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Title: Synthetic diagnostic for assessing spatial averaging of charge exchange recombination spectroscopy measurements

Abstract

A synthetic charge exchange recombination spectroscopy diagnostic based on the FIDASIM modeling suite has been created for the DIII-D tokamak. This synthetic diagnostic assumes that the ions have Maxwellian distribution functions on each flux surface and models emission from charge exchange events between the beam neutrals and a fully ionized impurity. This work was motivated by the observation of non-Gaussian spectra that may be caused by spatial averaging, atomic physics, or non-Maxwellian distribution functions. Measurements of non-Gaussian spectra commonly observed in the high confinement mode pedestal and in plasmas with large core gradients are compared to the synthetic diagnostic. Spatial averaging alone cannot account for the observations in these two cases, opening up the possibility of there being other causes such as non-Maxwellian distribution functions. Here, the synthetic diagnostic has also been used to resolve a long-standing issue: it is shown that the lower temperatures measured by using vertical view chords relative to tangential view chords are due to increased spatial averaging for vertical views due to the DIII-D neutral beams being approximately twice as tall as they are wide.

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [3]; ORCiD logo [1];  [3]
  1. General Atomics, San Diego, CA (United States)
  2. Univ. of California, Davis, CA (United States)
  3. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Publication Date:
Research Org.:
General Atomics, San Diego, CA (United States); Princeton Univ., NJ (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
OSTI Identifier:
1609187
Alternate Identifier(s):
OSTI ID: 1459475
Grant/Contract Number:  
FC02-04ER54698; AC02-09CH11466
Resource Type:
Accepted Manuscript
Journal Name:
Review of Scientific Instruments
Additional Journal Information:
Journal Volume: 89; Journal Issue: 10; Journal ID: ISSN 0034-6748
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; instruments & instrumentation; physics

Citation Formats

Chrystal, C., Sulyman, A. A., Haskey, S. R., Burrell, K. H., and Grierson, B. A. Synthetic diagnostic for assessing spatial averaging of charge exchange recombination spectroscopy measurements. United States: N. p., 2018. Web. doi:10.1063/1.5036964.
Chrystal, C., Sulyman, A. A., Haskey, S. R., Burrell, K. H., & Grierson, B. A. Synthetic diagnostic for assessing spatial averaging of charge exchange recombination spectroscopy measurements. United States. doi:10.1063/1.5036964.
Chrystal, C., Sulyman, A. A., Haskey, S. R., Burrell, K. H., and Grierson, B. A. Mon . "Synthetic diagnostic for assessing spatial averaging of charge exchange recombination spectroscopy measurements". United States. doi:10.1063/1.5036964. https://www.osti.gov/servlets/purl/1609187.
@article{osti_1609187,
title = {Synthetic diagnostic for assessing spatial averaging of charge exchange recombination spectroscopy measurements},
author = {Chrystal, C. and Sulyman, A. A. and Haskey, S. R. and Burrell, K. H. and Grierson, B. A.},
abstractNote = {A synthetic charge exchange recombination spectroscopy diagnostic based on the FIDASIM modeling suite has been created for the DIII-D tokamak. This synthetic diagnostic assumes that the ions have Maxwellian distribution functions on each flux surface and models emission from charge exchange events between the beam neutrals and a fully ionized impurity. This work was motivated by the observation of non-Gaussian spectra that may be caused by spatial averaging, atomic physics, or non-Maxwellian distribution functions. Measurements of non-Gaussian spectra commonly observed in the high confinement mode pedestal and in plasmas with large core gradients are compared to the synthetic diagnostic. Spatial averaging alone cannot account for the observations in these two cases, opening up the possibility of there being other causes such as non-Maxwellian distribution functions. Here, the synthetic diagnostic has also been used to resolve a long-standing issue: it is shown that the lower temperatures measured by using vertical view chords relative to tangential view chords are due to increased spatial averaging for vertical views due to the DIII-D neutral beams being approximately twice as tall as they are wide.},
doi = {10.1063/1.5036964},
journal = {Review of Scientific Instruments},
number = 10,
volume = 89,
place = {United States},
year = {2018},
month = {7}
}

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