X-RAY-PRODUCTION AND 2ND-HARMONIC GENERATION BY SUPERINTENSE FEMTOSECOND LASER-PULSES IN THE SOLIDS WITH RESTRICTED THERMAL CONDUCTION

Two new types of targets: ultrathin freely suspended carbon films and porous Si, both revealing thermoconductivity restriction leading to pl asma overheating upto electron temperature above 1 keV under ''moderat e'' intensities 10(15) - 10(16) W.cm(-2) has been investigated experim entally. For the ultrathin carbon film of 20-30 nm X-ray yield threefo ld increase has been observed. Computer simulations decribe well the o bserved behaviour of the X-ray yield, and the electron temperature of 700 eV was deducted for the him of 10 nn in thickness. For-Si produces greater X-ray flux under intensity of 10(16) W.cm(-2) as compared to the solid Si. If the intensity increased the total X-ray yield from pe r-Si undergoes ''saturation'', while the X-ray yield from solid Si fit s as approximate to I-2. Simple model to describe the ''overheating'' of Si plasma using a set of ultrathin films is developed. Some promisi ng advantages of new targets are discussed.