Search for lower hybrid drift fluctuations in a field-reversed configuration by means of carbon dioxide heterodyne scattering

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1986

OSTI ID:6742649

Carlson, A W

A measurement reported sets an upper bound on LHD like density fluctuations in an FRC, which is two orders of magnitude below the predicted levels. Particle loss from FRC's is known to occur anomalously fast, and this is usually attributed to effects of the LHD instability. If LHD waves are present, they can be measured using heterodyne detection of CO/sub 2/ laser light scattered from the associated density fluctuations. In this study the usual scattering system was successfully modified to compensate for severe refraction of the beams by the plasma. This system was calibrated by detection of an electrooptically modulated CO/sub 2/ laser beam, and by detection of light scattered from acoustic waves in salt. The plasma measurements made on the TRX-2 field reversed theta pinch covered all parameters at which LHD fluctuations might be expected to occur, namely wavenumbers from 30 to 240 cm/sup -1/, frequencies from 10 to 300 MHz, and radii from one centimeter inside the separatrix to two centimeters outside. The lack of detectable scattered light under any of these conditions indicates (deltan/n) < 1 x 10/sup -4/, compared to predictions of (deltan/n)approx.1 x 10/sup -2/ based on mode coupling theory, ion-trapping theory, and observed transport rates. Several mechanisms are discussed that may stabilize LHD in these plasmas. Several alternate explanations of the observed anomalous transport rates in FRC's are also discussed.

• Research Organization: Washington Univ., Seattle (USA)
• OSTI ID: 6742649
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
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ELECTROMAGNETIC RADIATION
LASER RADIATION
PINCH EFFECT
PLASMA DIAGNOSTICS
PLASMA DRIFT
PLASMA WAVES
RADIATIONS
REVERSE-FIELD PINCH
SCATTERING
STABILIZATION