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Title: Positron Production by X Rays Emitted By Betatron Motion in a Plasma Wiggler

Abstract

Positrons in the energy range of 3-30 MeV, produced by x rays emitted by betatron motion in a plasma wiggler of 28.5 GeV electrons from the SLAC accelerator, have been measured. The extremely high-strength plasma wiggler is an ion column induced by the electron beam as it propagates through and ionizes dense lithium vapor. X rays in the range of 1-50 MeV in a forward cone angle of 0.1 mrad collide with a 1.7 mm thick tungsten target to produce electron-positron pairs. The positron spectra are found to be strongly influenced by the plasma density and length as well as the electron bunch length. By characterizing the beam propagation in the ion column these influences are quantified and result in excellent agreement between the measured and calculated positron spectra.

Authors:
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Publication Date:
Research Org.:
Stanford Linear Accelerator Center (SLAC)
Sponsoring Org.:
USDOE
OSTI Identifier:
898155
Report Number(s):
SLAC-PUB-12322
TRN: US200706%%403
DOE Contract Number:
AC02-76SF00515
Resource Type:
Journal Article
Resource Relation:
Journal Name: Phys.Rev.Lett.97:175003,2006
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; BETATRONS; CONES; ELECTRON BEAMS; ELECTRONS; ENERGY RANGE; LITHIUM; PLASMA; PLASMA DENSITY; POSITRONS; PRODUCTION; SPECTRA; STANFORD LINEAR ACCELERATOR CENTER; TARGETS; TUNGSTEN; Accelerators,ACCPHY

Citation Formats

Johnson, D.K., Auerbach, D., Blumenfeld, I., Barnes, C.D., Clayton, C.E., Decker, F.J., Deng, S., Emma, P., Hogan, M.J., Huang, C., Ischebeck, R., Iverson, R., Joshi, C., Katsouleas, T.C., Kirby, N., Krejcik, P., Lu, W., Marsh, K.A., Mori, W.B., Muggli, P., O'Connell, C.L., and /UCLA /SLAC /Southern California U. Positron Production by X Rays Emitted By Betatron Motion in a Plasma Wiggler. United States: N. p., 2007. Web.
Johnson, D.K., Auerbach, D., Blumenfeld, I., Barnes, C.D., Clayton, C.E., Decker, F.J., Deng, S., Emma, P., Hogan, M.J., Huang, C., Ischebeck, R., Iverson, R., Joshi, C., Katsouleas, T.C., Kirby, N., Krejcik, P., Lu, W., Marsh, K.A., Mori, W.B., Muggli, P., O'Connell, C.L., & /UCLA /SLAC /Southern California U. Positron Production by X Rays Emitted By Betatron Motion in a Plasma Wiggler. United States.
Johnson, D.K., Auerbach, D., Blumenfeld, I., Barnes, C.D., Clayton, C.E., Decker, F.J., Deng, S., Emma, P., Hogan, M.J., Huang, C., Ischebeck, R., Iverson, R., Joshi, C., Katsouleas, T.C., Kirby, N., Krejcik, P., Lu, W., Marsh, K.A., Mori, W.B., Muggli, P., O'Connell, C.L., and /UCLA /SLAC /Southern California U. Thu . "Positron Production by X Rays Emitted By Betatron Motion in a Plasma Wiggler". United States. doi:. https://www.osti.gov/servlets/purl/898155.
@article{osti_898155,
title = {Positron Production by X Rays Emitted By Betatron Motion in a Plasma Wiggler},
author = {Johnson, D.K. and Auerbach, D. and Blumenfeld, I. and Barnes, C.D. and Clayton, C.E. and Decker, F.J. and Deng, S. and Emma, P. and Hogan, M.J. and Huang, C. and Ischebeck, R. and Iverson, R. and Joshi, C. and Katsouleas, T.C. and Kirby, N. and Krejcik, P. and Lu, W. and Marsh, K.A. and Mori, W.B. and Muggli, P. and O'Connell, C.L. and /UCLA /SLAC /Southern California U.},
abstractNote = {Positrons in the energy range of 3-30 MeV, produced by x rays emitted by betatron motion in a plasma wiggler of 28.5 GeV electrons from the SLAC accelerator, have been measured. The extremely high-strength plasma wiggler is an ion column induced by the electron beam as it propagates through and ionizes dense lithium vapor. X rays in the range of 1-50 MeV in a forward cone angle of 0.1 mrad collide with a 1.7 mm thick tungsten target to produce electron-positron pairs. The positron spectra are found to be strongly influenced by the plasma density and length as well as the electron bunch length. By characterizing the beam propagation in the ion column these influences are quantified and result in excellent agreement between the measured and calculated positron spectra.},
doi = {},
journal = {Phys.Rev.Lett.97:175003,2006},
number = ,
volume = ,
place = {United States},
year = {Thu Jan 25 00:00:00 EST 2007},
month = {Thu Jan 25 00:00:00 EST 2007}
}
  • Positrons in the energy range of 3-30 MeV, produced by x rays emitted by betatron motion in a plasma wiggler of 28.5 GeV electrons from the SLAC accelerator, have been measured. The extremely high-strength plasma wiggler is an ion column induced by the electron beam as it propagates through and ionizes dense lithium vapor. X rays in the range of 1-50 MeV in a forward cone angle of 0.1 mrad collide with a 1.7 mm thick tungsten target to produce electron-positron pairs. The positron spectra are found to be strongly influenced by the plasma density and length as well asmore » the electron bunch length. By characterizing the beam propagation in the ion column these influences are quantified and result in excellent agreement between the measured and calculated positron spectra.« less
  • In the E-167 plasma wakefield accelerator (PWFA) experiments in the Final Focus Test Beam (FFTB) at the Stanford Linear Accelerator Center (SLAC), an ultra-short, 28.5 GeV electron beam field ionizes a neutral column of Lithium vapor. In the underdense regime, all plasma electrons are expelled creating an ion column. The beam electrons undergo multiple betatron oscillations leading to a large flux of broadband synchrotron radiation. With a plasma density of 3 x 10{sup 17}cm{sup -3}, the effective focusing gradient is near 9 MT/m with critical photon energies exceeding 50 MeV for on-axis radiation. A positron source is the initial applicationmore » being explored for these X-rays, as photo-production of positrons eliminates many of the thermal stress and shock wave issues associated with traditional Bremsstrahlung sources. Photo-production of positrons has been well-studied; however, the brightness of plasma X-ray sources provides certain advantages. In this paper, we present results of the simulated radiation spectra for the E-167 experiments, and compute the expected positron yield.« less
  • The successful utilization of an ion channel in a plasma to wiggle a 28.5 GeV electron beam to obtain broad band X-ray radiation is reported. The ion channel is induced by the electron bunch as it propagates through an under-dense 1.4 meter long lithium plasma. The quadratic density dependence of the spontaneously emitted betatron X-ray radiation and the divergence angle of (1 {approx} 3) x 10{sup -4} radian of the forward emitted X-rays as a consequence of betatron motion in the ion channel are in good agreement with theory. The absolute photon yield and the peak spectral brightness at 1.42more » KeV photon energy are estimated.« less
  • A novel multipole wiggler and an associated beam line have been installedin the accumulation ring for the TRISTAN project at the National Laboratory forHigh Energy Physics (KEK). An intense source of circularly polarizedsynchrotron radiation in the energy ranging 40 to 80 keV has been achieved forthe first time. A degree of circular polarization, /ital P//sub /ital c///congruent/0.7,at 60 keV of photon energy was in good agreement with a theoretical predictionin the 6-GeV operation of the accumulation ring.
  • We have compared the circularly polarized x-ray flux obtained from an elliptical multipole wiggler to that obtained from a planar undulator combined with phase retarding crystal optics. This comparison is carried out for low (3.5{endash}13 keV) and high (50{endash}100 keV) x-ray energies. For both these energy regimes, we demonstrate that phase retarding crystal optics are not only a viable alternative to specialized insertion devices but in some cases provide a superior source of circularly polarized x rays. {copyright} {ital 1996 American Institute of Physics.}