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At least 1,765 records · Page 98
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Streaming Readout of the CLAS12 Forward Tagger Using TriDAS and JANA2

An effort is underway to develop streaming readout data acquisition system for the CLAS12 detector in Jefferson Lab’s experimental Hall-B. Successful beam tests were performed in the spring and summer of 2020 using a 10GeV electron beam from Jefferson Lab’s CEBAF accelerator. The prototype system combined elements of the TriDAS and CODA data acquisition systems with the JANA2 analysis/reconstruction framework. This successfully merged components that included an FPGA stream source, a distributed hit processing system, and software plugins that allowed offline analysis written in C++ to be used for online event filtering. Details of the system design and performance are presented.

Ameli, Fabrizio↗
DOE OSTI2011

Qweak - A Search For New Physics

Qweak is a currently running experiment at the Thomas Jefferson National Accelerator Lab in Newport News Virginia USA that will use parity-violating elastic electron-proton scattering to measure the weak charge of the proton (Q{sup P}{sub weak}). Longitudinally polarized electrons scatter off a liquid hydrogen target and pass through a toroidal-field magnetic spectrometer. In order to perform a 4% measurement of Q{sup P}{sub weak}, we will need to measure the momentum transfer (Q{sup 2}) to 0.5%. The Q{sup 2} will be measured using a tracking system consisting of two gas electron multipliers (GEM), four horizontal drift chambers (HDC), and four vertical drift chambers (VDC). I will outline the design of the full apparatus and discuss the details of the Q{sup 2} and Q{sup P}{sub weak} measurements that will be complete in 2012 with a brief update on the experiment's progress.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Electromagnetic production of hyperon resonances

The study of hyperon resonances has entered a new era of precision with advent of high-statistics photoproduction data from the CLAS detector at Jefferson Lab. These data have multi-particle final states, allowing clean identification of exclusive reactions associated with strange mesons and baryons. Examples of physics results are: evidence for isospin interference in the decay of the {Lambda}(1405) resonance; a strong suggestion of meson cloud effects in the structure of the {Sigma}(1385) resonance; data from K* photoproduction that will test the existence of the purported K{sub 0}(800) meson. Properties of other hyperon resonances will also be studied in the near future.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

New results on the neutron spin polarizabilities at low Q{sup 2}

Thomas Jefferson National Accelerator Facility (Jefferson Lab) has become one of the premier facilities for the study of nucleon spin structure. Over the past two decades, several high precision measurements of the polarized structure functions g1(x,Q{sup 2}) and g2(x,Q{sup 2}) have been performed that have extensively covered the region between 0.02 and 5 GeV{sup 2}. Spin moments have been formed from the measured structure functions. These proceedings will concentrate on experiment E97-110, which was performed in Hall A to study the neutron and {sup 3}He spin structure at four-momentum transfers squared (Q{sup 2}) = 0.02 - 0.26 GeV{sup 2}. This range allows us to make a benchmark-check of Chiral Perturbation Theory calculations. Previous results for the neutron spin polarizability, {delta}LT , down to 0.1 GeV{sup 2} have shown significant disagreement with the calculations. Preliminary results on the generalized spin polarizabilities, {gamma}0 and {delta}LT , for the neutron were presented at the conference and will be discussed here.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Baryon spectroscopy at CLAS and CLAS12

The N* programme at CLAS in Jefferson Lab is dedicated to the study of the spectrum of baryon resonances and the search for missing resonances. Recent developments in polarized beams and targets at CLAS have made it possible to measure many of the single and double polarization observables which are necessary to disentangle the contributing processes. In particular, CLAS is well on the way to making the first complete measurement on pseudoscalar meson production. The current status of the N* program is presented together with preliminary results from recently completed experiments. A brief overview of the hadron spectroscopy capabilities of the upgraded CLAS12 detector is also be presented, with emphasis on the plans for a tagged, quasi real photon beam.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Spin physics with CLAS and CLAS12

An extensive experimental program to measure the spin structure of the nucleon has been conducted in Hall B at Jefferson Lab with the CEBAF Large Acceptance Spectrometer (CLAS) in the last decade. Using a longitudinally polarized beam scattering off longitudinally polarized NH{sub 3} and ND{sub 3} targets, inclusive Deep Inelastic Scattering (DIS), Semi-Inclusive DIS (SIDIS) and DVCS experiments were carried out that make a significant contributions to the existing data. The inclusive double spin asymmetry A{sub ||} was measured over a large range in Q{sup 2} and W, providing data of impressively high precision that give a better understanding of the structure of the nucleon in the DIS and the valence quarks regions. Using parameterizations A2 and F1 from world data, the virtual photon asymmetry A1 and the structure function g1 were extracted in a Q{sup 2} range from 0.05 to 5 GeV{sup 2} and a W range from 1.08 to 3.0 GeV. As a result of the extended kinematical range, first moments of structure functions were measured over a large range in Q{sup 2} and duality was tested. Furthermore, newly proposed experiments, using an upgraded accelerator at Jefferson Laboratory and an improved CLAS detector (CLAS12), are expected to increase the statistical precision of the current measurements and extend them to kinematic regions presently not accessible, such as high x. This will improve significantly our knowledge of the structure of the nucleon, including parton distribution functions, duality and higher twists contributions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

K*{sup +} Photoproduction at CLAS

The study of hyperon resonances has entered a new era of precision with advent of high-statistics photoproduction data from the CLAS detector at Jefferson Lab and elsewhere. These data have multi-particle final states, allowing clean identification of exclusive reactions associated with strange mesons and baryons. In this paper, cross sections for K* photoproduction are presented that will provide a future test of the existence of the purported K{sub 0}(800) meson via comparison with theoretical models.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Meson Spectroscopy at CLAS and CLAS12

We report on meson spectroscopy using the CLAS at Jefferson Lab. We study photo-production of exotic mesons and strangeonia on the largest data sample ever to be produced at photon energies of about 5 GeV. We also describe an experiment to continue meson spectroscopy at CLAS12 (CLAS energy upgrade) using electroproduction at very low Q{sup 2}(''quasireal photons'') up to photon energies of 10 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Studies of Nucleon Form Factors with 12 GeV CEBAF and SuperBigBite

The elastic electromagnetic form factors are among the most fundamental quantities that describe the ground-state structure of the proton and neutron. Precision data of the form factors over a wide kinematical range provide a powerful test of current theories of hadron structure. A number of experiments aiming to measure the electric and magnetic elastic form factors of the neutron, G{sub E}{sup n} and G{sub M}{sup n}, and proton, G{sub E}{sup p}, at very high momentum transfer, up to the range of Q{sup 2} = 10-14 (GeV/c){sup 2}, are planned to be carried out with the future 11 GeV electron beam of the upgraded CEBAF at Jefferson Lab. These experiments will determine the nucleon form factors with unprecedented precision to Q{sup 2}-values up to three times higher than those of existing data. We review the approved proposals and the conceptual design of a new spectrometer, SuperBigBite, that will be used in these and other future experiments at Jefferson Lab.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

An Alternative View of the Dynamical Origin of the P11 Nucleon Resonances: Results from the Excited Baryon Analysis Center

We present an alternative interpretation for the dynamical origin of the P{sub 11} nucleon resonances, which results from the dynamical coupled-channels analysis at Excited Baryon Analysis Center of Jefferson Lab. The results indicate the crucial role of the multichannel reaction dynamics in determining the N* spectrum. An understanding of the spectrum and structure of the excited nucleon (N*) states is a fundamental challenge in the hadron physics. The N* states, however, couple strongly to the meson-baryon continuum states and appear only as resonance states in the {gamma}N and {pi}N reactions. One can expect from such strong couplings that the (multichannel) reaction dynamics will affect significantly the N* states and cannot be neglected in extracting the N* parameters from the data and giving physical interpretations. It is thus well recognized nowadays that a comprehensive study of all relevant meson production reactions with {pi}N,{eta}N,{pi}{pi}N,KY, {hor_ellipsis} final states is necessary for a reliable extraction of the N* parameters. To address this challenging issue, the Excited Baryon Analysis Center (EBAC) of Jefferson Lab has been conducting the comprehensive analysis of the world data of {gamma}N,{pi}N {yields} {pi}N,{eta}N,{pi}{pi}N,KY, {hor_ellipsis} reactions systematically, covering the wide energy and kinematic regions. The analysis is pursued with a dynamical coupled-channels (DCC) model, the EBAC-DCC model, within which the unitarity among relevant meson-baryon channels, including the three-body {pi}{pi}N channel, is fully taken into account.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Application of spatially resolved high resolution crystal spectrometry to inertial confinement fusion plasmas

High resolution ({lambda}/{Delta}{lambda}{approx} 10 000) 1D imaging x-ray spectroscopy using a spherically bent crystal and a 2D hybrid pixel array detector is used world wide for Doppler measurements of ion-temperature and plasma flow-velocity profiles in magnetic confinement fusion plasmas. Meter sized plasmas are diagnosed with cm spatial resolution and 10 ms time resolution. This concept can also be used as a diagnostic of small sources, such as inertial confinement fusion plasmas and targets on x-ray light source beam lines, with spatial resolution of micrometers, as demonstrated by laboratory experiments using a 250-{mu}m {sup 55}Fe source, and by ray-tracing calculations. Throughput calculations agree with measurements, and predict detector counts in the range 10{sup -8}-10{sup -6} times source x-rays, depending on crystal reflectivity and spectrometer geometry. Results of the lab demonstrations, application of the technique to the National Ignition Facility (NIF), and predictions of performance on NIF will be presented.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

Energy distribution measurement of narrow-band ultrashort x-ray beams via K-edge filters subtraction

The characterization of novel x-ray sources includes the measurement of the photon flux and the energy distribution of the produced beam. The aim of BEATS2 experiment at the SPARC-LAB facility of the INFN National Laboratories of Frascati (Rome, Italy) is to investigate possible medical applications of an x-ray source based on Thomson relativistic back-scattering. This source is expected to produce a pulsed quasi-monochromatic x-ray beam with an instantaneous flux of 10{sup 20} ph/s in pulses 10 ps long and with an average energy of about 20 keV. A direct measurement of energy distribution of this beam is very difficult with traditional detectors because of the extremely high photon flux. In this paper, we present a method for the evaluation of the energy distribution of quasi-monochromatic x-ray beams based on beam filtration with K-edge absorbing foils in the energy range of interest (16-22 keV). The technique was tested measuring the energy distribution of an x-ray beam having a spectrum similar to the expected one (SPARC-LAB Thomson source) by using a tungsten anode x-ray tube properly filtered and powered. The energy distribution obtained has been compared with the one measured with a HPGe detector showing very good agreement.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2013

Robofurnace: A semi-automated laboratory chemical vapor deposition system for high-throughput nanomaterial synthesis and process discovery

Laboratory research and development on new materials, such as nanostructured thin films, often utilizes manual equipment such as tube furnaces due to its relatively low cost and ease of setup. However, these systems can be prone to inconsistent outcomes due to variations in standard operating procedures and limitations in performance such as heating and cooling rates restrict the parameter space that can be explored. Perhaps more importantly, maximization of research throughput and the successful and efficient translation of materials processing knowledge to production-scale systems, relies on the attainment of consistent outcomes. In response to this need, we present a semi-automated lab-scale chemical vapor deposition (CVD) furnace system, called “Robofurnace.” Robofurnace is an automated CVD system built around a standard tube furnace, which automates sample insertion and removal and uses motion of the furnace to achieve rapid heating and cooling. The system has a 10-sample magazine and motorized transfer arm, which isolates the samples from the lab atmosphere and enables highly repeatable placement of the sample within the tube. The system is designed to enable continuous operation of the CVD reactor, with asynchronous loading/unloading of samples. To demonstrate its performance, Robofurnace is used to develop a rapid CVD recipe for carbon nanotube (CNT) forest growth, achieving a 10-fold improvement in CNT forest mass density compared to a benchmark recipe using a manual tube furnace. In the long run, multiple systems like Robofurnace may be linked to share data among laboratories by methods such as Twitter. Our hope is Robofurnace and like automation will enable machine learning to optimize and discover relationships in complex material synthesis processes.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Q{sub weak} experiment update and applications/opportunities at lower energies

The Q{sub weak} experiment has recently completed data-taking at Jefferson Lab. The primary focus of the experiment is to perform a precision measurement of the proton's neutral weak charge. The Standard Model gives a definite prediction for the weak charge. Any deviation from that can be interpreted as evidence for new physics beyond the Standard Model. This precision, low energy measurement is sensitive to new physics signatures at energy scales up to 2 TeV. The experiment measures the parity-violating asymmetry in the scattering of 1.165 GeV longitudinally polarized electrons on the proton at low momentum transfer (Q{sup 2} ∼ 0.025 (GeV/c){sup 2}). This paper provides a brief status report on the experiment with a focus on instrumentation and techniques that are applicable to lower beam energy realizations of parity-violating electron scattering measurements. Estimates of anticipated errors on the proton's weak charge expected if the Q{sub weak} apparatus were used at a lower beam energy are also discussed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Comparison of γZ-structure function models

The γZ-box is an important contribution to the proton's weak charge. The γZ-box is calculated dispersively and depends on γZ-structure functions, F{sub 1,2,3}{sup γZ}(x,Q{sup 2}). At present there is no data for these structure functions and they must be modeled by modifying existing fits to electromagnetic data. Each group that has studied the γZ-box used different modifications. The results of the PVDIS experiment at Jefferson Lab may provide a first test of the validity of each group's models. I present details of the different models and their predictions for the PVDIS result.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Experimental concept and design of DarkLight, a search for a heavy photon

This talk gives an overview of the DarkLight experimental concept: a search for a heavy photon A′ in the 10-90 MeV/c{sup 2} mass range. After briefly describing the theoretical motivation, the talk focuses on the experimental concept and design. Topics include operation using a half-megawatt, 100 MeV electron beam at the Jefferson Lab FEL, detector design and performance, and expected backgrounds estimated from beam tests and Monte Carlo simulations.

43 PARTICLE ACCELERATORS↗