Measurements of the internal magnetic field on DIII-D using intensity and spacing of the motional Stark multiplet
- University of California San Diego, La Jolla, California 92093 (United States)
- General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States)
- Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
We describe a version of a motional Stark effect (MSE) diagnostic based on the relative line intensities and spacing of Stark split D{sub {alpha}} emission from the neutral beams. This system, named B-Stark, has been recently installed on the DIII-D tokamak. To find the magnetic pitch angle, we use the ratio of the intensities of the {pi}{sub 3} and {sigma}{sub 1} lines. These lines originate from the same upper level and so are not dependent on the level populations. In future devices, such as ITER, this technique may have advantages over diagnostics based on MSE polarimetry. We have done an optimization of the viewing direction for the available ports on DIII-D to choose the installation location. With this placement, we have a near optimal viewing angle of 59.6 deg. from the vertical direction. All hardware has been installed for one chord, and we have been routinely taking data since January 2007. We fit the spectra using a simple Stark model in which the upper level populations of the D{sub {alpha}} transition are treated as free variables. The magnitude and direction of the magnetic field obtained using this diagnostic technique compare well with measurements from MSE polarimetry and EFIT.
- OSTI ID:
- 21266671
- Journal Information:
- Review of Scientific Instruments, Vol. 79, Issue 10; Conference: HTPD08: 17. topical conference on high-temperature plasma diagnostics, Albuquerque, NM (United States), 11-15 May 2008; Other Information: DOI: 10.1063/1.2966596; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
- Country of Publication:
- United States
- Language:
- English
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