Influence of the chirp and repetition rate of ultrashort laser pulses on the K{sub}α yield from laser-produced plasmas

摘要

The process of incoherent hard X-ray generation from laser-produced plasmas is investigated concerning the influence of the chirp of the irradiating laser pulse as well as the repetition rate of the laser system. By focussing ultrashort laser pulses onto a metal surface hard X-ray photons with photon energies of several keV are produced. The ultrashort laser pulses generate a plasma on the surface of the solid state target, whereupon the electrons of the plasma are accelerated back into the target producing incoherent hard X-ray radiation. Since the electrons are accelerated by the electric field of the irradiating laser pulse, the X-ray generation process ceases with the decay of that pulse. This gives rise to the conclusion that the X-ray pulse duration is of the same order as the pulse duration of the exciting laser pulse. Therefore the generation of hard X-rays with ultrashort pulses is a suitable method for time-resolved X-ray experiments. The dynamics of optical or acoustic phonons in semiconductors or other periodic structures has been investigated [1, 2].