ИСТИНА

Wide variety of electron acceleration mechanisms were proposed to impact to electron acceleration from dense plasma under relativistic femtosecond laser-plasma interaction - jxB and ponderomotive acceleration, resonant and stochastic heating, parametric instabilities, and even wakefield acceleration could play a dominant role. Besides of the laser pulse intensity, its duration and temporal structure (pre-pulses, leading edge sharpness, ASE level and duration) determine pre-plasma scale and length, that in its turn give rise to the different acceleration mechanisms. In this paper we present experimental results and numerical 3D PIC simulations on hard x-ray and gamma-emission from plasma created by the ultrashort relativistic laser pulse. We used Ti:Sapphire laser system, which generates femtosecond pulses (40fs, 100mJ, 10Hz) of relativistic intensity (up to 1019 W/cm2). For the contrast measuring (in picosecond range) the third-order autocorrelator with dynamic range >1010 and delay limits 150ps was built. The laser pulse profile has one pre-pulse at 12.5ps with amplitude of 10-3-10-7, ASE level of ~10-5-10-8 and one pre-pulse at 12 ns with amplitude of 10-1-10-8. Pulse duration was changed by the grating compressor detuning. Numerical simulatons were done using fully relativistic 3D PIC code Mandor.