A system for producing a controllable beam of radiation is controllable electronically, and includes no parts that must move relative to one another while in operation to form the beam. The direction and cross-section of the beam may be controlled electronically by controlling an electron beam. Various embodiments provide an X-ray collimator that allows forming a scanning X-ray beam of desired size and flux independently of the aperture material thickness without requiring movement of the aperture or physical components that create the aperture. Some embodiments provide an X-ray collimator that allows forming a scanning X-ray beam of desired size and flux independently of the beam angle.