Multiframe interferometric study of a laser irradiated plasma in the presence of the two plasmon decay instability

The temporal development of the electron density distribution in a CO2-laser produced plasma is studied interferometrically at 10.5 GHz framing rates with 50 psec resolution. The plasma is produced in a helium gas jet target and has a maximum density of 5×1018 cm−3. Thomson scattering of probe ruby laser radiation in a second experiment shows that the two plasmon decay instability is excited in this plasma and appears in multiple bursts. Excellent correlation between the temporal variations of the density scale length just below quarter critical density and that of the two plasmon decay wave intensity demonstrates the instability quenching property of ponderomotive profile steepening.