Showing papers by "W. Meyer published in 1995"
Tohoku University1, Stanford University2, University of Pennsylvania3, American University4, University of Virginia5, University of Wisconsin-Madison6, University of Massachusetts Amherst7, DSM8, University of Michigan9, Lawrence Livermore National Laboratory10, University of Basel11, Naval Postgraduate School12, Thomas Jefferson National Accelerator Facility13, University of Liverpool14, College of William & Mary15, Old Dominion University16, Temple University17, University of Bonn18, Kent State University19, CERN20
TL;DR: In this article, the authors measured the ratio [ital g][sup [ital p]][sub 1]/[ital F][sup[ital p]-sub 1]-over the range 0.8 and 1.10 using deep-inelastic scattering of polarized electrons from polarized ammonia.
Abstract: We have measured the ratio [ital g][sup [ital p]][sub 1]/[ital F][sup [ital p]][sub 1] over the range 0.029[lt][ital x][lt]0.8 and 1.3[lt][ital Q][sup 2][lt]10 (GeV/[ital c])[sup 2] using deep-inelastic scattering of polarized electrons from polarized ammonia. An evaluation of the integral [integral][ital g][sup [ital p]][sub 1]([ital x],[ital Q][sup 2])[ital dx] at fixed [ital Q][sup 2]=3 (GeV/[ital c])[sup 2] yields 0.127[plus minus]0.004(stat)[plus minus]0.010(syst), in agreement with previous experiments, but well below the Ellis-Jaffe sum rule prediction of 0.160[plus minus]0.006. In the quark-parton model, this implies [Delta][ital q]=0.27[plus minus]0.10.
236 citations
Tohoku University1, Stanford University2, University of Pennsylvania3, American University4, University of Virginia5, University of Wisconsin-Madison6, University of Massachusetts Amherst7, University of Auvergne8, Thomas Jefferson National Accelerator Facility9, University of Michigan10, Lawrence Livermore National Laboratory11, University of Basel12, Naval Postgraduate School13, Old Dominion University14, Temple University15
TL;DR: This work was supported by Department of Energy Contracts No.
Abstract: This work was supported by Department of Energy Contracts No. DE-AC05-84ER40150 (CEBAF), No. W-2795-Eng-48 (LLNL), No. DE-AC0376SF00515 (SLAC), No. DE-FG03-88ER40439 (Stanford), No. DE-FG05-88ER40390 and No. DEFG05-86ER4026 (Virginia), and No. DE-AC02-76ER00881 (Wisconsin); by National Science Foundation Grants No. 9114958 (American), No. 9307710 (Massachusetts), No. 9217979 (Michigan), No. 9104975 (ODU) and No. 9118137 (U. Penn.); by the Schweizersche Nationalfonds (Basel); by the Commonwealth of Virginia (Virginia); by the Centre NAtional de la Recherche Scientifique and the Commissariat a l'Energie Atomique (French groups); and by the Japanese Ministry of Education, Science and Culture (Tohoku).
164 citations
Tohoku University1, Stanford University2, University of Pennsylvania3, American University4, University of Virginia5, University of Wisconsin-Madison6, University of Massachusetts Amherst7, University of Auvergne8, University of Michigan9, Lawrence Livermore National Laboratory10, University of Basel11, Naval Postgraduate School12, Thomas Jefferson National Accelerator Facility13, Old Dominion University14, Temple University15
64 citations
01 Mar 1995-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this paper, the most important paramagnetic defect, the so-called F-center, created during these irradiations has been studied in a conventional EPR spectrometer at liquid nitrogen temperature.
Abstract: Samples of 7LiH, 6LiD, 6LiH have been irradiated at the Bonn 20 MeV electron preaccelerator under various temperatures and with different radiation doses. The most important paramagnetic defect, the so-called F-center, created during these irradiations has been studied in a conventional EPR spectrometer at liquid nitrogen temperature. Also several samples have been dynamically polarized in both a 4He evaporation cryostat (1 K) and in a 3He4He dilution refrigerator (200 mK) at a magnetic field of 2.5 and 5 T. Finally some selected samples have been exposed to an intense (up to 70 nA) and high energy (1.2 GeV) electron beam at the Bonn Electron Stretcher and Accelerator ELSA.
17 citations
TL;DR: The total cross section for {gamma}{ital p} near threshold has been measured using the PHOENICS tagging system at the ELSA electron facility of the Physikalisches Institut der Universitaet Bonn, and in the energy region the production cross section is consistent with {ital S}-wave production.
Abstract: The total cross section for {gamma}{ital p}{r_arrow}{eta}{ital p} near threshold has been measured using the PHOENICS tagging system at the ELSA electron facility of the Physikalisches Institut der Universitaet Bonn. The photons are created by bremsstrahlung, and are tagged by measuring the momentum of each electron after the photon has been emitted. The recoil proton from {gamma}{ital p}{r_arrow}{eta}{ital p} is detected by the AMADEUS counter setup in coincidence with the tagging system. Data were taken with AMADEUS at 3.3{degree} in the laboratory, where the large Jacobian increases our event rate so that we obtain the cross section from threshold ({ital E}{sub {gamma}}=707.2 MeV) to {ital E}{sub {gamma}}{congruent}720 MeV with adequate statistics. The {gamma}{ital p}{r_arrow}{eta}{ital p} events are identified by kinematics, {ital dE}/{ital dx}, and timing information. We find that in our energy region the production cross section is consistent with {ital S}-wave production.
16 citations
01 Mar 1995-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: A large-scale high-pressure gaseous 3 He polarized target has been developed for use with a high-intensity polarized electron beam at the Stanford Linear Accelerator Center as discussed by the authors, which was used successfully in an experiment to study the spin structure of the neutron.
Abstract: A large-scale high-pressure gaseous 3 He polarized target has been developed for use with a high-intensity polarized electron beam at the Stanford Linear Accelerator Center. This target was used successfully in an experiment to study the spin structure of the neutron. The target provided an areal density of about 7 × 10 21 nuclei/cm 2 and operated at 3 He polarizations between about 30% and 40% for the six-week duration of the experiment.
16 citations
01 Mar 1995-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this article, a superconducting holding magnet, placed inside a polarizing refrigerator, has been developed for the measurement of the Gerasimov-Drell-Hearn sum rule with polarized real photons at the Mainz microtron MAMI and the Bonn electron stretcher accelerator ELSA.
Abstract: A new concept of a small superconducting holding magnet, placed inside a polarizing refrigerator, has been developed for frozen spin targets. The superconducting wire has been wound on the inner cooling shield of the vertical dilution refrigerator of the Bonn frozen spin target. The maximum field of the magnet is 0.35 T. The total thickness of the superconducting coil consisting of the wire and the copper carrier is of the order of 500 μm. Based on this concept, a frozen spin target is under construction for the measurement of the Gerasimov-Drell-Hearn sum rule with polarized real photons at the Mainz microtron MAMI and the Bonn electron stretcher accelerator ELSA.
15 citations
01 Mar 1995-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: The Bonn frozen spin target is used for meson photoproduction experiments in combination with the facility PHOENICS at ELSA as mentioned in this paper, where the maximum polarization field of 7 T is provided by a superconducting solenoid.
Abstract: The Bonn frozen spin target is used for meson photoproduction experiments in combination with the facility PHOENICS at ELSA. The maximum polarization field of 7 T is provided by a superconducting solenoid. For electron scattering experiments a target apparatus which uses a superconducting 4 T magnet in a Helmholtz configuration is employed. For dynamic nuclear polarization of protons or deuterons various microwaves sources with frequencies of 70 GHz, 98 GHz or 140 GHz are available. Ammonia, butanol and lithium hydrids are used as target materials. The main part of the polarization detection system is the so-called Liverpool nuclear magnetic resonance module, which ensures a high flexibility for the polarization measurements of different nuclear species, e.g. 15 N at 2.5 T ( f L =10.8 MHz) and protons at 50 T ( f L =213 MHz).
10 citations
01 Mar 1995-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this paper, the local depolarization of the target material 14 NH 3 at the electron beam spot has been investigated by hitting it with 1.2 GeV electrons from the electron stretcher accelerator ELSA of the Bonn University.
Abstract: Polarized target experiments with intense particle beams suffer from the depolarization effects due to radiation damage and beam heating. The local depolarization of the target material 14 NH 3 at the electron beam spot has been investigated by hitting it with 1.2 GeV electrons. This beam has been delivered from the electron stretcher accelerator ELSA of the Bonn University. The polarized target consists of a 4 T superconducting magnet with a Helmholtz configuration and a 4 He evaporation cryostat which operates at a temperature around 1 K. The heating of the target chips by the electron beam has been measured up to an intensity of 70 nA using a specific set-up of the nuclear magnetic resonance apparatus for the polarization measurements.
3 citations
Journal Article•
TL;DR: A large-scale high-pressure gaseous 3 He polarized target has been developed for use with a high-intensity polarized electron beam at the Stanford Linear Accelerator Center as mentioned in this paper, which was used successfully in an experiment to study the spin structure of the neutron.
1 citations