Density fluctuation measurements by far-forward collective scattering in the MST reversed-field pinch

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

DOI:https://doi.org/10.1063/1.4728098· OSTI ID:22093917

Ding, W. X.; Lin, L.; Brower, D. L. ^[1]; Duff, J. R.; Sarff, J. S. ^[2]

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1. Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095 (United States)
2. Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)

The multichannel polarimeter-interferometer system on the MST reversed-field pinch can be utilized to measure far-forward collective scattering from electron density fluctuations. The collective scattering system has 11 viewing chords with {approx}8 cm spacing. The source is a 432 {mu}m (694 GHz) far infrared laser and the scattered power is measured using a heterodyne detection scheme. Collective scattering provides a line-integrated measurement of fluctuations within the divergence of the probe beam covering wavenumber range: k{sub Up-Tack} < 1.3 cm{sup -1}, corresponding k{sub Up-Tack }{rho}{sub s} < 1.3 ({rho}{sub s} is the ion-sound Larmor radius), the region of primary interest for turbulent fluctuation-induced transport. The perpendicular wavenumber consists of toroidal, poloidal, and radial contributions, which vary with chord position. Coherent modes associated with tearing instabilities and neutral-beam driven fast particles are observed along with broadband turbulence at frequencies up to 500 kHz. Changes in frequency are consistent with a Doppler shift due to parallel plasma flow.

• OSTI ID: 22093917
• Journal Information: Review of Scientific Instruments, Journal Name: Review of Scientific Instruments Journal Issue: 10 Vol. 83; ISSN 0034-6748; ISSN RSINAK
• Country of Publication: United States
• Language: English

Related Subjects

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
DOPPLER EFFECT
ELECTRON DENSITY
FLUCTUATIONS
INTERFEROMETERS
IONS
LARMOR RADIUS
LASER RADIATION
MAGNETOHYDRODYNAMICS
PLASMA
PLASMA BEAM INJECTION
PLASMA DENSITY
PLASMA DIAGNOSTICS
POLARIMETERS
REVERSE-FIELD PINCH
REVERSED-FIELD PINCH DEVICES
SCATTERING
TEARING INSTABILITY
TURBULENCE