An x-ray illumination beam system includes an electron emitter and a target having one or more target microstructures. The one or more microstructures may be the same or different material, and may be embedded or placed atop a substrate formed of a heat-conducting material. The x-ray source may emit x-rays towards an optic system, which can include one or more optics that are matched to one or more target microstructures. The matching can be achieved by selecting optics with the geometric shape, size, and surface coating that collects as many x-rays as possible from the source and at an angle that satisfies the critical reflection angle of the x-ray energies of interest from the target. The x-ray illumination beam system allows for an x-ray source that generates x-rays having different spectra and can be used in a variety of applications.