Physics of the ion acoustic wave driven by the stimulated Brillouin scattering instability

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1984

OSTI ID:5803774

Clayton, C E

The ion acoustic wave excited in the stimulated Brillouin scattering (SBS) instability is probed via collective ruby-laser Thomson scattering in order to understand the low saturation level observed in the instability. Many of the features observed in the Brillouin backscattered CO/sub 2/ laser light from the underdense gas-target plasma are also observed in the Thomson scattered ruby light - from which it is learned that the ion acoustic wave grows exponentially and then saturates as the CO/sub 2/ pump power is increased. The primary advantage of the ruby Thomson scattering diagnostic is in its capability of providing simultaneous space and time resolved measurements of the ion wave amplitude. From these first such detailed measurements, it was found that the ion wave grows exponentially in space at a rate that agrees with the linear convective SBS theory. However, at higher pump powers, the ion wave saturates at an inferred amplitude of anti-n/n/sub 0/ approx. = 5 to 10%. Further increases in the pump power appear to result in an increase in the length over which the ion wave is saturated. A nearly constant SBS reflectivity in this saturated regime, however, suggests that the saturated ion wave does not contribute as much to the scattered power as would be expected from Bragg scattering theory. This apparent contradiction can be resolved if ion trapping is responsible for the saturation of the ion wave.

• Research Organization: California Univ., Los Angeles (USA)
• OSTI ID: 5803774
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700107 -- Fusion Energy-- Plasma Research-- Instabilities
700108* -- Fusion Energy-- Plasma Research-- Wave Phenomena
BRILLOUIN EFFECT
COHERENT SCATTERING
ELECTROMAGNETIC RADIATION
ENERGY-LEVEL TRANSITIONS
EXCITATION
INELASTIC SCATTERING
INSTABILITY
ION ACOUSTIC WAVES
ION WAVES
LASER RADIATION
OPTICAL PUMPING
PLASMA DIAGNOSTICS
PLASMA INSTABILITY
PLASMA WAVES
PUMPING
RADIATIONS
SCATTERING
THOMSON SCATTERING