Core density gradient fluctuation measurement by differential interferometry in the helically symmetric experiment stellarator

Journal Article · Mon Oct 15 00:00:00 EDT 2012 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.4730999· OSTI ID:22093921

Deng, C. B.; Brower, D. L. ^[1]

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1. Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095 (United States)

The interferometer system on the Helically Symmetric eXperiment (HSX) stellarator uses an expanded beam and linear detector array to realize a multichord measurement. Unlike conventional interferometry which determines the plasma phase shift with respect to a reference, directly evaluating the phase between two adjacent chords can be employed to measure the change in plasma phase with impact parameter. This approach provides a measure of the equilibrium density gradient or the density gradient fluctuations and is referred to as differential interferometry. For central chords, measurements are spatially localized due to a geometrical weighting factor and can provide information on core density gradient fluctuations. The measurement requires finite coherence between fluctuations in the two spatially offset chords. This technique is applied on the HSX stellarator to measure both broadband turbulence and coherent modes. Spatial localization is exploited to isolate core turbulence changes associated with change in magnetic configuration or heating location.

• OSTI ID: 22093921
• Journal Information: Review of Scientific Instruments, Vol. 83, Issue 10; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
CONFIGURATION
FLUCTUATIONS
HEATING
HSX STELLARATOR
IMPACT PARAMETER
INTERFEROMETERS
INTERFEROMETRY
MAGNETOHYDRODYNAMICS
MICROWAVE RADIATION
PHASE SHIFT
PLASMA
PLASMA DENSITY
PLASMA DIAGNOSTICS
RADIOWAVE RADIATION
SYMMETRY
TURBULENCE