A system for generating tunable pulsed monochromatic X-rays comprises a tabletop terawatt laser delivering 10 Joules of energy in 10 ps at a wavelength of 1.1 microns. The light beam from the laser is counter-propagated against an electron beam produced by a linear accelerator. X-ray photons are generated by inverse Compton scattering that occurs as a consequence of the "collision" that occurs between the electron beam and IR photons generated by the laser.
The system uses a novel pulse structure comprising, in a preferred embodiment, a single micropulse. The LINAC is configured to generate an electron beam having 1 nanocoulomb of charge in a microbunch having a pulse length of about 5 picoseconds or less (or an electron beam brightness of 10.sup.12 A/m.sup.2 -radian.sup.2 @ 500 A). A beam alignment sub-system is used at the laser beam--electron beam interaction zone and directs the X-ray beam, in a preferred embodiment, through a beryllium window and onto mosaic crystals which divert the beam into a beam transport system toward the imaging target.