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Title: Laser Electron Gamma Source. Biennial progress report

Abstract

The LEGS facility provides intense, polarized, monochromatic {gamma}-ray beams by Compton backscattering laser light from relativistic electrons circulating in the X-Ray storage ring of the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory. With the start of ring operations at 2.8 GeV, LEGS {gamma}-ray energies now extend to 370 MeV. Considerable progress has been made in the development of a new laser system that will increase the beam energies to 470 MeV, and this system is expected to come into operation before the next biennial report. The total flux is administratively held at 6 {times} 10{sup 6} s{sup {minus}1}. The {gamma}-ray energy is determined, with a resolution of 5.5 MeV, by detecting the scattering electrons in a magnetic spectrometer. This spectrometer can `tag` all {gamma}-rays with energies from 185 MeV up to the Compton edge. The beam spot size at the target position is 8 mm (V) {times} 18 mm (H), FWHM. For a single laser wavelength, the linear polarization of the beam is 98% at the Compton edge and decreases to 50% at about 1/2 the energy of the edge. By choosing the laser wavelengths appropriately the polarization can be maintained above 85% throughout the tagging range. Duringmore » the last two years, experimental running at LEGS occupied an average of 3000 hours annually. Highlights of some of the programs are discussed below.« less

Authors:
 [1]; ; ; ; ; ;  [2];  [3];  [4]
  1. ed.
  2. Brookhaven National Lab., Upton, NY (United States)
  3. Univ. of Virginia, Charlottesville, VA (United States). Dept. of Physics
  4. Brookhaven National Lab., Upton, NY (United States)|[Virginia Polytechnic Institute & State Univ., Blacksburg, VA (United States). Dept. of Physics
Publication Date:
Research Org.:
Brookhaven National Lab., Upton, NY (United States)
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
10179224
Report Number(s):
BNL-60698
ON: DE94017815; TRN: 94:016725
DOE Contract Number:
AC02-76CH00016
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: Jun 1994
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; GAMMA SOURCES; POLARIZATION; RADIATION FLUX; PROGRESS REPORT; NSLS; LASER RADIATION; COMPTON EFFECT; 430303; EXPERIMENTAL FACILITIES AND EQUIPMENT

Citation Formats

Sandorfi, A.M., Caracappa, A., Kuczewski, A., Kistner, O.C., Lincoln, F., Miceli, L., Thorn, C.E., Hoblit, S., and Khandaker, M.. Laser Electron Gamma Source. Biennial progress report. United States: N. p., 1994. Web. doi:10.2172/10179224.
Sandorfi, A.M., Caracappa, A., Kuczewski, A., Kistner, O.C., Lincoln, F., Miceli, L., Thorn, C.E., Hoblit, S., & Khandaker, M.. Laser Electron Gamma Source. Biennial progress report. United States. doi:10.2172/10179224.
Sandorfi, A.M., Caracappa, A., Kuczewski, A., Kistner, O.C., Lincoln, F., Miceli, L., Thorn, C.E., Hoblit, S., and Khandaker, M.. Wed . "Laser Electron Gamma Source. Biennial progress report". United States. doi:10.2172/10179224. https://www.osti.gov/servlets/purl/10179224.
@article{osti_10179224,
title = {Laser Electron Gamma Source. Biennial progress report},
author = {Sandorfi, A.M. and Caracappa, A. and Kuczewski, A. and Kistner, O.C. and Lincoln, F. and Miceli, L. and Thorn, C.E. and Hoblit, S. and Khandaker, M.},
abstractNote = {The LEGS facility provides intense, polarized, monochromatic {gamma}-ray beams by Compton backscattering laser light from relativistic electrons circulating in the X-Ray storage ring of the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory. With the start of ring operations at 2.8 GeV, LEGS {gamma}-ray energies now extend to 370 MeV. Considerable progress has been made in the development of a new laser system that will increase the beam energies to 470 MeV, and this system is expected to come into operation before the next biennial report. The total flux is administratively held at 6 {times} 10{sup 6} s{sup {minus}1}. The {gamma}-ray energy is determined, with a resolution of 5.5 MeV, by detecting the scattering electrons in a magnetic spectrometer. This spectrometer can `tag` all {gamma}-rays with energies from 185 MeV up to the Compton edge. The beam spot size at the target position is 8 mm (V) {times} 18 mm (H), FWHM. For a single laser wavelength, the linear polarization of the beam is 98% at the Compton edge and decreases to 50% at about 1/2 the energy of the edge. By choosing the laser wavelengths appropriately the polarization can be maintained above 85% throughout the tagging range. During the last two years, experimental running at LEGS occupied an average of 3000 hours annually. Highlights of some of the programs are discussed below.},
doi = {10.2172/10179224},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Jun 01 00:00:00 EDT 1994},
month = {Wed Jun 01 00:00:00 EDT 1994}
}

Technical Report:

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  • The LEGS facility provides intense, polarized, monochromatic {gamma}-ray beams by Compton backscattering laser light from relativistic electrons circulating in the X-Ray storage ring of the National Synchrotron Light Source at Brookhaven national Laboratory. Since 1990, experiments have concentrated on single polarization observables (polarized beams on unpolarized targets) in nuclear reactions involving the {Delta} resonance. Highlights of the last two years are given. An updated status of LEGS, and recent publications, is available on the WWW via http://WWW.LEGS.BNL.GOV/{approximately}LEGS/. In 1997 a new phase of operations will begin, focusing on double-polarization measurements with circularly polarized photon beams and longitudinally polarized nucleon targets.more » This work requires the development of (i) a new frozen-spin hydrogen-deuteride target that provides high polarizations for both nuclear species, and (ii) a new large acceptance detector array for measuring total reaction cross sections in both neutral and charged-particle channels. Progress on these instrumentation developments is an ongoing effort of the LEGS Spin Collaboration (LSC) and is discussed in the last section of this report.« less
  • This report briefly discusses the Laser Electron Gamma Source facility and the following experiments conducted here: polarization in D(gamma, p)n and N-N tensor forces for energies less than 225 Mev; constraints on the nuclear tensor force from D(gamma, p)n for energies less than 315 Mev; the p(gamma, neutral pion) reaction and the E2 excitation of delta resonance; quasi-two- and three-body absorption in helium 3(gamma, N-N); and the delta-nucleon interaction in D(gamma,p-negative pion)p and D(gamma, p-n)neutral pions. (LSP).
  • This report briefly discusses the Laser Electron Gamma Source facility and the following experiments conducted here: polarization in D(gamma, p)n and N-N tensor forces for energies less than 225 Mev; constraints on the nuclear tensor force from D(gamma, p)n for energies less than 315 Mev; the p(gamma, neutral pion) reaction and the E2 excitation of delta resonance; quasi-two- and three-body absorption in helium 3(gamma, N-N); and the delta-nucleon interaction in D(gamma,p-negative pion)p and D(gamma, p-n)neutral pions. (LSP).
  • When completed, the Laser Electron Gamma Source (LEGS) is expected to provide intense beams of monochromatic and polarized (circular or linear) gamma rays with energies up to 500 MeV. The gamma-ray beams will be produced by Compton backscattering uv laser light from the electrons circulating in a storage ring. Progress with installation of the facility is described, particularly the Ar-ion laser and tagging spectrometer. Tests of the tagging spectrometer coponents is reported, and a second laser is described for higher energy operation. Estimates are given of expected beam parameters. Experimental equipment for the planned research projects to be carried outmore » at the LEGS facility is discussed. (LEW)« less
  • Recent approaches to the problem of the gamma-ray laser have focused upon upconversion techniques in which metastable nuclei are pumped with long-wavelength radiation. At the nuclear level the storage of energy can approach tera-Joules (10/sup 12/ J) per liter for thousands of years. However, any plan to use such a resource for a gamma-ray laser poses problems of a broad interdisciplinary nature requiring the fusion of concepts taken from relatively unrelated fields of physics. Since 1978, the Center has pursued an approach for the upconversion of longer-wavelength radiation incident upon isomeric nuclear populations that can avoid many of the difficultiesmore » encountered with traditional concepts of single-photon pumping. Recent experiments have confirmed the general feasibility and have indicated that a gamma-ray laser is feasible if the right combination of energy levels and branching ratios exists in some real material. Resolution of the question of the feasibility of a gamma-ray laser now rests upon the determination of: 1) the identity of the best candidate, 2) the threshold level of laser output, and 3) the upconversion driver for that material.« less