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Abstract: PSFC/JA-00-23
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High Resolution Edge Thomson Scattering Measurements on
the Alcator C-Mod Tokamak
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J. W. Hughes, D. A. Mossessian, A. E. Hubbard, E. S. Marmar, D. Johnson*,
D. Simon*
*Plasma Physics Laboratory, Princeton University, Princeton,
NJ 08544
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A high resolution Thomson scattering diagnostic is in operation on
the Alcator C-Mod tokamak, measuring radial profiles of electron temperature
and density at the plasma edge. Photons are scattered from an Nd-YAG laser
beam pulsed at 30 Hz (1.3-J, 8-ns pulse), and are measured by a filter
polychromator with four spectral channels. The polychromator measures Te
in the range of 15-800 eV and ne of 0.3-3x1020 m-3.
Twenty scattering volumes are located about the last closed flux surface,
spaced for a nominal resolution of 1.3 mm in midplane radial coordinates.
High resolution is essential for measuring edge Te and ne
profiles on C-Mod, since these quantities exhibit gradient scale lengths
as small as 2 mm in H-mode. The steep profiles at the H-mode
edge are fit to a parameterized pedestal function for ease of analysis.
Measured profiles are compared with edge profiles from electron cyclotron
emission and visible continuum diagnostics. |
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| 08/22/00 |
Full text: PDF
(12 pages, 209 KB) |