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At least 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Adiabatic and isothermal configurations for Re 4 Si 7 transverse thermoelectric power generators

We report that transverse thermoelectric generators (TTEGs) have the potential to overcome two challenging problems that limit the commercial application of classical thermoelectric generators (TEGs): the significant irreversible efficiency losses in the contacts and the thermal degradation of the contacts at the hot end. TTEGs are built from a single material that can generate a thermoelectric current in a direction that is orthogonal to a temperature gradient. They only require a single set of contacts that are displaced away from the hot end. Here, we experimentally explore the device design considerations for optimizing the performance of this far less explored class of thermal-to-electric generation devices. We fabricate Re 4 Si 7 TTEGs and show that there is no measurable loss in efficiency with a single set of contacts that are midway between the hot and cold ends. We show that a new effect must be considered: the appearance of transverse thermal gradients that lead to significant differences between the performance of TTEGs implemented in isothermal and adiabatic geometries. The isothermal TTEG configuration leads to much higher device efficiencies. Overall, this work highlights how different the design of TTEGs is from that of conventional TEGs and the importance of controlling the device geometry for optimum waste heat recovery.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2024

Electron-impact excitation data for W 2+ in support of tungsten spectroscopy and re-deposition measurements for magnetically-confined plasmas

Abstract To better understand plasma wall interactions involving tungsten, accurate atomic structure and electron-impact driven collisional processes for near-neutral ion stages of tungsten are required. Complementing existing work on neutral and singly ionised tungsten, atomic structure and collisional calculations for W 2+ electron-impact excitation have been completed. These excitation calculations are an important component of S/XB coefficients for near-neutral charge states, which may be used to spectroscopically infer re-deposition of tungsten at the plasma-solid boundary of fusion relevant devices. With W 2+ in particular having emission lines that can be observed at ultraviolet (UV) wavelengths, while higher charge states of tungsten are unlikely to have lines possible to observe outside of the vacuum UV range. The atomic structure was generated using the General-purpose Relativistic Atomic Structure Package (GRASP 0 ), implementing the Multi-configuration Dirac Fock approach. This structure was the basis for a subsequent Dirac R -matrix electron-impact excitation calculation to provide Maxwellian averaged rate coefficients. A synthetic spectrum was generated from this data using a collisional-radiative model to predict the strongest W III spectral lines and these lines were compared to emission from the Compact Toroidal Hybrid (CTH) plasma device. Several of the strongest W III lines are observed in CTH and agree well with the modelled line wavelengths and intensities, a table of these lines is provided that could be observed in other devices.

McCann, M. (ORCID:0000000215321240)↗
DOE OSTI2023

In-field strain and temperature measurements in a (RE)Ba 2 Cu 3 O 7–x coil via Rayleigh-backscattering interrogated optical fibers

(RE)Ba 2 Cu 3 O 7-x (REBCO) conductors have overcome technical challenges related to manufacturing quality, length homogeneity, scale-up of piece-length, and joints. There is one remaining technical challenge, however, which is common to all high temperature superconductors and lies in effective detection of failure to prevent material degradation. An innovative technique based on optical fibers interrogated by Rayleigh backscattering has been shown to have advantages over voltage taps at detecting incipient faults. Prior work has experimentally demonstrated the technique in several implementation scenarios, including direct integration of optical fibers into superconducting conductors and cables to create a class of ‘SMART’ conductors and cables that are able to monitor their own health. In this paper, the magnet monitoring technique based on Rayleigh backscattering interrogated optical fibers has been experimentally studied in a model coil subject to external magnetic field, where different fiber integration methods are used to increase selectivity of the fiber sensor to temperature. Results show that the spectral shift displays different features during strain and thermal transients. The implications of the results in terms of potential and limitations of each sensor as well as strain-temperature decoupling are discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Variation in supercurrent connectivity and vortex pinning of state-of-the-art pulsed laser deposited RE Ba 2 Cu 3 O 7- x coated conductors

REBa 2 Cu 3 O 7-x (REBCO, RE: rare earth) coated conductors (CCs) suffer from great critical current I c differences between different manufacturers, I c variations within individual manufacturers, and often significant lengthwise fluctuations. The understanding of such variations is complicated by the lack of a direct correlation between I c and the critical current density J c . In fact, although J c is the fundamental property determined by the local vortex pinning landscape, I c is often limited by variable current blocking mechanisms. An important practical complexity is commercial practices of performing J c and I c evaluations based on I c at 77 K and self-field (sf), where connectivity variation dominates over vortex pinning variations. However, at higher fields and lower temperatures, vortex pinning becomes more complex and highly variable, making predictions of I c and J c at arbitrary temperature T, magnetic field H, and field orientation θ, quite uncertain. To address some aspects of this problem, we conducted detailed spool-to-spool performance characterization on recently manufactured REBCO CCs. Despite J c (77 K, sf) varies by only ∼11%, J c (77 K, 1 T) of its minimum and maximum (for H//ab-plane) show variations of ∼21% and ∼32%, respectively. This emphasizes the shortcoming in using J c (77 K, sf) as parameter for evaluating even the low field performance. An even more remarkable spool-to-spool J c variation of ∼68% was observed at 20 K and 15 T for H//ab-plane. To identify the origin of such lack of reproducibility we performed microstructural characterizations, which revealed, within the REBCO layer, large variation in the density of copper oxide (CuO x ) particles ranging from 0.1 to 2 μm in size. We believe that they play a decisive role in reducing the effective cross-section of the REBCO layer by not simply blocking current themselves, but also by nucleating off-axis REBCO grains, whose misoriented grain boundaries adversely impact REBCO grain-to-grain connectivity. The REBCO growth associated with high density CuO x particles also leads to the more disordered spatial arrangement of BaHfO 3 precipitate arrays, which, when self-aligning along the ab-planes, generate stronger pinning enhancing J c (H//ab) at all temperatures. In this way, we established that variations of both connectivity and vortex pinning are thus directly coupled. Our results also explain why the so-called ‘lift-factor’, typically defined by the ratio between I c (T, H) and I c (77 K, sf), frequently turns out to be unreliable.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Modeling of ExB effects on tungsten re-deposition and transport in the DIII-D divertor

Mixed-material DIVIMP-WallDYN modelling, now incorporating ExB drifts, is presented that simultaneously reproduces tungsten (W) erosion and deposition patterns observed during the DIII-D Metal Rings Campaign, in which a toroidally symmetric set of W-coated tiles were installed in the carbon (C) DIII-D divertor. Since most reactor plasma facing component (PFC) designs call for mixed-material environments, including ITER’s W/Be enviroment, the divertor targets will quickly evolve into reconstitued surfaces of multiple elements. This work identifies controlling physics that affects material migration patterns in the divertor, which impact PFC lifetimes and impurity leakage from the divertor to the core. These simulations indicate that radial and poloidal ExB transport dominates over parallel force balance for high-Z impurities such as W in the divertor region of DIII-D. It is demonstrated that ExB drifts are required to reproduce the experimental observation of non-local W and C co-accumulation in a band ~7-9 cm outboard of the outer-strike-point (OSP) W source, for attached Lmode conditions in the unfavorable ion grad-B drift direction. In addition, W gross erosion is localized to the region outboard of the OSP, as the formation of C co-deposits suppresses W erosion at the strike point. Time-dependent simulations with scaled ExB impurity drifts (60% of the OEDGE-calculated drift velocity) and W re-erosion quantitatively reproduce these features, including depth-resolved W/C ratios, within a factor of 2 over ~115 seconds of accumulated plasma exposure. The location of co-deposition regions is shown to be well represented by an analytic leakage model, driven largely by poloidal ExB drifts. Qualitative agreement is also found between campaign-integrated W deposition measurements and simulations for the favorable ion grad-B drift direction, the standard mode of operation for most tokamaks. Furthermore, these results imply that a longterm inward radial migration of material from the outer divertor through the private flux region may occur in future devices.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Extreme high-field superconductivity in thin Re films

We report the high-field superconducting properties of thin, disordered Re films via magnetotransport and tunneling density of states measurements. Films with thicknesses in the range of 9 to 3 nm had normal-state sheet resistances of ~0.2 kΩ to ~1 kΩ and corresponding transition temperatures in the range of 6 to 3 K. Tunneling spectra were consistent with those of a moderate coupling BCS superconductor. Notwithstanding these unremarkable superconducting properties, the films exhibited an extraordinarily high upper critical field. Here, we estimate their zero temperature H c2 to be more than twice the Pauli limit. Indeed, in 6-nm samples the estimated reduced critical field H c2 /T c ~ 5.6T/K is among the highest reported for any elemental superconductor. Although the sheet resistances of the films were well below the quantum resistance R Q = h/4e 2 , their H c2 's approached the theoretical upper limit of a strongly disordered superconductor for which k F ℓ ~ 1.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Re-Assembly and Test of a COMB Dipole Magnet With STAR Wires

Rare-Earth Barium Copper Oxide (REBCO) coated conductors are an attractive option for application in high field accelerator magnets due to their high critical field and the convenience of fabrication without heat treatment compared to some other superconductors. A small REBCO accelerator magnet was previously fabricated and tested in liquid nitrogen, demonstrating over 90% critical current retention in the coils. This paper describes the magnet re-assembly with a different support structure and its test in liquid helium at 1.8–4.5 K. The magnet quench history along with the instrumentation data is presented and discussed.

43 PARTICLE ACCELERATORS↗
DOE OSTI2025

SST-TG-P1F4R3200: Decaying Stably-Stratified Turbulence (SST), Initialized Using Taylor-Green Vortices (TG) at Prandtl Number Pr=1, Froude Number Fr=4, Reynolds Number Re=3200

This dataset comprises direct numerical simulations (DNS) of decaying stably-stratified turbulence influenced by a linear background density gradient, initialized using an array of Taylor-Green vortices, as described in [Riley & de Bruyn Kops (2003)](https://doi.org/10.1063/1.1578077). The initial Prandtl, Froude, and Reynolds numbers are (Pr, Fr, Re) = (1, 4, 3200). A total of 15,000 snapshots are recorded at uniform time intervals, each with a spatial resolution of 512x512x256 grid points. Four flow variables are associated with each snapshot: the three velocity components (u,v,w) and the perturbed density field (rho) away from the background gradient. All fields are stored in binary format (32-bit little-endian), each with a size of 255 MB, yielding a total dataset size of 15.3 TB. Further details are referenced in the attached README file, and a current list of publications and associated analysis tools are provided at https://stratified-turbulence.github.io/web/.

42 ENGINEERING↗
DOE OSTI2025

SST-TG-P50F4R3200: Decaying Stably-Stratified Turbulence (SST), Initialized Using Taylor-Green Vortices (TG) at Prandtl Number Pr=50, Froude Number Fr=4, Reynolds Number Re=3200

This dataset comprises direct numerical simulations (DNS) of decaying stably-stratified turbulence influenced by a linear background density gradient, initialized using an array of Taylor-Green vortices, extending the Pr=1 simulations performed in [Riley and de Bruyn Kops (2003)](https://doi.org/10.1063/1.1578077). The initial Prandtl, Froude, and Reynolds numbers are (Pr, Fr, Re) = (50, 4, 3200). A total of 1,680 snapshots are recorded at uniform time intervals, each with a spatial resolution of 3584x3584x1792 grid points. Four flow variables are associated with each snapshot: the three velocity components (u,v,w) and the perturbed density field (rho) away from the background gradient. All fields are stored in binary format (32-bit little-endian), each with a size of 85.8 GB, yielding a total dataset size of 577 TB. Further details are referenced in the attached README file, and a current list of publications and associated analysis tools are provided at https://stratified-turbulence.github.io/web/.

42 ENGINEERING↗
DOE OSTI2025

SST-TG-P7F4R3200: Decaying Stably-Stratified Turbulence (SST), Initialized Using Taylor-Green Vortices (TG) at Prandtl Number Pr=7, Froude Number Fr=4, Reynolds Number Re=3200

This dataset comprises direct numerical simulations (DNS) of decaying stably-stratified turbulence influenced by a linear background density gradient, initialized using an array of Taylor-Green vortices, extending the Pr=1 simulations performed in [Riley and de Bruyn Kops (2003)](https://doi.org/10.1063/1.1578077). The initial Prandtl, Froude, and Reynolds numbers are (Pr, Fr, Re) = (7, 4, 3200). A total of 15,250 snapshots are recorded at uniform time intervals, each with a spatial resolution of 1280x1280x640 grid points. Four flow variables are associated with each snapshot: the three velocity components (u,v,w) and the perturbed density field (rho) away from the background gradient. All fields are stored in binary format (32-bit little-endian), each with a size of 4 GB, yielding a total dataset size of 244 TB. Further details are referenced in the attached README file, and a current list of publications and associated analysis tools are provided at https://stratified-turbulence.github.io/web/.

42 ENGINEERING↗
DOE OSTI2020

Effects on Human Non-Small Lung Cancer Cell growth of Cu(II), Au(III) and Re(I) Complexes Containing N-donor Pyridyl Ligands: A Senior Undergraduate Research Project

Hands-on synthetic laboratory experiences are critically important for undergraduate chemistry majors. A senior undergraduate research experience at the College of Wooster is presented in the current work. The inorganic complexes [Cu(phenan) 2 (NO 3 ) 2 ] (1; phenan = phenanthridine) and [Au(phenan)Cl 3 ](2) were prepared by metallation of the phenan ligand in a 1:1 CH 3 OH/CH 2 Cl 2 mixture at room temperature. Complex 1 is a new inorganic coordination compound. The structures were confirmed by X-ray crystallography. Complex 1 reveals a distorted octahedral geometry around the central Cu (II) metal ion. In complex 2, the Au(III) atom exhibits a square planar geometry. In addition, we investigated [Cu(dmeobpy)(H 2 O) 2 ][NO 3 ] 2 (3; dmeobpy = 4,4’-dimethoxy-2,2’-bipyridine), [Cu(bap)(NO 3 ) 2 ](4; bap = 2,6-bis(azaindole)pyridine) and [Re(CO) 3 (dmeobpy)Cl] (5). The cytoxocities of 1-5, phenan, dmeobpy, bap and cisplatin were evaluated against several human non-small cell lung cancer cell lines (NCI-H1975, HCC827, NCI-H460, and NCI-A549). Compound 1 exhibited modest antitumor activity against the HCC827 cell line, with an IC 50 value of 19 µM. Compound 3 exhibits lower cytotoxic activity than 1. Finally, the cytotoxic activity of complex 5 (IC 50 < 11 µM) is significantly greater than 1 and 3 against the H1975 cancer cell line.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Re-evaluating Pleistocene–Holocene occupation of cave sites in north-west Thailand: new radiocarbon and luminescence dating

Established chronologies indicate a long-term ‘Hoabinhian’ hunter-gatherer occupation of Mainland Southeast Asia during the Terminal Pleistocene to Mid-Holocene (45 000–3000 years ago). Here, the authors re-examine the ‘Hoabinhian’ sequence from north-west Thailand using new radiocarbon and luminescence data from Spirit Cave, Steep Cliff Cave and Banyan Valley Cave. The results indicate that hunter-gatherers exploited this ecologically diverse region throughout the Terminal Pleistocene and the Pleistocene–Holocene transition, and into the period during which agricultural lifeways emerged in the Holocene. Hunter-gatherers did not abandon this highland region of Thailand during periods of environmental and socioeconomic change.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

TEAMER: Performance mapping of Re Vision's Persistance PTO

Contains datasets from experimental measurements that were used to validate Re Vision's Persistence PTO's efficiency and performance. These measurements were obtained using a dynamometer test bench setup. The data includes open-circuit voltage and loss measurements to validate machine characteristics, efficiency mapping tests to determine the generator's performance mapping, and efficiency mapping tests to determine the converter's efficiency over the feasible operating range. This data was collected between June 2023 and September 2023. The data was collected at the National Renewable Energy Laboratory's Flatirons Campus, Colorado, United States. The data was collected using NREL's 5-kW dynamometer test bench, equipped with a torque sensor and various voltage and current sensors fed to a dedicated data acquisition system. Units for the data are included in the data file headers for each data series. A text editor or spreadsheet software such as Excel is required to view the *.csv data. The data are also provided in *.mat files. To view data plots, a Matlab script with *.mat files are provided.

16 TIDAL AND WAVE POWER↗
DOE OSTI2025

Array-Based Seismic Measurements of OSIRIS-REx’s Re-Entry

The return home of the OSIRIS-REx spacecraft in September 2023 marked only the fifth time that an artificial object entered the Earth’s atmosphere at interplanetary velocities. Although rare, such events serve as valuable analogs for natural meteoroid re-entries; enabling study of hypersonic dynamics, shock wave generation, and acoustic-to-seismic coupling. Here, in this study, we report on the signatures recorded by a dense (100 m scale) 11-station array located almost directly underneath the capsule’s point of peak atmospheric heating in northern Nevada. Seismic data are presented, which allow inferences to be made about the shape of the shock wave’s footprint on the surface, the capsule’s trajectory, and its flight parameters.

58 GEOSCIENCES↗
DOE OSTI2025

Preface to the Focus Section on Geophysical Observations of the OSIRIS-REx Sample Return Capsule Re-Entry

Here, this focus issue of Seismological Research Letters compiles observational results and theoretical interpretations related to the OSIRIS-REx SRC re-entry and multidisciplinary analyses highlighting broader scientific applications of such events (Carr et al., 2025; Clemente et al., 2025; Fernando et al., 2025; KC et al., 2025; Silber and Bowman, 2025). The articles contribute toward a geophysical understanding of how hypersonic objects interact with Earth’s atmosphere and how generated acoustic waves propagate through the atmosphere and couple into the ground as measurable seismic signals.

58 GEOSCIENCES↗
DOE OSTI2021

Re-Analysis of DARHT Axis 2 S4 Magnet Sweep Measurements

The Dual-Axis Radiographic Hydrodynamic Test (DARHT) facility provides flash radiography capabilities using two electron Linear Induction Accelerators (LIA’s). Understanding fundamental properties of the electron beams is essential to optimizing spot size and dose for radiography. This work describes distribution measurements of a single-kicked electron beam (16.5MeV, 1.7kA, 60ns) at a location downstream at imaging station C on DARHT Axis 2. The beam at station C is focused by the S4 solenoid located upstream. The beam distribution is measured by imaging optical transition radiation (OTR) from electrons striking a 51-µm thick titanium foil. This data and analysis were originally published by Ekdahl. The results here are a re-analysis of the asymmetric halo emittance contribution as compared to the emittance resulting from the FWHM of the distribution. This is accomplished using xtr2 fits to the data which include non-linear magnetic field effects in S4. Also examined are the calculated S4 spherical aberration contributions to the emittance using xtr.

43 PARTICLE ACCELERATORS↗