A radiation emission device characterized by a cylindrical cathode enclosed by an elongated envelope having a body section and two end sections is disclosed. The device includes an anode terminal, coupled to the body section, which serves to provide electrical energy to excite metallic material inside the envelope. The device further includes a pair of cataphoresis terminals located along each end section to prevent the excited metallic material from drifting into contact with radiation transmission windows located at the terminus of each end section.