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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 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Structure-mechanical properties correlation in bulk LiPON glass produced by nitridation of metaphosphate melts

The glassy solid electrolyte Lithium phosphorous oxynitride (LiPON) has been widely researched in thin film solid state battery format due to its outstanding stability when cycled against lithium. In addition, recent reports show thin film LiPON having interesting mechanical behaviors, especially its ability to resist micro-scale cracking via densification and shear flow. Here, in the present study, we have produced bulk LiPON glasses with varying nitrogen contents by ammonolysis of LiPO 3 melts. The resulting compositions were determined to be LiPO 3-3z/2 N z , where 0 ≤ z ≤ 0.75, and the z value of 0.75 is among the highest ever reported for this series of LiPON glasses. The short-range order structures of the different resulting compositions were characterized by infrared, Raman, 31 P magic angle spinning nuclear magnetic resonance, and X-ray photoelectron spectroscopies. Instrumented nano-indentation was used to measure mechanical properties. It was observed that similar to previous studies, both trigonally coordinated (N t ) and doubly bonded (N d ) N co-exist in the glasses in about the same amounts for z ≤ 0.36, the limit of N content in most previous studies. For glasses with z > 0.36, it was found that the fraction of the N t increased significantly while the fraction of N d correspondingly decreased. The incorporation of nitrogen increased both the elastic modulus and hardness of the glass by approximately a factor of 1.5 when N/P ratio reaches 0.75. At the same time, an apparent embrittlement of the glass was observed due to nitridation, which was revealed by nanoindentation with an extra sharp nanoindenter tip.

25 ENERGY STORAGE↗
DOE OSTI2026

Optical nanofiber testbeds for benchmarking membrane-waveguide photonic integrated circuit platforms toward on-chip quantum inertial sensing

Recent advances in cold atom interferometry with optical and magnetic atom guides have set the stage for quantum inertial sensors capable of operating in dynamic environments. In this work, we present three key innovations—evanescent-field (EF) atom guides, optical nanofiber testbeds, and membrane-waveguide photonic integrated circuit (PIC) platforms—to advance EF-guided atom interferometry. First, we demonstrate EF atom guides on optical nanofiber testbeds, which serve as performance benchmarks for our membrane-waveguide PIC platforms. Second, we achieve low-power (⁠ ~ 5 mW) guiding of freely moving, laser-cooled 133 Cs atoms in two-color, traveling-wave EF optical dipole traps at the novel, heat-efficient magic wavelengths of 793 and 937 nm (i.e., “793/937-nm EF atom guides”). Concurrently, we design and fabricate membrane-waveguide PIC platforms for these EF atom guides; in our prior work, we showed that these structures safely accommodate 4–6 times the required optical trap power under vacuum and enable dense cold atom generation via magneto-optical trapping in the vicinity of the optical wavguide for efficient loading. Third, we verify preserved atomic coherence via microwave fields and EF-coupled Doppler-free Raman beams; to our knowledge, this is the first report of coherence fringes driven by co-propagating EF-coupled Raman beams with only 150 nW of total optical power. By providing a direct comparison between optical nanofiber testbeds and membrane-waveguide PIC platforms, our results lay critical groundwork for the on-chip realization of EF-guided atom interferometry and the development of fully integrated, compact, lightweight, and low-power quantum accelerometers and gyroscopes.

Orozco, Adrian [Sandia National Laboratories (SNL-↗
DOE OSTI2023

Giant proximity exchange and flat Chern band in 2D magnet-semiconductor heterostructures

van der Waals (vdW) heterostructures formed by two-dimensional (2D) magnets and semiconductors have provided a fertile ground for fundamental science and spintronics. We present first-principles calculations finding a proximity exchange splitting of 14 meV (equivalent to an effective Zeeman field of 120 T) in the vdW magnet semiconductor heterostructure MoS 2 /CrBr 3 , leading to a 2D spin-polarized half-metal with carrier densities ranging up to 10 13 cm -2 . We consequently explore the effect of large exchange coupling on the electronic band structure when the magnetic layer hosts chiral spin textures such as skyrmions. A flat Chern band is found at a “magic” value of magnetization $\overline{m}$ ~ 0.2 for Schrödinger electrons, and it generally occurs for Dirac electrons. The magnetic proximity–induced anomalous Hall effect enables transport-based detection of chiral spin textures, and flat Chern bands provide an avenue for engineering various strongly correlated states.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Hamiltonian engineering of spin-orbit–coupled fermions in a Wannier-Stark optical lattice clock

Engineering a Hamiltonian system with tunable interactions provides opportunities to optimize performance for quantum sensing and explore emerging phenomena of many-body systems. An optical lattice clock based on partially delocalized Wannier-Stark states in a gravity-tilted shallow lattice supports superior quantum coherence and adjustable interactions via spin-orbit coupling, thus presenting a powerful spin model realization. The relative strength of the on-site and off-site interactions can be tuned to achieve a zero density shift at a “magic” lattice depth. This mechanism, together with a large number of atoms, enables the demonstration of the most stable atomic clock while minimizing a key systematic uncertainty related to atomic density. Interactions can also be maximized by driving off-site Wannier-Stark transitions, realizing a ferromagnetic to paramagnetic dynamical phase transition.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

Mapping twist-tuned multiband topology in bilayer WSe 2

Semiconductor moiré superlattices have been shown to host a wide array of interaction-driven ground states. However, twisted homobilayers have been difficult to study in the limit of large moiré wavelengths, where interactions are most dominant. In this study, we conducted local electronic compressibility measurements of twisted bilayer WSe 2 (tWSe 2 ) at small twist angles. We demonstrated multiple topological bands that host a series of Chern insulators at zero magnetic field near a “magic angle” around 1.23°. Using a locally applied electric field, we induced a topological quantum-phase transition at one hole per moiré unit cell. Finally, our work establishes the topological phase diagram of a generalized Kane-Mele-Hubbard model in tWSe 2 , demonstrating a tunable platform for strongly correlated topological phases.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Gauss Sum Strong Simulation v.0.1

Universal quantum circuits can be formulated in the Pauli measurement-based formalism as input T gate magic states, Clifford gates, and then multi-Pauli measurements. This code simulates single-Pauli measurements to show some theoretical bounds on the cost of full multi-Pauli measurements. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. SAND2020-14080 O

SciDAC↗
DOE OSTI2021

Weak Simulation v.0.1

The SPARSIFY algorithm implemented by the code allows for classical simulation of universal quantum computer sample outcomes. The code sparsifies the stabilizer decomposition of a qubit t-tensored T gate magic state to some additive error. This is accomplished by either independent L1 sampling or with correlated L1 sampling to supplement an independent subset, which offers a more efficient decomposition: for a given t, a sparser decomposition is sufficient with correlated L1 sampling to satisfy a given additive error. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. SAND2021-8296 O

SciDAC↗
DOE OSTI2022

Weak Simulation v.1.0

SAND2022-3281 O Weak Simulation sparsifies the stabilizer decomposition of a qubit t-tensored T gate magic state to some additive error. It can accomplish this either by independent L1 sampling like in the popular SPARSIFY algorithm or with correlated L1 sampling, which offers a more efficient decomposition. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.

SciDAC↗
DOE OSTI2022

Effect of superconductivity on the shape of flat bands

Abstract For the first time, basing both on experimental facts and our theoretical consideration, we show that Fermi systems with flat bands should be tuned with the superconducting state. Experimental measurements on magic-angle twisted bilayer graphene of the Fermi velocity V F as a function of the temperature T c of superconduction phase transition have revealed , where N s (0) is the density of states at the Fermi level. We show that the high- T c compounds exhibit the same behavior. Such observation is a challenge to theories of high- T c superconductivity, since V F is negatively correlated with T c , for . We show that the theoretical idea of forming flat bands in strongly correlated Fermi systems can explain this behavior and other experimental data collected on both and twisted bilayer graphene. Our findings place stringent constraints on theories describing the nature of high- T c superconductivity and the deformation of flat band by the superconducting phase transition.

Physics↗
DOE OSTI2021

Giant terahertz polarization rotation in ultrathin films of aligned carbon nanotubes

For easy manipulation of polarization states of light for applications in communications, imaging, and information processing, an efficient mechanism is desired for rotating light polarization with a minimum interaction length. Here, we report giant polarization rotations for terahertz (THz) electromagnetic waves in ultrathin ( ∼ <#comment/> 45 n m ), high-density films of aligned carbon nanotubes. We observed polarization rotations of up to ∼ <#comment/> 20 ∘ <#comment/> and ∼ <#comment/> 110 ∘ <#comment/> for transmitted and reflected THz pulses, respectively. The amount of polarization rotation was a sensitive function of the angle between the incident THz polarization and the nanotube alignment direction, exhibiting a “magic” angle at which the total rotation through transmission and reflection becomes exactly 90°. Our model quantitatively explains these giant rotations as a result of extremely anisotropic optical constants, demonstrating that aligned carbon nanotubes promise ultrathin, broadband, and tunable THz polarization devices.

Baydin, Andrey (ORCID:0000000225673506)↗
DOE OSTI2022

Leaf gas exchange raw data, 2015 - 2017, at Manaus, Brazil

This data package contains raw leaf gas exchange data from the NGEE Tropics K34 tower site on a plateau near Manaus, Brazil. Data was collected using sensor and leaf sample measurements. Leaves on a target tree were chosen by accessing a branch near the tower. In some cases, the branch was naturally positioned near the tower and in other cases, a small rope was used to pull the branch closer to the tower for better access to leaves. Mature leaves were targeted in nearly all cases. The gas exchange system was hauled with a climbing rope to the level of the branch on the tower and the sensor head/leaf enclosure was installed near the branch of interest using a magic arm. We measured leaf gas exchange from 5:00 AM to 5:00 PM, randomly cycling through the approximately 20 leaves in the targeted branch(es). Data were collected over two time periods, detailed within the files. The attached data files contain raw data, sensor manuals, and PDFs with detailed methods and procedures separated into multiple folders. Data is in Excel file format. See data references for data package containing related metadata. This dataset replaces the leaf gas exchange data of two retired packages, NGT0019 and NGT0040.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

When not to use machine learning: A perspective on potential and limitations

Abstract The unparalleled success of artificial intelligence (AI) in the technology sector has catalyzed an enormous amount of research in the scientific community. It has proven to be a powerful tool, but as with any rapidly developing field, the deluge of information can be overwhelming, confusing, and sometimes misleading. This can make it easy to become lost in the same hype cycles that have historically ended in the periods of scarce funding and depleted expectations known as AI winters. Furthermore, although the importance of innovative, high-risk research cannot be overstated, it is also imperative to understand the fundamental limits of available techniques, especially in young fields where the rules appear to be constantly rewritten and as the likelihood of application to high-stakes scenarios increases. In this article, we highlight the guiding principles of data-driven modeling, how these principles imbue models with almost magical predictive power, and how they also impose limitations on the scope of problems they can address. Particularly, understanding when not to use data-driven techniques, such as machine learning, is not something commonly explored, but is just as important as knowing how to apply the techniques properly. We hope that the discussion to follow provides researchers throughout the sciences with a better understanding of when said techniques are appropriate, the pitfalls to watch for, and most importantly, the confidence to leverage the power they can provide. Graphical abstract

36 MATERIALS SCIENCE↗
DOE OSTI2021

Magnetron R&D for high efficiency CW RF sources for industrial accelerators

The scheme of using high-efficiency magnetrons to drive radiofrequency accelerators has been demonstrated at 2450 MHz in CW mode *. Magnetron test stands at JLab and GA have been set up to further test the noise figure and the locking speed of the injection phase-lock method. For higher power applications, power combining experiments using a TM010 cavity-type combiner and a magic tee for the binary combiner while using a single clean injection signal has been carried out at 2450 MHz. The frequency pulling effect between the magnetron and a low-Q cavity has been shown to enhance the frequency locking bandwidth compared to the injection phase-lock alone. The principle has been studied by the equivalent circuit simulation, analytical model, and finally confirmed experimentally on the magnetrons. Due to the pandemic delay in 2020, the equivalent high power tests using a 75kW, 915MHz industrial magnetron will be done in 2021 and will be reported in a future paper.

Wang, H.↗
DOE OSTI2026

A reactive ferroelectric tuner for microphonics compensation

Jefferson Lab (JLab) is actively pursuing an extensive research program focused on developing advanced Nb₃Sn superconducting technology for particle accel-eration. Due to the brittle nature of Nb₃Sn coatings, a Ferroelectric Tuner (FRT) currently represents the most viable approach for microphonics compensation in these next-generation cavities. We suggest a novel, fast-responding FRT integrated directly into the main coupler, eliminating the need for an additional RF port. Leveraging a unique RF design based on a magic-T configuration, this advanced FRT will enable micro-phonics compensation in the ±30 Hz range without undesirable changes to the external quality factor.

Accelerator Physics↗
DOE OSTI2023

Demonstration of Magnetron as an Alternative RF Source for SRF Accelerators

Magnetron has been considered as alternate high-efficiency, low-cost RF sources for linacs and storage rings [1] for national labs and industrial applications. After the demonstration of magnetrons power to drive and combine for a radio frequency cavity at 2450 MHz in CW mode, we have used trim coils adding to a water-cooled magnetron and amplitude modulation feedback to further suppress the side-band noise to -46.7 dBc level. We also demonstrated the phase-locking to an industrial grade cooking magnetron transmitter at 915 MHz with a 75 kW CW power delivered to a water load by using a -26.6 dBc injection signal [2]. The sideband noise from the 3-Phase SCRs DC power supply can be reduced to -16.2 dBc level. Further noise reduction and their power combining scheme using magic-tee and cavity type combiners for higher power application (2x75kW) are to be presented. We intent to use one power station to drive the normal conducting and superconducting RF cavities for the inductrial linac. We also going to demonstarte a vertical SRF cavity test with a high input coupling Q using a 2.45GHz magnetron and comparing with a baseline test result using a solid state amplifier.

Wang, H.↗
DOE OSTI2024

Towards a data-driven model of hadronization using normalizing flows

We introduce a model of hadronization based on invertible neural networks that faithfully reproduces a simplified version of the Lund string model for meson hadronization. Additionally, we introduce a new training method for normalizing flows, termed MAGIC, that improves the agreement between simulated and experimental distributions of high-level (macroscopic) observables by adjusting single-emission (microscopic) dynamics. Our results constitute an important step toward realizing a machine-learning based model of hadronization that utilizes experimental data during training. Finally, we demonstrate how a Bayesian extension to this normalizing-flow architecture can be used to provide analysis of statistical and modeling uncertainties on the generated observable distributions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Collaborative Research: Polymer Macrocycles: A novel topology to control dynamics of rubbery materials

Understanding the dynamics of polymers of different topologies is an important field of study and one of the most important unanswered questions in this field is "how do circular polymers move," particularly in the melt state. New information suggests that molecular topology, specifically circular rings, impacts the response of materials in nanometer- scale confinement. The work performed here tackles these subjects through a collaboration in which specialists in polymer synthesis, polymer rheology and scattering methods, and in the physics of nanoconfinement work together to investigate the thermophysical behavior of circular macromolecules. The project goals are to use a novel synthesis method of "green" oxidative polymerization to produce high purity macrocycles and to investigate their linear viscoelastic behavior in order to fully characterize the dynamics of circular macromolecules to sizes that correspond to linear molecule entanglement densities higher than previously obtainable with synthetic polymers. Chemical chain end characterization and critical edge fractionation coupled with direct visualization of the prepared polymers through the use of polymer amplification methods are proposed in order to quantify the numbers of circular and linear molecules in each sample. The study of the linear viscoelastic response of blends of linear and circular molecules is also to be undertaken in the project. Nonlinear viscoelastic measurements, including extensional viscosity, are to be made. Strong differences in behavior between linear chains and circular ones also provides an important opportunity for new technology to break the "magic triangle" for tires: it is believed that improving one of the three key attributes - traction, wear, rolling resistance - necessarily sacrifices at least one of the others. Rubber made from cyclic polymers has the potential to break out of this triangle by reducing the so-called Payne effect in reinforced rubbers because circular macromolecules are less sensitive to nanoconfinement than their linear counterparts. The work has as one objective to characterize the impact of nanoconfinement on the behavior of large circular macromolecules. In addition, the dynamics of carbon black filled circular macromolecules are to be studied to test the hypothesis that the resulting rubbery materials will exhibit a reduced Payne effect.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2020

Development of Operando Nuclear Magnetic Resonance Capabilities for Solid-State Battery Research

Mechanistic information regarding solid-solid interfaces in solid-state batteries remains elusive as its observation requires a non-destructive operando technique. Such a technique does not currently exist. Solid-state nuclear magnetic resonance (NMR) is uniquely suited to address this challenge as it is sensitive to chemistry, structure, and dynamics and can measure buried interfaces. However solid-state NMR requires high speed spinning of the sample at the ‘magic angle’ (MAS) to obtain adequate resolution. The metallic current collectors in a battery are detrimental to spinning in magnetic fields as they generate eddy currents which prevent spinning and dampen the NMR signal. Furthermore, the spinning nature of the MAS NMR experiment requires a wireless means of charging for operando capabilities. These challenges were addressed in this research and operando MAS NMR enabled by optical wireless charging was demonstrated. By limiting the size of the metallic components, we were able to spin a sample holder with electrical leads and a solid-state battery up to a few kilohertz, fast enough for high-resolution NMR. We achieved wireless charging by attaching a photovoltaic cell to the head of the NMR rotor and used a laser to transmit power to the photovoltaic cell. Demonstration of the optical wireless charging was performed by polarizing a liquid electrolyte during an operando MAS NMR measurement. This novel capability is a transformative technique for investigating the mechanistic electrochemical processes in solid-state samples.

25 ENERGY STORAGE↗