High current density M-type cathodes for vacuum electron devices

We investigated high current density emission capabilities of M-type cathodes used for vacuum electron devices (VEDs). The experimental results of emission and lifetime evaluating in both close-spaced diode structure and electron gun testing vehicles are given. Emission current densities measured in the diode structure at 1020 °CBr in the CW mode were above 10 A/cm2; while in electron gun testing vehicles, emission current densities were above 8 A/cm2 in CW mode and above 32 A/cm2 in pulsed mode, respectively. The current density above 94 A/cm2 has been acquired in no. 0306 electron gun vehicle while the practical temperature is 1060 °CBr. For a comparison some of the data from I-scandate cathodes are presented. Finally, several application examples in practical travelling wave tubes (TWTs) and multi beam klystrons (MBKs) are also reported.