A vacuum container houses a source of electrons and two electrodes—a positive anode and a negative cathode—with a significant voltage difference between them. The cathode, often a heated filament, emits electrons, while the anode is built robustly to endure the impact of these electron streams, commonly known as cathode rays. Upon striking the anode, the kinetic energy of the cathode rays transforms into heat (98%) and x-rays (2%). To manage the heat generated, the tube is cooled by circulating water through a jacket that surrounds it.