Directional Tubes. In directional X-ray tubes, the anode is set at an angle to the electron beam. When the high-speed electrons strike the target, X-radiation is generated in a solid spherical pattern. The massive anode functions as an absorber for the radiation traveling into the anode. In most X-ray tubes, lead-absorbing materials are used to restrict the exiting radiation to a cone-shaped field passing through a window. The shielding reduces the leakage radiation hazard to personnel, and prevents additional scattered radiation from surrounding materials and areas. In some portable equipment, shielding of the X-ray tube has been omitted for the advantage of lightweight. In some very high-energy units such as betatrons and linear accelerators, the target is comparatively thin and offers little absorption to the very high-energy radiation being generated. The radiation beam from the front of the target is shielded to provide a directional pattern, conical in shape.
Rod Anode X-Ray tubes. These tubes are designed to produce a radiation beam in a circular pattern. These tubes are used for circumferential radiography, particularly weldments in pipe. By use of an absorbing sleeve the circular radiation pattern can be reduced to a directional beam.
