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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

An integrated photonic engine for programmable atomic control

Abstract Solutions for scalable, high-performance optical control are important for the development of scaled atom-based quantum technologies. Modulation of many individual optical beams is central to applying arbitrary gate and control sequences on arrays of atoms or atom-like systems. At telecom wavelengths, miniaturization of optical components via photonic integration has pushed the scale and performance of classical and quantum optics far beyond the limitations of bulk devices. However, material platforms for high-speed telecom integrated photonics lack transparency at the short wavelengths required by leading atomic systems. Here, we propose and implement a scalable and reconfigurable photonic control architecture using integrated, visible-light modulators based on thin-film lithium niobate. We combine this system with techniques in free-space optics and holography to demonstrate multi-channel, gigahertz-rate visible beamshaping. When applied to silicon-vacancy artificial atoms, our system enables the spatial and spectral addressing of a dynamically-selectable set of these stochastically-positioned point emitters.

Science & Technology - Other Topics↗
DOE OSTI2022

Carbon nanotubes decorated with Pt as a viable electrocatalyst system using electrochemical atomic layer deposition

Surface limited redox replacement (SLRR) is an electrochemical deposition method designed to deposit metal thin films, typically onto other metals, that are mere monolayers in thickness, where such low dimensions allows catalyst-support interactions to affect catalyst efficiency. Here we explore the growth of Pt, using iterative Cu-mediated SLRR cycles, directly onto carbon nanotubes (CNTs) which are potentially good candidates as electrocatalyst supports due to their electrical conductivity and chemical resistance. Here scanning electron microscope images showed that Pt grew as nanoparticles, and hydrogen underpotential deposition from cyclic voltammetry showed that the active surface area approached an asymptotic value around eight iterations. Catalytic activity, measured using the oxygen reduction reaction, reached a maximum at ten iterations. Both are shown to be influenced by the growth mode, but electrochemical modeling indicates that the trend in activity is also due to a change in activation energy, possibly due to changes in Pt electronic structure due to interactions with the CNTs. Durability cycling showed a greater than 85% retention of surface area for the first 10,000 cycles of accelerated stress testing but decayed steadily to about 50% after 30,000 cycles. This performance may be related to the phenomenon that limits surface area growth.

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

Probing Metastable Domain Dynamics via Automated Experimentation in Piezoresponse Force Microscopy

The dynamics of complex topological defects in ferroelectric materials is explored using automated experimentation in piezoresponse force microscopy. Specifically, a complex trigger system (i.e., “FerroBot”) is employed to study metastable domain-wall dynamics in Pb 0.6 Sr 0.4 TiO 3 thin films. Several regimes of superdomain wall dynamics have been identified, including smooth domain-wall motion and significant reconfiguration of the domain structures. We have further demonstrated that microscopic mechanisms of the domain-wall dynamics can be identified; i.e., domain-wall bending can be separated from irreversible domain reconfiguration regimes. In conjunction, phase-field modeling was used to corroborate the observed mechanisms. As such, the observed superdomain dynamics can provide a model system for classical ferroelectric dynamics, much like how colloidal crystals provide a model system for atomic and molecular systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Piezoelectrically actuated silicon-nitride-based high-speed spatial light modulator

Advancements in light modulator technology have been driving discoveries and progress across various fields. The problem of large-scale coherent optical control of atomic quantum systems—including cold atoms, ions, and solid-state color centers—presents among the most stringent requirements. This motivates a new generation of high-speed large-scale modulator technology operating in the visible to near-infrared wavelength range. We introduce a scalable modulator technology based on piezoelectrically actuated silicon nitride resonant waveguide gratings fabricated on 200 mm diameter silicon wafers with CMOS-compatible processes. We present a proof-of-concept device with 4 × 4 individually addressable 50 μ m × 50 μ m pixels or channels, each containing a resonant waveguide grating with a ~ 780 nm design wavelength, supporting > 100 MHz modulation speeds, and a spectral response with > 20 dB extinction.

integrated optics↗
DOE OSTI2020

Laser field control of subradiant states of a system of several atoms in a configuration close to a regular polygon

Some collective excitations of an ensemble of closely spaced (two-level) atoms can be characterised by extremely low rates of radiation decay, which is of considerable interest for storing quantum information. Such (dark) states are realised, for example, in planar geometry when atoms are located at the nodes of a regular polygon. However, the decay rate of such excitations increases markedly when the geometry deviates from ideal. Using the example of small deformation of a square in a rhombus, we show that an increase in the decay rate of the dark state due to symmetry breaking can be compensated for by adjusting the transition frequency of some atoms exposed to external laser radiation. (paper)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Multi-task graph neural networks for simultaneous prediction of global and atomic properties in ferromagnetic systems *

Abstract We introduce a multi-tasking graph convolutional neural network, HydraGNN, to simultaneously predict both global and atomic physical properties and demonstrate with ferromagnetic materials. We train HydraGNN on an open-source ab initio density functional theory (DFT) dataset for iron-platinum with a fixed body centered tetragonal lattice structure and fixed volume to simultaneously predict the mixing enthalpy (a global feature of the system), the atomic charge transfer, and the atomic magnetic moment across configurations that span the entire compositional range. By taking advantage of underlying physical correlations between material properties, multi-task learning (MTL) with HydraGNN provides effective training even with modest amounts of data. Moreover, this is achieved with just one architecture instead of three, as required by single-task learning (STL). The first convolutional layers of the HydraGNN architecture are shared by all learning tasks and extract features common to all material properties. The following layers discriminate the features of the different properties, the results of which are fed to the separate heads of the final layer to produce predictions. Numerical results show that HydraGNN effectively captures the relation between the configurational entropy and the material properties over the entire compositional range. Overall, the accuracy of simultaneous MTL predictions is comparable to the accuracy of the STL predictions. In addition, the computational cost of training HydraGNN for MTL is much lower than the original DFT calculations and also lower than training separate STL models for each property.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1994

The Materials Chemistry of Atomic Oxygen with Applications to Anisotropic Etching of Submicron Structures in Microelectronics and the Surface Chemistry Engineering of Porous Solids

Neutral atomic oxygen is the most abundant component of the ionospheric plasma in the low Earth orbit environment (LEO; 200 to 700 kilometers altitude) and can produce significant degradation of some spacecraft materials. In order to produce a more complete understanding of the materials chemistry of atomic oxygen, the chemistry and physics of O-atom interactions with materials were determined in three radically different environments: (1) The Space Shuttle cargo bay in low Earth orbit (the EOIM-3 space flight experiment), (2) a high-velocity neutral atom beam system (HVAB) at Los Alamos National Laboratory (LANL), and (3) a microwave-plasma flowing-discharge system at JSC. The Space Shuttle and the high velocity atom beam systems produce atom-surface collision energies ranging from 0.1 to 7 eV (hyperthermal atoms) under high-vacuum conditions, while the flowing discharge system produces a 0.065 eV surface collision energy at a total pressure of 2 Torr. Data obtained in the three different O-atom environments referred to above show that the rate of O-atom reaction with polymeric materials is strongly dependent on atom kinetic energy, obeying a reactive scattering law which suggests that atom kinetic energy is directly available for overcoming activation barriers in the reaction. General relationships between polymer reactivity with O atoms and polymer composition and molecular structure have been determined. In addition, vacuum ultraviolet photochemical effects have been shown to dominate the reaction of O atoms with fluorocarbon polymers. Finally, studies of the materials chemistry of O atoms have produced results which may be of interest to technologists outside the aerospace industry. Atomic oxygen 'spin-off' or 'dual use' technologies in the areas of anisotropic etching in microelectronic materials and device processing, as well as surface chemistry engineering of porous solid materials are described.

Koontz, Steve L.↗
NASA NTRS1988

Design and demonstration of a system for the deposition of atomic-oxygen durable coatings for reflective solar dynamic power system concentrators

A system for the vacuum deposition of atomic-oxygen durable coatings for reflective solar dynamic power systems (SDPS) concentrators was designed and demonstrated. The design issues pertinent to SDPS were developed by the Government Aerospace Systems Division of the Harris Corporation and are described in NASA-CR-179489. Both design and demonstration phases have been completed. At the time of this report the deposition system was ready for coating of facets for SDPS concentrators. The materials issue relevant to the coating work were not entirely resolved. These issues can only be resolved when substrates which are comparable to those which will be used in flight hardware are available. The substrates available during the contract period were deficient in the areas of surface roughness and contamination. These issues are discussed more thoroughly in the body of the report.

Mcclure, Donald J.↗
DOE OSTI2022

Determination of Multimode Motional Quantum States in a Trapped Ion System

Trapped atomic ions are a versatile platform for studying interactions between spins and bosons by coupling the internal states of the ions to their motion. Measurement of complex motional states with multiple modes is challenging, because all motional state populations can only be measured indirectly through the spin state of ions. Here we present a general method to determine the Fock state distributions and to reconstruct the density matrix of an arbitrary multimode motional state. Further, we experimentally verify the method using different entangled states of multiple radial modes in a five-ion chain. This method can be extended to any system with Jaynes-Cummings-type interactions.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2024

Guided cold atom inertial sensors with membrane integrated photonics on atom trap integrated platforms

A guided cold-atom inertial sensor system comprises an atom trap integrated platform, a laser system, a magnetic field system, a control system, and a computing system. The laser system and magnetic field system are adapted to form a magneto-optical trap (MOT) about a suspended waveguide of the atom trap integrated platform made of membrane integrated photonics. After loading cold atoms from a MOT, the photonic atom trap integrated platform generates one-dimensional guided atoms with an evanescent field optical dipole trap (EF-ODT) along the optical waveguide to create guided atomic accelerometers/gyroscopes. Motion of atomic wavepackets in a superposition state is created along the guided atom geometry by way of state-dependent momentum kicks. The light-pulse sequence of guided atom interferometry splits, redirects, and recombines atomic wavepackets, which allows measurement of atom interference fringes sensitive to inertial forces via a probe laser.

Lee, Jongmin↗
DOE OSTI2020

Performance Limits for Maritime Wide-Area Search (MWAS) Radar

One of the earliest applications for radar was to search for and find maritime vessels on the open sea. Proper design and operation of an airborne Maritime Wide Area Search (MWAS) radar requires an understanding of system performance characteristics and limitations, and furthermore understanding the trades amongst a large number of interdependent system parameters. This report identifies and explores those characteristics and limits, and how they depend on hardware system parameters and environmental conditions. Ultimately, this leads to a characterization of parameters that offer optimum performance for the overall MWAS radar system. While the information herein is not new to the literature, its collection into a single report hopes to offer some value in reducing the 'seek time'. Acknowledgements This report was funded by General Atomics Aeronautical Systems, Inc. (GA-ASI) Mission Systems under Cooperative Research and Development Agreement (CRADA) SC08/01749 between Sandia National Laboratories and GA-ASI. General Atomics Aeronautical Systems, Inc. (GA-ASI), an affiliate of privately-held General Atomics, is a leading manufacturer of Remotely Piloted Aircraft (RPA) systems, radars, and electro-optic and related mission systems, including the Predator/Gray Eagle-series and Lynx Multi-mode Radar. -

42 ENGINEERING↗
DOE OSTI2021

System and method for monitoring atomic absorption during a surface modification process

A processing system monitors and/or controls a surface modification process occurring on a substrate within a processing chamber. An optical processing module having a light emission submodule to output a generated light signal and an optical detection submodule to detect a resultant light signal, is connected via fiber optic cables to light illuminating and light receiving components located within the chamber. A processor determines an amount of atomic absorption by an atomic element encountered by a probing beam passing between the illuminating and receiving components, based on the intensity of the generated light signal, the intensity of the received light signal and optionally the spontaneous emission of the atomic element in the absence of illumination by a probing beam. Based on the determined amount, the system derives a plurality of parameters of the modified substrate, their spatial and temporal uniformity, and information about process conditions in the processing chamber.

Atanasoff, George↗