An apparatus for Flash X-ray irradiation of material includes a Flash X-ray source comprised of an electron gun and an anode. The electron gun comprises a field emission cold cathode having an electron emitting surface, and a grid for controlling electron flow from the cathode to the anode. The anode has an electron-receiving main surface and an X-ray emitting, oppositely facing main surface. The X-ray emitting surface, emits X-radiation into an irradiation volume. The X-ray emitting surface of the anode has orthogonally oriented first and second dimensions of greater than 2 millimeters each. A high voltage pulse power supply powers the Flash X-ray source. The electron gun, anode and high voltage pulse power supply are so constructed as to create sufficient X-radiation in said irradiation volume to achieve a desired level of irradiation of material in said volume.