DC Emission Characteristic of Nanosized-Scandia-Doped Impregnated Dispenser Cathodes

To meet the requirements for advanced vacuum electron devices and modern electron beam instruments, dc emission properties of nanosized-scandia-doped impregnated (SDI) cathodes have been investigated in a closely spaced diode configuration system with water-cooled copper anode. The SDI cathodes were made from nanosized-scandia-doped tungsten powder, which was produced by a spray-drying process. A space-charge-limited dc current density of over 60 A/cm
²
has been measured at 950 °C
_b
. An on-going life test with a dc load of 30 A/cm
²
at 950 °C
_b
has completed more than 2000 h of operation to date. The electron cooling for dc beam emission is discussed.