Critical Layer Penetration in a Cold Z-Pinch Plasma by High-Intensity 10.6Microns Laser Radiation.

摘要

The intensity dependence of transmission of high-intensity 10.6micrometer laser radiation through an overdense cold Z-pinch plasma has been measured to determine a threshold for transmission. A holographic cinema of plasma evolution,obtained independently of the CO2laser,provided initial information about the target plasma. An intensity threshold for transmission was measured to be about 2.5 x 10to the 11 W/sq cm for incidence on the pre-pinch plasma,and 2 x 10to the eleven W/sq cm for the post-pinch plasma. As the laser intensity was increased above threshold,compression of the transmitted pulse was observed from its incident width of 38nsec to a transmitted width of 15nsec at maximum intensity of 4 x 10to the eleven W/cm. Coincidence measurements between the incident and transmitted pulse indicated the blockage of the first portion of the pulse and subsequent transmission of the remainder. Analysis of the laser-induced shock indicated about 60to 70percent energy absorptition. Enhanced optical continuum emission from the interaction volume was attributed to plasma heating.