Theoretical investigation of an ultrashort-pulse coherent x-ray source at 45 Å

A scheme to obtain ultrashort-pulse coherent x rays, via population inversion following inner-shell photoionization, is analyzed for C at 45 {}. We calculate that a driving laser with a pulse duration of 40 fs, a 10 μm×1 cm line focus, and an energy of 1 J gives an effective gain length product (gl) of 10. At saturation (gl~18) we expect an output of ~0.1 μJ per pulse. The short duration of x-ray lasing (<100 fs) combined with a 10-Hz repetition rate (Pavg=1 μW) makes this source of coherent x rays ideal for pump-probe experiments to study fast dynamical processes in chemistry and material science.