Abstract
New results obtained in experiments on laser irradiation (I = 10^14^ W/cm^2^, ฮป = 1.055 micrometer) of lowdensity (1โ30 mg/cm^3^) fibrous and foamโlike materials are presented and discussed. Influence of lowโdensity material microstructure of irradiated plane samples on processes of laser light absorption, Xโray conversion, energy transport, plasma formation and homogenization was investigated. The pronounced effect of material microstructure on the parameters and dynamics of produced plasma has been found out using the variety of complementary Xโray and optical methods. The extension of hot plasma region inside irradiated samples as well as the energy transport rate was observed to be several times higher for samples of foamโlike polystyrene than for samples of fibrous agar. The experiments with cascade targets consisting of several mylar films (film thickness and filmโtoโfilm spacing were varied) were carried out with the aim to model the polystyrene microstructure in a simplified manner. The lowโdensity fibrous samples with external and internal soft Xโray sources (converters) were also irradiated. Preferences of either fiber or foamโlike material utilization in target constructions for specific research problems are considered. (ยฉ 2005 WILEYโVCH Verlag GmbH & Co. KGaA, Weinheim)