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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

22 GeV CEBAF with Novel Fixed Field Alternating Gradient Design

Extending the energy reach of CEBAF up to 22 GeV within the existing tunnel is being explored. Proposed energy upgrade can be achieved by increasing the number of recirculations, while using the existing CEBAF SRF cavity system. Presented scheme is based on an exciting new approach to acceleratie electrons efficiently with multiple passes in a single FFA beam line. Encouraged by recent success of the CBETA Test Accelerator, a proposal was formulated raise CEBAF energy by replacing the highest-energy arcs with Fixed Field Alternating Gradient (FFA) arcs. The new pair of arcs configured with FFA lattice would support simultaneous transport of additional 6 passes with energies spanning a factor of two, using the non-scaling FFA principle implemented with Halbach-derived permanent magnets - a novel magnet technology that significantly saves energy and lowers operating costs. One of the challenges of the multi-pass (11) linac optics is to provide uniform focusing in a vast range of energies, using fixed field lattice. Here, we propose a triplet lattice scaled up with increasing momentum along the linac. This would provide a stable periodic solution covering energy ratio of 1:33. The current CEBAF configured with a 123 MeV injector, makes optical matching in the first linac virtually impossible due to extremely high energy span ratio (1:175). Therefore, we envision replacement of the current injector with a 650 MeV 3-pass recirculating injector based on the existing LERF facility. Finally, the 22 GeV CEBAF would promise to deliver in 10-passes a beam with normalized emittance of 80 mm·mrad and with a relative energy spread of 1.5 × 10-3. Further recirculation beyond 22 GeV is limited by large, 974 MeV per electron, energy loss due to synchrotron radiation.

Bogacz, Slawomir↗
DOE OSTI2020

Lasing from Finite Plasmonic Nanoparticle Lattices

Small lasers can generate coherent light for integrated photonics, in-vivo cellular imaging, and solid-state lighting. Unlike conventional lasers, plasmonic lasers can generate coherent light at sub-wavelength scales, although cavity architectures based on metal films and semiconducting gain exhibit large radiative losses and lack directional emission. In contrast, two-dimensional (2D) metal nanoparticle arrays surrounded by organic dyes can support lasing with high directionality at room temperature. Yet, the relationship between the number of nanoparticles in a finite lattice and their lasing emission characteristics is unknown. Here we show that the number of units in 2D gold nanoparticle lattices is critical to generate robust cavity resonances and lasing emission. Narrower lattice plasmons associated with stronger electromagnetic near fields are observed as nanoparticle number increases. Experimentally, we demonstrate lasing from a 30x30 nanoparticle lattice. Semi-quantum modeling indicates lower lasing thresholds and faster population inversion dynamics with higher nanoparticle numbers. These findings indicate that finite lattices of nanoparticles integrated with gain can function as independent, coherent light sources for optical multiplexing and lab-on-a-chip applications.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2023

On polarization and snake arrangements in RHIC: Case of RHIC and EIC HSR tunes p and 3He

This Tech. Note summarizes the outcomes of numerical simulations of strong resonance crossing using RHIC lattice, as a tentative assessment of HSR expectations, with variants including: regular RHIC tunes, HSR fractional tune values, collision or injection optics, and various 2, 4 or 6 snake configurations. This is a first part of simulation studies regarding RHIC and the EIC HSR lattices, a second part concerns the latter specifically and will be released in a separate Tech Note.

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

Performance and properties evolution of near-term accident tolerant fuel: Cr-doped UO 2

Chromium-doped UO 2 fuel has received significant interest due to the ability for chromium to produce pellets with large average grain size (>30 μm), which has shown to increase fission gas retention during operation. Sintering of chromium-doped UO 2 pellets was pursued with oxygen potential and sintering atmosphere controlled to tailor the final microstructure of the material. Chromium additions in this study ranged from 750 to 7800 ppm. Cr concentrations were studied pre and post sintering using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Effects of chromium content on lattice parameter and microstructure were examined with X-ray diffraction (XRD) and scanning electron microscopy (SEM). Contraction of the UO 2 lattice parameter was observed, as well as enlargement of grain size with increasing chromium content up to 4900 ppm Cr 2 O 3 . In addition, SEM indicated Cr incorporation within the matrix and the formation of chromium oxide precipitates throughout the microstructure at high Cr concentrations. Evaluation of thermophysical properties of Cr-doped UO 2 pellets were conducted up to 1200 °C to illustrate their evolution with increased dopant concentration and microstructural changes. The results show that grain size is maximized at 52 μm with Cr 2 O 3 concentration equal to 4900 ppm; however, grain size decreases at higher Cr 2 O 3 concentrations. No significant changes were observed in specific heat capacity, linear thermal expansion, and coefficient of thermal expansion compared to undoped UO 2 . The thermal conductivity also decreased through the incorporation of Cr 2 O 3 dopants above 750 ppm and is shown to be ~15 % lower than reported UO 2 values.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2025

Sharp spectroscopic fingerprints of disorder in an incompressible magnetic state

Disorder significantly impacts the electronic properties of conducting quantum materials by inducing electron localization and thus altering the local density of states and electric transport. In insulating quantum magnetic materials, the effects of disorder are less understood and can drastically impact fluctuating spin states like quantum spin liquids. In the absence of transport tools, disorder is typically characterized using chemical methods or by semi-classical modeling of spin dynamics. This requires high magnetic fields that may not always be accessible. Here, we show that magnetization plateaus—incompressible states found in many quantum magnets—provide an exquisite platform to uncover small amounts of disorder, regardless of the origin of the plateau. Using optical magneto-spectroscopy on the Ising-Heisenberg triangular-lattice antiferromagnet K 2 Co(SeO 3 ) 2 exhibiting a 1/3 magnetization plateau, we identify sharp spectroscopic lines, the fine structure of which serves as a hallmark signature of disorder. Through analytical and numerical modeling, we show that these fingerprints not only enable us to quantify minute amounts of disorder but also reveal its nature—as dilute vacancies. Remarkably, this model explains all details of the thermomagnetic response of our system, including the existence of multiple plateaus. Our findings provide a new approach to identifying disorder in quantum magnets.

Infrared spectroscopy↗
DOE OSTI2022

Electron-phonon coupling in the charge density wave state of CsV 3 Sb 5

Metallic materials with kagome lattice structure are interesting because their electronic structures can host flat bands, Dirac cones, and van Hove singularities, resulting in strong electron correlations, nontrivial band topology, charge density wave (CDW), and unconventional superconductivity. Recently, kagome lattice compounds AV 3 Sb 5 (A=K, Rb, Cs) are found to have intertwined CDW order and superconductivity. The origin of the CDW has been suggested to arise from Fermi-surface instabilities of van Hove singularity (saddle point) near the M points with weak electron-phonon coupling. In this work, we use neutron scattering experiments to demonstrate that the CDW order in CsV 3 Sb 5 is associated with static lattice distortion and a sudden hardening of the $B_{3u}$ longitudinal optical phonon mode at the Brillouin zone boundary, thus establishing that the wave vector dependent electron-phonon coupling must also play an important role in the CDW order of AV 3 Sb 5 .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Toward coherent quantum computation of scattering amplitudes with a measurement-based photonic quantum processor

In recent years, applications of quantum simulation have been developed to study the properties of strongly interacting theories. This has been driven by two factors: on the one hand, needs from theorists to have access to physical observables that are prohibitively difficult to study using classical computing; on the other hand, quantum hardware becoming increasingly reliable and scalable to larger systems. In this work, we discuss the feasibility of using quantum optical simulation for studying scattering observables that are presently inaccessible via lattice QCD and are at the core of the experimental program at Jefferson Laboratory, the future Electron-Ion Collider, and other accelerator facilities. We show that recent progress in measurement-based photonic quantum computing can be leveraged to provide deterministic generation of required exotic gates and implementation in a single photonic quantum processor. Published by the American Physical Society 2024

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Visualization of Chiral Electronic Structure and Anomalous Optical Response in a Material with Chiral Charge Density Waves

Chiral materials have attracted significant research interests as they exhibit intriguing physical properties, such as chiral optical response, spin-momentum locking, and chiral induced spin selectivity. Recently, layered transition metal dichalcogenide 1T–TaS 2 has been found to host a chiral charge density wave (CDW) order. Nevertheless, the physical consequences of the chiral order, for example, in electronic structures and the optical properties, are yet to be explored. Here, we report the spectroscopic visualization of an emergent chiral electronic band structure in the CDW phase, characterized by windmill-shaped Fermi surfaces. Further, we uncover a remarkable chirality-dependent circularly polarized Raman response due to the salient in-plane chiral symmetry of CDW, although the ordinary circular dichroism vanishes. Chiral Fermi surfaces and anomalous Raman responses coincide with the CDW transition, proving their lattice origin. Our Letter paves a path to manipulate the chiral electronic and optical properties in two-dimensional materials and explore applications in polarization optics and spintronics.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Robust multiresonant nonlocal metasurfaces by rational design

Abstract Dielectric metasurfaces supporting optical resonances have become a promising platform for quantum and nonlinear optics. However, resonant metasurfaces remain limited in their capacity to independently control the behavior of many distinct resonances despite efforts in computational optimization and inverse design. In this work, we overcome longstanding limitations by introducing a generalized rational design paradigm based on symmetry. Specifically, we use symmetry-broken metasurfaces with periodic “quadromer” lattices comprised of four nanostructures per unit cell to enable extensive control of multiple optical resonances. The rationally designed metasurfaces are readily fabricable, and we experimentally demonstrate metasurfaces that support up to four high Q-factor resonances with deliberately chosen free-space polarizations, spectral separations, and mode profiles. Our design paradigm may unlock new applications for multiresonant metasurfaces in quantum and nonlinear optics, optical sensing, and augmented reality displays.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2021

Vibrational properties and thermal transport in quaternary chalcogenides: The case of Te-based compositions

Vibrational thermal properties of CuZn 2 InTe 4 , AgZn 2 InTe 4 , and Cu 2 CdSnTe 4 , derived from binary II-VI zinc-blendes, are reported based on first-principles calculations. While the chalcogenide atoms in these materials have the same lattice positions, the cation atom arrangements vary, resulting in different crystal symmetries and subsequent properties. The compositional differences have important effects on the vibrational thermal characteristics of the studied materials, which demonstrate that low-frequency optical phonons hybridize with acoustic phonons and lead to enhanced phonon-phonon scattering and low lattice thermal conductivities. The phonon density of states, mode Grüneisen parameters, and phonon scattering rates are also calculated, enabling deeper insight into the microscopic thermal conduction processes in these materials. Compositional variations drive differences among the three materials considered here; nonetheless, their structural similarities and generally low thermal conductivities (0.5–4 W/m K at room temperature) suggest that other similar II-VI zinc-blende derived materials will also exhibit similarly low values, as also corroborated by experimental data. Finally, this, combined with the versatility in designing a variety of motifs on the overall structure, makes quaternary chalcogenides interesting for thermal management and energy conversion applications that require low thermal conductivity.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Triangular lattice quantum dimer model with variable dimer density

Abstract Quantum dimer models are known to host topological quantum spin liquid phases, and it has recently become possible to simulate such models with Rydberg atoms trapped in arrays of optical tweezers. Here, we present large-scale quantum Monte Carlo simulation results on an extension of the triangular lattice quantum dimer model with terms in the Hamiltonian annihilating and creating single dimers. We find distinct odd and even $${{\mathbb{Z}}}_{2}$$ Z 2 spin liquids, along with several phases with no topological order: a staggered crystal, a nematic phase, and a trivial symmetric phase with no obvious broken symmetry. We also present dynamic spectra of the phases, and note implications for experiments on Rydberg atoms.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

Uncovering the phonon spectra and lattice dynamics of plastically deformable InSe van der Waals crystals

Stacking two-dimensional (2D) van der Waals (vdW) materials in a layered bulk structure provides an appealing platform for the emergence of exotic physical properties. As a vdW crystal with exceptional plasticity, InSe offers the opportunity to explore various effects arising from the coupling of its peculiar mechanical behaviors and other physical properties. Here, we employ neutron scattering techniques to investigate the correlations of plastic interlayer slip, lattice anharmonicity, and thermal transport in InSe crystals. Not only are the interlayer slip direction and magnitude well captured by shifts in the Bragg reflections, but we also observe a deviation from the expected Debye behaviour in the heat capacity and lattice thermal conductivity. Combining the experimental data with first-principles calculations, we tentatively attribute the observed evidence of strong phonon-phonon interactions to a combination of a large acoustic-optical frequency resonance and a nesting effect. These findings correlate the macroscopic plastic slip and the microscopic lattice dynamics, providing insights into the mechano-thermo coupling and modulation in 2D vdW materials.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Low-alpha Operation of the Iota Storage Ring

Operation with ultra-low momentum-compaction factor (alpha) is a desirable capability for many storage rings and synchrotron radiation sources. For example, low-alpha lattices are commonly used to produce picosecond bunches for the generation of coherent THz radiation and are the basis of a number of conceptual designs for EUV generation via steady-state microbunching (SSMB). Achieving ultra-low alpha requires not only a high-level of stability in the linear optics but also flexible control of higher-order compaction terms. Operation with lower momentum-compaction lattices has recently been investigated at the IOTA storage ring at Fermilab. A procedure for lowering the ring compaction using the linear optics along with compensations from the higher-order magnets was developed with the aid of a model, and an experimental technique for measuring the momentum compaction was developed. The lowest momentum compaction achieved during the available run-time was $3.4\times10^{-4}$, around 15 times lower than previously operated. These feasibility studies ensure an improved experimental understanding of the IOTA optics and potentially will enable new research programs at the facility.

43 PARTICLE ACCELERATORS↗
DOE OSTI2025

Enantioselective Se lattices for stable chiroptoelectronic processing media

Chiroptoelectronic devices are crucial for applications in quantum computing, spin optical communications, and magnetic recording. However, the limited efficiency and low stability of conventional circularly polarized light (CPL)-sensing materials have restricted their broader use. Here, we introduce atomic chiral Se nanorod (NRs) films as broadband CPL detectors, leveraging the intrinsic chirality and stability of Se nanocrystals. We also perform incident circular polarization (ICP)-Raman optical activity (ROA) to explore the chiroptical activity of the large-area films. The Se NRs thin films detected CPL across a broad range from ultraviolet (UV) to short-wavelength infrared (SWIR), with a responsivity dissymmetry factor of up to 0.4, maintaining high stability under ambient conditions for longer than 13 months. CPL-sensitive Se NRs with intrinsic chirality have potential applications in chiral photonic synapses, chiral spin devices, and CPL-sensitive photocatalysts. ICP-ROA mapping also advances the analysis of 2D chiral materials.

Nanophotonics and plasmonics↗
DOE OSTI2020

Size Dependence of Lattice Parameter and Electronic Structure in CeO2 Nanoparticles

Intrinsic properties of a compound (e.g. electronic structure, crystallographic structure, optical and magnetic properties) define notably its chemical and physical behavior. In the case of nanomaterials, these fundamental properties depend on the occurrence of quantum mechanical size effects and on the considerable increase of the surface to bulk ratio. However, the literature on this size-dependence and on the involved mechanisms is quite elusive and scarce. Here, we explore the size-dependence of both crystal and electronic properties of CeO2 nanoparticles (NPs) with different sizes by state-of-the art spectroscopic techniques. XRD, XPS and HERFD-XANES demonstrate that the as-synthesized NPs crystallize in the fluorite structure and they are predominantly composed of CeIV ions. The strong dependence of the lattice parameter with the NPs size was attributed to the presence of adsorbed species at the NPs surface thanks to FTIR and TGA measurements. In addition, the size-dependence of the eg level in the Ce LIII XANES spectra was experimentally observed by HERFD-XANES and confirmed by theoretical calculations.

Lanthanide, CeO2, HEFRD-XANES, Electronic structur↗
DOE OSTI2025

Quantum computing universal thermalization dynamics in a (2 + 1)D Lattice Gauge Theory

Simulating non-equilibrium phenomena in strongly-interacting quantum many-body systems, including thermalization, is a promising application of near-term and future quantum computation. By performing experiments on a digital quantum computer consisting of fully-connected optically-controlled trapped ions, we study the role of entanglement in the thermalization dynamics of a Z 2 lattice gauge theory in 2+1 spacetime dimensions. Using randomized-measurement protocols, we efficiently learn a classical approximation of non-equilibrium states that yields the gap-ratio distribution and the spectral form factor of the entanglement Hamiltonian. These observables exhibit universal early-time signals for quantum chaos, a prerequisite for thermalization. Our work, therefore, establishes quantum computers as robust tools for studying universal features of thermalization in complex many-body systems, including in gauge theories.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2021

Disentangling electronic, lattice, and spin dynamics in the chiral helimagnet Cr 1/3 NbS 2

We investigate the static and ultrafast magneto-optical response of the hexagonal chiral helimagnet Cr 1/3 NbS 2 above and below the helimagnetic ordering temperature. The presence of a magnetic easy plane contained within the crystallographic $ab$-plane is confirmed, while degenerate optical pump-probe experiments reveal significant differences in the dynamic between the parent, NbS 2 , and Cr-intercalated compounds. Time-resolved magneto-optical Kerr effect measurements show a two-step demagnetization process, where an initial, subpicosecond relaxation and subsequent buildup (τ > 50ps) in the demagnetization dynamic scale similarly with increasing pump fluence. Despite theoretical evidence for partial gapping of the minority spin channel, suggestive of possible half-metallicity in Cr 1/3 NbS 2 , such a long demagnetization dynamic likely results from spin-lattice relaxation as opposed to minority state blocking. However, comparison of the two-step demagnetization process in Cr 1/3 NbS 2 with other 3d intercalated transition metal dichalcogenides reveals a behavior that is unexpected from conventional spin-lattice relaxation, and may be attributed to the complicated interaction of local moments with itinerant electrons in this material system.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗