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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Design and Prototyping of a Novel Toroidal Magnet System for MOLLER Experiment at Jefferson Lab

The Thomas Jefferson National Accelerator Facility (JLab) has designed a unique spectrometer system to measure the weak interaction between electrons. The experiment— Measurement of Lepton-Lepton Electroweak Reaction (MOLLER)—requires leveraging the recent 12 GeV electron beam upgrade and will run in JLab for three years. Focusing the signal for the MOLLER experiment requires five water-cooled toroidal magnets, each with unique geometry and with 7-fold symmetry. The five magnets operate in a vacuum and provide the magnetic field required to separate the incident beam electrons scattered from the target electrons (Møller scattering) and protons (elastic e-p scattering) in a liquid hydrogen target. The conceptual design was developed by the MOLLER Collaboration and was given to JLab in the form of amp turns and physical location, with additional physics requirements. This article presents prototyping of the coils and magnet support system and discusses the lessons learned during the process along with the plans for full magnet testing and installation. The JLab Magnet Group along with the MOLLER Collaboration developed the specification document that includes keep out zones to design the set of magnets. JLab contracted the design of the first toroid magnet (TM0) of the magnet system to Massachusetts Institute of Technology. The other four toroid magnets (TM1 through TM4) have been designed by JLab and are in the process of fabrication and assembly. Prototype coils of TM1-TM4 were fabricated by Everson-Tesla Incorporated, PA (USA). Finally, this article presents the unique challenges of the design, alignment, high current density, operating range, high radiation dose, and vacuum environment.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

Magnetic Field Mapping Design for the MOLLER Spectrometer Magnets at Jefferson Lab

The Thomas Jefferson National Accelerator Facility (JLab) has developed a unique spectrometer system to study the weak interaction between electrons. The "Measurement of Lepton-Lepton Electroweak Reaction" (MOLLER) experiment, utilizing JLab's recent 12 GeV electron beam upgrade, is scheduled to operate for three years. Central to the MOLLER experiment are five water-cooled toroidal magnets, each with a unique geometry and seven-fold symmetry, designed to focus the particles. These magnets generate the magnetic field needed to separate incident beam electrons scattered from target electrons (Møller scattering) and protons (elastic e-p scattering) within a liquid hydrogen target. Here, this paper details the magnet field measuring technique developed to map all five MOLLER toroidal magnets at multiple locations inside and along the bore. It covers the design, mounting, and operation of the probe, along with the calibration procedure to determine the field and to prepare a field map for GEANT4 analysis. Additionally, the paper addresses the challenges of accurately measuring low magnetic fields.

Ghoshal, Probir K. [Thomas Jefferson National Acce↗
DOE OSTI2023

Design and Prototyping of a Novel Toroid Magnet System for the MOLLER Experiment at Jefferson Lab

The Thomas Jefferson National Accelerator Facility (JLab) has designed a unique spectrometer system to measure the weak interaction between electrons. The experiment ?Measurement of Lepton-Lepton Electroweak Reaction? (MOLLER) requires leveraging the recent 12 GeV electron beam upgrade and will run in JLab for 3 years. Focusing the signal for the MOLLER experiment requires five water-cooled toroidal magnets, each with unique geometry and with 7-fold symmetry. This system of magnets provides the magnetic field required to separate the incident beam electrons scattered from the target electrons (Møller scattering) and protons (elastic e-p scattering) in a liquid hydrogen target. The conceptual design was developed by the MOLLER collaboration and was given to JLab in the form of amp turns and physical location, with additional physics requirements. This paper presents prototyping of the coils and magnet support system and discusses the lessons learned during the process along with the plans for full magnet testing and installation. The JLab Magnet Group along with the MOLLER collaboration developed the specification document that includes keep out zones to design the set of magnets. JLab contracted the design of the first toroid magnet in the magnet (TM0) to Massachusetts Institute of Technology. The other four toroid magnets (TM1 through TM4) have been designed by JLab and are in the process of fabrication and assembly. Prototype coils of TM1-TM4 have been fabricated by Everson-Tesla Incorporated, PA (USA). The manuscript presents the unique challenges of the design, alignment, high current density, operating range, high radiation dose, and vacuum environment.

Kashy, David↗
DOE OSTI2013

Electron polarimetry at low energies in Hall C at JLab

Although the majority of Jefferson Lab experiments require multi-GeV electron beams, there have been a few opportunities to make electron beam polarization measurements at rather low energies. This proceedings will discuss some of the practical difficulties encountered in performing electron polarimetry via Mo/ller scattering at energies on the order of a few hundred MeV. Prospects for Compton polarimetry at very low energies will also be discussed. While Mo/ller scattering is likely the preferred method for electron polarimetry at energies below 500 MeV, there are certain aspects of the polarimeter and experiment design that must be carefully considered.

43 PARTICLE ACCELERATORS↗
DOE OSTI2020

A VXS [VITA41] Trigger Processor for the 12GEV Experimental Programs at Jefferson Lab

The VXS_Trigger_Processor [VTP] was developed and commissioned for CLAS12 in the fall of 2016. This board is a VITA41 switch card and it collects data from a variety of front-end TDC and Flash ADC modules. The VTP has since been used in several experiments at Jefferson Lab serving as the L1 trigger module for a variety of detector types, such as stacked calorimeters, strip calorimeters, time-of-flight, Cerenkov, hodoscopes, drift chambers, and silicon strips. Trigger algorithms implemented include cluster finding (1D, 2D), drift chamber segment and road finding, geometry matching between various detectors, particle counting, and general global trigger bit processing. The VTP is also capable of reading out each front-end crate with up to 40Gbps Ethernet which is an enormous increase compared to the currently used 200MB/s VME bus. Recent progress has been made to show that a firmware and software upgrade can enable existing Jefferson Lab front-end crates to operate in a streaming DAQ mode. In February 2020, tests will be performed on a full calorimeter and matched hodoscope which are components of the CLAS12 Forward Tagger detector system with beam in Hall B. This paper details the hardware performance, triggered, and streaming applications that have been implemented using the VTP for several experiments at Jefferson Lab.

ABBOTT, David↗
DOE OSTI2018

Jefferson Lab at 12 GeV: The Science Program

Jefferson Lab’s upgrade of its Continuous Electron Beam Accelerator Facility (CEBAF) has recently been completed. The project involved an upgrade of the accelerator to achieve a maximum beam energy of 12 GeV and the construction of a fourth end station, Experimental Hall D, as well as new detector equipment for two of the three existing halls (A, B, and C). A broad experimental program has been developed to map the nucleon’s intrinsic quark distributions in transverse space and in longitudinal momentum through measurements of deeply exclusive and semi-inclusive processes, and to probe color confinement by studying the spectrum of hadrons with active gluon degrees of freedom in the wave function. Other programs include the forward parton distribution function at large quark momentum fraction χ, the quark and gluon polarized distribution functions, measurements of electromagnetic form factors of the nucleon ground state and of nucleon resonance transitions at short distances, and the exploration of physics beyond the Standard Model in high-precision parity-violating processes and in the search for signals of dark matter. The higher beam energy is also suitable for exploration of quark hadronization properties using the nucleus as a laboratory. This review highlights major areas of hadron and nuclear science that will be the focus of the first 5 years of operation.

3D imaging↗
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

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↗
DOE OSTI2017

Testing of the SIDIS framework at Jefferson Lab Hall C using precise measurements of light meson electroproduction

Semi-inclusive deep inelastic scattering (SIDIS) has proved to be an important tool for unveiling the inner structure of the core of the atom, the nucleons and their basic constituents. Azimuthal spin asymmetries in polarized SIDIS are directly related to transverse momentum dependent parton distributions (TMDs) and fragmentation functions. The TMDs allow one to probe the 3D dynamical structure of partons inside the nucleon. Understanding the nature of the SIDIS process is essential for TMD studies, in particular at modest energies where deviations from the leading-order factorized picture may be a significant. Precise maps of the meson cross sections and their ratios at low transverse momentum and Jefferson Lab beam energies provide a stringent test of the use of the standard SIDIS framework in terms of factorized parton distributions convoluted with fragmentation functions. The magnetic spectrometers in Hall C at Jefferson Lab are well suited for such precision measurements of fully L/T separated cross sections and their ratios. The addition of neutral particle detection enables additional opportunities. Plans for upcoming experiments that will investigate the SIDIS process at the 12 GeV Jefferson Lab will be presented.

Kinney, Edward↗
DOE OSTI2023

Performance and Commissioning of the BigBite Timing Hodoscope for Nucleon Form Factor Measurements at Jefferson Lab

The BigBite Timing Hodoscope detector is the primary subject of this thesis. The Super BigBite Spectrometer is a Jefferson Lab Hall A Collaboration project that has and will continue to measure nucleon electromagnetic form factors. This spectrometer includes the Timing Hodoscope which provides high resolution particle timing data for scattered electrons in the electron arm of BigBite. The Timing Hodoscope utilizes 90, 25 × 25 × 600 mm3 scintillator bars stacked on top of each other to form a single detector plane, and these bars are connected to 180 photo-multiplier tubes via light guides. Particles collide with the scintillating material creating a shower of optical photons and these particle events in the bars are collected to generate signals that are readout by the data acquisition (DAQ) electronics. NINO ASIC amplifier-discriminator cards output signals from the photo-multiplier tubes into analogue and logic signals, which are sent to analogue-to-digital (ADC) and time-to-digital (TDC) converter data acquisition readout modules. This data is then used for analysis of the detector. The focus of this thesis is the construction, commissioning, calibration, and performance of the BigBite Timing Hodoscope before and during the first of five nucleon electromagnetic form factor experiments at Jefferson Lab Hall A. Before the neutron magnetic form factor, G n M, experiment, cosmic ray data was collected during commissioning to confirm proper operation of the Timing Hodoscope electronics by observing the ADC and TDC data. Commissioning studies for charge normalization, gain matching, and other ADC and TDC detector data variables were performed before moving the detector into Hall A. Following installation in Hall A, several calibration studies were implemented to fine-tune the detector in preparation for use in the experiment. The calibration studies included analysis of timing cuts, TDC alignment, the time-walk effect, time difference offsets, and scintillator velocity corrections. Once the Timing Hodoscope was well-calibrated, data-taking during the experiment commenced and the beam-on-target data was used to characterize the Timing Hodoscope performance during the G n M experiment run-time. The performance analysis included studies observing energy deposit, cluster size, rates, accidentals, pile-up, tracking efficiency, position resolution, and time resolution. After application of physics cuts to ensure a data set comprised of particle tracks corresponding to elastic electrons, which is the main data of interest for measurement of G n M, the Timing Hodoscope is shown on average across all kinematic settings to have a >98% tracking efficiency, a position resolution of 4-6 cm in the non-dispersive plane and 1.5-2 cm in the dispersive plane, and a time resolution of 500-750 ps. These performance results are compared to a GEANT4 based performance simulation of the BigBite Timing Hodoscope for reference, showing to what degree the measured performance values match those taken from the simulation.

Marinaro, Ralph↗
DOE OSTI2026

Performance of the Pair Spectrometer in Hall D at Jefferson Lab

This article describes the performance of the pair spectrometer installed in experimental Hall D at Jefferson Lab and its successfully operation in multiple experiments with the GlueX detector. The primary purpose of the pair spectrometer is the precise determination of the flux of beam photons incident on the GlueX target, a critical input for physics analyses such as absolute cross-section measurements. The photon energy spectrum is determined by reconstructing electron–positron pairs produced in a thin converter inserted into the photon beam. The spectrometer is integrated into the GlueX trigger system, whose electronics enable continuous real-time monitoring of the photon flux and the recording of e+e- pair candidates for offline analysis. In addition, the pair spectrometer provides a versatile test facility for evaluating calorimeter prototypes using leptons with well-defined energies produced via electromagnetic pair production.

Somov, Alexander [Jefferson Lab]↗
DOE OSTI2016

Nuclear Physics Research at Jefferson Lab

The Florida International University (FIU) experimental nuclear physics group consists of four to five faculty, four to eight graduate students, at times one postdoctoral scholar, and several undergraduate students. Our research is mainly conducted at Jefferson Lab's Continuous Electron Accelerator Beam Facility. We are studying the electroprodcution of strangeness and also the interaction of strange baryons, hyperons, with nuclear matter; the effects of two-photon exchange on nuclear form factor measurements; the short range correlations in nuclei; and the production of exotic mesons. Over the entire period of this project, members of the group have been leading the data acquisition and analysis efforts as co-spokespersons of 12 Jefferson Lab experiments, as well as contributed to the efforts of the broader JLab user community. This has resulted in the publication of over 300 papers in peer reviewed journals and conference proceedings. Twelve students received their Ph.D. and four their M.S. based on analysis of data collected during this project.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Latest results from FROST at Jefferson Lab

The spectrum of broad and overlapping nucleon excitations can be greatly clarified by use of a polarized photon beam incident on a polarized target in meson photoproduction experiments. At Jefferson Lab, a program of such measurements has made use of the Jefferson Lab FROzen Spin Target (FROST). An overview of preliminary results are presented.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

New CTEQ-Jefferson Lab (CJ) analysis of parton distributions

We present preliminary results of a new global QCD analysis of PDFs from the CTEQ-Jefferson Lab Collaboration (dubbed "CJ15"), which includes several new data sets and recent theoretical developments. In particular, we study the constraints from new D0 data on *W* boson asymmetries on the *d/u* PDF ratio at large *x*, and, indirectly, on the models of nuclear corrections in the deuteron. The analysis also considers for the first time the impact of Jefferson Lab data on the free neutron/deuteron structure function ratio at large *x*, and reanalyzes the light antiquark asymmetry in the proton from Drell-Yan data using more flexible parametrizations and nuclear corrections to deuterium cross sections. The results provide a new set of baseline PDFs which can be used to more reliably calibrate the effect of future data from the LHC.

Keppel, Cynthia↗
DOE OSTI2015

New CTEQ-Jefferson Lab (CJ15) Analysis of Parton Distributions

We present the results of a new global QCD analysis of PDFs from the CTEQ-Jefferson Lab collaboration (dubbed "CJ15"), which includes several new data sets and recent theoretical developments. In particular, we study the constraints from new D0 data on W boson asymmetries on the d/u PDF ratio at large x, and, indirectly, on the models of nuclear corrections in the deuteron. The analysis also considers for the first time the impact of Jefferson Lab data on the free neutron/deuteron structure function ratio at large x, and reanalyzes the light antiquark asymmetry in the proton from Drell-Yan data using more flexible parametrizations and nuclear corrections to deuterium cross sections. The results provide a new set of baseline PDFs which can be used to more reliably calibrate the effects of future data from the LHC.

Melnitchouk, W.↗
DOE OSTI2016

Nucleon and Nuclear Structure Studies in Electroproduction with the CLAS Detector at Jefferson Lab

A diverse program for studying the structure of nucleons and nuclei is underway using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab. A wealth of data has been obtained in inclusive, semi-inclusive, and exclusive electroproduction reactions using a variety of unpolarized and polarized beams and targets. The results include studies of excited nucleon states, measurements of nucleon, proton and neutron Form Factors (FFs), Parton Distribution Functions (PDFs), Transverse Momentum Distributions (TMDs), and Generalized Parton Distributions (GPDs), as well as Short Range Correlations (SRCs) in nuclei and Color Transparency phenomena. Jefferson Lab's electron accelerator, CEBAF, doubled its energy to 12~GeV and the upgrade of the experimental equipment is near completion in the experimental halls. The upgraded CLAS detector, CLAS12, enables execution of a broader physics program, with the main focus on uncovering the TMDs and GPDs using semi-inclusive and exclusive reactions in a new kinematic domain. In this talk, an overview of the CLAS electroproduction measurements with 6~GeV CEBAF and prospects of nucleon and nuclear structure studies with the 12~GeV machine and the CLAS12 detector will be discussed.

Stepanyan, Stepan↗
DOE OSTI2017

Final Assembly and Factory Testing of the Jefferson Lab SHMS Spectrometer Quadrupole and Dipole Superconducting Magnets

Jefferson Lab is constructing an 11 Gev/c electron spectrometer called the Super High Momentum Spectrometer (SHMS) as part of the 12 GeV JLAB upgrade for experimental Hall C. Three of the five superconducting(SC) SHMS magnets are under construction at SigmaPhi in Vannes France as a result of an international competition for design and fabrication. The three magnets Q2 and Q3 60 cm bore quadrupoles and the 60 cm warm bore dipole are complete or near complete and have many design features in common. All three magnets share a common superconductor, collaring system, cryostat design, cold to warm support, cryogenic interface, burnout resistant current leads, DC power supply, quench protection, instrumentation and controls. The three magnets are collared, installed in cryostats and welded up and in various stages of final testing. The Q2 quadrupole is due to ship from France to America in August arriving during this ASC conference and has passed all final hipot, leak and pressure tests. The dipole is in leak and pressure testing as of July 2016 while the Q3 quadrupole requires some outer vacuum vessel assembly. Delivery of the Q3 and Dipole magnets will follow the Q2 at about 1 month intervals. Lastly, factory testing have included hipot and electrical tests, magnetic tests at low field, mechanical alignments to center the coils, leak tests and ASME Code required pressure tests. Upon installation in Hall C at JLAB cold testing will commence.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Transversely Polarized Solid Target for Hall B at Jefferson Lab

The physics program for Hall B at Jefferson Lab includes multiple, high-impact experiments scattering electrons from transversely polarized protons. These experiments will measure, for example, the Transverse Momentum Distributions and the Generalized Parton Distribution for protons, using, respectively, semi-inclusive deep inelastic scattering and deeply virtual Compton scattering. In this talk I will discuss the technical challenges to implementing a polarized solid-state target in the Hall B experimental environment, examine potential solutions, and describe the current status of the target design.

Keith, Christopher↗