Initial operation of the divertor Thompson scattering diagnostic on DIII-D

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The first Thomson scattering measurements of n{sub e} and T{sub e} in the divertor region of a tokamak are reported. These data are used as input to boundary physics codes such as UEDGE and DEGAS and to benchmark the predictive capabilities of these codes. These measurements have also contributed to the characterization of tokamak disruptions. A Nd:YAG laser (20 Hz, 1 J, 15 ns, 1064 nm) is directed vertically through the lower divertor region of the DIII-D tokamak. A custom, aspherical collection lens (f /6.8) images the laser beam from 1-21 cm above the target plates into eight spatial channels ... continued below

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30 p.

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Carlstrom, T. N.; Hsieh, C.L. & Stockdale, R. E. May 1996.

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  • General Atomic Company
    Publisher Info: General Atomics, San Diego, CA (United States). Systems Integration Div.
    Place of Publication: San Diego, California

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The first Thomson scattering measurements of n{sub e} and T{sub e} in the divertor region of a tokamak are reported. These data are used as input to boundary physics codes such as UEDGE and DEGAS and to benchmark the predictive capabilities of these codes. These measurements have also contributed to the characterization of tokamak disruptions. A Nd:YAG laser (20 Hz, 1 J, 15 ns, 1064 nm) is directed vertically through the lower divertor region of the DIII-D tokamak. A custom, aspherical collection lens (f /6.8) images the laser beam from 1-21 cm above the target plates into eight spatial channels with 1.5 cm vertical and 0.3 cm radial resolution. 2D mapping of the divertor region is achieved by sweeping the divertor X-point location radially through the fixed laser beam location. Fiber optics carry the light to polychromators whose interference filters have been optimized for low T{sub e} measurements. Silicon avalanche photo diodes measure both the scattered and plasma background light. Temperatures and densities are typically in the range of 5-200 eV and 1 - 10 x 10{sup 19} m{sup -3} respectively. Low temperatures, T{sub e} < 1 eV, and high densities, n{sub e} > 8x10{sup 20} m{sup -3} have been observed in detached plasmas. Background light levels have not been a significant problem. Reduction of the laser stray light permits Rayleigh calibration. Because of access difficulties, no in-vessel vacuum alignment target could be used. Instead, an in situ laser alignment monitor provides alignment information for each laser pulse. Results are compared with Langmuir probe measurements where good agreement is found except for regions of high n{sub e} and low T{sub e} as measured by Thomson scattering.

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30 p.

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OSTI as DE97001823

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  • 11. annual high-temperature plasma diagnostics conference, Monterey, CA (United States), 12-16 May 1996

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  • Other: DE97001823
  • Report No.: GA-A--22337
  • Report No.: CONF-960543--40
  • Grant Number: AC03-89ER51114
  • Office of Scientific & Technical Information Report Number: 420389
  • Archival Resource Key: ark:/67531/metadc676817

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  • May 1996

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  • July 25, 2015, 2:20 a.m.

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  • April 18, 2016, 3:44 p.m.

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Carlstrom, T. N.; Hsieh, C.L. & Stockdale, R. E. Initial operation of the divertor Thompson scattering diagnostic on DIII-D, article, May 1996; San Diego, California. (digital.library.unt.edu/ark:/67531/metadc676817/: accessed August 16, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.