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 {Angstrom}. We calculate that a driving laser with a pulse duration of 40 fs, a 10 {mu}m{times}1 cm line focus, and an energy of 1 J gives an effective gain length product (gl) of 10. At saturation (gl{approximately}18) we expect an output of {approximately}0.1 {mu}J per pulse. The short duration of x-ray lasing ({lt}100 fs) combined with a 10-Hz repetition rate (P{sub avg}=1 {mu}W) makes this source of coherent x rays ideal for pump-probe experiments to study fast dynamical processes in chemistry and material science. {copyright} {ital 1998} {ital The American Physical Society}