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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Probing nuclear gluons with heavy flavors at an Electron-Ion Collider

We explore the feasibility of direct measurements of nuclear gluon densities using heavy-quark production (open charm, beauty) at a future Electron-Ion Collider (EIC). We focus on the regions x > 0.3 (EMC effect) and x ~ 0.05 -0.1 (antishadowing), where the nuclear modifications of the gluon density offer insight into non-nucleonic degrees of freedom and the QCD structure of nucleon-nucleon interactions. We describe the charm production rates and momentum distributions in nuclear deep-inelastic scattering (DIS) at large x_B, and comment on the possible methods for charm reconstruction using next-generation detectors at the EIC (pi/K identification, tracking, vertex detection).

Chudakov, Eugene↗
DOE OSTI2011

Extracting a free neutron structure function from proton and deuteron deep inelastic scattering data

Due to the lack of a free neutron target the structure function of the neutron cannot be measured directly and is therefore extracted from deuteron and proton DIS data. Because the deuteron is a bound nuclear system, in order to extract the neutron structure function, one needs to apply model dependent theoretical corrections which dominate the uncertainty at the large xB region. We present here a correlation between the magnitude of the EMC effect and the amount of two nucleon Short Range Correlation (2N-SRC) pairs in nuclei. Using this correlation we propose a phenomenological procedure to extract the free neutron structure function in the xB range of 0.3 to 0.7.

Hen, O.↗
NASA NTRS1985

Energy spectra of high energy atmospheric neutrinos

Focusing on high energy neutrinos ( or = 1 TeV), a new calculation of atmospheric neutrino intensities was carried out taking into account EMC effects observed in P-A collisions by accelerator, recent measurement of primary cosmic ray spectrum and results of cosmic ray muon spectrum and charge ratio. Other features of the present calculation are (1) taking into account kinematics of three body decays of kaons and charm particles in diffusion equations and (2) taking into account energy dependence of kaon production.

Mitsui, K.↗
DOE OSTI2015

Preliminary Results on the Experimental Investigation of the Structure Functions of Bound Nucleons

We present preliminary results on an experimental study of the nuclear modification of the longitudinal (σ L ) and transverse (σ T ) structure functions of nucleons bound in nuclear targets. The origin of these modifications (commonly referred as as the EMC effect) is not fully understood. Our measurements of R= σ L /σ T for nuclei (R A ) and for deuterium (RD) indicate that nuclear modifications of the structure functions of bound nucleons are different for the longitudinal and transverse structure functions, and that contrary to expectation from several theoretical models, R A < R D .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Preliminary Results on the Experimental Investigation of the Structure Functions of Bound Nucleons

We present preliminary results on an experimental study of the nuclear modification of the longitudinal ($\sigma_L$) and transverse ($\sigma_T$) structure functions of nucleons bound in nuclear targets. The origin of these modifications (commonly referred as as the EMC effect) is not fully understood. Our measurements of R= $\sigma_L / \sigma_T$ for nuclei ($R_A$) and for deuterium ($R_D$) indicate that nuclear modifications of the structure functions of bound nucleons are different for the longitudinal and transverse structure functions, and that contrary to expectation from several theoretical models, $R_A< R_D$.

Bodek, Arie↗
DOE OSTI2017

Open Charm Production and Nuclear Gluon Densities

Open Charm Production and Nuclear Gluon Densities Very little is known about nuclear gluon densities. We explore the direct measurements of nuclear gluon densities via open charm and beauty production at an Electron-Ion Collider (EIC). In the high-x ranges x ~ 0.05-0.15 (antishadowing) and x>0.3 (EMC effect) strong modifications are expected relative to the incoherent sum of nucleon gluon distributions. These effects offer insight into non-nucleonic degrees of freedom and the QCD structure of nucleon-nucleon interactions. We describe the charm production rates in nuclear deep-inelastic scattering (DIS) at large x_B, and comment on methods for charm reconstruction using next-generation detectors at the EIC (pi/K identification, tracking, vertex detection). Presenter : Prof. HYDE, Charles (Old Dominion University)

Hyde, Charles↗
DOE OSTI2015

DIS on Light Nuclei with Spectator Tagging: New Applications at Intermediate and Small x

An Electron-Ion Collider would enable next-generation measurements of DIS on light nuclei (deuteron, 3He, ...) with detection of nucleons and fragments in the nuclear fragmentation region ("spectator tagging"). Such measurements allow one to control the nuclear configuration during the high-energy process and could greatly advance our understanding in several areas of partonic structure and QCD: (a) precision measurements of neutron structure functions (including spin) in electron-deuteron scattering with proton tagging, eliminating nuclear binding through on-shell extrapolation in the recoil proton momentum; (b) controlled studies of the nuclear modifications of quark and gluon densities (EMC effect, anti-shadowing), using the recoil momentum dependence to control the size of nuclear configurations; (c) novel studies of coherence and nuclear shadowing at x << 0.1 using tagged DIS. We present an overview of the physics applications of spectator tagging at intermediate and small x and comment on theoretical challenges and experimental requirements. We report about results of an R&D project aiming to demonstrate the feasibility of spectator tagging with EIC and quantify the physics impact.

Weiss, Christian↗
DOE OSTI2015

Neutron structure with (un)polarized deuterons and forward spectator tagging at the Electron-Ion Collider

An Electron-Ion Collider (EIC) would enable novel measurements of neutron structure through deep-inelastic electron-deuteron scattering with coincidence tagging of the forward-moving spectator proton. The free neutron structure functions can be obtained by extrapolating the measured recoil momentum distributions to the on-shell point. Such measurements provide essential information for the flavor separation of the nucleon parton densities, the nucleon spin decomposition, and precision studies of QCD evolution in the flavor-singlet and nonsinglet sectors. The EMC effect in light nuclei can be elucidated by measuring the recoil momentum dependence of the nuclear modification. A Jefferson Lab LDRD project has supported a study of neutron structure measurements with spectator tagging at an EIC, with Monte Carlo simulation of the physical processes and the accelerator and detector requirements. We present results of a model-independent extraction of the free neutron structure function $F_2^n$, as well as the spin structure function $g_1^n$, through on-shell extrapolation in the spectator momentum.

Park, Kijun↗
DOE OSTI2018

Jefferson Lab Tritium Program

Electromagnetic probes of few-body nucleon systems play a pivotal role in our attempts to understand the structure of both nuclei and the protons and neutrons that comprise them. Of particular interest, are light nuclei where, among other motivating factors, models are more easily developed. The simplest asymmetric nuclear system is the A=3 system. While experiments involving 3He are relatively common, the combined study of the mirror nuclei 3He and 3H can provide much deeper insight. This provided the onus for the development of a tritium target system. After considerable effort the Jefferson Lab Tritium Program became operational with first beam in December of 2017. Since that time, data have been successfully collected for two experiments with two more now in process and expected to be completed by late 2018. These experiments range in scope from the study of Short Range Correlations to the Hypernuclear ?N interaction to the A=3 EMC effect and ratio of u/d in the nucleon. In this talk, the challenges of working with tritium and the development of the tritium target system are presented. Selected preliminary results and target performance will also be discussed.

Meekins, David↗
DOE OSTI2025

Shining a Light on the Nucleus: Photonuclear Measurements from Correlations to Charmonium

The atomic nucleus is comprised of a collection of nucleons (protons and neutrons), which are bound together by the nucleon-nucleon (NN) interaction that originates from Quantum Chromodynamics (QCD). While most nucleons experience the force from the rest of the nu- cleus as a single net “mean-field” interaction that binds them relatively weakly, a small but impactful fraction are in configurations called “Short-Range Correlations” (SRCs), in which they pair with another nucleon at very short distance to experience strong interactions, sig- nificant binding, and high momentum. Hard, high-energy scattering reactions in which an SRC pair is broken apart, knocking both nucleons out of the nucleus, provide the ability to probe the details of these SRC configurations in the nucleus. Previous measurements have had limited statistics and kinematic reach, and the theoretical tools available were in- sufficient to draw quantitative conclusions regarding the ground-state properties of SRCs. The studies described in this thesis represent the first global analysis of SRC breakup mea- surements in order to present a unified picture of SRCs within light- to medium-size nuclei. This includes the use of a novel theoretical framework, the Generalized Contact Formalism, which connects scattering cross-section measurements and the ground-state properties of the SRC pair, to quantitatively interpret a variety of electron-scattering measurements. This is brought to culmination by a report on the first measurement of SRC pairs via the use of hard meson photoproduction reactions, which, despite differing significantly from the me- chanics of electron-scattering, is well-described under a common framework, pointing to a consistent and universal picture of SRCs across reaction channels. I also report on the first measurement of J/¿ photoproduction in the near- and below-threshold kinematic region, giving the first insights to the gluonic structure of bound nucleons in the large-x “valence” region and providing constraints on a gluonic “EMC effect”. In addition to these studies, I provide details on the search for Primakoff production of axion-like particles using the pho- toproduction data taken for this experiment, and I conclude by describing studies of nucleon spin structure measurements that will be performed at the forthcoming U.S. Electron-Ion Collider.

Pybus, Jackson↗
DOE OSTI2019

Modified structure of protons and neutrons in correlated pairs

The atomic nucleus is made of protons and neutrons (nucleons), which are themselves composed of quarks and gluons. Understanding how the quark-gluon structure of a nucleon bound in an atomic nucleus is modified by the surrounding nucleons is an outstanding challenge. Although evidence for such modification-known as the EMC effect-was first observed over 35 years ago, there is still no generally accepted explanation for its cause. Recent observations suggest that the EMC effect is related to close-proximity short-range correlated (SRC) nucleon pairs in nuclei. Here we report simultaneous, high-precision measurements of the EMC effect and SRC abundances. We show that EMC data can be explained by a universal modification of the structure of nucleons in neutron-proton SRC pairs and present a data-driven extraction of the corresponding universal modification function. This implies that in heavier nuclei with many more neutrons than protons, each proton is more likely than each neutron to belong to an SRC pair and hence to have distorted quark structure. This universal modification function will be useful for determining the structure of the free neutron and thereby testing quantum chromodynamics symmetry-breaking mechanisms and may help to discriminate between nuclear physics effects and beyond-the-standard-model effects in neutrino experiments.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1997

Design Guidelines for Shielding Effectiveness, Current Carrying Capability, and the Enhancement of Conductivity of Composite Materials

These guidelines address the electrical properties of composite materials which may have an effect on electromagnetic compatibility (EMC). The main topics of the guidelines include the electrical shielding, fault current return, and lightning protection capabilities of graphite reinforced polymers, since they are somewhat conductive but may require enhancement to be adequate for EMC purposes. Shielding effectiveness depends heavily upon the conductivity of the material. Graphite epoxy can provide useful shielding against RF signals, but it is approximately 1,000 times more resistive than good conductive metals. The reduced shielding effectiveness is significant but is still useful in many cases. The primary concern is with gaps and seams in the material just as it is with metal. Current carrying capability of graphite epoxy is adequate for dissipation static charges, but fault currents through graphite epoxy may cause fire at the shorting contact and at joints. The effect of lightning on selected graphite epoxy material and mating surfaces is described, and protection methods are reviewed.

Evans, R. W.↗
NASA NTRS1996

Development of Design Standards and Guidelines for Electromagnetic Compatibility and Lightning Protection for Spacecraft Utilizing Composite Materials

Preliminary design guidelines necessary to assure electromagnetic compatibility (EMC) of spacecraft using composite materials, are presented. A database of electrical properties of composite materials which may have an effect on EMC is established. The guidelines concentrate on the composites that are conductive but may require enhancement to be adequate for EMC purposes. These composites are represented by graphite reinforced polymers. Methods for determining adequate conductivity levels for various EMC purposes are defined, along with the methods of design which increase conductivity of composite materials and joints to adequate levels.

Source record↗
DOE OSTI2024

Tagged deep inelastic scattering measurement on deuterium with the LAD experiment

Here, the origin of the modification of the quark structure of nucleons in the nuclear medium can be tested with tagged recoil nucleon measurements from deep inelastic scattering off electrons on deuterium. The LAD experiment at the Thomas Jefferson National Laboratory (JLab) will measure the modification of the neutron structure function for high-momentum, highly-virtual neutrons by measuring the spectator recoil protons in coincidence with the scattered electron. An update on the experimental setup and projected results is presented. The experiment will collect data in Fall 2024.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS2019

Gateway Electromagnetic Environmental Effects (E3) Requirements

Electromagnetic Compatibility (EMC) is essential to the success of any vehicle design that incorporates a complex assortment of electronic, electrical, and electromechanical systems and sub-systems that is expected to meet operational and performance requirements while exposed to a changing set of electromagnetic environments composed of both man-made and naturally occurring threats. The combined aspects of these environments are known as Electromagnetic Environmental Effects (E3). The attainment of EMC is accomplished through the application of sound engineering principles and practices that enable a complex vehicle or vehicles to operate successfully when exposed to the effects of its expected and/or specified electromagnetic environments.

Stecklein, Jonette M.↗
NASA NTRS1985

The Effects of Simulated Weightlessness on Susceptibility to Viral and Bacterial Infections Using a Murine Model

Certain immunological responses may be compromised as a result of changes in environmental conditions, such as the physiological adaptation to and from the weightlessness which occurs during space flight and recovery. A murine antiorthostatic model was developed to simulate weightlessness. Using this model, the proposed study will determine if differences in susceptibility to viral and bacterial infections exist among mice suspended in an antiorthostatic orientation to simulate weightlessness, mice suspended in an orthostatic orientation to provide a stressful situation without the condition of weightlessness simulation, and non-suspended control mice. Inbred mouse strains which are resistant to the diabetogenic effects of the D variant of encephalomyocarditis virus (EMC-D) and the lethal effects of Salmonella typhimurium will be evaluated. Glucose tolerance tests will be performed on all EMC-D-infected and non-infected control groups. The incidence of EMC-D-induced diabetes and the percentage survival of S. typhimurium-infected animals will be determined in each group. An additional study will determine the effects of simulated weightlessness on murine responses to exogenous interferon.

Gould, C. L.↗
NASA NTRS2019

On the Maximum Expected Electric Field in Electrically Small, Undermoded Enclosures

This paper reports the experimental validation of an improved statistical model for the prediction of maximum expected electric field in electrically small and under-moded enclosures. The aerospace community is interested in application of Hill's statistical models to design of avionics boxes for shielding effectiveness and for tailoring EMC test requirements for critical applications. However, it is observed that the probability distribution for mean-squared electric field in an electrically small enclosure differs from the exponential distribution which is widely used in reverberation chamber testing. It is postulated here that the difference is attributable to the under-moded character of the small enclosure.

Bremner, Paul↗