PLASMA DIAGNOSTICS IN INTERACTION OF POWERFUL LASER PULSES WITH INHOMOGENEOUS LOW-DENSITY MEDIA

摘要

Complementary optical and X-ray diagnostic methods were developed and successfully used in experiments on detailed study of various physical processes in low-density (1-10 mg/cm~3) agar targets irradiated with powerful laser beams: 1. X-ray imaging of hot plasma region in the agar target interior with pin-hole cameras, crystal spectrographs, and streak-camera allowed us to study features of laser light absorption and formation of plasma region in a porous medium, and to determine main parameters (including the ion temperature for the first time) of produced hot plasma; 2. spectrally and temporally resolved measurements of fundamental laser frequency harmonics provided information on the problem of plasma homogenization in low-density porous media; 3. multiframe optical side-on shadowgraphy of the accelerated matter in combination with streak-camera recording of the luminosity in visible at the rear surface of laser-irradiated agar samples were shown to be suitable and very informative diagnostics for investigation of energy transport inside porous targets. It should be emphasized that the use of all above mentioned methods simultaneously in each laser shot is very desirable to provide reliable information for understanding of complicated physical processes and mechanisms being under investigation.