Initial operation of the divertor Thomson scattering diagnostic on DIII-D
- General Atomics, San Diego, California 92186-9784 (United States)
- Lawrence Livermore National Laboratory, Livermore, California (United States)
Thomson scattering measurements of {ital n{sub e}} and {ital 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{endash}D Tokamak. A custom, aspherical collection lens {ital (f/6.8)} images the laser beam from 1 to 21 cm above the target plates into eight spatial channels with 1.5 cm vertical and 0.3 cm radial resolution. Two-dimensional mapping of the divertor region is achieved by sweeping the divertor {ital 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 {ital T{sub e}} measurements. Silicon avalanche photodiodes measure both the scattered and plasma background light. Temperatures and densities are typically in the range of 5{endash}200 eV and 1{endash}10{times}10{sup 19} m{sup {minus}3}, respectively. Low temperatures, {ital T{sub e}{lt}1} eV, and high densities, {ital n{sub e}}{gt}8{times}10{sup 20} m{sup {minus}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 {ital 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 {ital n{sub e}} and low {ital T{sub e}} as measured by Thomson scattering. {copyright} {ital 1997 American Institute of Physics.}
- Research Organization:
- General Atomics, San Diego, CA (United States)
- DOE Contract Number:
- AC03-89ER51114
- OSTI ID:
- 452846
- Report Number(s):
- CONF-960543-; ISSN 0034-6748; TRN: 97:006596
- Journal Information:
- Review of Scientific Instruments, Vol. 68, Issue 2; Conference: 11. annual high-temperature plasma diagnostics conference, Monterey, CA (United States), 12-16 May 1996; Other Information: PBD: Feb 1997
- Country of Publication:
- United States
- Language:
- English
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