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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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44 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Puzzling 𝐵⁡(𝐸⁢2;0 + → 2 + ) strength in the proton dripline nucleus 36 Ca

Recent measurements of the 𝐸⁢2 transition rate from the ground state to the first 2 + excited state of the proton dripline nucleus 36 Ca show an unusual pattern when compared to its isotopic neighbor 38 Ca: despite having a higher 𝐸 𝑥 ⁡(2$^{+}_{1}$) excitation energy, the 𝐵⁡(𝐸⁢2;0$^{+}_{1}$ → 2$^{+}_{1}$) rate in 36 Ca is larger. The question that naturally arises is to what extent this observation can be attributed to the unbound character of the 2$^{+}_{1}$ state. To understand the influence of the continuum space on the low-energy properties of 36 Ca, we carried out Gamow shell model calculations that can account for the continuum coupling effects associated with the occupation of unbound 𝑓⁡𝑝 shells. We found that in the threshold 2 + state, 36 Ca is spatially diffused, which impacts the observed 𝐵⁡(𝐸⁢2) trend.

20 ≤ A ≤ 38↗
DOE OSTI2020

Physics Division Strategic Plan Fiscal Years 2020-2024

The vision of the Physics Division (PHY) at Argonne National Laboratory is to continue enhancing its role as a world-leading institution in basic nuclear physics research and its applications. Key to this vision is for PHY to continue to safely and effectively operate and evolve the capabilities of the Argonne Tandem Linac Accelerator System (ATLAS) facility to best serve its users. ATLAS is the Department of Energy (DOE) accelerator facility for low-energy nuclear physics research. The research carried out by PHY covers many themes in contemporary science but can be distilled into five areas of focus. These themes are interconnected, with continuously evolving synergies between the various groups and facilities in PHY and the broader Laboratory. This five-year strategic plan serves to illustrate our current capabilities and new directions related to these five areas of focus (ATLAS also develops an independent strategic plan): Accelerator research and design. The goal of this theme is to design, fabricate, test, and implement novel accelerator systems, with a focus on high-intensity ion and electron systems. These R&D activities have led to enhancements in the ATLAS accelerator system. Among others, the division’s accelerator systems are in use or planned for use at Fermilab, the Advanced Photon Source, and in a broad variety of applications at the Facility for Rare Isotope Beams (FRIB). Atom trapping and fundamental symmetries. The goal of this theme is to explore and exploit the uses of advanced laser cooling and trapping techniques to manipulate atoms. There are three main areas of focus. First is in the application of the atom trap trace analysis (ATTA) technique for age determination of groundwater and ice by using radio-krypton dating. The next two trapping-based programs involve tests of fundamental symmetries in nature: the cooling and trapping of radium-225 with the aim of determining limits on an observation of its electric dipole moment and precision measurements of the beta decay properties of helium-6 to set limits on the tensor coupling constant. This is complemented by measurements of similar properties in lithium-8 and boron-8. Nuclear astrophysics. The goal of this theme is to enhance our understanding of how elements are created in the universe via explosive nucleosynthesis and how stars evolve. To meet the challenges of this theme, many of the capabilities of ATLAS are being enhanced, including the development of new beams through a new in-flight separator (RAISOR) and the anticipated neutron-generator upgrade of the Californium Rare Isotope Breeder Upgrade facility (nuCARIBU). These are coupled to state-of-the-art instruments such as the Canadian Penning Trap, Helical Orbit Spectrometer, Gammasphere, GRETINA, Multi-Sampling Ionization Chamber, the Fragment Mass Analyzer, and Argonne Gas-filled Fragment Analyzer, and a new low-background experimental area for decay studies. Nuclear structure. The goal of this theme is to understand the structure of nuclei, both stable and radioactive, in terms of single-particle properties, their shapes, and the dynamics governing reactions between them. These include questions such as what are the limits of nuclear stability and what are the properties of super heavy nuclei. As with the nuclear astrophysics theme, the capabilities of ATLAS, guided by the ATLAS user community, are continuously being enhanced to this end. The Division has strategic initiatives to play a leading role in the development of instrumentation and research programs at the FRIB. Quantum chromodynamics (QCD) and hadron physics. The goal of this theme is to lead major research programs focused on revealing the quark and gluon structure of protons, neutrons, nuclei, and short-lived mesons and baryons. These involve major programs at Jefferson Lab, Fermilab, and smaller facilities. They are complemented by theoretical endeavors centered on the question of how hadrons and their properties emerge from QCD. Out of these activities arise strategic initiatives to play a major role in the forthcoming Electron-Ion Collider (EIC).

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Fast Emulation of Expensive Simulations using Approximate Gaussian Processes [Slides]

Nuclear Computational Low-Energy Initiative (NUCLEI) collaboration uses Density Functional Theory (DFT) simulations to predict the structure and binding energies of nuclei over a wide range of proton (Z) and neutron (N) numbers. The DFT simulations utilize a particular parameterization of a Skyrme energy density functional called UNEDF1 which depends on 12 free parameters that must be fit to data (M Kortelainen et al 2014). Fitting involves comparing (e.g.) predicted binding energies of nuclei to experimentally measured values. We use only binding energies as observables, but DFT with UNEDF1 will predict structure (shape) observables as well. In this work, assessing the capability of approximate GP emulators to balance emulator accuracy with computational speed to facilitate improved UNEDF1 calibration. Sparse GPs are straightforward to train and accurate. Calibration is not straightforward with MCMC (using MH or HMC/NUTS). We produced reusable software for continuing and building on this work as well as accessing and using Darwin cluster compute resources

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2022

A Case Study of the Glycoside Hydrolase Enzyme Mechanism Using an Automated QM-Cluster Model Building Toolkit

Glycoside hydrolase enzymes are important for hydrolyzing the β-1,4 glycosidic bond in polysaccharides for deconstruction of carbohydrates. The two-step retaining reaction mechanism of Glycoside Hydrolase Family 7 (GH7) was explored with different sized QM-cluster models built by the Residue Interaction Network ResidUe Selector (RINRUS) software using both the wild-type protein and its E217Q mutant. The first step is the glycosylation, in which the acidic residue 217 donates a proton to the glycosidic oxygen leading to bond cleavage. In the subsequent deglycosylation step, one water molecule migrates into the active site and attacks the anomeric carbon. Residue interaction-based QM-cluster models lead to reliable structural and energetic results for proposed glycoside hydrolase mechanisms. The free energies of activation for glycosylation in the largest QM-cluster models were predicted to be 19.5 and 31.4 kcal mol −1 for the wild-type protein and its E217Q mutant, which agree with experimental trends that mutation of the acidic residue Glu217 to Gln will slow down the reaction; and are higher in free energy than the deglycosylation transition states (13.8 and 25.5 kcal mol −1 for the wild-type protein and its mutant, respectively). For the mutated protein, glycosylation led to a low-energy product. This thermodynamic sink may correspond to the intermediate state which was isolated in the X-ray crystal structure. Hence, the glycosylation is validated to be the rate-limiting step in both the wild-type and mutated enzyme.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1982

Unusual structure of the dayside low-latitude magnetopause energetic electron layer

An analysis of high time resolution energetic electron data from an ISEE 1 spacecraft crossing of the magnetopause on Nov. 6, 1977 is presented. Low-energy proton measurements were taken with an ultralow energy and charge analyzer and energetic electron measurements were made with an ultralow energy wide-angle telescope (ULEWAT). Electrons were observed in four rate channels between 75 and 1300 keV and particle angular distributions are provided. The ecliptic was scanned by the particle angular detector as the spacecraft rotated at 19.7 rpm. Trapped energetic electrons were found to drift from dusk to dawn by way of the midnight sector. The electrons which started at midnight met the magnetopause at the dawnside, were entrained on the field lines, and resulted in a filamentary small-scale structure. A diffusion time scale across the magnetosheath was determined to be a few seconds, and electrons diffused tailward or into the interplanetary medium

Scholer, M.↗
NASA NTRS1991

Energetic particles at Uranus

The energetic particle measurements by the low-energy charged-particle and cosmic-ray instruments on the Voyager 2 spacecraft in the magnetosphere of Uranus are reviewed. Upstream events were observed outside the Uranian bow shock, probably produced by ion escape from the magnetosphere. Evidence of earthlike substorm activity was discovered within the Uranian magnetosphere. A proton injection event was observed within the orbit of Umbriel and proton events were observed in the magnetotail plasma-sheet boundary layer that are diagnostic of earthlike substorms. The magnetospheric composition is totally dominated by protons, with only a trace abundance of H(2+) and no evidence for He or heavy ions; the Uranian atmophere is argued to be the principal plasma source. Phase-space densities of medium energy protons show inward radial diffusion and are quantitatively similar to those observed at the earth, Jupiter, and Saturn. These findings and plasma wave data suggest the existence of structures analogous to the earth's plasmasphere and plasmapause.

Cheng, Andrew F.↗
NASA NTRSDate not supplied

Intense High-Energy ESP Events and Self-Excited Waves at Inner Heliospheric Distances

Energetic Storm Particle (ESP) events are particle intensity increases associated with the passage of interplanetary (IP) shocks. Although ESP events at 1 AU are usually a low-energy phenomenon (i.e., at proton energies <10 MeV), occasionally they may reach energies of >100 MeV. An analysis of the ESP events observed at proton energies >40 MeV over the last four solar cycles shows that these high-energy particle intensity increases tend to occur when unrelated IP structures such as intervening coronal mass ejections and other unlinked shocks are present in the solar wind through which the IP shock generating the ESP event propagates. The acceleration of particles by IP shocks becomes more efficient when particles repeatedly interact with the traveling shocks. These multiple interactions may be favored by either the effects that these unrelated IP structures produce in the particle transport, or by amplified magnetic field fluctuations excited by the accelerated particles. However, the search for these self-excited waves at IP shocks at 1 AU has been often unsuccessful, with just a handful of events showing enhanced field fluctuations that can resonate with the energetic particles. Modeling results indicate that particle acceleration to the highest energies by the shocks occurs close to the Sun, resulting in large intensities of self-excited waves. We have initiated a search for ESP events in the inner heliosphere with evidence for self-excited waves and few cases observed by Parker Solar Probe will be shown.

David Lario↗
DOE OSTI2022

Compact high gradient ion accelerating structure

A high gradient linear accelerating structure can propagate high frequency waves at a negative harmonic to accelerate low-energy ions. The linear accelerating structure can provide a gradient of 50 MV/m for particles at a β of between 0.3 and 0.4. The high gradient structure can be a part of a linear accelerator configured to provide an energy range from an ion source to 450 MeV/u for 12 C 6+ and 250 MeV for protons. The linear accelerator can include one or more of the following sections: a radiofrequency quadrupole (RFQ) accelerator operating at the sub-harmonic of the S-band frequency, a high gradient structure for the energy range from ˜45 MeV/u to ˜450 MeV/u.

Kutsaev, Sergey↗