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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

Deeply Virtual Exclusive Reactions with CLAS

Deeply virtual exclusive reactions offer an unique opportunity to study the structure of the nucleon at the parton level as one has access to Bjorken x{sub B} and momentum transfer to the nucleon t at the same time. Such processes can reveal much more information about the structure of the nucleon than either inclusive electroproduction or elastic form factors alone. Dedicated experiments to study Deeply Virtual Compton Scattering (DVCS) and Deeply Virtual Meson Production (DVMP) have been carried out in Hall B at Jefferson Lab. DVCS helicity–dependent and helicity–independent cross sections and beam spin asymmetries have been measured with CLAS, as well as cross sections and asymmetries for the {pi}{sup }0, {eta} , {rho}{sup }0, {rho}{sup +}, {omega} and {phi} for exclusive electroproduction. The data were taken in a wide kinematic range in Q{sup 2}=1–4.5 GeV{sup 2}, x{sub B}=0.1–0.5, and {absval t} up to 2 GeV{sup 2}. We will discuss the interpretation of these data in terms of traditional Regge and Generalized Parton Distributions (GPDs) models. The successful description of the recent CLAS pseudoscalar meson exclusive production data by GPD-based model provides a unique opportunity to access the transversity GPDs. We view the work presented in this report as leading into the program of the Jefferson Lab 12 GeV upgrade. The increased energy and luminosity will allow us to acquire data at much higher Q{sup 2} and x{sub B}, and perform Rosenbluth L/T separations of the cross sections.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Scaling growth rates for perovskite oxide virtual substrates on silicon

Abstract The availability of native substrates is a cornerstone in the development of microelectronic technologies relying on epitaxial films. If native substrates are not available, virtual substrates - crystalline buffer layers epitaxially grown on a structurally dissimilar substrate - offer a solution. Realizing commercially viable virtual substrates requires the growth of high-quality films at high growth rates for large-scale production. We report the stoichiometric growth of SrTiO 3 exceeding 600 nm hr −1 . This tenfold increase in growth rate compared to SrTiO 3 grown on silicon by conventional methods is enabled by a self-regulated growth window accessible in hybrid molecular beam epitaxy. Overcoming the materials integration challenge for complex oxides on silicon using virtual substrates opens a path to develop new electronic devices in the More than Moore era and silicon integrated quantum computation hardware.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Virtual sensing-enabled digital twin framework for real-time monitoring of nuclear systems leveraging deep neural operators

Abstract Real-time monitoring is a foundation of nuclear digital twin technology, crucial for detecting material degradation and maintaining nuclear system integrity. Traditional physical sensor systems face limitations, particularly in measuring critical parameters in hard-to-reach or harsh environments, often resulting in incomplete data coverage. Machine learning-driven virtual sensors offer a transformative solution by complementing physical sensors in monitoring critical degradation indicators. This paper introduces the use of Deep Operator Networks (DeepONet) to predict key thermal-hydraulic parameters in the hot leg of pressurized water reactor. DeepONet acts as a virtual sensor, mapping operational inputs to spatially distributed system behaviors without requiring frequent retraining. Our results show that DeepONet achieves low mean squared and Relative L2 error, making predictions 1400 times faster than traditional CFD simulations . These characteristics enable DeepONet to function as a real-time virtual sensor, synchronizing with the physical system to track degradation conditions and provide insights within the digital twin framework for nuclear systems.

Hossain, Raisa↗
DOE OSTI2025

Label-based Virtual Directories In dCache

Traditional filesystems organize data in directories. These directories are typically a collection of files whose grouping is based on a single criterion, e.g., the starting date of an experiment, experiment name, beamline ID, measurement device, or instrument. However, each file in a directory can belong to several logical groups, such as a special event type, experiment condition, or a part of a selected dataset. dCache is a storage system developed to store large amounts of scientific data, used by many HEP and Photon Science experiments. With recent developments in dCache, we have introduced a concept of file tagging, which dynamically groups files with the same label into virtual directories. The file labels can be added, removed, renamed, and deleted through the admin interface or via REST API. The files in virtual directories are exposed through all protocols supported by dCache. This contribution will describe the details of the implementation for file tagging in dCache and present our future development plans on automatic metadata extractions, a feature that will significantly simplify data management. Additionally, we are exploring the future use of virtual directories as a way to translate scientific data catalogs into filesystem views for direct data analysis.

Sahakyan, Marina [DESY]↗
DOE OSTI2011

Plasma-based multistage virtual cathode radiation

A plasma-based multistage virtual cathode radiation is proposed. Multistage virtual cathode can be formed as an electron beam passes through a high dense ion background. The reflected electrons can be coupled with transverse magnetic wave, and electromagnetic radiation is detected. Unlike the traditional virtual cathode devices, the beam current can be decreased greatly due to the effect of ions, and single mode operation can be achieved by adjusting the beam density. Besides, the radiation frequency, which is proportional to the beam density, covers from 10 to 100 GHz. The output power flux density reaches a magnitude of GWm{sup -2}.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Effect of self-magnetic fields on the nonlinear dynamics of relativistic electron beam with virtual cathode

The report is devoted to the results of the numerical study of the virtual cathode (VC) formation conditions in the relativistic electron beam (REB) under the influence of the self-magnetic and external axial magnetic fields. The azimuthal instability of the relativistic electron beam leading to the formation of the vortex electron structure in the system was found out. This instability is determined by the influence of the self-magnetic fields of the relativistic electron beam, and it leads to the decrease of the critical value of the electron beam current (current when the non-stationary virtual cathode is formed in the drift space). The typical dependencies of the critical current on the external uniform magnetic field value were discovered. The effect of the beam thickness on the virtual cathode formation conditions was also analyzed.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2012

Experimental investigation of virtual cathode sheath in the presence of secondary electrons produced by streaming ions

The potential profiles near a negatively biased stainless steel plate or mesh immersed in an unmagnetized weakly collisional plasma were investigated experimentally. The results show that deep virtual cathode structures arise inside the sheath region in front of the plate caused by secondary electrons produced by streaming ions hitting the surface of the plate. The characteristics of the virtual cathode depend on the incoming ion energy, neutral gas pressure, and bulk plasma density. In addition, the replacement of the plate with the mesh results in the suppression of the virtual cathode because of the equivalent reduction in the secondary electron yield.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Biparametric analyses of charge trapping in Cd{sub 0.9}Zn{sub 0.1}Te based virtual Frisch grid detectors

Detector grade Cd{sub 0.9}Zn{sub 0.1}Te (CZT) single crystals were grown from zone refined Cd, Zn, and Te ({approx}7 N) precursor materials, using a tellurium solvent method. Detectors with virtual Frisch grid configuration were fabricated using these crystals. I-V measurements revealed low leakage currents at room-temperature, {approx}11 nA for one such detector D1 and {approx}8 nA for another detector D2 at 1100 V. The spectroscopic performances of the two CZT virtual Frisch grid detectors have been evaluated and compared for high energy gamma ray detection. Detector D1 showed a well-resolved pulse-height spectrum with an energy resolution of {approx}1.6% for the 662 keV gamma rays. Detector D2 also showed a distinct 662 keV peak but with a broader pulse-height distribution. A digital biparametric correlation study of the depth of interaction and energy deposited by the 662 keV gamma rays was carried out. A different kind of correlation pattern from that observed normally for hole trapping was noticed in the case of detector D2. Correlation of results from thermally stimulated current measurement studies suggested that the anomalous biparametric correlation pattern was due to the trapping of holes but modified by the virtual Frisch grid effect. The results also suggested that the effect of electron trapping could not be ruled out either. Finally, a digital correction scheme was applied to recover the {sup 137}Cs spectrum from the effect of charge loss.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2013

Generalized space-charge limited current and virtual cathode behaviors in one-dimensional drift space

This paper reports the space-charge limited current (SLC) and virtual cathode behaviors in one-dimensional grounded drift space. A simple general analytical solution and an approximate solution for the planar diode are given. Through a semi-analytical method, a general solution for SLC in one-dimensional drift space is obtained. The behaviors of virtual cathode in the drift space, including dominant frequency, electron transit time, position, and transmitted current, are yielded analytically. The relationship between the frequency of the virtual cathode oscillation and the injected current presented may explain previously reported numerical works. Results are significant in facilitating estimations and further analytical studies.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Suppression of stochastic pinning in magnetic nanowire devices using “virtual” domain walls

We have investigated the pinning and depinning of “virtual” domain walls in planar magnetic nanowires. Such virtual walls are created when a conventional domain wall becomes annihilated at a narrow gap between two segments of a discontinuous nanowire. By using focused magneto-optical Kerr effect magnetometry to study the repeatability of their depinning, we show that virtual walls exhibit single-mode depinning distributions, characterized by remarkably low, sub-Oersted standard deviations. This is in stark contrast to the depinning of domain walls from conventional notch-shaped defects, which typically exhibit multi-mode depinning field distributions spanning tens to hundreds of Oersteds. High-resolution magnetic soft x-ray microscopy measurements are used to reveal that this high level of repeatability is the result of a simple mediated-nucleation process, which decouples the depinning mechanism from structure of the initially injected DWs. Our work serves as an example of how the complex and dynamical stochastic behaviors exhibited by domain walls in nanowires can be controlled.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

Proof-of-principle demonstration of a virtual flow meter-based transducer for gaseous helium monitoring in particle accelerator cryogenics

A transducer based on a virtual flow meter is proposed for monitoring helium distribution and consumption in cryogenic systems for particle accelerators. The virtual flow meter allows technical and economical constraints, preventing installation of physical instruments in all the needed measurement points, to be overcome. Virtual flow meter performance for the alternative models of Samson [ http://www.samson.de (2015)] and Sereg-Schlumberger [ http://www.slb.com/ (2015)] is compared with the standard IEC 60534-2-1 [Industrial-process control valves—Part 2-1: Flow capacity—sizing equations for fluid flow under installed conditions (2011), https://webstore.iec.ch/publication/2461], for a large temperature range, for both gaseous and liquid helium phases, and for different pressure drops. Then, the calibration function of the transducer is derived. Finally, the experimental validation for the helium gaseous state on the test station for superconducting magnets in the laboratory SM18 [Pirotte et al., AIP Conf. Proc. 1573, 187 (2014)] at CERN is reported.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Design of virtual SCADA simulation system for pressurized water reactor

The Virtual SCADA system is a software-based Human-Machine Interface that can visualize the process of a plant. This paper described the results of the virtual SCADA system design that aims to recognize the principle of the Nuclear Power Plant type Pressurized Water Reactor. This simulation uses technical data of the Nuclear Power Plant Unit Olkiluoto 3 in Finland. This device was developed using Wonderware Intouch, which is equipped with manual books for each component, animation links, alarm systems, real time and historical trending, and security system. The results showed that in general this device can demonstrate clearly the principles of energy flow and energy conversion processes in Pressurized Water Reactors. This virtual SCADA simulation system can be used as instructional media to recognize the principle of Pressurized Water Reactor.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2018

InGaP solar cell on Ge-on-Si virtual substrate for novel solar power conversion

InGaP single-junction solar cells are grown on lattice-matched Ge-on-Si virtual substrates using metal-organic chemical vapor deposition. Optoelectronic simulation results indicate that the optimal collection length for InGaP single-junction solar cells with a carrier lifetime range of 2–5 ns is wider than approximately 1 μ m. Electron beam-induced current measurements reveal that the threading dislocation density (TDD) of InGaP solar cells fabricated on Ge and Ge-on-Si substrates is in the range of 10 4 –3 × 10 7 cm -2 . We demonstrate that the open circuit voltage ( V oc ) of InGaP solar cells is not significantly influenced by TDDs less than 2 × 10 6 cm -2 . Fabricated InGaP solar cells grown on a Ge-on-Si virtual substrate and a Ge substrate exhibit V oc in the range of 0.96 to 1.43 V under an equivalent illumination in the range of ~0.5 Sun. Finally, the estimated efficiency of the InGaP solar cell fabricated on the Ge-on-Si virtual substrate (Ge substrate) at room temperature for the limited incident spectrum spanning the photon energy range of 1.9–2.4 eV varies from 16.6% to 34.3%.

14 SOLAR ENERGY↗
DOE OSTI2018

Study of virtual displays based on raster optical elements

The paper is devoted to the study of the ultimate resolution of virtual displays with raster systems. Raster systems in such displays are used for an essential reduction of their longitudinal overall dimensions. Three schemes are considered: in the first one each element of the raster system forms an image of one pixel only, in the second one each element of the raster system forms a small part of a virtual image, the third scheme is analogous to the first one, but is implemented in the form of a contact lens. For each scheme, we analyse the overall dimensions of the optical system and the characteristics of the virtual image, i.e., the ultimate resolution and the nonuniformity of its illumination. (paper)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Complexity of virtual 3-manifolds

Virtual 3-manifolds were introduced by Matveev in 2009 as natural generalizations of classical 3-manifolds. In this paper, we introduce a notion of complexity for a virtual 3-manifold. We investigate the values of the complexity for virtual 3-manifolds presented by special polyhedra with one or two 2-components. On the basis of these results, we establish the exact values of the complexity for a wide class of hyperbolic 3-manifolds with totally geodesic boundary. Bibliography: 24 titles. (paper)

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2021

The 23rd National School on Neutron & X-Ray Scattering 2021—Virtual School with Remote Experiments

The National School on Neutron and X-ray Scattering (NXS) has been a yearly “institution” for North American graduate students interested in neutron and X-ray scattering since its inception 23 years ago. For the second year in a row, it was forced to go virtual. Nevertheless, the aim was to include user experiments and maximize interactions in this second virtual iteration rather than simply repeat the lecture series of the first virtual iteration. In this paper, we share our newly adopted methods and experiences.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Virtualization of the ATLAS software environment on a shared HPC system

The shared HPC cluster NEMO at the University of Freiburg has been made available to local ATLAS users through the provisioning of virtual machines incorporating the ATLAS software environment analogously to a WLCG center. This concept allows to run both data analysis and production on the HPC host system which is connected to the existing Tier2/Tier3 infrastructure. Schedulers of the two clusters were integrated in a dynamic, on-demand way. An automatically generated, fully functional virtual machine image provides access to the local user environment. The performance in the virtualized environment is evaluated for typical High-Energy Physics applications.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Doubly virtual ( π 0 , η , η ' ) → γ * γ * transition form factors in the light-front quark model

We report our investigation on the doubly virtual transition form factors (TFFs) F P γ * ( Q 1 2 , Q 2 2 ) for the P → γ * ( q 1 ) γ * ( q 2 ) ( P = π 0 , η , η ' ) transitions using the light-front quark model (LFQM). Performing a LF calculation in the exactly solvable manifestly covariant Bethe-Salpeter (BS) model as the first illustration, we use the q 1 + = 0 frame and find that both LF and manifestly covariant calculations produce exactly the same results for F P γ * ( Q 1 2 , Q 2 2 ) . This confirms the absence of the LF zero mode in the doubly virtual TFFs. We then map this covariant BS model to the standard LFQM using the more phenomenologically accessible Gaussian wave function provided by the LFQM analysis of meson mass spectra. For the numerical analyses of F P γ * ( Q 1 2 , Q 2 2 ) , we compare our LFQM results with the available experimental data and the perturbative QCD (pQCD) and vector meson dominance (VMD) model predictions. As ( Q 1 2 , Q 2 2 ) → ∞ , our LFQM result for doubly virtual TFF is consistent with the pQCD prediction, i.e., F P γ * ( Q 1 2 , Q 2 2 ) ~ 1 / ( Q 1 2 + Q 2 2 ) , while it differs greatly from the result of the VMD model, which behaves as F P γ * VMD ( Q 1 2 , Q 2 2 ) ~ 1 / ( Q 1 2 Q 2 2 ) . Our LFQM prediction for F η ' γ * ( Q 1 2 , Q 2 2 ) shows an agreement with the very recent experimental data obtained from the BABAR Collaboration for the ranges of 2 < ( Q 1 2 , Q 2 2 ) < 60 GeV 2 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗