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Title: Visible imaging and spectroscopy of disruption runaway electrons in DIII-D

Abstract

The first visible light images of synchrotron emission from disruption runaway electrons are presented. The forward-detected continuum radiation from runaways is identified as synchrotron emission by comparing two survey spectrometers and two visible fast cameras viewing in opposite toroidal directions. Analysis of the elongation of 2D synchrotron images of oval-shaped runaway beams indicates that the velocity pitch angle v{sub Up-Tack }/v{sub ||} ranges from 0.1 to 0.2 for the detected electrons, with energies above 25 MeV. Analysis of synchrotron intensity from a camera indicates that the tail of the runaway energy distribution reaches energies up to 60 MeV, which agrees with 0D modeling of electron acceleration in the toroidal electric field generated during the current quench. A visible spectrometer provides an independent estimate of the upper limit of runaway electron energy which is roughly consistent with energy determined from camera data. Synchrotron spectra reveal that approximately 1% of the total post-thermal quench plasma current is carried by the detected high-energy runaway population with energies in the range of 25-60 MeV; the bulk of the plasma current thus appears to be carried by relativistic electrons with energy less than 25 MeV. In addition to stable oval shapes, runaway beams with othermore » shapes and internal structure are sometimes observed.« less

Authors:
; ;  [1]; ;  [2]; ;  [3];  [4]
  1. University of California, San Diego, La Jolla, California 92093-0417 (United States)
  2. Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831 (United States)
  3. General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States)
  4. Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550 (United States)
Publication Date:
OSTI Identifier:
22130424
Resource Type:
Journal Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 20; Journal Issue: 4; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1070-664X
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; APPROXIMATIONS; BEAM-PLASMA SYSTEMS; CAMERAS; COMPARATIVE EVALUATIONS; ELECTRIC FIELDS; ELECTRON BEAMS; ELECTRON DETECTION; ELONGATION; IMAGES; MEV RANGE 10-100; PLASMA CONFINEMENT; PLASMA DIAGNOSTICS; RELATIVISTIC RANGE; RUNAWAY ELECTRONS; SPECTROMETERS; SPECTROSCOPY; SYNCHROTRON RADIATION; SYNCHROTRONS; TOKAMAK DEVICES; VISIBLE SPECTRA

Citation Formats

Yu, J. H., Hollmann, E. M., Moyer, R. A., Commaux, N., Jernigan, T. C., Eidietis, N. W., Humphreys, D. A., and James, A. N. Visible imaging and spectroscopy of disruption runaway electrons in DIII-D. United States: N. p., 2013. Web. doi:10.1063/1.4801738.
Yu, J. H., Hollmann, E. M., Moyer, R. A., Commaux, N., Jernigan, T. C., Eidietis, N. W., Humphreys, D. A., & James, A. N. Visible imaging and spectroscopy of disruption runaway electrons in DIII-D. United States. https://doi.org/10.1063/1.4801738
Yu, J. H., Hollmann, E. M., Moyer, R. A., Commaux, N., Jernigan, T. C., Eidietis, N. W., Humphreys, D. A., and James, A. N. 2013. "Visible imaging and spectroscopy of disruption runaway electrons in DIII-D". United States. https://doi.org/10.1063/1.4801738.
@article{osti_22130424,
title = {Visible imaging and spectroscopy of disruption runaway electrons in DIII-D},
author = {Yu, J. H. and Hollmann, E. M. and Moyer, R. A. and Commaux, N. and Jernigan, T. C. and Eidietis, N. W. and Humphreys, D. A. and James, A. N.},
abstractNote = {The first visible light images of synchrotron emission from disruption runaway electrons are presented. The forward-detected continuum radiation from runaways is identified as synchrotron emission by comparing two survey spectrometers and two visible fast cameras viewing in opposite toroidal directions. Analysis of the elongation of 2D synchrotron images of oval-shaped runaway beams indicates that the velocity pitch angle v{sub Up-Tack }/v{sub ||} ranges from 0.1 to 0.2 for the detected electrons, with energies above 25 MeV. Analysis of synchrotron intensity from a camera indicates that the tail of the runaway energy distribution reaches energies up to 60 MeV, which agrees with 0D modeling of electron acceleration in the toroidal electric field generated during the current quench. A visible spectrometer provides an independent estimate of the upper limit of runaway electron energy which is roughly consistent with energy determined from camera data. Synchrotron spectra reveal that approximately 1% of the total post-thermal quench plasma current is carried by the detected high-energy runaway population with energies in the range of 25-60 MeV; the bulk of the plasma current thus appears to be carried by relativistic electrons with energy less than 25 MeV. In addition to stable oval shapes, runaway beams with other shapes and internal structure are sometimes observed.},
doi = {10.1063/1.4801738},
url = {https://www.osti.gov/biblio/22130424}, journal = {Physics of Plasmas},
issn = {1070-664X},
number = 4,
volume = 20,
place = {United States},
year = {Mon Apr 15 00:00:00 EDT 2013},
month = {Mon Apr 15 00:00:00 EDT 2013}
}