A system for generating a tunable X-ray pulse comprises a first electron beam source configured to direct a first electron pulse of predetermined energy and pulse length towards a first interaction zone, a laser beam source configured to direct a first photon pulse of predetermined energy and pulse length towards the first interaction zone to interact with the first electron pulse. The first interaction produces a substantially monochromatic second photon pulse of higher photon energy directed towards a second interaction zone, and a second electron beam source configured to direct a second electron pulse of predetermined energy and pulse length towards the second interaction zone so that the second interaction produces an X-ray pulse of predetermined energy and pulse length in a cascaded inverse Compton scattering (ICS) configuration.