Interaction of CO₂ Laser Light with Focus Plasma

Abstract

The interaction between a CO2 laser light and the high temperature plasma produced by dense plasma focus device is investigated experimentally. The absorption of laser light energy more than 50% was observed during the compressed pinch phase, but this absorption energy is not explained simply by the classical inverse bremsstrahlung (-10%). The upper-hybrid resonance absorption is expected in our experiment, because the plasma is pinched by the self-generated magnetic field of MG range. The backscattered energy of the extraordinary wave was reduced below half the value of the ordinary wave. This reduction is explained by the upper-hybrid resonance absorption. The frequency modulation of 4 GHz was observed in the spectrum analysis of the backscattered light. This modulation indicates the existence of the two-stream instability in the pinch plasma.