Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Applied physics”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Next-generation neutron detection using a 6 Li glass scintillator composite

Neutron detectors are crucial in fundamental science, nuclear security, safeguards, and civil applications. 3 He-filled gas proportional counters are the gold standard for thermal neutron detection, prized for their efficiency, neutron/gamma discrimination, and stability; however, the scarcity of 3 He has prompted the search for alternatives. Here, we introduce a neutron detector design based on a scintillating composite consisting of 6 Li glass scintillator particles dispersed in an organic matrix. A detector consisting of this scintillating composite, photomultiplier tubes (PMTs) for optical detection, and electronics for reading out the PMT signal in both pulse and current modes was prototyped and characterized using various neutron and gamma sources. The prototype achieves a measured intrinsic detection efficiency of 6.70 ± 0.01%, a die-away time of 10.3 ± 0.1 μs, a negligible gamma misidentification probability, and response linearity up to at least 3.7 × 10 6 incident neutrons/s established via a cross-calibration technique. This detector holds the potential to outperform traditional 3 He-gas-based neutron detection systems, offering a viable alternative amidst the ongoing 3 He shortage and promising advancements in neutron detection technology.

47 OTHER INSTRUMENTATION↗
DOE OSTI2025

The persistent shadow of the supermassive black hole of M87. II. Model comparisons and theoretical interpretations

The Event Horizon Telescope (EHT) observation of M87∗ in 2018 has revealed a ring with a diameter that is consistent with the 2017 observation. The brightest part of the ring is shifted to the southwest from the southeast. In this paper, we provide theoretical interpretations for the multi-epoch EHT observations for M87∗ by comparing a new general relativistic magnetohydrodynamics model image library with the EHT observations for M87∗ in both 2017 and 2018. The model images include aligned and tilted accretion with parameterized thermal and nonthermal synchrotron emission properties. The 2018 observation again shows that the spin vector of the M87∗ supermassive black hole is pointed away from Earth. A shift of the brightest part of the ring during the multi-epoch observations can naturally be explained by the turbulent nature of black hole accretion, which is supported by the fact that the more turbulent retrograde models can explain the multi-epoch observations better than the prograde models. The EHT data are inconsistent with the tilted models in our model image library. Assuming that the black hole spin axis and its large-scale jet direction are roughly aligned, we expect the brightest part of the ring to be most commonly observed 90 deg clockwise from the forward jet. This prediction can be statistically tested through future observations.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Metal-ion-controlled growth and nanoindentation response of 3D, bicontinuous Cu–Fe thin films

Bicontinuous, nanocomposite thin film morphologies depend largely on the deposition conditions applied during physical vapor deposition. With the introduction of high power impulse magnetron sputtering (HiPIMS), the range of potential morphologies achieved during deposition has been increased. In this work, we compare the deposition outcomes between traditional direct-current magnetron sputtering (DCMS) and HiPIMS for a thin film co deposit of Cu and Fe. Modular control of the columnarity, porosity and roughness was achieved by varying the Cu and Fe metal ion currents during deposition. The directionality of the nanostructured phase-separated morphology was also controlled as the ion current increased. At zero ion current for both Cu and Fe sputtered species during DCMS, the film exhibited lateral concentration modulations of Cu and Fe. The directionality of the Cu- and Fe-rich phases shifted to vertical concentration modulations at low ion currents of I Fe = 1A and I Cu = 0:1A and to lateral concentration modulations at relatively moderate ion currents of I Fe = 5A and I Cu = 2A: At high ion currents of I Fe = 18A and I Cu = 2A; a more randomized phase domain structure was observed on the nanoscale. This structural shift is rationalized using an interdiffusion model. Here, the role of different kinds of phase separated morphologies, achieved during DCMS deposition, on the mechanical properties has also been studied. Results indicated increase in hardness, indentation modulus and flow strength values with the increase in indentation strain rates. Bicontinuous Cu-Fe nanocomposites are found to be stronger than multilayer Cu-Fe samples.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Spin wavepackets in the Kagome ferromagnet Fe 3 Sn 2 : Propagation and precursors

The propagation of spin waves in magnetically ordered systems has emerged as a potential means to shuttle quantum information over large distances. Conventionally, the arrival time of a spin wavepacket at a distance, d , is assumed to be determined by its group velocity, v g . Here, we report time-resolved optical measurements of wavepacket propagation in the Kagome ferromagnet Fe 3 Sn 2 that demonstrate the arrival of spin information at times significantly less than d / v g . We show that this spin wave “precursor” originates from the interaction of light with the unusual spectrum of magnetostatic modes in Fe 3 Sn 2 . Related effects may have far-reaching consequences toward realizing long-range, ultrafast spin wave transport in both ferromagnetic and antiferromagnetic systems.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Rippled metamaterials with scale-dependent tailorable elasticity

Thermally induced ripples are intrinsic features of nanometer-thick films, atomically thin materials, and cell membranes, significantly affecting their elastic properties. Despite decades of theoretical studies on the mechanics of suspended thermalized sheets, controversy still exists over the impact of these ripples, with conflicting predictions about whether elasticity is scale-dependent or scale-independent. Experimental progress has been hindered so far by the inability to have a platform capable of fully isolating and characterizing the effects of ripples. This knowledge gap limits the fundamental understanding of thin materials and their practical applications. Here, we show that thermal-like static ripples shape thin films into a class of metamaterials with scale-dependent, customizable elasticity. Utilizing a scalable semiconductor manufacturing process, we engineered nanometer-thick films with precisely controlled frozen random ripples, resembling snapshots of thermally fluctuating membranes. Resonant frequency measurements of rippled cantilevers reveal that random ripples effectively renormalize and enhance the average bending rigidity and sample-to-sample variations in a scale-dependent manner, consistent with recent theoretical estimations. The predictive power of the theoretical model, combined with the scalability of the fabrication process, was further exploited to create kirigami architectures with tailored bending rigidity and mechanical metamaterials with delayed buckling instability.

Applied Physical Sciences↗
DOE OSTI2025

Multistage nucleation pathway in LiF molten salt mirrors the crystal–melt interface structure

Despite over a century of studies, fundamental questions remain about the processes governing crystal nucleation from melts or solutions. Research over the past three decades has presented mounting evidence for kinetic pathways of crystal nucleation that are more complex than envisioned by the simplest forms of classical theory. Such observations have been presented for colloidal and elemental systems with covalent and metallic bonding. Despite the technological and geochemical importance of molten salts, similar studies for these ionically bonded systems are currently lacking. Here we develop a machine learning interatomic potential for a model ionic system: LiF. The potential features quantum-level accuracy for both liquid and multiple solid polymorphs over wide temperature and pressure ranges and accurately reproduces experimentally measured properties. Thanks to the efficiency of the potential, which enables microsecond-scale molecular dynamics simulations, induction times for nucleation of LiF solids from their melts are computed over a range of undercoolings. With the aid of a set of robust local order parameters established here, the simulations reveal that homogeneous crystal nucleation in undercooled melts preferentially initiates from liquid regions showing slow dynamics and high bond orientational order simultaneously, and the second-shell order of both precritical nuclei and the surface of postcritical nuclei is dominated by hexagonal close packing and body-centered cubic local structure, even though the nucleus core is dominated by face-centered cubic structure corresponding to the stable rocksalt crystal structure. Finally, we establish a connection between the crystallization pathway and the equilibrium crystal-melt interface structure.

Applied Physical Sciences↗
DOE OSTI2023

Prompt fission neutron multiplicity in the 239 Pu(n, f) reaction and its energy dependence

Measuring prompt fission neutrons to high precision is an experimental challenge, especially for radioactive fissioning nuclides. However, accurate average multiplicities, $\overline{v}_{p}$, and kinetic energy distributions of prompt fission neutrons are essential for fundamental and applied nuclear physics. We present here a recent measurement of the 239 Pu (n,f) $\overline{v}_{p}$ as a function of the incident-neutron energy, over the range 1-700 MeV. The measurement was performed with a cutting-edge setup and an innovative technique, which allowed to minimize and account for the main sources of bias. An unprecedented precision was therefore achieved. Our data are compared to GEF predictions as well as to evaluated libraries. For the first time, at low energies, the ENDF/B-VIII.0 nuclear data evaluation is validated with an independent measurement and the evaluated uncertainty reduced by up to 60%. This work paves the way to precisely measure prompt fission neutron multiplicities on highly radioactive nuclei.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2026

PIBHI 2025: status and perspectives of ECR ion sources

The article summarizes the discussions held during the PIBHI 2025 workshop (https://agenda.infn.it/e/pibhi2025) highlighting the most significant points to have emerged. The main goal of the workshop was to foster dialogue on topics relevant to the ECR ion sources (ECRIS) community through dedicated and thematic round tables. The outcomes of these discussions are outlined below, with particular focus on the remaining open questions in the field.

43 PARTICLE ACCELERATORS↗
DOE OSTI2026

Advancing extreme pulsed lasers through measurements: summary of the pulsed laser metrology workshop

In this report we present consensus findings produced during the pulsed laser metrology (PLM) workshop (Boulder, CO, USA, August 2025). The workshop was a meeting of 35 scientists from private industry, academia, and U.S. government to compile a list of the metrology needs to support extreme pulsed laser development and implementation. We define ‘extreme pulsed lasers’ loosely as those with peak powers above 1 TW or multi-Joule pulse energies. Such lasers are being increasingly used and investigated for use in high energy particle acceleration, short wavelength radiation generation, laser-based fusion, etc. The rapid growth of these fields and the proliferation of extreme lasers for these applications, coupled with the extreme electric fields they generate and relative scarcity of such lasers, presents unique challenges to accuracy in their measurement. The PLM workshop was a two-day event designed to hear from users, developers, and researchers on the current state of optical metrology associated with these extreme pulsed lasers. The goal was to identify the most important measurement challenges limiting development and implementation of these lasers in practical applications. We report here the conclusions and recommendations of this workshop. The hope is that this document will become the first of many iterations which track the status of measurement needs supporting extreme pulsed lasers.

Lasers↗
DOE OSTI2025

Cosmological perturbations from a new approach to inflation

In a previous paper, we proposed a new approach to the beginning of inflation—a lingering universe [Melcher et al. Phys. Rev. D 110, 063517 (2024).]—that is a quasistatic phase prior to inflation. The Universe begins in a lingering state with a nearly vanishing Hubble parameter. This calls into question the absolute age of the Universe, as the Hubble time can be nearly infinite. It also provides promise for addressing the initial singularity of inflation and issues with quantum field theory in de Sitter spacetime. Such models arise in classical cosmologies with nonvanishing spatial curvature (inspired by PLANCK 2018 data) and independently by models that arise in string cosmology. Here, in this paper, we consider the importance of cosmological perturbations for the stability of the lingering phase and how this influences cosmological observations. Our goal is to establish observables in this new paradigm for the origin of inflation, which is in contrast to eternal inflation and cyclic cosmologies. We also address questions of stability and the transition to inflation.

cosmology↗
DOE OSTI2025

On-chip pulse shaping of entangled photons

The miniaturization of optical systems via integrated photonics is critical to the ultimate scalability and performance of photonic quantum processors, yet many longstanding optical signal processing capabilities—such as Fourier-transform pulse shaping—remain unrealized on chip. In this work, we demonstrate on-chip spectral shaping of entangled photons using a multichannel microring-resonator-based silicon photonic pulse shaper. Achieving line-by-line phase control on a 3 GHz grid for two frequency-bin-entangled qudits, the pulse shaper's fine spectral resolution enables control of nanosecond-scale temporal features, which are observed by direct coincidence detection of biphoton correlation functions that show excellent agreement with theory. This work marks a demonstration of biphoton pulse shaping using an integrated spectral shaper and holds significant promise for applications in photonic quantum information processing.

Entanglement manipulation↗
DOE OSTI2023

Large-area photon calorimeter with Ir-Pt bilayer transition-edge sensor for the CUPID experiment

CUPID is a next-generation neutrinoless double-β decay experiment that will require cryogenic light detectors to improve background suppression, via the simultaneous readout of heat and light channels from its scintillating crystals. In this work, we showcase light detectors based on an alternative Ir-Pt bilayer transition-edge sensor. We have performed a systematic study to improve the thermal coupling between the photon absorber and the sensor, and thereby its responsivity. Our first devices meet CUPID's baseline noise requirement of < 100 eV rms. Our detectors have risetimes of approximately 180μs and measured timing jitter of < 20μs for the expected signal to noise at the Q value of the decay, which achieves the CUPID's criterion of rejecting two-neutrino double-β decay pile-up events. In conclusion, the current work will inform the fabrication of future devices, culminating in the final TES design and a scaleable readout scheme for CUPID.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2023

Efficient core-excited state orbital perspective on calculating x-ray absorption transitions in determinant framework

X-ray absorption spectroscopy (XAS) is an explicit probe of the unoccupied electronic structure of materials and an invaluable tool for fingerprinting various electronic properties and phenomena. Computational methods capable of simulating and analyzing such spectra are therefore in high demand for complementing experimental results and for extracting valuable insights therefrom. In particular, a recently proposed first-principles approach titled many-body XAS (MBXAS), which approximates the final (initial) state as a Slater determinant constructed from Kohn-Sham (KS) orbitals optimized in the absence (presence) of the relevant core electron has shown promising prospects in evaluating the transition amplitudes. In this article, we show that the MBXAS approach can be rederived using a transition operator expressed entirely in the basis of core-excited state KS orbitals and that this reformulation offers substantial practical and conceptual advantages. In addition to circumventing previous issues of convergence with respect to the number of unoccupied ground-state orbitals, the aforementioned representation reduces the computational expense by rendering the calculation of such orbitals unnecessary altogether. Furthermore, the reformulated approach also provides a direct pathway for comparing the many-body approximation with the so-called single-particle treatment and indicates the relative importance in observed XAS intensity of the relaxation of the valence occupied subspace induced by the core excitation. Finally, using the core-excited state basis, we define auxiliary orbitals for x-ray absorption and demonstrate their utility in explaining the spectral intensity by contrasting them with single-particle approximations to the excited state.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2023

Precision pulse shape simulation for proton detection at the Nab experiment

The Nab experiment at Oak Ridge National Laboratory, USA, aims to measure the beta-antineutrino angular correlation following neutron β decay to an anticipated precision of approximately 0.1%. The proton momentum is reconstructed through proton time-of-flight measurements, and potential systematic biases in the timing reconstruction due to detector effects must be controlled at the nanosecond level. In conclusion, we present a thorough and detailed semiconductor and quasiparticle transport simulation effort to provide precise pulse shapes, and report on relevant systematic effects and potential measurement schemes.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

Purely Cubic Spin Splittings with Persistent Spin Textures

Purely cubic spin splittings in the band structure of bulk insulators have not been extensively investigated yet despite the fact that they may pave the way for novel spin-orbitronic applications and can also result in a variety of promising spin phenomena. By symmetry analysis and first-principles simulations, we report symmetry-enforced purely cubic spin splittings (SEPCSS) that can even lead to persistent spin textures. In particular, these SEPCSS can be thought to be complementary to the cubic Rashba and cubic Dresselhaus types of spin splittings. Strikingly, the presently discovered SEPCSS are expected to exist in the large family of materials crystallizing in the $\bar{6}m2$ and $\bar{6}$ point groups, including the Ge 3 Pb 5 O 11 , Pb 7 Br 2 F 12 , and Pb 7 Cl 2 F 12 compounds.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Dimensionality-Induced Change in Topological Order in Multiferroic Oxide Superlattices

We construct ferroelectric (LuFeO 3 ) m /(LuFe 2 O 4 ) superlattices with varying index m to study the effect of confinement on topological defects. We observe a thickness-dependent transition from neutral to charged domain walls and the emergence of fractional vortices. In thin LuFeO 3 layers, the volume fraction of domain walls grows, lowering the symmetry from P6 3 cm to P3c1 before reaching the nonpolar P6 3 /mmc state, analogous to the group-subgroup sequence observed at the high-temperature ferroelectric to paraelectric transition. Our study shows how dimensional confinement stabilizes textures beyond those in bulk ferroelectric systems.

36 MATERIALS SCIENCE↗