Prototype tests of a combined CO{sub 2} laser interferometer/polarimeter for ITER (abstract)
- General Atomics, 13-410, P. O. Box 85608, San Diego, California 92186-5608 (United States)
Line density measurements on ITER are expected to be provided by a conventional vibration-compensated CO{sub 2} laser interferometer. This type of interferometer relies on maintaining an accurate measurement of hundreds of vibration fringes during the entire time history of the plasma. Because of the very long pulse lengths (1000 s) and the possibility of fringe counting errors, a second method that measures the Faraday rotation of a laser beam with a tangential laser beam path through the plasma will be used to provide a history-independent measurement of the line density with somewhat reduced accuracy. These two measurements can be accomplished in a combined interferometer/polarimeter system that uses a single CO{sub 2} laser and detector. We have constructed a prototype of this type of system, which uses two acousto-optic modulators to generate two beams, shifted from the laser frequency by 40 and 45 MHz. These probe beams are converted to left- and right-hand circular polarization and combined into a single probe beam. Vibrations are simulated by moving a mirror in the reference beam path, and the Faraday rotation is simulated by rotating the linear polarized probe beam. Frequency analysis of the interference signal from a single detector is used to separate the phase of the interferometer and the phase of the polarization rotation. Limits on the phase resolution of the two methods and possible sources of error will be presented. {copyright}{ital 1999 American Institute of Physics.}
- OSTI ID:
- 295645
- Report Number(s):
- CONF-980605-; ISSN 0034-6748; TRN: 99:001831
- Journal Information:
- Review of Scientific Instruments, Vol. 70, Issue 1; Conference: 12. topical conference on high-temperature plasma diagnostics, Princeton, NJ (United States), 7-11 Jun 1998; Other Information: PBD: Jan 1999
- Country of Publication:
- United States
- Language:
- English
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