Evolution of Parametrically Excited Instabilities in a Magneto-Plasma Column.
Interim rept. Apr 74-Jun 77,
POLYTECHNIC INST OF NEW YORK BROOKLYN DEPT OF ELECTRICAL ENGINEERING AND ELECTROPHYSICS
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Experiments on parametric decay instabilities have been conducted in a hollow cathode arc generated plasma in a static magnetic field. A phenomenological model is used to describe the observed phenomena, and to determine the decay rate at various power levels, the linear and non-linear damping terms. An accurate estimate of the threshold power level is also obtained. And with the pump power switched from the fixed level to another, also above the threshold, the growth of the waves is also studied. The linear dependence of the decay and growth rate y on power is clearly demonstrated, and the experimental values are compared to theoretically calculated ones to obtain the physical picture. The natural or linear damping of the electrostatic ion cyclotron wave is found to be due to ion-neutral collision. The non-linear damping term which yields information on the saturation mechanisms of the wave, is found to be proportional to the square of the amplitude.
- Plasma Physics and Magnetohydrodynamics