Study of fast electron transport in thin foil targets irradiated by ultrashort intense laser pulses

We report on the propagation of fast electrons generated in the interaction of ultrashort, ultra-high-intensity laser pulses with thin metallic foils and double-layer targets. Implicit estimation of the fast electron source size was done by measuring the X-ray source size from the rear as well front sides of the target foils, using the knife-edge technique. A significantly larger (~4 times) source size was measured from the rear surface compared to that from the front surface. The variation of the X-ray source size was studied as a function of the laser pulse duration and the amplified spontaneous emission pre-pulse contrast. The half divergence cone angle of the fast electron generated by irradiating the target at a laser intensity of ~1.3 × 1018 W cm−2 was estimated to be 37°. These results can be important in understanding the propagation of fast electrons through solid materials under different intensity and pre-pulse conditions.