Role of three-wave scattering in the saturation of electron beam driven Langmuir waves

Thesis/Dissertation · Tue Jan 01 04:00:00 EST 1985

OSTI ID:5569661

Casey, J A

Theory predicts that the three-wave backscatter of electron beam driven Langmuir waves is stimulated by ion-acoustic waves of frequency 2 omega/sub p/c/sub s//v/sub b/ (omega/sub p/ = plasma frequency, c/sub s/ = ion-acoustic speed, v/sub b/ = beam velocity). Suppression of Langmuir wave growth should therefore result from scattering away from wave numbers destabilized by the electron beam. In this thesis, this effect is observed in an unmagnetized double plasma device (electron temperature approx. = 5 eV, electron density approx. = 3 x 10/sup 8/ cm/sup -3/ in Argon), by externally introducing narrow-band ion-acoustic turbulence (bandwidth (deltaomega/omega) < 0.1, intensity (deltan/n) approx. = 0.03) into an electron beam-plasma system (beam energy approx. = 50-90 eV, beam temperature < 1 eV, beam density approx. = 1-10% n/sub e/). Suppression of electron-beam resonant Langmuir wave growth is seen when tuning the low-frequency turbulence through the predicted resonance at 2 omega/sub p/c/sub s/v/sub b/. In addition, as the intensity of ion-acoustic waves increases, greater suppression of Langmuir wave growth occurs. Modification of the electron beam by quasi-linear plateau formation is associated with large Langmuir wave energy densities. The suppression of Langmuir wave growth by stimulated scattering lowers the energy density of the waves and consequently reduces this modification and stabilizes the beam.

• Research Organization: Colorado Univ., Boulder (USA)
• OSTI ID: 5569661
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700108* -- Fusion Energy-- Plasma Research-- Wave Phenomena
BACKSCATTERING
BEAM-PLASMA SYSTEMS
BEAMS
ELECTRON BEAMS
LEPTON BEAMS
PARTICLE BEAMS
PLASMA WAVES
RESONANCE
SCATTERING
TURBULENCE