Hard X-Ray Emission from Femtosecond Laser Interaction in Overdense Plasmas

Abstract

The recent development of ultra-short pulse lasers has made possible the investigation of laser matter interaction at ultra-high intensities. For sub-picosecond pulses, a hot and overdense plasma is produced very rapidly during the rise of the pulse and further laser interaction occurs with this plasma. One of the results of the interaction is the generation of fast electrons and of intense hard X-ray emission. The X-ray pulse duration is determined by the mean free path of the fast electrons in the target material. It can be very short (< 1 ps) and its intensity sufficient to be detected by the usual methods. With high laser pulse repetition rates, it has been demonstrated¹ that one can obtain an instantaneous signature of fast X-ray dense-matter interaction processes. The high energy of the X-ray photons (up to ~ 1 MeV) makes it possible to study small size objects and even to excite nuclear levels.