A new fast-ion D{sub {alpha}} diagnostic for DIII-D
- University of California, Irvine, California 92697 (United States)
- General Atomics, San Diego, California 92186 (United States)
The fast-ion D{sub {alpha}} (FIDA) technique is a charge-exchange recombination spectroscopy measurement that exploits the large Doppler shift of Balmer-alpha light from energetic hydrogenic atoms to infer the fast-ion density. Operational experience with the first dedicated FIDA diagnostic on DIII-D is guiding the design of the second-generation instrument. In the first instrument, dynamic changes in background light associated with plasma instabilities usually dominate measurement uncertainties. Accordingly, the design of the new instrument minimizes scattering of cold D{sub {alpha}} light while monitoring its level. The first instrument uses a vertical view to avoid bright interference from the injected-neutral beams. The sightline of the new instrument includes a toroidal component but only measures blueshifted fast-ion light that is Doppler shifted away from the redshifted light of the injected neutrals. The new views are more sensitive to fast ions that circulate in the direction of the plasma current and less sensitive to the trapped-ion and countercirculating populations. Details of the design criteria and solutions are presented.
- OSTI ID:
- 21266509
- 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: 10.1063/1.2956828; (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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