High current density Scandate cathodes

Research is in progress to develop high current density cathodes. Typical M-type cathodes can operate at high current density by elevating the temperature; however, this leads to increased barium diffusion and significantly reduced lifetime. The addition of scandium to the emitter surface lowers the work function and allows high current density operation at lower temperature, thereby, reducing barium diffusion. Unfortunately, the scandium is removed from the surface by various processes and is difficult to replace. Consequently, the performance degrades with time. This research is pursuing configurations that insure a continuing source of scandate to the emitter surface.