Plasma formation dynamics for laser interaction with near critical foam matter

Summary form only given, as follows. Experimental study of the laser pulse interaction with low density porous matter is presented. The experiments were carried out on a laser facility with wavelength 0.53 /spl mu/m, pulse duration 2.5 ns, focal spot diameter 15 /spl mu/m and flux density on the target surface /spl sim/5 10/sup 14/ W/cm/sup 2/. Targets were prepared from porous polypropylene (CH)/sub x/ with an average density /spl sim/0.02 g/cm/sup 3/ and cell size /spl sim/50 /spl mu/m. The dynamics of plasma formation was investigated by means of registration of scattered laser radiation and selfluminosity of the plasma with spatial and temporal resolution. The experimental data show an essential difference of plasma processes occurring in the porous targets and solid ones with the same chemical composition. The general features of the porous targets are a volume distributed absorption, when a laser beam forms a low density "channel" inside a porous matter, and larger spatial scales of the transverse energy transport.