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Results for “Nuclear Configuration Interaction”

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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Monolithic active pixel radiation detector with shielding techniques

A monolithic active pixel radiation detector including a method of fabricating thereof. The disclosed radiation detector can include a substrate comprising a silicon layer upon which electronics are configured. A plurality of channels can be formed on the silicon layer, wherein the plurality of channels are connected to sources of signals located in a bulk part of the substrate, and wherein the signals flow through electrically conducting vias established in an isolation oxide on the substrate. One or more nested wells can be configured from the substrate, wherein the nested wells assist in collecting charge carriers released in interaction with radiation and wherein the nested wells further separate the electronics from the sensing portion of the detector substrate. The detector can also be configured according to a thick SOA method of fabrication.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Reactivity-initiated accident simulation to inform transient testing of candidate advanced cladding

This paper leverages three-dimensional reactor-core-simulation capabilities to provide information on appropriate experimental test conditions for candidate advanced cladding materials in a control-rod-ejection event. These test conditions use three-dimensional nodal kinetics simulations of a reactivity-initiated accident (RIA) in a representative state-of-the-art pressurized water reactor with both nuclear-grade iron-chromium-aluminum (FeCrAl) and silicon-carbide (SiC-SiC)-based cladding materials. The effort yields boundary conditions for experimental mechanical tests, specifically peak cladding strain during the power pulse following the rod ejection. The impact of candidate cladding materials on the reactor kinetics behavior of RIA progression versus that of reference Zr cladding is predominantly due to differences in -1) fuel mass/volume/specific power density, -2) spectral effects due to parasitic neutron absorption, -3) control rod worth due to hardened (or softened) spectrum, and -4) initial conditions due to power peaking and neutron transport cross sections in the equilibrium cycle cores resulting from hardened (or softened) spectrum. This study shows minimal impact of SiC-SiC-based cladding configurations on the transient response versus reference Zircaloy cladding. However, the FeCrAl cladding response indicates similar energy deposition, but with significantly shorter pulses of higher magnitude. Therefore, the FeCrAl-based cases have a more rapid fuel thermal expansion rate, and the resultant pellet-cladding interaction occurs more rapidly. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2017

Multistate, multichannel coupled diabatic state representations of adiabatic states coupled by conical intersections. CH 2 OH photodissociation

In this work, a coupled diabatic state representation, H d , of the 1, 2, 3 2 A states of CH 2 OH suitable for the description of the three channel, three state photodissociation process CH 2 OH(1 2 A) + hv → CH 2 OH(2, 3 2 A) → CH 2 O(X, A) + H, cis-CHOH + H, trans-CHOH + H, is reported. The representation is based on electronic structure data (energies, energy gradients, and derivative couplings) obtained exclusively from multireference configuration interaction single and double excitation wave functions. Diabat shifting is employed to improve the representation’s agreement with accurate experimental energetics. A careful analysis of the numerous minima, saddle points, and conical intersection seams is reported. The computed T 0 (3 2 A) ~ 35 220 cm -1 is in excellent agreement with the experimental estimate of 35 053 cm -1 , and the computed channel dissociation energies, D 0 , for CH 2 O 9453 (10 160), cis-HCOH 30 310.2 (29 923), and trans-HCOH 28 799 (28 391) cm -1 are in good accord with the measured values given parenthetically. Lastly, these accurate energetics over a wide range of nuclear configurations strongly support the ability of this H d to enable quality simulations of nonadiabatic dynamics.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Barrier penetration in a discrete-basis formalism

The dynamics of a many-particle system are often modeled by mapping the Hamiltonian into a Schrödinger equation. An alternative approach is to solve the Hamiltonian equations directly in a model space of many-body configurations. In a previous paper the numerical convergence of the two approaches was compared with a simplified treatment of the Hamiltonian representation. Here, we extend the comparison to the nonorthogonal model spaces that would be obtained by the generator-coordinate method. With a suitable choice of the collective-variable grid, a configuration-interaction Hamiltonian can reproduce the Schrödinger dynamics very well. Furthermore, the method as implemented here requires that the barrier height is not much larger than the zero-point energy in the collective coordinates of the configurations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2026

Opportunities for imaging light nuclei with a second interaction region at the Electron-Ion Collider

The upcoming Electron-Ion Collider (EIC) will address several outstanding puzzles in modern nuclear physics. Key questions—such as the partonic structure of nucleons and nuclei and the origin of their mass and spin—can be explored through high-energy electron-proton and electron-nucleus collisions. Here, to maximize its scientific reach, the EIC community has advocated for the addition of a second interaction region equipped with a detector complementary to the EIC general purpose collider detector, ePIC. The preconceptual design of this interaction region aims to provide a different configuration from the first interaction region, which enhances forward acceptance at very small scattering angles (𝜃 ∼0 mrad). This machine configuration would significantly benefit exclusive, tagging, and diffractive physics programs, complementing those of the ePIC experiment. In particular, accessing coherent diffractive processes on light nuclei by tagging of the full, intact nucleus is essential for mapping their spatial parton distributions. In this work, we present an exploratory study of the detection capabilities for light nuclei at a second EIC interaction region, with a detailed discussion of the accessible kinematic phase space and its implications for imaging.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Axial, scalar, and tensor charges of the nucleon from 2+1+1-flavor Lattice QCD

We present results for the isovector axial, scalar, and tensor charges 𝑔$^{𝑢−𝑑}_{𝐴}$, 𝑔$^{𝑢−𝑑}_{𝑆}$, and 𝑔$^{𝑢−𝑑}_{𝑇}$ of the nucleon needed to probe the Standard Model and novel physics. The axial charge is a fundamental parameter describing the weak interactions of nucleons. The scalar and tensor charges probe novel interactions at the TeV scale in neutron and nuclear 𝛽-decays, and the flavor-diagonal tensor charges 𝑔$^{𝑢}_{𝑇}$, 𝑔$^{𝑑}_{𝑇}$, and 𝑔$^{𝑠}_{𝑇}$ are needed to quantify the contribution of the quark electric dipole moment (EDM) to the neutron EDM. The lattice-QCD calculations were done using nine ensembles of gauge configurations generated by the MILC Collaboration using the highly improved staggered quarks action with 2+1+1 dynamical flavors. These ensembles span three lattice spacings 𝑎 ≈0.06,0.09, and 0.12 fm and light-quark masses corresponding to the pion masses 𝑀 𝜋 ≈ 135,225, and 315 MeV. High-statistics estimates on five ensembles using the all-mode-averaging method allow us to quantify all systematic uncertainties and perform a simultaneous extrapolation in the lattice spacing, lattice volume, and light-quark masses for the connected contributions. Our final estimates, in the $\overline{MS}$ scheme at 2 GeV, of the isovector charges are 𝑔$^{𝑢−𝑑}_{𝐴}$ = 1.195⁢(33)⁢(20), 𝑔$^{𝑢−𝑑}_{𝑆}$ = 0.97⁢(12)⁢(6), and 𝑔$^{𝑢−𝑑}_{𝑇}$ = 0.987⁢(51)⁢(20). The first error includes statistical and all systematic uncertainties except that due to the extrapolation Ansatz, which is given by the second error estimate. Combining our estimate for 𝑔$^{𝑢−𝑑}_{𝑆}$ with the difference of light quarks masses (𝑚 𝑑 − 𝑚 𝑢 ) QCD = 2.67⁢(35) MeV given by the Flavor Lattice Average Group, we obtain (𝑀 𝑁 − 𝑀 𝑃 ) QCD = 2.59⁢(49) MeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Structure of Cl 38 and the quest for a comprehensive shell model interaction

The higher-spin structure of 38 Cl ($N=21$) was investigated following the 26 Mg( 14 C, $pn$) reaction at 30 and 37 MeV beam energies. The outgoing protons were detected in an $E-ΔE$ Si telescope placed at 0° close to the target with a Ta beam stopper between the target and telescope. Multiple $γ$ rays were detected in time coincidence with the protons using an enhanced version of the FSU $γ$-detection array. The level scheme was extended up to 8420 keV with a likely spin of 10 $ℏ$. A new multishell interaction was developed guided by the experimental information. This FSU interaction was built by fitting to the energies of 270 experimental states from 13 C to 51 Ti. Calculations using the FSU interaction reproduce observed properties of 38 Cl rather well, including the spectroscopic factors. The interaction has been successfully used to interpret the 1p1h and 2p2h configurations in some nearby nuclei as well.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

Oralloy (93.2 235 U) Bare Metal Annuli And Disks

A multitude of critical experiments with highly enriched uranium metal were conducted in the 1960s and 1970s at the Oak Ridge Critical Experiments Facility (ORCEF) in support of criticality safety operations at the Y-12 Plant. These experiments served to evaluate the storage, casting, and handling limits for the Y-12 Plant while also providing data for verification of different calculation methods and associated cross-sections for nuclear criticality safety applications. These included both solid cylinders and annuli of various diameters, interacting cylinders of various diameters, parallelepipeds, and reflected cylinders and annuli. The experiments described here involve a series of delayed critical stacks of bare oralloy HEU annuli and disks. Three of these experiments consist of stacking bare HEU annuli of varying diameters to obtain critical configurations. These annuli have nominal inner and outer diameters (ID/OD) including: 7 inches (") ID – 9" OD, 9" ID – 11" OD, 11" ID – 13" OD, and 13? ID – 15" OD. The nominal heights range from 0.125" to 1.5". The three experiments themselves range from 7" – 13", 7" – 15", and 9" – 15" in diameter, respectively. The fourth experiment ranges from 7" – 11", and along with different annuli, it also includes an 11" disk and several 7" diameter disks. All four delayed critical experiments were configured and evaluated by J. T. Mihalczo, J. J. Lynn, and D. E. McCarty from December of 1962 to February 1963 with additional information in their corresponding logbook.

42 ENGINEERING↗
DOE OSTI2022

The Gamow shell model with realistic interactions: a theoretical framework for ab initio nuclear structure at drip-lines

Abstract Ab initio approaches are among the most advanced models to solve the nuclear many-body problem. In particular, the no-core–shell model and many-body perturbation theory have been recently extended to the Gamow shell model framework, where the harmonic oscillator basis is replaced by a basis bearing bound, resonance and scattering states, i.e. the Berggren basis. As continuum coupling is included at basis level and as configuration mixing takes care of inter-nucleon correlations, halo and resonance nuclei can be properly described with the Gamow shell model. The development of the no-core Gamow shell model and the introduction of the Q ¯ ˆ -box method in the Gamow shell model, as well as their first ab initio applications, will be reviewed in this paper. Peculiarities compared to models using harmonic oscillator bases will be shortly described. The current power and limitations of ab initio Gamow shell model will also be discussed, as well as its potential for future applications.

Physics↗
DOE OSTI2020

Systems and methods for relay ionization

The invention generally relates to systems and methods for relay ionization of a sample. In certain aspects, the invention provides systems that include an ion source that generates ions, a sample emitter configured to hold a sample, and a mass spectrometer. The system is configured such that the ions generated by the ion source are directed to interact with the sample emitter, thereby causing the sample to be discharged from the sample emitter and into the mass spectrometer.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2017

Measurement of electron antineutrino oscillation based on 1230 days of operation of the Daya Bay experiment

Here, a measurement of electron antineutrino oscillation by the Daya Bay Reactor Neutrino Experiment is described in detail. Six 2.9-GWth nuclear power reactors of the Daya Bay and Ling Ao nuclear power facilities served as intense sources of ¯ν e ’s. Comparison of the ¯ν e rate and energy spectrum measured by antineutrino detectors far from the nuclear reactors (~1500–1950 m) relative to detectors near the reactors (~350–600 m) allowed a precise measurement of ¯ν e disappearance. More than 2.5 million ¯ν e inverse beta-decay interactions were observed, based on the combination of 217 days of operation of six antineutrino detectors (December, 2011–July, 2012) with a subsequent 1013 days using the complete configuration of eight detectors (October, 2012–July, 2015). The ¯ν e rate observed at the far detectors relative to the near detectors showed a significant deficit, R = 0.949 ± 0.002(stat) ± 0.002(syst). The energy dependence of ¯ν e disappearance showed the distinct variation predicted by neutrino oscillation. Analysis using an approximation for the three-flavor oscillation probability yielded the flavor-mixing angle sin 2 2θ 13 = 0.0841 ± 0.0027(stat) ± 0.0019(syst) and the effective neutrino mass-squared difference of |Δm 2 ee | = (2.50 ± 0.06(stat) ± 0.06(syst)) × 10 –3 eV 2 . Analysis using the exact three-flavor probability found Δm 2 32 = (2.45 ± 0.06(stat) ± 0.06(syst)) × 10 –3 eV 2 assuming the normal neutrino mass hierarchy and Δm 2 32 = (–2.56 ± 0.06(stat) ± 0.06(syst)) × 10 –3 eV 2 for the inverted hierarchy.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1995

Shapes and stability of algebraic nuclear models

A generalization of the procedure to study shapes and stability of algebraic nuclear models introduced by Gilmore is presented. One calculates the expectation value of the Hamiltonian with respect to the coherent states of the algebraic structure of the system. Then equilibrium configurations of the resulting energy surface, which depends in general on state variables and a set of parameters, are classified through the Catastrophe theory. For one- and two-body interactions in the Hamiltonian of the interacting Boson model-1, the critical points are organized through the Cusp catastrophe. As an example, we apply this Separatrix to describe the energy surfaces associated to the Rutenium and Samarium isotopes.

Lopez-Moreno, Enrique↗
DOE OSTI2015

Representability evaluation of fuel debris nuclear characteristics by heterogeneous core of Stacy - 14581

Decommissioning is underway in the Fukushima Daiichi Nuclear Power Station (1FNPS). Criticality control is one of the important safety issues in the decommissioning, especially during fuel debris removal. In 1FNPS, part of fuel debris might be in the form of molten-core-concrete-interaction (MCCI) product. It has been shown that the MCCI product can be critical not only under water but even with water bound in concrete. Further study of criticality characteristics by computation is being conducted to clarify its criticality risk. Furthermore, the risk assessment by computation needs validation by experiment. Japan Atomic Energy Agency is preparing critical experiments with simulated fuel debris in the Static Experiment Critical Facility (STACY), whose solution core will be converted into a new core using fuel rods and light-water moderator. It is difficult to build core configurations composed of water and fuel rods which contain homogeneous mixtures of uranium dioxide (UO{sub 2}) and structural materials of boiling light water reactors. In the modified STACY, it is being planned to simulate fuel debris by arranging UO{sub 2} fuel rods and structural material rods in water. In this study, difference in heterogeneity between the experimental core and possible fuel debris conditions is evaluated by comparing infinite multiplication factors and neutron energy spectra. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2016

Electron-deuteron DIS with spectator tagging at EIC: Development of theoretical framework

An Electron-Ion Collider (EIC) would enable next-generation measurements of deep-inelastic scattering (DIS) on the deuteron with detection of a forward-moving nucleon (p, n) and measurement of its recoil momentum ("spectator tagging''). Such experiments offer full control of the nuclear configuration during the high-energy process and can be used for precision studies of the neutron's partonic structure and its spin dependence, nuclear modifications of partonic structure, and nuclear shadowing at small x. We review the theoretical description of spectator tagging at EIC energies (light-front nuclear structure, on-shell extrapolation in the recoil nucleon momentum, final-state interactions, diffractive effects at small x) and report about on-going developments.

Cosyn, Wim B.↗
DOE OSTI2022

Optical quantum memory for noble-gas spins based on spin-exchange collisions

Optical quantum memories, which store and preserve the quantum state of photons, rely on a coherent mapping of the photonic state onto matter states that are optically accessible. Here we outline and characterize schemes to map the state of photons onto long-lived but optically inaccessible collective states of noble-gas spins. The mapping employs coherent spin-exchange interaction arising from random collisions with alkali vapor. We propose efficient storage strategies in two operating regimes and analyze their performance for several proposed experimental configurations.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Sensitivity and discovery potential of nEXO to neutrinoless double beta decay

The next-generation Enriched Xenon Observatory (nEXO) is a proposed experiment to search for neutrinoless double beta (0νββ) decay in 136 Xe with a target half-life sensitivity of approximately 10 28 years using 5 × 10 3 kg of isotopically enriched liquid-xenon in a time projection chamber. This improvement of two orders of magnitude in sensitivity over current limits is obtained by a significant increase of the 136 Xe mass, the monolithic and homogeneous configuration of the active medium, and the multi-parameter measurements of the interactions enabled by the time projection chamber. Furthermore, the detector concept and anticipated performance are presented based upon demonstrated realizable background rates.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗