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At least 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

Quasi elastic cross sections for the Bi-209(e, e-prime p) Pb-208 reaction: Jefferson Lab experiment E06007

Quasi elastic cross sections were measured for the first time for both negative and positive missing momenta for the {sup 209}Bi(e,e'p){sup 208}Pb reaction leading to the ground state and hole states of (208)Pb. Experimental cross sections obtained between -0.3 GeV/c to 0.3 GeV/c agree with theoretical calculations using RDWIA techniques both in shape and magnitude for the ground state. The data for the ground state production of {sup 208}Pb are consistent with a theoretical model assuming a single proton(1.06 +- 0.10) in the 1h9/2 orbit in {sup 209}Bi.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Studies of GPDs at Jefferson Lab: results and future experiments

Here, the Generalized Parton Distributions (GPDs) have emerged as a universal tool to describe hadrons in terms of their elementary constituents, the quarks and the gluons. Deeply Virtual Compton Scattering (DVCS) on a proton or neutron (N), eN → e'N'γ, is one of the simplest processes that can be described in terms of GPDs. The amplitudes of DVCS and Bethe-Heitler, process where a photon is emitted by the incident or scattered electron, can be accessed via cross section measurements or exploiting their interference which give rise to spin asymmetries. Spin asymmetries, cross sections and cross-section differences can be connected to different combinations of the four leading order GPDs (H, E, $\tilde{H} $, $\tilde{E} $) for the two quark flavors depending on the observable and the type of target.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Redesigning the Jefferson Lab Hall A beam line for high precision parity experiments

The Continuous Electron Beam Accelerator Facility (CEBAF) was built with a thermionic electron source and the three original experimental hall lines reflected this. A few years after beam delivery began a parity violation experiment was approved and two polarimeters were installed in the Hall A beam line. The beam raster system was placed after the new Compton polarimeter, before one accelerator quadrupole and four quadrupoles in the new Moller polarimeter. It was very difficult to meet experimental requirements on envelope functions and raster shape with this arrangement so a sixth quadrupole was installed downstream of the Moller polarimeter to provide an additional degree of freedome. All of the parity experiments in Hall A have been run with this still-unsatisfactory configuration. The MOLLER experiment is predicated on achieving a 2% error on a 32 ppb asymmetry. Beam line changes are required to meet the systematic error budget. This work documents the existing beam line, an interim change which can be accomplished during a annual maintenance down, and the final configuration for MOLLER and subsequent experiments.

47 OTHER INSTRUMENTATION↗
DOE OSTI2015

Design and Fabrication of the Superconducting Horizontal Bend Magnet for the Super High Momentum Spectrometer at Jefferson Lab

A collaboration exists between NSCL and JLab to design and build JLab's Super High Momentum Spectrometer (SHMS) horizontal bend magnet that allows the bending of the 12 GeV/c particles horizontally by 3° to allow SHMS to reach angles as low as 5.5°. Two full size coils have been wound and are cold tested for both magnetic and structural properties. Each coil is built from 90 layers of single-turn SSC outer conductor cable. An initial test coil with one third the turns was fabricated to demonstrate that the unique saddle shape with fully contoured ends could be wound with Rutherford superconducting cable. Learned lessons during the trial winding were integrated into the two complete full-scale coils that are now installed in the helium vessel. The fabrication of the iron yoke, cold mass, and thermal shield is complete, and assembly of the vacuum vessel is in progress. This paper presents the process and progress along with the modified magnet design to reduce the fringe field in the primary beam region and also includes the impact of the changes on coil forces and coil restraint system.

43 PARTICLE ACCELERATORS↗
DOE OSTI2015

A Bulk Superconducting Magnetic System for the CLAS12 Target at Jefferson Lab

A feasibility study of a bulk magnetic system for the target of an experiment to measure the transverse spin effects in semi-inclusive deep inelastic scattering (SIDIS) at 11 GeV with a transversely polarized target using the CLAS12 detector is presented. An experiment has been approved with the highest priority rating to study spin azimuthal asymmetries in SIDIS using 11-GeV polarized electron beams from the upgraded CEBAF facility and the CLAS12 detector equipped with a transversely polarized target. The transverse target in CLAS12 requires the shielding of a volume inside the longitudinal field of the main solenoid. In the shielded region, a transverse target magnet can operate; for the proposed magnetic configuration, the main solenoid maximum magnetic induction is 2 T. A bulk MgB 2 cylinder cooled in liquid helium is proposed both to shield the longitudinal field of the main solenoid and to provide a transverse field induction up to 1.2 T for the hydrogen deuteride ice (HD-ice) target. The installation and magnetization procedure will be described. The magnetization procedure has to be compatible with the polarization and installation procedure of the HD-ice target. The design of a test bench to measure the transverse magnetization of a MgB2 bulk cylinder cooled by a coldhead is presented together with the scheduled measurements.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

Commissioning of horizontal-bend superconducting magnet for Jefferson Lab's 11-GeV super high momentum spectrometer

Commissioning characteristics of the Superconducting High Momentum Spectrometer (SHMS) Horizontal Bend (HB) magnet was presented. Pre-commissioning peer review of the magnet uncovered issues with eddy currents in the thermal shield, resulting in additional testing and modeling of the magnet. A three-stage test plan was discussed. A solution of using a small dump resistor and a warm thermal shield was presented. Analyses illustrated that it was safe to run the magnet to full test current. As a result, the HB magnet was successfully cooled to 4 K and reached its maximum test current of 4000 A.

47 OTHER INSTRUMENTATION↗
DOE OSTI2021

Deeply Virtual Compton Scattering Using a Positron Beam in Hall-C at Jefferson Lab

In this study we propose to use the High Momentum Spectrometer of Hall C combined with the Neutral Particle Spectrometer (NPS) to perform high precision measurements of the Deeply Virtual Compton Scattering (DVCS) cross section using a beam of positrons. The combination of measurements with oppositely charged incident beams is the only unambiguous way to disentangle the contribution of the DVCS 2 term in the photon electroproduction cross section from its interference with the Bethe-Heitler amplitude. This provides a stronger way to constrain the Generalized Parton Distributions of the nucleon. A wide range of kinematics accessible with an 11 GeV beam off an unpolarized proton target will be covered. The $\mathcal{Q}^2$-dependence of each contribution will be measured independently.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

The Jefferson Lab 12 GeV program on nucleon structure

This slide-show presents the experiments planned at JLab with their 12 GeV upgrade. Experiments reported address: the use of hadron spectra as probes of QCD; the transverse structure of hadrons; the longitudinal structure of hadrons; the 3-dimensional structure of hadrons; hadrons and cold nuclear matter; and low-energy tests of the Standard Model and fundamental symmetries.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Constraining GPDs at Jefferson Lab

This slide-show presents work on DeeplyVirtual Compton Scattering(DVCS), DeeplyVirtual MesonProduction (DVMP), and the GPD program atJLab12 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Recent Results of TMD Measurements from Jefferson Lab Hall A

This slide-show presents results on transverse momentum distributions. The presentation covers: target single-spin asymmetry (SSA) (in parity conserving interactions); • Results of JLab Hall A polarized {sup 3}He target TMD measurement; • Semi-­inclusive deep-inelastic scattering channels (E06-010); • Target single-spin asymmetry A{sub UT}, Collins and Sivers SSA on neutron; • Double-spin asymmetry A{sub LT}, extract TMD g{sub 1T} on neutron; • Inclusive channels SSA (E06-010, E05-015, E07-013) • Target SSA: inclusive {sup 3}He(e,e’) quasi-elastic scattering; • Target SSA: inclusive {sup 3}He(e,e’) deep inelastic-elastic scattering; • New SIDIS experiments planned in Hall-A for JLab-12 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

MODBUS APPLICATION AT JEFFERSON LAB

Modbus is a client/server communication model. In our applications, the embedded Ethernet device XPort is designed as the server and a SoftIOC running EPICS Modbus is the client. The SoftIOC builds a Modbus request from parameter contained in a demand that is sent by the EPICS application to the Modbus Client interface. On reception of the Modbus request, the Modbus server activates a local action to read, write, or achieve some other action. So, the main Modbus server functions are to wait for a Modbus request on 502 TCP port, treat this request, and then build a Modbus response.

Yan, Jianxun↗
DOE OSTI2017

Design of imaginary transition gamma booster synchrotron for the Jefferson Lab EIC (JLEIC)

Baseline design of the JLEIC booster synchrotron is presented. Its aim is to inject and accumulate heavy ions and protons at 285 MeV, to accelerate them to about 7 GeV, and finally to extract the beam into the ion collider ring. The Figure-8 ring features two 2600 achromatic arcs configured with negative momentum compaction optics, designed to avoid transition crossing for all ion species during the course of acceleration. The lattice also features a specialized high dispersion injection insert optimized to facilitate the transverse phase-space painting in both planes for multi-turn ion injection. Furthermore, the lattice has been optimized to ease chromaticity correction with two families of sextupoles in each plane. The booster ring is configured with super-ferric, 3 Tesla bends. We are presently launching optimization of the booster synchrotron design to operate in the extreme space-charge dominated regime.

Bogacz, Alex↗