Experimental investigation of fast electron transport through K? imaging and spectroscopy in relativistic laser-solid interactions

The study of the basic physical processes underlying the generation of fast electrons during the interaction of high-intensity short laser pulses with solid materials and the transport of these fast electrons through the target material are of great importance for the fast ignition concept for inertial confinement fusion and for the development of ultra-short X-ray sources. We report on the experimental investigation of fast electron transport phenomena by means of the spatial and spectral characterization of the X-ray emission from layered targets using bent crystal spectrometers and a new diagnostic technique based on a pinhole-camera equipped with a CCD detector working in single-photon regime for multi-spectral X-ray imaging [1]. In particular, differences of fast electron transport features depending on the atomic number and/or the resistivity of the target material have been studied. The experiments were carried out at relativistic laser intensities, both in the longer (?ps) pulse interaction regime relevant for fast ignition studies [2] and in the short-pulse (?100 fs) interaction conditions related to basic physics studies as well as to the development of ultrashort K? X-ray sources.