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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 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Demonstration of neutrinoless double beta decay searches in gaseous xenon with NEXT

The NEXT experiment aims at the sensitive search of the neutrinoless double beta decay in 136 Xe, using high-pressure gas electroluminescent time projection chambers. The NEXT-White detector is the first radiopure demonstrator of this technology, operated in the Laboratorio Subterráneo de Canfranc. Achieving an energy resolution of 1% FWHM at 2.6 MeV and further background rejection by means of the topology of the reconstructed tracks, NEXT-White has been exploited beyond its original goals in order to perform a neu- trinoless double beta decay search. The analysis considers the combination of 271.6 days of 136 Xe-enriched data and 208.9 days of 136Xe-depleted data. A detailed background modeling and measurement has been developed, ensuring the time stability of the radiogenic and cosmogenic contributions across both data samples. Limits to the neutrinoless mode are obtained in two alternative analyses: a background-model-dependent approach and a novel direct background-subtraction technique, offering results with small dependence on the background model assumptions. With a fiducial mass of only 3.50 ± 0.01 kg of 136 Xe-enriched xenon, 90% C.L. lower limits to the neutrinoless double beta decay are found in the $T^{0v}_{1/2} > 5.5 \times 10^{23} - 1.3 \times 10^{24}$ yr range, depending on the method. The presented techniques stand as a proof-of-concept for the searches to be implemented with larger NEXT detectors.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Background discrimination for neutrinoless double beta decay in liquid xenon using Cherenkov light

Neutrinoless double beta decays in liquid xenon produce a significant amount of Cherenkov light, with a photon number and angular distribution that distinguishes these events from common backgrounds. A GEANT4 simulation was used to simulate Cherenkov photon production and measurement in a liquid xenon detector and a multilayer perceptron was used to analyze the resulting distributions to classify events based on their Cherenkov photons. Our results show here that a modest improvement in the sensitivity of neutrinoless double beta decay searches is possible using this technique, but the kinematics of the neutrinoless double beta decay and electron scattering in liquid xenon substantially limit this approach.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2010

Fully electromagnetic gyrokinetic eigenmode analysis of high-beta shaped plasmas

A new, more efficient method to compute unstable linear gyrokinetic eigenvalues and eigenvectors has been developed for drift-wave analysis of plasmas with arbitrary flux-surface shape, including both transverse and compressional magnetic perturbations. In high-beta, strongly shaped plasmas like in the National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 40, 557 (2000)], numerous branches of closely spaced unstable eigenmodes exist. These modes are difficult and time-consuming to adequately resolve with the existing linear initial-value solvers, which are further limited to the most unstable eigenmode. The new method is based on an eigenvalue approach and is an extension of the GYRO code [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)], reusing the existing discretization schemes in both real and velocity-space. Unlike recent methods, which use an iterative solver to compute eigenvalues of the relatively large gyrokinetic response matrix, the present scheme computes the zeros of the much smaller Maxwell dispersion matrix using a direct method. In the present work, the new eigensolver is applied to gyrokinetic stability analysis of a high-beta, NSTX-like plasma. We illustrate the smooth transformation from ion-temperature-gradient (ITG)-like to kinetic-ballooning (KBM)-like modes, and the formation of hybrid ITG/KBM modes, and further demonstrate the existence of high-k Alfvenic drift-wave 'cascades' for which the most unstable mode is a higher excited state along the field line. A new compressional electron drift wave, which is driven by a combination of strong beta and pressure gradient, is also identified for the first time. Overall, we find that accurate calculation of stability boundaries and growth rates cannot, in general, ignore the compressional component {delta}B{sub ||} of the perturbation.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2011

Effect of pressure-driven MHD instabilities on confinement in reactor-relevant high-beta helical plasmas

Through the experiment data analysis in the large helical device (LHD), the influence of the global MHD instability and the relatively short wave length MHD instabilities driven turbulence on the confinement performance in reactor-relevant high-beta helical plasmas is studied. The comparison of the energy confinement time between just before global MHD instability disappears and after that, and the estimation of the saturated mode structure by the multi-channel soft x-ray measurement enable us to quantitatively estimate the influence of the global interchange type MHD instability with different saturated mode structures on the confinement performance. According to the comparison between thermal conductivities in experiments and those predicted by theoretical transport models, the transport properties in the peripheral region of high beta LHD plasmas are quite similar with anomalous transport model based on an interchange type MHD instability driven turbulence, and that result is supported by the dependence of the density fluctuation with relatively short wave length on beta value.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2011

Decay Spectroscopy for Nuclear Astrophysics: {beta}-delayed Proton Decay

Decay spectroscopy is one of the oldest indirect methods in nuclear astrophysics. We have developed at TAMU techniques to measure beta- and beta-delayed proton decay of sd-shell, proton-rich nuclei. The short-lived radioactive species are produced in-flight, separated, then slowed down (from about 40 MeV/u) and implanted in the middle of very thin Si detectors. These allowed us to measure protons with energies as low as 200 keV from nuclei with lifetimes of 100 ms or less. At the same time we measure gamma-rays up to 8 MeV with high resolution HPGe detectors. We have studied the decay of {sup 23}Al, {sup 27}P, {sup 31}Cl, all important for understanding explosive H-burning in novae. The technique has shown a remarkable selectivity to beta-delayed charged-particle emission and works even at radioactive beam rates of a few pps. The states populated are resonances for the radiative proton capture reactions {sup 22}Na(p,{gamma}){sup 23}Mg(crucial for the depletion of {sup 22}Na in novae), {sup 26m}Al(p,{gamma}){sup 27}Si and {sup 30}P(p,{gamma}){sup 31}S(bottleneck in novae and XRB burning), respectively. More recently we have radically improved the technique using a gas based detector we call AstroBox.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

High-precision {beta} decay half-life measurements of proton-rich nuclei for testing the CVC hypothesis

The experimental study of super-allowed nuclear {beta} decays serves as a sensitive probe of the conservation of the weak vector current (CVC) and allows tight limits to be set on the presence of scalar or right-handed currents. Once CVC is verified, it is possible to determine the V{sub ud} element of the CKM quark-mixing matrix. Similarly, the study of nuclear mirror {beta} decays allows to arrive at the same final quantity V{sub ud}. Whereas dedicated studies of 0{sup +}{yields}0{sup +} decays are performed for several decades now, the potential of mirror transitions was only rediscovered recently. Therefore, it can be expected that important progress is possible with high-precision studies of different mirror {beta} decays. In the present piece of work the half-life measurements performed by the CENBG group of the proton-rich nuclei {sup 42}Ti, {sup 38-39}Ca, {sup 30-31}S and {sup 29}P are summarised.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Disentangling the various Mechanisms of neutrinoless double beta decay to extract the neutrino mass

It is well known that there exist many mechanisms that may contribute to neutrinoless double beta decay. By exploiting the fact that the associated nuclear matrix elements are target dependent we show that, given definite experimental results on a sufficient number of targets, one can determine or sufficiently constrain all lepton violating parameters including the mass term. As a specific example we show that, given the observation of the 0{nu}{beta}{beta}-decay in three different nuclei, e.g. {sup 76}Ge, {sup 100}Mo and {sup 130}Te, and assuming just three active lepton number violating parameters, e.g. light and heavy neutrino mass mechanisms in left handed currents as well as R-parity breaking SUSY mechanism, one may determine all lepton violating parameters, provided that they are relatively real.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2013

Correlation measurements in nuclear {beta}-decay using traps and polarized low energy beams

Precision measurements in nuclear {beta}-decay provide sensitive means to test discrete symmetries in the weak interaction and to determine some of the fundamental constants in semi-leptonic decays, like the coupling of the lightest quarks to charged weak bosons. The main motivation of such measurements is to find deviations from Standard Model predictions as possible indications of new physics. In this contribution I will focus on two topics related to precision measurements in nuclear {beta}-decay: i) the determination of the V{sub ud} element of the Cabibbo-Kobayashi-Maskawa quark mixing matrix from nuclear mirror transitions and ii) the search for exotic scalar or tensor contributions from {beta}{nu} angular correlations. The purpose is to underline the role being played by experimental techniques based on the confinement of radioactive species with atom and ion traps as well as the plans to use low energy polarized beams.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Shell model nuclear matrix elements for competing mechanisms contributing to double beta decay

Recent progress in the shell model approach to the nuclear matrix elements for the double beta decay process are presented. This includes nuclear matrix elements for competing mechanisms to neutrionless double beta decay, a comparison between closure and non-closure approximation for {sup 48}Ca, and an updated shell model analysis of nuclear matrix elements for the double beta decay of {sup 136}Xe.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2014

Realistic fission models, new beta-decay half-lives and the r-process in neutron star mergers

Almost half of heavy nuclei beyond iron are considered to be produced by rapid neutron capture process (r-process). This process occurs in the neutron-rich environment such as core-collapse supernovae or neutron star mergers, but the main production site is still unknown. In the r-process of neutron star mergers, nuclear fission reactions play an important role. Also beta-decay half-lives of magic nuclei are crucial for the r-process. We have carried out r-process nucleosynthesis calculations based upon new theoretical estimates of fission fragment distributions and new beta-decay half-lives for N=82 nuclei measured at RIBF-RIKEN. We investigate the effect of nuclear fission on abundance patterns in the matter ejected from neutron star mergers with two different fission fragment mass distributions. We also discuss how the new experimental beta-decay half-lives affect the r-process.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

Properties of low-lying intruder states in {sup 34}Al and {sup 34}Si populated in the beta-decay of {sup 34}Mg

The results of the IS530 experiment at ISOLDE revealed new information concerning several nuclei close to the N ≈ 20 'Island of Inversion' - {sup 34}Mg, {sup 34}Al, {sup 34}Si. The half-life of {sup 34}Mg was found to be three times larger than the adopted value (63(1) ms instead of 20(10) ms). The beta-gamma spectroscopy of {sup 34}Mg performed for the first time in this experiment, led to the first experimental level scheme for {sup 34}Al, also showing that the full beta strength goes through the predicted 1{sup +} isomer in {sup 34}Al [1] and/or excited states that deexcite to it. The subsequent beta-decay of the 1{sup +} isomer in {sup 34}Al allowed the observation of new gamma lines in {sup 34}Si, (tentatively) associated with low-spin high-energy excited states previously unobserved.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

The COBRA experiment – Status and prospects on the search of neutrinoless double beta-decay

The Cadmium-Zinc-Telluride 0-ν Double Beta Research Apparatus (COBRA) [1] is a next-generation experiment searching for the existence of neutrinoless double beta-decay (0νββ-decay). The observation of 0νββ-decay would be an unambiguous sign for physics beyond the Standard Model such as lepton number violating processes and would prove the Majorana character of neutrinos. Furthermore, the study of 0νββ-decay could probe the absolute neutrino mass and allows for the identification of the neutrino mass hierarchy realized in nature assuming light Majorana neutrino exchange. Currently a demonstrator setup at the underground facility LNGS (Italy) built of 4×4×4 coplanar grid (CPG) detectors collects high quality low background physics data with FADC pulse shape sampling. The detectors are made of natural abundant CdZnTe (CZT), which is a commercially available room temperature semiconductor. It contains several double beta isotopes, the most promising of which is {sup 116}Cd with a Q-value of 2813.5 keV – which is well above the highest naturally occurring prominent γ-lines.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Electron acceleration during the decay of nonlinear Whistler waves in low-beta electron-ion plasma

Relativistic electron acceleration through dissipation of a nonlinear, short-wavelength, and monochromatic electromagnetic whistler wave in low-beta plasma is investigated by utilizing a one-dimensional fully relativistic electromagnetic particle-in-cell code. The nonlinear (large-amplitude) parent whistler wave decays through the parametric instability which enhances electrostatic ion acoustic waves and electromagnetic whistler waves. These waves satisfy the condition of three-wave coupling. Through the decay instability, the energy of electron bulk velocity supporting the parent wave is converted to the thermal energy perpendicular to the background magnetic field. Increase of the perpendicular temperature triggers the electron temperature anisotropy instability which generates broadband whistler waves and heats electrons in the parallel direction. The broadband whistler waves are inverse-cascaded during the relaxation of the electron temperature anisotropy. In lower-beta conditions, electrons with a pitch angle of about 90° are successively accelerated by inverse-cascaded whistler waves, and selected electrons are accelerated to over a Lorentz factor of 10. The result implies that the nonlinear dissipation of a finite-amplitude and short-wavelength whistler wave plays an important role in producing relativistic nonthermal electrons over a few MeV especially at lower beta plasmas.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Towards precise and accurate calculations of neutrinoless double-beta decay

We present the results of a National Science Foundation Project Scoping Workshop, the purpose of which was to assess the current status of calculations for the nuclear matrix elements governing neutrinoless double-beta decay and determine if more work on them is required. After reviewing important recent progress in the application of effective field theory, lattice quantum chromodynamics, and ab initio nuclear-structure theory to double-beta decay, we discuss the state of the art in nuclear-physics uncertainty quantification and then construct a roadmap for work in all these areas to fully complement the increasingly sensitive experiments in operation and under development. The roadmap includes specific projects in theoretical and computational physics as well as the use of Bayesian methods to quantify both intra- and inter-model uncertainties. Here, the goal of this ambitious program is a set of accurate and precise matrix elements, in all nuclei of interest to experimentalists, delivered together with carefully assessed uncertainties. Such calculations will allow crisp conclusions from the observation or non-observation of neutrinoless double-beta decay, no matter what new physics is at play.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Drift kinetic theory of the NTM magnetic islands in a finite beta general geometry tokamak plasma

In (Imada et al 2019 Nucl. Fusion 59 046016 and references therein) a new 4D drift kinetic nonlinear theory, valid in the limit of a low beta, small inverse aspect ratio, circular cross section, toroidal geometry, to describe the plasma response to the neoclassical tearing mode (NTM) magnetic perturbation is derived. In (Dudkovskaia et al 2021 Plasma Phys. Control. Fusion 63 054001) this theory is reduced in a low collisionality limit, which allows a dimensionality reduction to a 3D problem to efficiently resolve the collisional dissipation layer in the vicinity of the trapped-passing boundary. (Dudkovskaia et al 2021 Plasma Phys. Control. Fusion 63 054001) adopts an improved model for the magnetic drift frequency, which reduces the threshold magnetic island half-width from $8.73\rho_{b i}$, where $\rho_{b i}$ is the trapped ion banana orbit width, to $1.46 \rho_{b i}$, making it in closer agreement with experimental observations for the large aspect ratio tokamak equilibrium. In the present paper, the theory is extended to a high beta, arbitrary tokamak geometry to capture the plasma shaping effects on the NTM threshold physics with the focus on the non-zero triangularity discharges that are known to have a strong impact on the plasma MHD stability. First, it is found that the higher triangularity plasma is more prone to NTMs which is in agreement with the 2/1 tearing mode onset relative frequency measurements in DIII-D. Second, the NTM threshold dependence on the tokamak inverse aspect ratio obtained in (Dudkovskaia et al 2021 Plasma Phys. Control. Fusion 63 054001) is refined and extended to a finite aspect ratio limit. Third, the NTM threshold dependence on poloidal beta is obtained and benchmarked against the EAST threshold island width measurements.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Survey of neutrino flavor predictions and the neutrinoless double beta decay funnel

The neutrinoless double beta decay experimental effort continues to make tremendous progress with hopes of covering the inverted neutrino mass hierarchy in coming years and pushing from the quasidegenerate hierarchy into the normal hierarchy. As neutrino oscillation data are starting to suggest that the mass ordering may be normal, we may well be faced with staring down the funnel of death: a region of parameter space in the normal ordering where—for a particular cancellation among the absolute neutrino mass scale, the Majorana phases, and the oscillation parameters—the neutrinoless double beta decay rate may be vanishingly small. To answer the question of whether this region of parameter space is theoretically preferred, we survey five broad categories of flavor model structures which make various different predictions for parameters relevant for neutrinoless double beta decay to determine how likely it is that the rate may be in this funnel region. We find that a non-negligible fraction of predictions surveyed are at least partially in the funnel region. Our results can guide model builders and experimentalists alike in focusing their efforts on theoretically motivated regions of parameter space. Published by the American Physical Society 2024

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Beta Radiation Hardness of GYGAG(Ce) Transparent Ceramic Scintillators

GYGAG(Ce) transparent ceramic garnet scintillators were irradiated with electrons from 0.5 to 2 MeV with fluences from 10 16 e – /cm 2 to 10 19 e – /cm 2 , corresponding to doses from 0.3 to 310 Gigarad. Absorption spectra were measured before and after irradiations. Light yields from alpha, beta, and gamma excitations were measured before and after irradiation and compared to preirradiation values to gain a deeper understanding of how electron irradiations can affect light yield, as well as defects generated in both the surface and bulk. Within experimental error, no degradation in light yield was observed for the electron-irradiated samples, as measured via beta or gamma excitation, with minimal degradation observed via alpha excitation. A small increase in optical absorption near the wavelength of emission was observed following the largest dose irradiation. These results suggest that GYGAG(Ce) is radiation hard to electron irradiation up to 10 19 e – /cm 2 and doses up to 310 Gigarad. Furthermore, this robustness to irradiation indicates that transparent ceramic garnets may prove useful for applications such as scintillation-based nuclear batteries by allowing for higher energy beta emitters, increased power densities, and enabling long service lifetimes.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Population Genomic Analysis of 1,777 Extended-Spectrum Beta-Lactamase-Producing Klebsiella pneumoniae Isolates, Houston, Texas: Unexpected Abundance of Clonal Group 307

Klebsiella pneumoniae is a major human pathogen responsible for high morbidity and mortality rates. The emergence and spread of strains resistant to multiple antimicrobial agents and documented large nosocomial outbreaks are especially concerning. To develop new therapeutic strategies for K. pneumoniae, it is imperative to understand the population genomic structure of strains causing human infections. To address this knowledge gap, we sequenced the genomes of 1,777 extended-spectrum beta-lactamase-producing K. pneumoniae strains cultured from patients in the 2,000-bed Houston Methodist Hospital system between September 2011 and May 2015, representing a comprehensive, population-based strain sample. Strains of largely uncharacterized clonal group 307 (CG307) caused more infections than those of well-studied epidemic CG258. Strains varied markedly in gene content and had an extensive array of small and very large plasmids, often containing antimicrobial resistance genes. Some patients with multiple strains cultured over time were infected with genetically distinct clones. We identified 15 strains expressing the New Delhi metallo-beta-lactamase 1 (NDM-1) enzyme that confers broad resistance to nearly all beta-lactam antibiotics. Transcriptome sequencing analysis of 10 phylogenetically diverse strains showed that the global transcriptome of each strain was unique and highly variable. Experimental mouse infection provided new information about immunological parameters of host-pathogen interaction. We exploited the large data set to develop whole-genome sequence-based classifiers that accurately predict clinical antimicrobial resistance for 12 of the 16 antibiotics tested. We conclude that analysis of large, comprehensive, population-based strain samples can assist understanding of the molecular diversity of these organisms and contribute to enhanced translational research.

59 BASIC BIOLOGICAL SCIENCES↗