model, and has also provided useful information on the magnetic non-uniformities due to the edge effects and to the tolerance on permanent magnet remanence.

43 PARTICLE ACCELERATORS↗

DOE OSTI2018

Evaluation of dose recalculation vs dose deformation in a commercial platform for deformable image registration with a computational phantom

Deformable image registration (DIR) is an important tool for mapping both dose and contours of a new set of planning images when recurrent, that is, adaptive radiotherapy, or further treatment, that is, re-treatment, is required. The aim of this study was to evaluate the need for plan recalculation in deformed anatomies and to develop a reliable workflow for validating the DIR algorithm to be applied to dose warping such as dose accumulation (DA) for adaptive radiation therapy, and dose summation (DS) in the case of re-treatment. A set of 3 computational phantoms was developed to validate the application of B-Spline-based registrations for dose mapping among the various computed tomography image data sets. Two different versions were defined for each phantom to simulate clinical needs: adaptive radiotherapy and re-treatment; a DIR was performed to obtain a displacement vector field (DVF) for dose applications. Comparison of calculated and deformed doses was carried out by means of known markers inside the virtual phantoms. The differences were evaluated using a 3% dose index as acceptance criteria. A paired Wilcoxon signed-rank test was carried out to test the statistical significance of differences within the markers. Significant differences were only observed for the deformed dose in the DA test; no significant differences were observed for recalculated dose values in the DA and DS tests. The dose index is in accordance with these results. The warping dose process obtained by registering various sets of images was validated; a recalculation approach seems to be more accurate for DA purposes and image-guided adaptive radiation therapy (IGART) applications.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2011

Dislocation Dynamics Simulations of Junctions in Hexagonal Close-Packed Crystals

The formation and strength of dislocations in the hexagonal closed packed material beryllium are studied through dislocation junctions and the critical stress required to break them. Dislocation dynamics calculations (using the code ParaDiS) of junction maps are compared to an analytical line tension approximation in order to validate our model. Results show that the two models agree very well. Also the critical shear stress necessary to break 30{sup o} - 30{sup o} and 30{sup o} - 90{sup o} dislocation junctions is computed numerically. Yield surfaces are mapped out for these junctions to describe their stability regions as function of resolved shear stresses on the glide planes. The example of two non-coplanar binary dislocation junctions with slip planes [2-1-10] (01-10) and [-12-10] (0001) corresponding to a prismatic and basal slip respectively is chosen to verify and validate our implementation.

36 MATERIALS SCIENCE↗

DOE OSTI2011

Surface Currents and Winds at the Delaware Bay Mouth

Knowledge of the circulation of estuaries and adjacent shelf waters has relied on hydrographic measurements, moorings, and local wind observations usually removed from the region of interest. Although these observations are certainly sufficient to identify major characteristics, they lack both spatial resolution and temporal coverage. High resolution synoptic observations are required to identify important coastal processes at smaller scales. Long observation periods are needed to properly sample low-frequency processes that may also be important. The introduction of high-frequency (HF) radar measurements and regional wind models for coastal studies is changing this situation. Here we analyze synoptic, high-resolution surface winds and currents in the Delaware Bay mouth over an eight-month period (October 2007 through May 2008). The surface currents were measured by two high-frequency radars while the surface winds were extracted from a data-assimilating regional wind model. To illustrate the utility of these monitoring tools we focus on two 45-day periods which previously were shown to present contrasting pictures of the circulation. One, the low-outflow period is from 1 October through 14 November 2007; the other is the high-outflow period from 3 March through 16 April 2008. The large-scale characteristics noted by previous workers are clearly corroborated. Specifically the M2 tide dominates the surface currents, and the Delaware Bay outflow plume is clearly evident in the low frequency currents. Several new aspects of the surface circulation were also identified. These include a map of the spatial variability of the M2 tide (validating an earlier model study), persistent low-frequency cross-mouth flow, and a rapid response of the surface currents to a changing wind field. However, strong wind episodes did not persist long enough to set up a sustained Ekman response.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2025

Monitoring and modeling hydrologic conditions in Ukraine for hydropower generation

Study region: The Dnieper and Dniester Rivers of Ukraine. Study focus: The ongoing conflict in Ukraine has caused disruptions to electricity generation, of which hydroelectric sources contribute approximately 9 % to the country’s needs. With the takeover of the Zaporizhzhia nuclear power plant by enemy forces, the loss of the Kakhovka hydroelectric dam, and the future impacts of the conflict on electricity generation unclear, it may be valuable for the Ukrainian government to better understand how it could leverage hydroelectric power sources in the near future. Unfortunately, measurements of river discharge throughout Ukraine ceased data collection in the late 1980’s to early 1990’s. To address this data gap, we developed a protocol that combined satellite-based time-series measurements of river width at seven locations throughout Ukraine from 2013 to 2023 with reanalysis data, climate-model predictions, and hydrologic models to both provide a means of monitoring a proxy for near-real-time discharge and also predict near-term (i.e., 2023–2030) hydrologic patterns for the region. New hydrological insights for the region: We ran new algorithms on 144 WorldView-2 and WorldView-3 satellite images to map rivers and extract width, one of which was validated against river gauge data located along the same river but in a neighboring country. Hydrologic models using two climate scenarios found minimal change in annual discharge at all sites, but magnitude and timing of peak discharge showed a moderate trend. The results suggest that hydropower is underutilized in Ukraine.

13 HYDRO ENERGY↗

DOE OSTI2020

Bi-cross validation of spectral clustering hyperparameters

One challenge impeding the analysis of terabyte scale X-ray scattering data from the Linac Coherent Light Source (LCLS) is determining the number of clusters required for the execution of traditional clustering algorithms. Here, we demonstrate that the previous work using bi-cross validation to determine the number of singular vectors directly maps to the spectral clustering problem of estimating both the number of clusters and hyperparameter values. Here by applying this method to LCLS X-ray scattering data enables the identification of dropped shots without manually setting boundaries on detector fluence and provides a path toward identifying rare and anomalous events.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2013

Reconstructing an ancestral genotype of two hexachlorocyclohexane-degrading Sphingobium species using metagenomic sequence data

Over the last 60 years, the use of hexachlorocyclohexane (HCH) as a pesticide has resulted in the production of 44 million tons of HCH waste, which has been dumped in open sinks across the globe. Here, the combination of the genomes of two genetic subspecies (Sphingobium japonicum UT26 and Sphingobium indicum B90A; isolated from two discrete geographical locations, Japan and India, respectively) capable of degrading HCH, with metagenomic data from an HCH dumpsite (B450 mg HCH per g soil), enabled the reconstruction and validation of the last-common ancestor (LCA) genotype. Mapping the LCA genotype (3128 genes) to the subspecies genomes demonstrated that 420% of the genes in each subspecies were absent in the LCA. This includes two enzymes from the ‘upper’ HCH degradation pathway, suggesting that the ancestor was unable to degrade HCH isomers, but descendants acquired lin genes by transposon-mediated lateral gene transfer. In addition, anthranilate and homogentisate degradation traits were found to be strain (selectively retained only by UT26) and environment (absent in the LCA and subspecies, but prevalent in the metagenome) specific, respectively. One draft secondary chromosome, two near complete plasmids and eight complete lin transposons were assembled from the metagenomic DNA. Collectively, these results reinforce the elastic nature of the genus Sphingobium, and describe the evolutionary acquisition mechanism of a xenobiotic degradation phenotype in response to environmental pollution. This also demonstrates for the first time the use of metagenomic data in ancestral genotype reconstruction, highlighting its potential to provide significant insight into the development of such phenotypes.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2018

Engineering the entropy-driven free-energy landscape of a dynamic nanoporous protein assembly

De novo design and construction of stimuli-responsive protein assemblies that predictably switch between discrete conformational states remains an essential but highly challenging goal in biomolecular design. We previously reported synthetic, two dimensional protein lattices self-assembled via disulfide bonding interactions, which endows them with a unique capacity to undergo coherent conformational changes without losing crystalline order. Here, we carried out all-atom molecular dynamics simulations to map the free-energy landscape of these lattices, validated this landscape through extensive structural characterization by electron microscopy and established that it is predominantly governed by solvent reorganization entropy. Subsequent redesign of the protein surface with conditionally repulsive electrostatic interactions enabled us to predictably perturb the free-energy landscape and obtain a new protein lattice whose conformational dynamics can be chemically and mechanically toggled between three different states with varying porosities and molecular densities.

36 MATERIALS SCIENCE↗

DOE OSTI2014

Spatially resolved determination of the short-circuit current density of silicon solar cells via lock-in thermography

We present a spatially resolved method to determine the short-circuit current density of crystalline silicon solar cells by means of lock-in thermography. The method utilizes the property of crystalline silicon solar cells that the short-circuit current does not differ significantly from the illuminated current under moderate reverse bias. Since lock-in thermography images locally dissipated power density, this information is exploited to extract values of spatially resolved current density under short-circuit conditions. In order to obtain an accurate result, one or two illuminated lock-in thermography images and one dark lock-in thermography image need to be recorded. The method can be simplified in a way that only one image is required to generate a meaningful short-circuit current density map. The proposed method is theoretically motivated, and experimentally validated for monochromatic illumination in comparison to the reference method of light-beam induced current.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2025

Laser-driven flash x-ray radiography of a shocked metallic foil

Characterizing hydrodynamic instability evolution in millimeter-scale, high-Z foils is crucial for understanding complex phenomena in high-energy-density physics. Here, we demonstrate a proof-of-concept, laser-driven flash x-ray radiography platform tailored for two-dimensional linear density mapping in shocked high-Z foils. Using chromium (Cr) foils with internal shockwaves (∼100 μm width), our platform achieves a spatial resolution of 59.8 ± 1.4 μm by employing a broadband x-ray source extending into the hundreds of keV range. The setup combines a compound parabolic concentrator cone with a tantalum wire target, a magnetic field to deflect residual transmitted electrons, and a copper casing to shield the sides and rear of the image plate pack. By varying the delay of the short-pulse beam driving the flash x-ray source, we resolve shockwave dynamics, specifically the velocity, position, width, and density profile, within the Cr foil. Reported experimental results are consistent with the corresponding hydrodynamics and radiation transport simulations, which accurately reproduce the measured electron and x-ray source terms. These developments enable the conversion of shockwave radiographs into two-dimensional density maps, enhancing interpretability for hydrodynamic instability evolution applications and validating the simulation approach.

36 MATERIALS SCIENCE↗

DOE OSTI2017

Electrostatic confinement and manipulation of DNA molecules for genome analysis

Very large DNA molecules enable comprehensive analysis of complex genomes, such as human, cancer, and plants because they span across sequence repeats and complex somatic events. When physically manipulated, or analyzed as single molecules, long polyelectrolytes are problematic because of mechanical considerations that include shear-mediated breakage, dealing with the massive size of these coils, or the length of stretched DNAs using common experimental techniques and fluidic devices. Accordingly, we harness analyte “issues” as exploitable advantages by our invention and characterization of the “molecular gate,” which controls and synchronizes formation of stretched DNA molecules as DNA dumbbells within nanoslit geometries. Molecular gate geometries comprise micro- and nanoscale features designed to synergize very low ionic strength conditions in ways we show effectively create an “electrostatic bottle.” This effect greatly enhances molecular confinement within large slit geometries and supports facile, synchronized electrokinetic loading of nanoslits, even without dumbbell formation. Device geometries were considered at the molecular and continuum scales through computer simulations, which also guided our efforts to optimize design and functionalities. In addition, we show that the molecular gate may govern DNA separations because DNA molecules can be electrokinetically triggered, by varying applied voltage, to enter slits in a size-dependent manner. Lastly, mapping the Mesoplasma florum genome, via synchronized dumbbell formation, validates our nascent approach as a viable starting point for advanced development that will build an integrated system capable of large-scale genome analysis.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2011

Quantal density-functional theory in the presence of a magnetic field

We generalize the quantal density-functional theory (QDFT) of electrons in the presence of an external electrostatic field E(r)=-{nabla}v(r) to include an external magnetostatic field B(r)={nabla}xA(r), where (v(r),A(r)) are the respective scalar and vector potentials. The generalized QDFT, valid for nondegenerate ground and excited states, is the mapping from the interacting system of electrons to a model of noninteracting fermions with the same density {rho}(r) and physical current density j(r), and from which the total energy can be obtained. The properties ({rho}(r),j(r)) constitute the basic quantum-mechanical variables because, as proved previously, for a nondegenerate ground state they uniquely determine the potentials (v(r),A(r)). The mapping to the noninteracting system is arbitrary in that the model fermions may be either in their ground or excited state. The theory is explicated by application to a ground state of the exactly solvable (two-dimensional) Hooke's atom in a magnetic field, with the mapping being to a model system also in its ground state. The majority of properties of the model are obtained in closed analytical or semianalytical form. A comparison with the corresponding mapping from a ground state of the (three-dimensional) Hooke's atom in the absence of a magnetic field is also made.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2025

Phase-field model of alloy solidification far from chemical equilibrium at the solid-liquid interface

We further develop a recently introduced phase-field model of far-from-equilibrium alloy solidification under additive manufacturing conditions [K. Ji et al., Phys. Rev. Lett. 130, 026203 (2023)]. This model utilizes enhanced solute diffusivity within the spatially diffuse interface region to quantitatively capture solute trapping with a larger interface width, thereby making simulations on experimentally relevant length and timescales computationally feasible. The main developments presented here include testing the robustness of different variational formulations, extending the model to concentrated alloys by incorporating solid and liquid free energies from thermodynamic databases, as illustrated for hypoeutectic Al-Ag alloys with CALPHAD, extending convergence tests as a function of interface width to 3D, and carrying out simulations in both 2D and 3D to examine existing theories of microstructure development. Our results indicate that the simplest variational formulation that interpolates the bulk free-energy density between its solid and liquid forms is the most robust. Remarkably, for hypoeutectic Al-Ag alloys, this formulation yields a high-velocity nonequilibrium phase diagram that is independent of interface width, thereby demonstrating that the framework of enhanced solute diffusivity can be nontrivially extended to concentrated alloys. Other variational formulations have restricted ranges of materials or processing parameters that can be reliably modeled. We use 2D simulations to construct high-velocity microstructure selection maps for dilute Al-Cu alloys. The results validate the important role of latent heat rejection at the interface and extend the limited predictions of linear stability analysis [A. Karma and A. Sarkissian, Phys. Rev. E 47, 513 (1993)] and sharp-interface 1D simulations to fully nonlinear regimes. Furthermore, 3D simulations, carried out using a computationally tractable axisymmetric cellular/dendritic interface shape, demonstrate a good convergence similar to that observed in 2D as a function of interface width. Full 3D simulations, in turn, reveal that the standard theory of absolute stability is a good predictor of the upper critical velocity beyond which steady-state growth becomes unstable, despite the different morphological manifestations of this instability in 2D and 3D.

36 MATERIALS SCIENCE↗

DOE OSTI2025

Do Research Software Engineers and Software Engineering Researchers Speak the Same Language?

Anecdotal evidence suggests that research software engineers (RSEs) and software engineering researchers (SERs) often use different terminologies for similar concepts, creating communication challenges. To better understand these divergences, we have started investigating how software engineering fundamentals from the SER community are interpreted within the RSE community, identifying aligned concepts, knowledge gaps, and areas for potential adaptation. In conclusion, our preliminary findings reveal opportunities for mutual learning and collaboration, and our systematic methodology for terminology mapping provides a foundation for a crowdsourced extension and validation in the future.

Kehrer, Timo [Univ. of Bern (Switzerland)] (ORCID:↗

DOE OSTI2012

Plate-specific gain map correction for the improvement of detective quantum efficiency in computed radiography

Purpose: The purpose of this work is to improve the noise power spectrum (NPS), and thus the detective quantum efficiency (DQE), of computed radiography (CR) images by correcting for spatial gain variations specific to individual imaging plates. CR devices have not traditionally employed gain-map corrections, unlike the case with flat-panel detectors, because of the multiplicity of plates used with each reader. The lack of gain-map correction has limited the DQE(f) at higher exposures with CR. This current work describes a feasible solution to generating plate-specific gain maps. Methods: Ten high-exposure open field images were taken with an RQA5 spectrum, using a sixth generation CR plate suspended in air without a cassette. Image values were converted to exposure, the plates registered using fiducial dots on the plate, the ten images averaged, and then high-pass filtered to remove low frequency contributions from field inhomogeneity. A gain-map was then produced by converting all pixel values in the average into fractions with mean of one. The resultant gain-map of the plate was used to normalize subsequent single images to correct for spatial gain fluctuation. To validate performance, the normalized NPS (NNPS) for all images was calculated both with and without the gain-map correction. Variations in the quality of correction due to exposure levels, beam voltage/spectrum, CR reader used, and registration were investigated. Results: The NNPS with plate-specific gain-map correction showed improvement over the noncorrected case over the range of frequencies from 0.15 to 2.5 mm{sup -1}. At high exposure (40 mR), NNPS was 50%-90% better with gain-map correction than without. A small further improvement in NNPS was seen from carefully registering the gain-map with subsequent images using small fiducial dots, because of slight misregistration during scanning. Further improvement was seen in the NNPS from scaling the gain map about the mean to account for different beam spectra. Conclusions: This study demonstrates that a simple gain-map can be used to correct for the fixed-pattern noise in a given plate and thus improve the DQE of CR imaging. Such a method could easily be implemented by manufacturers because each plate has a unique bar code and the gain-map for all plates associated with a reader could be stored for future retrieval. These experiments indicated that an improvement in NPS (and hence, DQE) is possible, depending on exposure level, over a wide range of frequencies with this technique.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2014

SU-E-J-194: Dynamic Tumor Tracking End-To-End Testing Using a 4D Thorax Phantom and EBT3 Films

Purpose: To quantify the Vero linac dosimetric accuracy of the tumor dynamic tracking treatment using EBT3 film embedded in a 4D thorax phantom. Methods: A dynamic thorax phantom with tissue equivalent materials and a film insert were used in this study. The thorax phantom was scanned in 4DCT mode with a viscoil embedded in its film insert composed of lung equivalent material. Dynamic tracking planning was performed using the 50% phase CT set with 5 conformal beams at gantry angles of 330, 15, 60, 105 and 150 degrees. Each field is a 3cm by 3cm square centered at viscoil since there was no solid mass target. Total 3 different 1–2cos4 motion profiles were used with varied motion magnitude and cycle frequency. Before treatment plan irradiation, a 4D motion model of the target was established using a series of acquired fluoroscopic images and infrared markers motion positions. During irradiation, fluoroscopic image monitoring viscoil motion was performed to verify model validity. The irradiated films were scanned and the dose maps were compared to the planned Monte Carlo dose distributions. Gamma analyses using 3%–3mm, 2%–3mm, 3%–2mm, 2%–2mm criteria were performed and presented. Results: For each motion pattern, a 4D motion model was built successfully and the target tracking performance was verified with fluoroscopic monitoring of the viscoil motion and its model predicted locations. The film gamma analysis showed the average pass rates among the 3 motion profiles are 98.14%, 96.2%, 91.3% and 85.61% for 3%–3mm, 2%–3mm, 3%–2mm, 2%–2mm criteria. Conclusion: Target dynamic tracking was performed using patient-like breathing patterns in a 4D thorax phantom with EBT3 film insert and a viscoil. There was excellent agreement between acquired and planned dose distributions for all three target motion patterns. This study performed end-to-end testing and verified the treatment accuracy of tumor dynamic tracking.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2012

Fuel Cell Backup Power Geographical Visualization Map (Fact Sheet)

This NREL Hydrogen and Fuel Cell Technical Highlight describes a time-lapse geographical visualization map of early market use of fuel cells for telecommunications backup power. The map synthesizes data being analyzed by NREL's Technology Validation team for the U.S. Department of Energy (DOE) Fuel Cell Technologies Program with DOE's publicly available annual summaries of electric disturbance events.

08 HYDROGEN↗