Comparative analysis of planar and spherical cathodes in gridded electron guns for Inductive output tubes

Inductive Output Tube (IOT) is a vacuum electron tube capable of amplifying radio frequency (RF) power with high efficiency. It is popularly used as high power source in communication transmitters and particle accelerators operating at ultra-high frequency (UHF) band. The basic structure of IOT is similar to a Klystron except that the gun and input cavity are two distinctly separated components in Klystron whereas these two components are integrated together in case of an IOT which makes the electron gun and input cavity the most critical part to design and develop. The paper discusses the design results of two electron guns having different shapes of cathode emitting surfaces - spherical and planar. Both structures have been designed for same specifications and a comparative analysis has been presented. On the basis of the merits and demerits of these structures, the more preferable design has been pointed out to implement in IOTs.