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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Almost perfect in-phase and anti-phase chaotic and periodic phase synchronization in large arrays of diode lasers

In this paper we study phase synchronization in large arrays of weakly coupled single mode semiconductor laser diodes. We show that if the coupling topology is chosen appropriately, the laser array exhibits robust phase synchrony (including chaotic and non-chaotic phase synchrony). Furthermore, one can define coupling topologies that lead to chaotic anti-phase synchronization. To the best of our knowledge, chaotic anti-phase synchronization has not been observed in large arrays of coupled nonlinear oscillators. Additionally, when diodes are coupled via a decayed non-local coupling scheme, the leading spatial mode can be stable. This leads to an almost-perfect phase synchronous state where the phases are synchronized, but the system is not set exactly on the synchronization manifold. This almost-perfect phase synchronous state is robust to noise and frequency disorder and can be realized under periodic (fixed-intensity limit cycle) continuous-wave and chaotic behavior. The presented result is an example of the broader phenomenon of linear transverse mode selection taking place in a coupled oscillator system with nonlinear dynamics.

47 OTHER INSTRUMENTATION↗
DOE OSTI2018

Deep Very Large Array Observations of the Merging Cluster CIZA J2242.8+5301: Continuum and Spectral Imaging

Despite the progress that has been made in understanding radio relics, there are still open questions regarding the underlying particle acceleration mechanisms. In this paper, we present deep 1–4 GHz Very Large Array (VLA) observations of CIZA J2242.8+5301 ( z = 0.1921), a double radio relic cluster characterized by small projection on the plane of the sky. Our VLA observations reveal, for the first time, the complex morphology of the diffuse sources and the filamentary structure of the northern relic. Additionally, we discover new, faint, diffuse radio emission extending north of the main northern relic. Our Mach number estimates for the northern and southern relics, based on the radio spectral index map obtained using the VLA observations and existing LOw Frequency ARray (LOFAR) and Giant Metrewave Radio Telescope data, are consistent with previous radio and X-ray studies ( and ). However, color–color diagrams and models suggest a flatter injection spectral index than the one obtained from the spectral index map, indicating that projection effects might be not entirely negligible. The southern relic consists of five "arms." Embedded in it, we find a tailed radio galaxy that seems to be connected to the relic. A spectral index flattening, where the radio tail connects to the relic, is also measured. We propose that the southern relic may trace AGN fossil electrons that are reaccelerated by a shock, with an estimated strength of . High-resolution mapping of other tailed radio galaxies also supports a scenario where AGN fossil electrons are revived by the merger event and could be related to the formation of some diffuse cluster radio emission.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Composite Behavior of Nanopore Array Large Memristors

Synthetic nanopores were recently demonstrated with memristive and nonlinear voltage-current behaviors, akin to ion channels in a cell membrane. Such ionic devices are considered a promising candidate for the development of brain-inspired neuromorphic computing techniques. In this work, we show the composite behavior of nanopore-array large memristors, formed with different membrane materials, pore sizes, electrolytes, and device arrangements. Anodic aluminum oxide (AAO) membranes with 5 nm and 20 nm diameter pores and track-etched polycarbonate (PCTE) membranes with 10 nm diameter pores are tested and shown to demonstrate memristive and nonlinear behaviors with approximately 107–1010 pores in parallel when electrolyte concentration across the membranes is asymmetric. Ion diffusion through the large number of channels induces time-dependent electrolyte asymmetry that drives the system through different memristive states. The behaviors of series composite memristors with different configurations are also presented. In addition to helping understand fluidic devices and circuits for neuromorphic computing, the results also shed light on the development of field-assisted ion-selection-membrane filtration techniques as well as the investigations of large neurons and giant synapses. Further work is needed to de-embed parasitic components of the measurement setup to obtain intrinsic large memristor properties.

Chemistry↗
DOE OSTI2021

Very Large Array imaging rules out precessing radio jets in three DES–SDSS-selected candidate periodic quasars

ABSTRACT Periodic quasars have been suggested as candidates for hosting binary supermassive black holes (SMBHs), although alternative scenarios remain possible to explain the optical light-curve periodicity. To test the alternative hypothesis of precessing radio jet, we present deep 6 GHz radio imaging conducted with NSF’s Karl G. Jansky Very Large Array (VLA) in its C configuration for the three candidate periodic quasars, DES J024703.24−010032.0, DES J024944.66−000036.8, and DES J025214.67−002813.7. Our targets were selected based on their optical variability using 20 yr long multicolour light curves from the Dark Energy Survey (DES) and the Sloan Digital Sky Survey (SDSS). The new VLA observations show that all three periodic quasars are radio-quiet with the radio loudness parameters measured to be $R\equiv f_{6\, {\rm cm}}/f_{{\rm 2500}}$ of ≲1.0–1.5 and the k-corrected luminosities νLν[6 GHz] of ≲5–21 × 1039 erg s−1. They are in stark contrast to previously known periodic quasars proposed as binary SMBH candidates such as the blazar OJ 287 and PG1302−102. Our results rule out optical emission contributed from precessing radio jets as the origin of the optical periodicity in the three DES–SDSS-selected candidate periodic quasars. Future continued optical monitoring and complementary multiwavelength observations are still needed to further test the binary SMBH hypothesis as well as other competing scenarios to explain the optical periodicity.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Automated co-adding and energy calibration of large array microcalorimeter data with zero sample knowledge

State-of-the-art microcalorimeter spectrometers now contain large detector arrays with hundreds of individual pixels. Each individual pixel outputs a unique and non-linear response with respect to deposited energy. This work describes a pattern-recognition algorithm to combine these responses into a single energy-calibrated histogram, referred to as co-adding pixels. Photo-peaks from different pixels are matched together based upon how well the match aligns the centroids and heights of neighboring peaks. This usually results in around 100 co-adding calibration points from 30 to 300 keV for a several day acquisition of plutonium items with masses between 0.5 and 10 grams. An additional algorithm energy-calibrates this co-added spectrum using the fluoresced K x-ray emissions from a tantalum absorber and inherent x-ray escape peaks from the tin absorbers. Both algorithms operate without knowledge of the source and are fully automated. This work presents results from the acquisitions of high and low burnup plutonium, 10% enriched uranium, a 153 Gd calibration source, and a 57 Co+ 166m Ho calibration source. In all measurements, resolution defined as the full-width at half-maximum (FWHM) of photo-peaks is preserved between the individual pixel and co-added spectra at around 65 eV for incident photon energies between 60 and 208 keV. The energy calibration algorithm is approximate and yields a calibration curve off by an average of around 200 eV for incident photon energies between 60 and 208 keV.

47 OTHER INSTRUMENTATION↗
DOE OSTI2023

Development of a large array of Silicon Drift Detectors for high-rate synchrotron fluorescence spectroscopy

An array of small-area Silicon Drift Detectors (SDD), named Hera, has been developed at Brookhaven National Laboratory (BNL) in the past few years. Its primary application is high-rate spectroscopy at synchrotrons. Each SDD pixel is a 1 mm × 1 mm square to match the footprint of the original diode-based pixel detector called Maia, which was developed for the same application. The replacement of the diode with an SDD allows for better energy resolution at short shaping times and an increased stability of the detector. 32, 96, and 384-channel arrays were designed and fabricated and achieved a Full Width Half Maximum (FWHM) as low as 176 eV at 5.9 keV with peaking time of 1 μs at -13°C. The sensor design, simulation, fabrication, its readout system, and its spectroscopic performance are reported.

47 OTHER INSTRUMENTATION↗
DOE OSTI2018

Seismic Wave Coherence as a Function of Propagation Azimuth at the Large-N Array, Source Physics Experiment

The Large-N array of the Source Physics Experiment (SPE) consisted, in part, of 496 vertical component geophones that recorded the seismic wave field produced by the SPE-5 buried chemical explosion. Preliminary observations of the data showed a large degree of azimuthally dependent seismic scattering, particularly for post-P wave arrivals, hindering surface wave analysis. We document and quantify the azimuthal dependence of the wave field scattering in order to guide future coherent wave field processing methods. Specifically, we form three linear arrays, with different nominal source-receiver azimuths, by extracting a subset of the Large-N stations. For each linear array, we evaluate wave field coherence as a function of frequency and inter-station distance. For P waves, we observe that there is a strong azimuthal dependence of wave coherence, with the highest degree of scattering occurring in a northwest/southeast propagation direction. This suggests that there are structural elements beneath the Large-N array that affect the direct source to receiver body wave ray path. We also observe that the scattering of the post-P energy displays a coherence that is dependent on both frequency and azimuthal direction. This energy is preferentially coherent in the southwest-to-northeast propagation direction, consistent with the strike of the steeply dipping fault (Boundary fault) adjacent to the northeast side of the Large-N array, but only at low frequencies (<10 Hz). At higher frequencies, the azimuthally dependent wave coherence diminishes, suggesting that the scattering of high frequency portion of the post-P wave field is independent of the large-scale geologic structure at this site.

58 GEOSCIENCES↗
DOE OSTI2019

Azimuthally Dependent Seismic-Wave Coherence at the Source Physics Experiment Large-N Array

Abstract We report on azimuthally dependent seismic scattering at the Source Physics Experiment (SPE) using the large-N array. The large-N array recorded the seismic wavefield produced by the SPE-5 buried chemical explosion, which occurred in April 2016 at the Nevada National Security Site, U.S.A. By selecting a subset of vertical-component geophones from the large-N array, we formed 10 linear arrays, with different nominal source–receiver azimuths as well as six 2D arrays. For each linear array, we analyze wavefield coherency as a function of frequency and interstation distance. For both the P arrival and post-P arrivals, the coherency is higher in the northeast propagation direction, which is consistent with the strike of the steeply dipping Boundary fault adjacent to the northwest side of the large-N array. Conventional array analysis using a suite of 2D arrays indicates that the presence of the fault may help explain the azimuthal dependence of the seismic-wave coherency for all wave types. This fault, which separates granite from alluvium, may be acting as a vertically oriented refractor and/or waveguide.

58 GEOSCIENCES↗
DOE OSTI2019

Developing AlMn Films for Argonne TES Fabrication

The reference design for the next-generation cosmic microwave background (CMB) experiment, CMB-S4, relies on large arrays of transition-edge sensor (TES) bolometers coupled to Superconducting Quantum Interference Device (SQUID)-based readout systems. Mapping the CMB to near cosmic variance limits will enable the search for signatures of inflation and constrain dark energy and neutrino physics. AlMn TESes provide simple film manufacturing and highly uniform arrays over large areas to meet the requirements of the CMB-S 4 experiment. TES parameters such as critical temperature and normal resistance must be tuned to experiment specifications and can be varied based on geometry and steps in the fabrication process such as deposition layering, geometry, and baking time and temperature. Using four-terminal sensing, we measured T C and R N of AlMn 2000 ppm films and devices of varying thicknesses fabricated at Argonne National Laboratory to motivate device geometries and fabrication processes to tune T C to 150–200 mK and R N to ~10 mΩ. Furthermore, measurements of IV curves and time constants for the resulting devices of varying leg length were made using time-division SQUID multiplexing and determined TC, G, k, f 3db , and RN. We present the results of these tests along with the geometries and fabrication steps used to tune the device parameters to the desired limits.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Spatially Dependent Seismic Wavefield Scattering from an Underground Chemical Explosion: Analysis of the Source Physics Experiment Dry Alluvium Geology Large- N Array

Explosion sources have been observed to generate significant shear‐wave energy despite their isotropic nature. To investigate this phenomenon, we conduct an analysis of the seismic data collected as part of the Source Physics Experiment (SPE): Dry Alluvium Geology (DAG) and investigate the generation of shear‐wave energy via scattering. The data were produced by three underground chemical explosions and consist of three‐component seismograms, which were recorded by the DAG Large‐N array. Synthetic tests suggest that for the DAG experiments, small‐scale stochastic heterogeneities, defined as features with correlation lengths of 10–100s of meters, are more effective than large‐scale geologic structure (scales >1–10 km) at reproducing the scattering of explosion generated wavefields observed at DAG. We analyze the seismic data for spatially variable ratios between transversely and radially polarized seismic energy, and then estimate the mean free path of P and S waves. All analyses are conducted within a frequency band of 5–50 Hz. The ratio of transversely to radially polarized energy is the highest in the east and west portion of the Large‐N array. In addition, the magnitude of the estimated S‐wave mean free path is shorter in the eastern portion of the Large‐N array. This variation indicates that the eastern area of the DAG array is where more scattering is occurring, suggesting azimuthal dependence of P‐to‐P and P‐to‐S scattering. Furthermore, this azimuthal dependence of P‐to‐S scattering can have implications for explosion discrimination based on spectral ratios of seismic wave types, because the general assumption is that explosions do not generate shear‐wave energy. Synthetic tests modeling only larger‐scale geologic structure had lower transversely polarized energy (only four stations showing a transversely to radially polarized energy ratio greater than 1) and fewer stations (<10) displaying shorter (<300 m) mean free paths than what was observed in the DAG data results.

Darrh, Andréa Nicole↗
DOE OSTI2019

Velocity Structure at the Source Physics Experiment Phase I Site Obtained with the Large-N Array Data

The Source Physics Experiment (SPE) consists of a series of chemical explosions at the Nevada National Security Site. The goal of the SPE is to understand and model seismic-wave generation and propagation from these explosions. To achieve this goal, we need an accurate velocity model of the SPE site. A large-N seismic array deployed at the SPE site during one of the chemical explosions (SPE-5) provides great data for this purpose. The array consists of 996 geophones and covers an area of approximately 2 &times; 2.5 km. In addition to the SPE-5 explosion, the array recorded 53 large weight drops. Using the large-N seismic array recordings, we perform first-arrival analysis and obtain a 2D P-wave velocity model of the SPE site. We image a sharp transition from high-velocity Cretaceous granite to low-velocity Quaternary alluvium. Other geological units such as the Tertiary volcanic rocks and Paleozoic sedimentary rocks are also clearly shown. The results of this work provide important local geological information and will be incorporated into the larger 3D modeling effort of the SPE program to validate the predictive models developed for the site.

58 GEOSCIENCES↗
DOE OSTI2023

Multiscale architecture for fast optical addressing and control of large-scale qubit arrays

This paper presents a technique for rapid site-selective control of the quantum state of particles in a large array using the combination of a fast deflector (e.g., an acousto-optic deflector) and a relatively slow spatial light modulator (SLM). The use of SLMs for site-selective quantum state manipulation has been limited due to slow transition times that prevent rapid, consecutive quantum gates. By partitioning the SLM into multiple segments and using a fast deflector to transition between them, it is possible to substantially reduce the average time increment between scanner transitions by increasing the number of gates that can be performed for a single SLM full-frame setting. We analyzed the performance of this device in two different configurations: In configuration 1, each SLM segment addresses the full qubit array; in configuration 2, each SLM segment addresses a subarray and an additional fast deflector positions that subarray with respect to the full qubit array. With these hybrid scanners, we calculated qubit addressing rates that are tens to hundreds of times faster than using an SLM alone.

Graham, T. M.↗
DOE OSTI2021

Tuning Gold Nanoparticle Size with Fixed Interparticle Spacing in Large-Scale Arrays: Implications for Plasmonics and Nanoparticle Etching Masks

Gold nanoparticles play an important role in plasmonic arrays, including, but not limited to, photovoltaic, biomedical, sensing, optical, and catalytic applications. For plasmonic arrays, control over spatial variables of the array, such as nanoparticle size and spacing, must be judiciously cared for. In this work, we present here a multistep deposit/dewet process for nanoparticle ensemble fabrication that exploits thermally driven solid-state diffusional dewetting, coupled with Ostwald ripening, to tune the nanoparticle size or area coverage for a particular particle–particle spacing. The initial dewetting process defines the spatial period of the array, with subsequent dewetting steps growing the nanoparticles while adhering to the “seeded” period from the first dewetting. Following the fifth deposit/dewet cycle, relative to the first cycle, the mean nanoparticle height exhibited a percent increase of 90 and 66% for 5 and 7.5 nm multistep deposit/dewet processes, respectively, while minimally impacting the ensemble period. This provides unprecedented control over the spatial parameters of large-scale nanoparticle ensembles for plasmonic and etching-mask applications where a particular particle size and spacing are desired. Due to the simplicity of the technique and its area scalability, the cyclic deposition/dewetting process is shown here to be a method that can be easily scaled up to apply to large-area (up to meter-size) applications.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Physics-constrained Gaussian process model for prediction of hydrodynamic interactions between wave energy converters in an array

To improve the efficiency of wave farms and achieve maximum power generation, the layout of wave energy converters (WECs) in an array needs to be carefully designed so that the hydrodynamic interactions can be positively exploited. For this, the hydrodynamic characteristics of the WEC array in different layouts need to be calculated. However, such calculations using numerical models usually entail significant computational cost, especially for large arrays of WECs. To address the computational challenge, a physics-constrained Gaussian process (GP) model is proposed to replace the original expensive numerical model and predict the hydrodynamic characteristics of the WECs for any array layout. By exploring the relationship between the WEC array (i.e., the input) and different hydrodynamic characteristics (i.e., the output), here we summarize a set of physical constraints/features, including invariance, symmetry, and additivity. This prior knowledge about the input-output relationship is then directly embedded in the constructed GP model through the design of physics-constrained kernels. In particular, a double-sum invariant kernel is first developed to incorporate the invariance and symmetry features, and then an additive kernel is developed to incorporate the additive feature of the problem. The invariant kernel and the additive kernel are then integrated to construct the physics-constrained GP model. Compared to the standard GP model, the proposed physics-constrained GP models require less training data to achieve the desired accuracy in predicting the hydrodynamic characteristics and are also less vulnerable to the curse of dimensionality (i.e., good scalability for large arrays) due to the use of an additive kernel. The efficiency, accuracy, and scalability of the proposed approach are demonstrated through an application to predict the hydrodynamic characteristics for WEC arrays of different sizes and layouts.

16 TIDAL AND WAVE POWER↗