Nanostructured plasmas for enhanced gamma emission at relativistic laser interaction with solids

The hot plasma formed onto the surface of nanostructured targets by a relativistically intense (up to 4 x 10(18) W/cm(2)), high contrast femtosecond laser radiation is studied. The nanoscale structures (pores, spheres, grass) were produced via laser ablation or chemical etching of bulk silicon and molybdenum. We report one of the first experimentally observed manifold enhancements of gamma yield at the background of hot electron energy growth from 200 to >600 keV, compared to the case of initially flat substrate in the relativistic regime of interaction. The efficiency of hot particle production is significantly affected by the shape of the structures. Experimental results are supported by 2D3V Particle-In-Cell simulations of laser-plasma interaction. It is shown that a laser-based plasma source, formed onto the surface of a solid target may be utilized for phase contrast X-ray imaging in a wide energy range of photons.