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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 OSTI2025

High-pressure neutron diffraction at ultra-low temperature

Neutron diffraction is a powerful tool in the study of quantum materials and associated emergent phenomena as it allows for direct detection of magnetic structure even at ultra-low temperatures. As pressure can drive systems across quantum critical points and tune emergent behaviors at the quantum scale, coupling neutron diffraction with extreme conditions of high pressure at (ultra-)low temperatures has been a key research target over decades. This has proven challenging as magnetic neutron diffraction typically requires large sample volumes due to flux limitations, whereas high-pressure studies require small sample volumes due to pressure limitations. Combining these two contradictory requirements poses many difficulties, but also brings opportunities in research and development. Here, we address these shortcomings through the use of a diamond anvil cell equipped with polycrystalline anvils with relatively large sample volumes coupled with the high neutron flux made available by the high-pressure diffractometer of the Spallation Neutron Source. This particular diamond anvil cell configuration has previously proven useful for single-crystal samples and is here coupled with the ultra-low temperatures of a dilution refrigerator for the first time. Our study on a single crystal of Yb 2 ⁢O 3 successfully collected magnetic neutron diffraction data at 5.3 GPa below 200 mK inside a dilution refrigerator. We have performed a detailed analysis of the magnetic diffraction data to investigate the magnetic structure under pressure and observed a subtle shift in the transition temperature. This development will open the door for future studies on magnetic materials with these much-desired coupled extremes of high pressure and ultra-low temperatures.

Wu, Yan [Oak Ridge National Laboratory (ORNL), Oak↗
DOE OSTI2026

Gamma rays and gravitational waves from inelastic Higgs portal dark matter

We explore a simple and predictive dark matter scenario involving a complex scalar field, ϕ , coupled to the Higgs portal with no additional field content. In the UV, the field possesses a global U ( 1 ) symmetry which is broken by mass terms and Higgs portal interactions. In the mass basis, the complex field splits into a pair of real scalars with a small mass splitting (in analogy to pseudo-Dirac fermions), such that the Higgs portal acquires both diagonal and off-diagonal terms with respect to these eigenstates. In the parameter space where the off-diagonal interaction predominates, this scenario is safe from direct detection constraints. Moreover, this model provides a viable explanation for the longstanding Galactic Center γ -ray excess. Additionally, this model influences the Higgs potential in a way that could facilitate a strong first-order electroweak phase transition in the early Universe, potentially leading to a stochastic gravitational wave background that could fall within the reach of upcoming space-based detectors.

Hooper, Dan [Wisconsin U., Madison] (ORCID:0009000↗
DOE OSTI2025

First Limits on Light Dark Matter Interactions in a Low Threshold Two-Channel Athermal Phonon Detector from the TESSERACT Collaboration

We present results of a search for spin-independent dark matter-nucleus interactions in a 1 cm 2 by 1 mm thick (0.233 g) high-resolution silicon athermal phonon detector operated above ground. For interactions in the substrate, this detector achieves an rms baseline energy resolution of 361.5⁢(4) m⁢ eV (statistical error), the best for any athermal phonon detector to date. With an exposure of 0.233 g ×12 hours, we place the most stringent constraints on dark matter masses between 44 and 87 M⁢ eV/c 2 , with the lowest unexplored cross section of 4⁢ × 10 −32 c⁢m 2 at 87 M⁢ eV/c 2 . We employ a conservative salting technique to reach the lowest dark matter mass ever probed via direct detection experiment. This constraint is enabled by two-channel rejection of low energy backgrounds that are coupled to individual sensors.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

On-shot, high-intensity laser aberration measurements via ponderomotive electron ejection

We present a technique to assess the spatial aberration content of a focused multi-terawatt laser when fired at full power. This method leverages the direct detection of electrons ponderomotively accelerated from the focal volume formed in a low-pressure gaseous back-fill. Furthermore, our results show that the spatial distribution of emitted electrons exhibits distinct features correlated to the laser aberration type and magnitude. This work represents progress toward the complete and accurate in-situ spatiotemporal characterization of focused high-intensity lasers.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Scanning X-Ray Diffraction Microscopy for Diamond Quantum Sensing

An understanding of nano- and microscale crystal strain in chemical-vapor-deposition diamond is crucial to the advancement of diamond quantum technologies. In particular, the presence of such strain and its characterization presents a challenge to diamond-based quantum sensing and information applications-as well as for future dark-matter detectors, where the directional information about incoming particles is encoded in crystal strain. Here, we exploit nanofocused scanning x-ray diffraction microscopy to quantitatively measure crystal deformation from defects in diamond with high spatial and strain resolution. The combination of information from multiple Bragg angles allows stereoscopic three-dimensional modeling of strain-feature geometry; the diffraction results are validated via comparison to optical measurements of the strain tensor based on spin-state-dependent spectroscopy of ensembles of nitrogen-vacancy centers in the diamond. Finally, our results demonstrate both strain and spatial resolution sufficient for directional detection of dark matter via x-ray measurement of crystal strain and provide a promising tool for diamond growth analysis and improvement of defect-based sensing.

42 ENGINEERING↗
DOE OSTI2024

Anomalous thermal effect in Zr Te 5 observed via photothermal measurements

In this study, we explore the magneto-thermoelectric power (MTP) of $ZrTe$ 5 , a canonical Dirac semimetal, through a novel photothermal technique. Unlike conventional thermoelectric studies that rely on on-chip heaters and are limited by fabrication processes, especially for stress-sensitive materials, our approach utilizes photothermal effects to induce temperature gradients. Our experiments, applying a magnetic field approximately parallel and transverse to the photocurrent detection direction, reveal that the photothermal method efficiently and reliably extracts both diagonal and off-diagonal components of the thermoelectric coefficient of $ZrTe$ 5 . Here, we observe that the longitudinal MTP reproduces features previously reported in thermal transport studies, while the photoinduced transverse MTP confirms the anomalous Nernst effect. This photothermal measurement technique opens new avenues for investigating transport properties in a wide range of quantum materials, both in 3D and 2D systems.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Large- N c constraints for elastic dark-matter–light-nucleus scattering in pionless effective field theory

Recent proposals for the use of light nuclei as dark-matter direct detection targets necessitate a strong theoretical understanding of the nuclear physics involved. We perform relevant calculations for dark-matter–light-nucleus scattering in a combined pionless effective field theory and large-N c expansion, where N c is the number of quark colors. Here, we include a general set of one-nucleon currents that have been used in other effective theories, as well as novel two-nucleon contact currents. First, we obtain constraints for the relative sizes of the dark-matter couplings to the one- and two-nucleon currents through the large-N c expansion. Then, we use these constraints to make predictions for the relative sizes of spin-dependent and spin-independent cross sections for dark-matter scattering off of a nucleon, a deuteron, a triton, and helium-3.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Nuclear-level effective theory of 𝜇→𝑒 conversion: Formalism and applications

Over the next decade new 𝜇→𝑒 conversion searches at Fermilab (Mu2e) and J-PARC (COMET, DeeMe) are expected to advance limits on charged lepton flavor violation (CLFV) by more than four orders of magnitude. Here, by considering the consequence of 𝑃 and 𝐶⁢𝑃 on elastic 𝜇→𝑒 conversion and the structure of possible charge and current densities, we show that rates are governed by six nuclear responses and a single scale, 𝑞/𝑚 𝑁 , where 𝑞 ≈ 𝑚 𝜇 is the momentum transferred from the leptons to the nucleus. To relate this result to microscopic formulations of CLFV, we construct in nonrelativistic effective theory (NRET) the CLFV nucleon-level interaction, pointing out the relevance of the dimensionless scales 𝑦=($^{𝑞⁢𝑏}_2$) 2 ⁢ > |$\overrightarrow{𝑣}_N$⁢|>|$\overrightarrow{𝑣}_μ$⁢|>|$\overrightarrow{𝑣}_T$| , where 𝑏 is the nuclear size, $\overrightarrow{𝑣}_N$ and $\overrightarrow{𝑣}_μ$ are the nucleon and muon intrinsic velocities, and $\overrightarrow{𝑣}_T$ is the target recoil velocity. We discuss previous work, noting the lack of a systematic treatment of the various small parameters. Because the parameter 𝑦 is not small, a proper calculation of 𝜇→𝑒 conversion requires a full multipole expansion of the nuclear response functions, an apparently daunting task with Coulomb-distorted electron partial waves. We demonstrate that the multipole expansion can be carried out to high precision by introducing a simplifying local momentum 𝑞 eff for the electron. Previous work has been limited to simple charge or spin interactions, thereby treating the nucleus effectively as a point particle. We show that such formulations are not compatible with the general form of the 𝜇→𝑒 conversion rate, failing to generate three of the six allowed nuclear response functions. The inclusion of the nucleon velocity $\overrightarrow{𝑣}_N$ yields an NRET with 16 operators and a rate of the general form. Consequently, in the current discovery era for CLFV, it provides the most sensible starting point for experimental analysis, defining what can and cannot be determined about CLFV from the highly exclusive process of 𝜇→𝑒 conversion. Finally, we expand the NRET operator basis to account for the effects of $\overrightarrow{𝑣}_μ$, associated with the muon's lower component, generating corrections to the CLFV coefficients of the point-nucleus response functions. Using advanced shell-model methods, we compute 𝜇→𝑒 conversion rates for a series of experimental targets, deriving bounds on the coefficients of the CLFV operators. These calculations are the first to include a general basis of CLFV operators, full evaluation of the associated nuclear response functions, and an accurate treatment of electron and muon Coulomb effects. We discuss target selection as an experimental “knob” that can be turned to probe the microscopic origins of CLFV. We describe two types of coherence that enhance certain CLFV operators and selection rules that blind elastic 𝜇→𝑒 conversion to others. We discuss the matching of the NRET onto higher level effective field theories, such as those constructed at the light quark level, noting opportunities to build on existing work in direct detection of dark matter. We discuss the relation of 𝜇→𝑒 conversion to 𝜇→𝑒+𝛾 and 𝜇→3⁢𝑒, showing how MEG II and Mu3e results will complement those of Mu2e and COMET. Finally we describe a accompanying script—in Mathematica and Python versions—that can be used to compute 𝜇→𝑒 conversion rates in various nuclear targets for the full set of NRET operators.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Imprints of the early Universe on axion dark matter substructure

Despite considerable experimental progress large parts of the axionlike particle (ALP) parameter space remain difficult to probe in terrestrial experiments. In some cases, however, small-scale structure of the ALP dark matter (DM) distribution is strongly enhanced, offering opportunities for astrophysical tests. Such an enhancement can be produced by a period of prenucleosynthesis early matter domination (EMD). This cosmology arises in many ultraviolet completions and generates the correct relic abundance for weak coupling f a ~ 10 16 GeV , ALP masses in the range 10 - 13 eV < m a < 1 eV , and without fine-tuning of the initial misalignment angle. This range includes the QCD axion around 10 - 9 - 10 - 8 eV . EMD enhances the growth of ALP small-scale structure, leading to the formation of dense ALP miniclusters which can contain nearly all of DM (depending on ALP mass and reheating temperature). We study the interplay between the initial ALP oscillation, reheating temperature, and effective pressure to provide analytic estimates of the minicluster abundance and properties. ALP miniclusters in the EMD cosmology are denser and more abundant than in Λ CDM . While enhanced substructure generically reduces the prospects of direct detection experiments, we show that pulsar timing and lensing observations can discover these minihalos over a large range of ALP masses and reheating temperatures.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Multiphonon excitations from dark matter scattering in crystals

For direct detection of sub-MeV dark matter, a promising strategy is to search for individual phonon excitations in a crystal. We perform an analytic calculation of the rate for light dark matter ( keV < m DM < MeV ) to produce two acoustic phonons through scattering in cubic crystals such as GaAs, Ge, Si, and diamond. The multiphonon rate is always smaller than the rate to produce a single optical phonon, whenever the latter is kinematically accessible. In Si and diamond, there is a dark matter mass range for which multiphonon production can be the most promising process, depending on the experimental threshold.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Projected WIMP sensitivity of the LUX-ZEPLIN dark matter experiment

LUX-ZEPLIN (LZ) is a next generation dark matter direct detection experiment that will operate 4850 feet underground at the Sanford Underground Research Facility (SURF) in Lead, South Dakota, USA. Using a two-phase xenon detector with an active mass of 7 tonnes, LZ will search primarily for low-energy interactions with Weakly Interacting Massive Particles (WIMPs), which are hypothesized to make up the dark matter in our galactic halo. In this paper, the projected WIMP sensitivity of LZ is presented based on the latest background estimates and simulations of the detector. For a 1000 live day run using a 5.6 tonne fiducial mass, LZ is projected to exclude at 90% confidence level spin-independent WIMP-nucleon cross sections above $1.6 \times 10^{-48}$ cm$^{2}$ for a 40 $\mathrm{GeV}/c^{2}$ mass WIMP. Additionally, a $5\sigma$ discovery potential is projected reaching cross sections below the existing and projected exclusion limits of similar experiments that are currently operating. For spin-dependent WIMP-neutron(-proton) scattering, a sensitivity of $2.7 \times 10^{-43}$ cm$^{2}$ ($8.1 \times 10^{-42}$ cm$^{2}$) for a 40 $\mathrm{GeV}/c^{2}$ mass WIMP is expected. With underground installation well underway, LZ is on track for commissioning at SURF in 2020.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Implications of the Gaia sausage for dark matter nuclear interactions

The advent of the Gaia era has led to potentially revolutionary understanding of dark matter (DM) dynamics in our galaxy, which has important consequences for direct detection (DD) experiments. In this paper, we study how the empirical DM velocity distribution inferred from Gaia-sausage, a dominant substructure in the solar neighborhood, affects the interpretation of DD data. We survey different classes of operators in the nonrelativistic effective field theory that could arise from several relativistic benchmark models and emphasize that the Gaia velocity distribution could modify both the total number of events as well as the shape of the differential recoil spectra, the two primary observables in DD experiments. Employing the Euclideanized signal method, we investigate the effects of the Gaia distribution on reconstructing DM model parameters and identifying the correct DM model given a positive signal at future DD experiments. We find that for light DM with mass ~10 GeV, the Gaia distribution poses an additional challenge for characterizing DM interactions with ordinary matter, which may be addressed by combining complementary DD experiments with different targets and lowering the detection threshold. Meanwhile, for heavy DM with mass above ~30 GeV , depending on the type of DM model, there could be a (moderate) improvement in the sensitivity at future DD experiments.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Large-misalignment mechanism for the formation of compact axion structures: Signatures from the QCD axion to fuzzy dark matter

Axions are some of the best motivated particles beyond the Standard Model. We show how the attractive self-interactions of dark matter (DM) axions over a broad range of masses, from 10 –22 eV to 10 7 GeV, can lead to nongravitational growth of density fluctuations and the formation of bound objects. This structure formation enhancement is driven by parametric resonance when the initial field misalignment is large, and it affects axion density perturbations on length scales of order the Hubble horizon when the axion field starts oscillating, deep inside the radiation-dominated era. This effect can turn an otherwise nearly scale-invariant spectrum of adiabatic perturbations into one that has a spike at the aforementioned scales, producing objects ranging from dense DM halos to scalar-field configurations such as solitons and oscillons. We call this class of cosmological scenarios for axion DM production “the large-misalignment mechanism.” In this work, we explore observational consequences of this mechanism for axions with masses up to 10 eV. For axions heavier than 10 –5 eV, the compact axion halos are numerous enough to significantly impact Earth-bound direct detection experiments, yielding intermittent but coherent signals with repetition rates exceeding one per decade and crossing times less than a day. These episodic increases in the axion density and kinematic coherence suggest new approaches for axion DM searches, including for the QCD axion. Dense structures made up of axions from 10 –22 eV to 10 –5 eV are detectable through gravitational lensing searches, and their gravitational interactions can also perturb baryonic structures and alter star formation. At very high misalignment amplitudes, the axion field can undergo self-interaction-induced implosions long before matter-radiation equality, producing potentially-detectable low-frequency stochastic gravitational waves.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Investigation of background electron emission in the LUX detector

Dual-phase xenon detectors, as currently used in direct detection dark matter experiments, have observed elevated rates of signals from electron emission processes in the low energy region. While this background negatively impacts detector performance in various ways, its origins have only been partially studied. In this paper, we report a systematic investigation of the electron pathologies observed in the LUX dark matter experiment. We characterize different electron populations based on their emission intensities and their correlations with preceding energy depositions in the detector. By studying these electron backgrounds under different experimental conditions, we identified the possible mechanisms that may contribute to the electron emission. We report the observed electron event rate in LUX after background rejection, and discuss how such backgrounds can be further mitigated in ongoing and future xenon-based dark matter experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Light new physics in XENON1T

We examine the recently-reported low-energy electron recoil spectrum observed at the XENON1T underground dark matter direct detection experiment, in the context of new interactions with solar neutrinos. In particular we show that scalar and vector mediators with masses $\lesssim 50$ keV coupled to leptons could already leave a visible signature in the XENON1T experiment, similar to the observed peak below 7 keV. This signals that dark matter detectors are already competing with neutrino scattering experiments such as GEMMA, CHARM-II and Borexino. If these results from XENON1T are interpreted as a new signal of such physics, the parameters which fit the excess face challenges from astrophysics which seem very difficult to overcome. If they are rather viewed as a constraint on new couplings, they herald the start of an era of novel precise probes of physics beyond the standard model with dark matter detectors.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Constraints on millicharged particles from cosmic-ray production

We study cosmic-ray-atmosphere collisions as a permanent production source of exotic millicharged particles (MCPs) for all terrestrial experiments. [MCPs are also known as charged massive particles (CHAMPs).] Based on data from Super-K, this allows us to derive new limits on MCPs that are competitive with, or improve, the currently leading bounds from accelerator-based searches for masses up to 1.5 GeV. In models where a subdominant component of dark matter (DM) is fractionally charged, these constraints probe parts of the parameter space that is inaccessible for conventional direct-detection DM experiments, independently of assumptions about the DM abundance.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Simple theory of chiral fermion dark matter

We propose a theory of chiral fermion dark matter (DM) with an isospin-3/2 fermion of a dark sector SU(2) D gauge symmetry, which is arguably the simplest chiral theory. An isospin-3 scalar breaks SU(2) D down to a discrete non-Abelian group T' and generates the DM mass. The SU(2) D gauge symmetry protects the DM mass and guarantees its stability. We derive consistency conditions for the theory and study its DM phenomenology. In some regions of parameters of the theory a two-component DM scenario is realized, consisting of a fermion and a boson, with the boson being the lightest T' nonsinglet field. In the case of single-component fermionic DM, we find that internal consistency of the theory, perturbativity arguments, and the observed relic abundance limit the DM mass to be less than 280 GeV, except when s-channel resonance regions are open for annihilation. For a significant part of the parameter space, the theory can be tested in DM direct-detection signals at the LZ and XENONnT experiments.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

BICEP/ Keck XII: Constraints on axionlike polarization oscillations in the cosmic microwave background

Here, we present a search for axionlike polarization oscillations in the cosmic microwave background (CMB) with observations from the Keck Array . A local axion field induces an all-sky, temporally sinusoidal rotation of CMB polarization. A CMB polarimeter can thus function as a direct-detection experiment for axionlike dark matter. We develop techniques to extract an oscillation signal. Many elements of the method are generic to CMB polarimetry experiments and can be adapted for other datasets. As a first demonstration, we process data from the 2012 observing season to set upper limits on the axion-photon coupling constant in the mass range 10 – 21 – 10 – 18 eV , which corresponds to oscillation periods on the order of hours to months. We find no statistically significant deviations from the background model. For periods larger than 24 hr (mass m < 4.8 × 10 – 20 eV ), the median 95% confidence upper limit is equivalent to a rotation amplitude of 0.68°, which constrains the axion-photon coupling constant to g Φ γ < ( 1.1 × 10 – 11 GeV – 1 ) m / ( 10 – 21 eV ) , if axionlike particles constitute all of the dark matter. The constraints can be improved substantially with data already collected by the BICEP series of experiments. Current and future CMB polarimetry experiments are expected to achieve sufficient sensitivity to rule out unexplored regions of the axion parameter space.

79 ASTRONOMY AND ASTROPHYSICS↗