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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 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Superradiant Neutrino Lasers from Radioactive Condensates

Superradiance emerges from collective spontaneous emission in optically pumped gases, and is characterized by photon emission enhancements of up to $\frac{1}{4}$⁢𝑁 2 in an 𝑁 atom system. The gain mechanism derives from correlations developed within the decay medium rather than from stimulated emission as in lasing, so an analog of this process should be possible for fermionic final states. We introduce here the concept of superradiant neutrino emission from a radioactive Bose Einstein condensate, which can form the basis for a superradiant neutrino laser. A plausible experimental realization based on a condensate of electron-capture isotope 83 Rb could exhibit effective radioactive decay rates accelerated from 86.2 days to minutes in viably sized rubidium condensates of 10 6 atoms.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Tunability and Long-Range Enhancement of Resonance Energy Transfer Facilitated by Plasmonic Nanorods

Resonance energy transfer (RET) between molecules or quantum dots is an important process in many energy-related applications. Different environmental structures have been studied and demonstrated to be able to enhance the RET rates between a nearby donor–acceptor pair. In particular, cylindrical silver nanorods and nanowires have shown an extraordinary ability to transfer energy along their longitudinal axes over large distances. However, the detailed mechanism of such transfer and the effects on the molecular RET process are as yet elusive. In this study, we use the recently developed computational tool based on the plasmon-coupled RET method to systematically study the effects of nanorods with different dimensions on the RET rates. We find that highly frequency-dependent coupling factor (CF) spectra, whose amplitudes determine RET rates, can be obtained due to the localized surface plasmon polariton modes of the rods with nanoscale dimensions. Simple phenomenological models can be derived for the wavelengths of CF peaks in relation to the length and width of the nanorods, providing easy tunability for enhancing the RET rate in specific wavelength ranges. When coupled to longer rods with mesoscale lengths, exponential decay of the CF over long donor–acceptor distances with a small decay constant is observed, leading to the possibility of long-range RET processes. Furthermore, drumhead resonance modes emerge on the flat ends of the rod when the rod’s diameter reaches 300 nm, resulting in extra enhancement to RET rate compared to certain thinner rods. Furthermore, these findings shed new light on the mechanism of plasmonic enhancement with silver nanorods and establish design principles for how to optimally utilize these structures to manipulate RET processes for various applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Helicity amplitude analysis of χcJ → ϕϕ

Using (447.9 ± 2.3) million ψ(3686) events collected with the BESIII detector, the decays of χcJ → ΦΦ (J = 0, 1, 2) have been studied via the decay ψ(3686) → γχcJ. The branching fractions of the decays χcJ → ΦΦ (J = 0, 1, 2) are determined to be (8.59 ± 0.27 ± 0.20) × 10-4, (4.26 ± 0.13 ± 0.15) × 10-4, and (12.67 ± 0.28 ± 0.33) × 10-4, respectively, which are the most precise measurements to date. From a helicity amplitude analysis of the process ψ(3686) → γχcJ , χcJ → ΦΦ, Φ → K+K-, the polarization parameters of the χcJ → ΦΦ decays are determined for the first time.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

β-decay feeding intensity distributions of 71,73 Ni

This paper presents the β-decay feeding intensity distribution and Gamow-Teller transition strength distribution of 71,73 Ni. These quantities were measured using the technique of total absorption spectroscopy at the National Superconducting Cyclotron Laboratory with the Summing NaI(Tl) detector. These measurements provide sensitive constraints to theoretical models used to predict β-decay properties far from stability for astrophysical applications. Specifically, for the astrophysical r process, the majority of the involved nuclei are not accessible by current facilities, and the nuclear input is mainly provided by theory. Furthermore, the present work reports on two neutron-rich nickel isotopes in the region where the weak r process is expected to be relevant in stellar nucleosynthesis. The experimental results are compared to two theoretical models, namely the shell model and the quasiparticle random-phase approximation, to help further refine theoretical calculations and aid in future r-process studies.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Evolution of highly multimodal Rayleigh–Taylor instabilities

Rayleigh–Taylor (RT) instabilities are important fluid instabilities that arise in inertial confinement fusion (ICF) capsule implosions, and many other contexts. Multi-mode coupling is observed in experiments and plays a substantial role in material mix from RT instabilities. In this work, we study the evolution of highly multimodal perturbations (power law distribution) that approximate those found at manufactured material interfaces. We use simulations of over 2000 different perturbations in the LANL code xRAGE to identify distinct phases in the processes of bubble growth and bubble merger which can be visualized in a 2D phase portrait with clear regimes of mode growth and decay. Our results show that the dynamic evolution of the instability strongly depends on the mode of the perturbations and mode interactions. The merger process accelerates bubble growth. A non-Markovian region and a transition of the instability from: (1) initial exponential growth to (2) linear growth and to (3) quadratic growth and asymptotic behavior, are clearly captured in the phase space. We have developed a quantitative model of bubble growth that reproduces the dynamic behavior of ensembles of perturbations. Implications for ICF capsules designed for robustness against instabilities are discussed.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Higgs troika for baryon asymmetry

To explain the baryon asymmetry of the Universe, we extend the Standard Model (SM) with two additional Higgs doublets with small vacuum expectation values. The additional Higgs fields interact with SM fermions through complex Yukawa couplings, leading to new sources of $CP$ violation. We propose a simple flavor model with $\mathcal{O}$(1) or less Yukawa couplings for quarks and charged leptons, consistent with current flavor constraints. To generate neutrino masses and the baryon asymmetry, right-handed neutrinos in the ~ 0.1 - 10 TeV range couple to the "Higgs Troika." The new Higgs doublet masses are at or above the TeV scale, allowing for asymmetric decays into SM lepton doublets and right-handed neutrinos. The asymmetry in lepton doublets is then processed into a baryon asymmetry, similar to leptogenesis. Since the masses of the new fields could be near the TeV scale, there is potentially a rich high energy collider phenomenology, including observable deviations in the 125 GeV Higgs decay into muons and taus, as well as detectable low energy signals such as the electron EDM or $µ → eγ$. Hence, this is in principle a testable model for generation of baryon asymmetry.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Sub-single exciton optical gain threshold in colloidal semiconductor quantum wells with gradient alloy shelling

Colloidal semiconductor quantum wells have emerged as a promising material platform for use in solution-processable lasers. However, applications relying on their optical gain suffer from nonradiative Auger decay due to multi-excitonic nature of light amplification in II-VI semiconductor nanocrystals. Here, we show sub-single exciton level of optical gain threshold in specially engineered CdSe/CdS@CdZnS core/crown@gradient-alloyed shell quantum wells. This sub-single exciton ensemble-averaged gain threshold of (Ng)≈ 0.84 (per particle) resulting from impeded Auger recombination, along with a large absorption cross-section of quantum wells, enables us to observe the amplified spontaneous emission starting at an ultralow pump fluence of ~ 800 nJ cm –2 , at least three-folds better than previously reported values among all colloidal nanocrystals. Finally, using these gradient shelled quantum wells, we demonstrate a vertical cavity surface-emitting laser operating at a low lasing threshold of 7.5 μJ cm –2 . These results represent a significant step towards the realization of solution-processable electrically-driven colloidal lasers.

36 MATERIALS SCIENCE↗
DOE OSTI2020

$β$-delayed-neutron studies of 135,136 Sb and 140 I performed with trapped ions

In this work, Beta-delayed-neutron $(βn)$ spectroscopy was performed using the Beta-decay Paul Trap and an array of radiation detectors. The $βn$ branching ratios and energy spectra for 135,136 Sb and 140 I were obtained by measuring the time of flight of recoil ions emerging from the trapped ion cloud. These nuclei are located at the edge of an isotopic region identified as having $βn$ branching ratios that impact the $r$-process abundance pattern around the A ≈ 130 peak. For 135,136 Sb and 140 I, $βn$ branching ratios of 14.6(13)%, 17.6(29)%, and 7.6(28)% were determined, respectively. The $βn$ energy spectra obtained for 135 Sb and 140 I are compared with results from direct neutron measurements, and the $βn$ energy spectrum for 136 Sb has been measured for the first time.

42 ENGINEERING↗
DOE OSTI2023

Phosphor thermometry device for synchronized acquisition of luminescence lifetime decay and intensity on thermal barrier coatings

A phosphor thermometry device includes a laser that generates a laser pulse onto a thermal barrier coating (TBC) applied onto a substrate. A metallic bond coat layer is on the substrate. A ceramic top coat layer is on the bond coat layer and includes an undoped layer and a doped sensing layer having co-doped first and second rare-earth luminescent dopants that emit respective first and second different emission wavelengths upon excitation by the laser pulse. A detector receives reflected, convoluted luminescence signals from the TBC. First and second photomultiplier devices detect respective first and second different emission wavelengths of the convoluted luminescence signals. A controller receives and processes signals generated from respective first and second photomultiplier devices and determines luminescence lifetime decay and intensity variations for each of the respective first and second rare-earth luminescent dopants for temperature monitoring of the TBC.

Fouliard, Quentin↗
DOE OSTI2021

Fiducial $q_T$ resummation of color-singlet processes at N$^3$LL+NNLO

We present a framework for $q_T$ resummation at N 3 LL+NNLO accuracy for arbitrary color-singlet processes based on a factorization theorem in SCET. Our implementation CuTe-MCFM is fully differential in the Born kinematics and matches to large-$q_T$ fixed-order predictions at relative order $α^2_s$. It provides an efficient way to estimate uncertainties from fixed-order truncation, resummation, and parton distribution functions. In addition to W ± , Z and H production, also the diboson processes $\gamma\gamma$, Z$\gamma$, ZH and W ± H are available, including decays. We discuss and exemplify the framework with several direct comparisons to experimental measurements as well as inclusive benchmark results. In particular, we present novel results for $\gamma\gamma$ and Z$\gamma\gamma$ at N 3 LL+NNLO and discuss in detail the power corrections induced by photon isolation requirements.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Measurement of the $K^{+} → π^{+} γγ$ decay

A sample of 3984 candidates of the $K^{+} → π^{+} γγ$ decay, with an estimated background of 291 ± 14 events, was collected by the NA62 experiment at CERN during 2017–2018. In order to describe the observed di-photon mass spectrum, the next-to-leading order contribution in chiral perturbation theory was found to be necessary. The decay branching ratio in the full kinematic range is measured to be (9.61 ± 0.17) x 10 -7 . The first search for production and prompt decay of an axion-like particle with gluon coupling in the process $K^{+} → π^{+} a$, $a → γγ$ is also reported.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Microscopic mechanism of unusual lattice thermal transport in TlInTe 2

We investigate the microscopic mechanism of ultralow lattice thermal conductivity (κ l ) of TlInTe 2 and its weak temperature dependence using a unified theory of lattice heat transport, that considers contributions arising from the particle-like propagation as well as wave-like tunneling of phonons. While we use the Peierls–Boltzmann transport equation (PBTE) to calculate the particle-like contributions (κ l (PBTE)), we explicitly calculate the off-diagonal (OD) components of the heat-flux operator within a first-principles density functional theory framework to determine the contributions (κ l (OD)) arising from the wave-like tunneling of phonons. At each temperature, T, we anharmonically renormalize the phonon frequencies using the self-consistent phonon theory including quartic anharmonicity, and utilize them to calculate κ l (PBTE) and κ l (OD). With the combined inclusion of κ l (PBTE), κ l (OD), and additional grain-boundary scatterings, our calculations successfully reproduce the experimental results. Our analysis shows that large quartic anharmonicity of TlInTe 2 (a) strongly hardens the low-energy phonon branches, (b) diminishes the three-phonon scattering processes at finite T, and (c) recovers the weaker than T –1 decay of the measured κ l .

36 MATERIALS SCIENCE↗
DOE OSTI2020

Coupled nuclear–electronic decay dynamics of O2 inner valence excited states revealed by attosecond XUV wave-mixing spectroscopy

Multiple Rydberg series converging to the $O_2^+$ c $^{4}Σ^{-}_{u}$ state, accessed by 20-25 eV extreme ultraviolet (XUV) light, serve as important model systems for the competition between nuclear dissociation and electronic autoionization. The dynamics of the lowest member of these series, the $3sσ_g $ state around 21 eV, has been challenging to study owing to its ultra-short lifetime (<10 fs). Here, we apply transient wave-mixing spectroscopy with an attosecond XUV pulse to investigate the decay dynamics of this electronic state. Lifetimes of 5.8 ± 0.5 fs and 4.5 ± 0.7 fs at 95% confidence intervals are obtained for v = 0 and v = 1 vibrational levels of the 3s Rydberg state, respectively. A theoretical treatment of predissociation and electronic autoionization finds that these lifetimes are dominated by electronic autoionization. The strong dependence of the electronic autoionization rate on the internuclear distance because of two ionic decay channels that cross the 3s Rydberg state results in the different lifetimes of the two vibrational levels. The calculated lifetimes are highly sensitive to the location of the 3s potential with respect to the decay channels; by slight adjustment of the location, values of 6.2 and 5.0 fs are obtained computationally for the v = 0 and v = 1 levels, respectively, in good agreement with experiment. Overall, an intriguing picture of the coupled nuclear-electronic dynamics is revealed by attosecond XUV wave-mixing spectroscopy, indicating that the decay dynamics are not a simple competition between isolated autoionization and predissociation processes.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Effective action approach for preheating

Abstract We present a semiclassical non-perturbative approach for calculating the preheating process at the end of inflation. Our method involves integrating out the decayed particles within the path integral framework and subsequently determining world-line instanton solutions in the effective action. This enables us to obtain the effective action of the inflaton, with its imaginary part linked to the phenomenon of particle creation driven by coherent inflaton field oscillations. Additionally, we utilize the Bogoliubov transformation to investigate the evolution of particle density within the medium after multiple inflaton oscillations. We apply our approach to various final state particles, including scalar fields, tachyonic fields, and gauge fields. The non-perturbative approach provides analytical results for preheating that are in accord with previous methods.

Astronomy & Astrophysics↗
DOE OSTI2026

Quantum speed limit for the out-of-time-ordered correlator from an open-system perspective

Scrambling, the delocalization of initially localized quantum information, is commonly characterized by the out-of-time-ordered correlator (OTOC). Employing the OTOC–Renyi-2 entropy theorem, we derive a quantum speed limit for the OTOC, which sets a lower bound for the rate with which information can be scrambled. This bound becomes particularly tractable by describing the scrambling of information in a closed quantum system as an effective decoherence process of an open system interacting with an environment. We prove that decay of the OTOC can be bounded by the strength of the system-environment coupling and two-point environmental correlation functions. We validate our analytic bound numerically using the nonintegrable transverse field Ising model. Furthermore, our results provide a universal and model-agnostic quantitative framework for understanding the dynamical limits of information spreading across quantum many-body physics, condensed matter systems, and engineered quantum platforms.

Fermions↗
DOE OSTI2025

A Beamdump facility at Jefferson Lab

The potential of the intense secondary muon, neutrino, and (hypothetical) light dark matter beams at the Thomas Jefferson National Accelerator Facility (Jefferson Lab) is explored. These are produced in the high-power dumps with high-current electron beams. Light dark matter searches with the approved Beam Dump eXperiment (BDX) are driving the realization of a new underground vault behind Hall A that could be extended to a Beamdump Facility with little additional installations. High-energy muons created via the Bethe–Heitler process uniquely do not proceed through the more common pion production and decay channels. Several possible muon physics applications are highlighted. Neutrino detector technologies and experiments suitable for a beamdump facility are outlined.

Accelerator Physics↗
DOE OSTI2022

On the modeling of $t\bar{t}W^\pm$ signatures at the LHC

We discuss our recent progress on improving the theoretical description of the pp \to t\bar{t}W^\pm p p → t t ‾ W ± process with particular focus on fiducial signatures that include top-quark decays. We employ a wide range of techniques from parton shower matching, narrow width approximation to full off-shell computations to assess the importance of the different modeling approaches.

Kraus, Manfred↗
DOE OSTI2023

DarkNESS Project Testing

This internship involved the design and assembly of a mechanical system for testing skipper-Charge Couple Devices (CCDs) for the DarkNESS project. Skipper-CCDs are highly-sensitive sensors with ultra-low readout noise that are deployed for direct detection of dark matter. DarkNESS is a CubeSat that aims to use skipper CCDs to search for dark matter decaying into X-rays. Currently, in the testing phase, the design process involved creating 3D models of mechanical adapters to operate a prototype space Multi Chip Module (sMCM) package in existing testing chambers in the CCD lab at Fermilab's IERC. The drawings were sent out to be machined, and while waiting to receive the finished adapters, we assembled a vacuum chamber for skipper-CCD testing and performed initial testing of a single CCD controlled by the space Low Threshold Acquisition (sLTA) board that will be employed on the CubeSat. The results showed that the testing conditions are optimal for data to start being taken and analyzed.

Akouedjinoude, Kodjo↗