ИСТИНА

We present results of the experimental and numerical studies of the abnormally hot electron generation and high efficient gamma production by the proper preplasma profiling with prepulses. By the contrast to the widely used wakefield acceleration, occurring at lower densities (below 0,01 nc), the total number of encountered particles may be significantly increased in the case of an optimized pre-plasma layer of a subcritical density, forming at specific conditions a high charge bunch of high energy electrons already at slightly relativistic laser intensity. We also showed that the liquid gallium target could also provide for huge enhancement in electron and gamma prodiction due to metal microjets formation by a short prepulse and how initially structured targets may provide for better energy coupling and electron heating. We used the Ti:Sa laser system (p-pol, 800 nm, 10 Hz, 40 mJ, 45 ± 5 fs and Imax − 5×1018W/cm2, ASE & prepulses <10−8). For some experiments contrast rations at the nanosecond and picosecond time scales were adjusted to achieve the desired phenomena. In other experiments the Nd:YAG laser (1064 or 532 nm, 30-120 mJ, 6 ns, I~ 1012W/cm2) was used to create the controlled long and dense pre-plasma layer. This laser was locked with the Ti:Sa laser system with accuracy better than 1 ns. Different targets were used: metal plates made of Fe, Mo, W, thick polymer films and plates, as well as different structured targets. We also discussed some applications of our studies in nuclear physics, microelectronics, and other areas of research. For clarification of the electron acceleration mechanisms numerical simulations were done using a combination of 3D hydrodynamic code of pre-plasma formation, fully relativistic 3D3V PIC code for laser-plasma interaction and electron acceleration, and GEANT code for -production. Manifestation and interconnection of different acceleration processes depend strongly on the pre-plasma scalelength.