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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 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

π-/π+ Exclusive Pion Electroproduction Results from Jefferson Lab

Forward exclusive meson production is a particularly useful tool in the study of hadronic structure. Measurements at different squared four-momenta of the exchanged virtual photon, Q2, and at different four-momentum transfer, t, allow one to probe QCD's transition from meson-nucleon degrees of freedom at long distances to quark-gluon degrees of freedom at short scales. Furthermore, by forming ratios of separated response functions in pi? and pi+ electroproduction, there may be a partial cancellation of nonperturbative QCD contributions, allowing this transition to be more readily apparent. These strong theoretical motivations make worthwhile the significant experimental challenges needed to accurately separate the four response functions in forward, exclusive pi-/pi+ electroproduction off deuterium. We report the results of our study from Jefferson Lab Hall C, where for the first time ratios of separated response functions were extracted at several kinematic settings: Q2 = 0.6, 1.0, 1.6 GeV2 with W=1.95 GeV, and Q2=2.45 GeV2 with W=2.22 GeV, respectively.

Huber, Garth M.↗
DOE OSTI2022

SRF Cavity Fault Classification and Prediction at Jefferson Lab

Over the last few years several machine learning projects at Jefferson Lab have had a common focus to optimize operation of superconducting RF (SRF) cavities in the Continuous Electron Beam Accelerator Facility (CEBAF). In this talk we highlight work to identify and classify types of faults from C100-type cavities and then to extend those capabilities to provide real-time fault prediction. Early prediction may enable mitigation strategies to prevent some types of faults. In our approach we apply a two-step fault prediction pipeline. In the first step, a model distinguishes between faulty and normal signals. In the second step, signals flagged as faulty by the first model are classified into one of seven fault types based on learned signatures in the data. Initial results show that our model can successfully predict most fault types 200 ms before onset. In additional to model performance, we also highlight challenges in working with real-world data and challenges for deploying models.

Tennant, C.↗
DOE OSTI2023

Characterizing PuO 2 Powder at Oak Ridge National Laboratory for the Multi-Lab Plutonium Process Signatures Campaign FY 2022

This report highlights the development of advanced analytical capabilities at Oak Ridge National Laboratory to characterize PuO 2 powder to support the Multi-Lab Plutonium Process Signatures Campaign in FY 2022. Two samples from a batch of 76 statistical precipitation runs were packaged and shipped from Pacific Northwest National Laboratory to Oak Ridge National Laboratory at the beginning of FY 2022. Techniques were used to characterize the sample, including powder X-ray diffraction, Raman spectroscopy, and diffuse reflectance spectroscopy. A brief description of each technique, the results and discussion, and future work are described in this report. Opportunities to expand current capabilities and include additional analytical capabilities for the next campaign will also be discussed.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2015

Medium Energy Electron Ion Collider at Jefferson Lab

At Jefferson Lab, the conceptual design of a next generation facility, the medium energy electron ion collider (MEIC), to reach the frontier in Quantum Chromodynamics has been carried on for years. The MEIC will provide an electron beam with energy up to 10 GeV, a proton beam with energy up to 100 GeV, and heavy ion beams with corresponding energy per nucleon with the same magnetic rigidity. The center-of-mass energy goes up to 70 GeV. Both the proton beam and the light-ion beams have high polarization above 70%. Two detectors, a primary one with full acceptance and a high-luminosity one with less demanding specification, are proposed. With the implementation of the traditional electron cooling in both the ion booster ring and the ion collider ring, particularly ultrahigh luminosity close to 1034 cm-2s-1 per detector with large acceptance can be achieved. We will present the recent progress in MEIC design.

Zhang, He↗
DOE OSTI2019

Interaction Region Magnets for Future Electron-Ion Collider at Jefferson Lab

The Jefferson Lab Electron Ion Collider (JLEIC) is a pro-posed new machine for nuclear physics research. It uses the existing CEBAF accelerator as a full energy injector to deliver 3 to 12 GeV electrons into a new electron collider ring. An all new ion accelerator and collider complex will deliver up to 200 GeV protons. The machine has luminosity goals of 1034 cm-2 sec-1. The whole detector region including forward detection covers about 80 meters of the JLEIC complex. The interaction region design has recently been optimized to accommodate 200 GeV proton energy using conventional NbTi superconducting magnet technology. This paper will describe the requirements and preliminary designs for both the ion and electron beam magnets in the most complex 34.5 m long interaction region (IR) around the interaction point (IP). The interaction region has over thirty-four superconducting magnets operating at 4.5K; these include dipoles, quadrupoles, skew quadrupoles, solenoids, horizontal and vertical correctors and higher order multipole magnets. The paper will also dis-cuss the electromagnetic interaction between these magnets.

Rajput-Ghoshal, Renuka↗
DOE OSTI2019

Hadron Spectroscopy at Jefferson Lab

Hadron spectroscopy experiments provide crucial data to help understand the binding of quarks and gluons into hadrons. Currently, we are specially interested in the role that gluons play in these structures, knowing its importance in providing most of the nucleon?s mass and spin. Two experiments, GlueX (in Hall D) and CLAS12 (in Hall B), are using the Jefferson Lab?s 12-GeV electron beam to extend these measurements to higher masses and to collect very large statistics. GlueX uses a beam of linearly polarized photons using the technique of coherent bremsstrahlung (peaking polarization about 8.6 GeV). The MesonEX experiment at CLAS12 uses a quasi-real photon beam at equivalent energies and polarizations (using very low Q2 electron scattering). The data taken by those experiments will exceed by several orders of magnitude all previously obtained photoproduction data at those energies. We will report on the first results (beam asymmetries and J/ psi production) and current status on the search for hybrid mesons at GlueX. We will also discuss preliminary results from the CLAS12-MesonEX experiment from its first physics run.

Salgado, Carlos↗
DOE OSTI2019

Preliminary results searching for the onset of color transparency in A(e,e'p) in Hall C at Jefferson Lab

Color transparency (CT) is a fundamental phenomenon of QCD postulating that at high momentum transfer, one can preferentially measure hadrons that fluctuate to a small color neutral transverse size in the nucleus, and final state interactions within the nuclear medium are sup- pressed. CT is observed experimentally as a rise in the measured nuclear transparency as a function of the momentum transferred. While CT has been observed for mesons, it remains unconfirmed in baryons. Observation of CT in baryons would provide a new means to study the nuclear strong force and would be the first clear observation of hadrons fluctuating to a small size in the nucleus. An enhancement in the nuclear transparency was observed in A(p,2p) reactions at Brookhaven. This experiment, E1206107, seeks to confirm the measurement of pro- ton transparency as well as to measure the onset. During the spring of 2018, this experiment was the first to run in Hall C at Jefferson Lab using the recently upgraded 12 GeV electron beam and obtained four kinematic points at momentum transfer Q^2 from 8-14.3 GeV^2, overlapping the same region where Brookhaven previously observed an enhancement. This ex- periment used the High Momentum Spectrometer (HMS) and Super High Momentum Spectrometer (SHMS) in coincidence to measure A(e,e'p) on a carbon target. This talk will summarize the motivation to measure the onset of color transparency in baryons and will present preliminary results from this experiment. DOE Grant Number: DE-FG02-07ER41528

Szumila-Vance, Holly↗
DOE OSTI2019

Polarized Positron in Jefferson Lab Electron Ion Collider (JLEIC)

The Jefferson Lab Electron Ion Collider (JLEIC) is a proposed new nuclear physics facility designed to deliver high luminosity and high polarization electron-ion collisions. JLEIC employs high repetition rate collisions of short low emittance bunches to achieve the electron ion luminosity goal of 10^{33}-10^{34}cm^{-2}s^{-1} over a wide range of center-of-mass energy. With a growing physics interest, a positron-ion collision scheme is under study for JLEIC. The JLEIC positron-ion scheme will use CEBAF as the positron injector with minimal modification, so the Polarized Electrons for Polarized Positrons (PEPPo) based positron generation scheme is chosen. The major challenge of this scheme is to generate the polarized positron bunch trains with the time structure and peak beam current required for the injection/top-off of the electron collider ring. In this talk, we will address the details of this scheme, with the focus on the positron beam formation, as well as the preliminary collider parameters optimized for positron-ion luminosity.

Guo, Jiquan↗
DOE OSTI2018

The Search for the Color Transparency in Hall C at Jefferson Lab

Color transparency (CT) is a fundamental phenomenon of QCD postulating that at high momentum transfer hadrons fluctuate to a small color neutral transverse size in the nucleus, and final state interactions within the nuclear medium are suppressed. CT is observed experimentally as a rise in the measured nuclear transparency as a function of the momentum transferred. While CT has been observed for mesons, it remains unconfirmed in baryons. Observation of CT in baryons would provide a new handle for understanding the nuclear strong force and the first observations of hadrons fluctuating to a small size in the nucleus. An enhancement in the nuclear transparency was observed in A(p,2p) reactions at Brookhaven. This experiment seeks to confirm the measurement of proton transparency as well as to measure the onset. During the spring of 2018, this experiment was the first to run in Hall C at Jefferson Lab using the recently upgraded 12 GeV electron beam and obtained four kinematic points covering the region where Brookhaven previously observed an enhancement. This experiment used the High Momentum Spectrometer (HMS) and Super High Momentum Spectrometer (SHMS) in coincidence to measure A(e,e?p). This talk will summarize the status of the experiment since the completion of data taking this spring.

Szumila-Vance, Holly↗
DOE OSTI2018

Status of Jefferson Lab Electron-Ion Collider and its interaction region design

An Electron Ion Collider (EIC) has been identified in the Nuclear Physics Long Range Plan as the highest-priority facility for new construction. This talk presents an overview and status of the Jefferson Lab design of an EIC (JLEIC). It features frequent collisions of small electron and ion bunches providing a luminosity of 1033-1034 cm?1s?1 in a broad range of the center-of-mass energy. The small size of ion bunches is maintained against intra-beam scattering by a novel high-energy bunched beam electron cooling system. The figure-8 shape of the electron and all ion rings allows for preservation and ease of manipulation of the electron polarization and the spin of any ion species (p, d, 3He, Li, etc.). The interaction region is designed to accommodate a full-acceptance detector with complete coverage and geometry tagging in the forward and ultra-forward directions. The talk highlights recent progress on the JLEIC accelerator design with an emphasis on the integrated interaction region design.

Morozov, V.↗
DOE OSTI2018

Operation of Jefferson Lab Polarized Electron Sources

This contribution describes Jefferson Lab polarized electron sources where the world record of high current polarized electron beam was delivered. Polarized GaAs Superlattice photoguns with long lifetime represents a significant challenge for proposed facilities that must operate in excess of tens of mA of polarized average current. Damage due to ion bombardment is the dominant mechanism that reduces photocathode yield. Highlights of R&D to improve the performance of polarized electron sources and prolong the lifetime of strained-superlattice GaAs are presented.

Suleiman, Riad↗
DOE OSTI2017

SRF Systems for the Jefferson Lab Electron Ion Collider (JLEIC)

We report on the development of new CW SRF systems for the colliding rings of a proposed electron-ion collider (EIC) at Jlab. Jefferson Lab is developing new strongly HOM-damped SRF cavities for the ion collider ring and a high-energy electron cooler at 952.6 MHz. The baseline design JLEIC will re-use the PEP-II 476 MHz cavities for the electron ring with a possible future upgrade to 952.6 MHz SRF cavities at a later date. We discuss the design optimization of the new high current cavities and compare options for the strong HOM damping required. A concept for a modular cryostat to house these various cavities will be shown, and an overview of the challenging high-level parameters will be presented. These designs and concepts may be useful in other high current storage rings and ERLs.

Rimmer, Robert↗
DOE OSTI2017

Direct Comparison of M\o ller and Compton Polarimeters in Hall C at Jefferson Lab

Knowledge of the electron beam polarization is one of the most important systematic uncertainties in precision, parity-violating electron scattering experiments with next generation experiments aiming to measure the electron beam polarization to better than 0.5\%. At high energies, the most typical polarimetry techniques are M\o ller (polarized electron-electron) and Compton (polarized electron-photon) scattering. The use of two techniques with different systematic uncertainties provides confidence in the extracted beam polarization. Direct comparisons of the two polarimetry techniques are challenging in that Compton polarimeters typically desire maximum beam flux (high beam currents) while M\o ller polarimeters need to limit the beam current to avoid depolarization effects in the target. We have performed a direct comparison of the M\o ller and Compton polarimeters in experimental Hall C at Jefferson Lab. This test is unique in that the data were taken sequentially under identical beam conditions at ?4.5~?A. We found excellent agreement between the Hall C M\o ller and Compton polarimeters. Combined with high-current Compton data, we were also able to limit the beam current dependence of the beam polarization to 1\% or less up to a beam current of 180~?A.

Gaskell, David↗
DOE OSTI2017

Impact of Jefferson Lab Data on Global PDF Analysis

This talk will review new insights into the quark structure of the nucleon that have been made with recent global QCD analysis of parton distributions, using new analysis techniques to take into account the latest high-precision data from Jefferson Lab.

Melnitchouk, Wolodymyr↗
DOE OSTI2017

Overview of the SIDIS/TMD program at Jefferson Lab

The study of the single-hadron semi-inclusive deep inelastic scattering process (SIDIS) is a rapidly developing and expanding area of inquiry in hadronic physics, owing to the prospect of realizing a precision three-dimensional imaging of the quark structure of the nucleon in momentum space. Measurements of the azimuthal angular distributions of hadrons produced at large values of z = Eh=? and "small" transverse momentum pT ~ \Lambda_?QCD in deep inelastic lepton-nucleon scattering provides access to novel features of nucleon structure that are inaccessible in traditional inclusive DIS, including the e?ects of initial-state quark transverse momentum, transverse polarization of the parent nucleon and the struck quark, and "flavor tagging" due to the varying sensitivity of di?erent hadron species to di?fferent quark flavors. The Continuous Electron Beam Accelerator Facility (CEBAF) at Je?erson Lab has recently completed an upgrade to a maximum beam energy of 11 GeV at ?ve passes for electron scattering experiments. The energy upgrade of CEBAF, combined with its already unrivaled intensity, duty cycle and polarization, facilitates a three-dimensional nucleon imaging program of unprecedented precision in the valence region. In this talk,I will present a brief overview of the planned CEBAF SIDIS program in experimental Halls A, B and C.

Puckett, Andrew↗
DOE OSTI2017

New Deeply Virtual Compton Scattering results from Jefferson Lab

Deeply Virtual Compton Scattering (DVCS) is the easiest reaction that accesses the Generalized Parton Distributions (GPDs) of the nucleon. GPDs offer the exciting possibility of mapping the 3-D internal structure of protons and neutrons by providing a transverse image of the constituents as a function of their longitudinal momentum. A vigorous experimental program is currently pursued at Jefferson Lab (JLab) to study GPDs through DVCS. New results from Hall A will be shown and discussed. Special attention will be devoted to the applicability of the GPD formalism at the moderate values of momentum transfer (Q2) available at JLab. We will conclude with a brief overview of additional DVCS experiments under analysis and planned with the future Upgrade of JLab to 12 GeV.

Camacho, Carlos Munoz↗
DOE OSTI2017

Separated pi0 electroproduction cross sections off the nucleon at Jefferson Lab Hall A

We report final results for L/T separated pi0 electroproduction cross sections off the proton, the neutron and the deuteron, measured in Hall A of Jefferson Lab. We found a large transverse response for both the proton and neutron cases, pointing to a possible dominance of higher-twist transversity GPD contributions. For the first time, a flavor decomposition of the u and d quark contributions to the cross section will be shown.

Sabatie, Franck↗
DOE OSTI2017

Field Mapper for Superconducting Torus Magnet for the Jefferson Lab 12GeV Upgrade

As part of the Jefferson Lab 12 GeV upgrade, the Hall B magnet system requires two conduction cooled superconducting magnets ? a Torus and a Solenoid. The Torus consists of 6 trapezoidal coils connected in series with an operating current of 3770 A. During commissioning of the torus magnet, field mapping was carried out at different levels of operating current in order to determine the field profile and field error table. In order to meet the physics requirement of the field accuracy we need magnetic field strength measurements which are accurate at the 0.1% level, and we need to know radius and azimuth to 0.1 mm and z to 0.5 mm. The center line of the torus magnet is approximately 6 m from ground level and the overall height of the torus magnet is approximately 8.5 m. There is also limited space around the magnet and in between the coils. Field mapping had to be carried out along the Z axis (i.e. along the bore) and at 4 radial locations between each coil. These restrictions provided certain challenges for the magnetic field mapping task. The mapper prototype was built and tested prior to use on the Torus itself. In this presentation the field mapper design, prototyping and actual data collection procedure will be presented.

Rajput-Ghoshal, Renuka↗