Robustness Investigation on Nanosized-Scandia-Doped Dispenser Cathodes

In order for practical applications in vacuum electron devices, the robustness of scandia-doped dispenser (SDD) cathode is a major concern. Emission properties after air exposure and gas poisoning have, therefore, been studied. A full restoring of emission has been proved after the cathodes were exposed to air and reactivated for a time much shorter than initial activation. Poisoning experiments demonstrated that the poisoning pressure thresholds of residual gases for the SDD cathode are about half to one order of magnitude higher at equivalent temperatures but with higher emission level in comparison with that of an excellent M cathode. The cathode is easier to recover after poisoning and can operate stably in a nonideal environment. These features are thought to be related to the surface Ba-Sc-O structure which has closely chemical association, better stability for air exposure, relatively high tolerance to gas poisoning, and the semiconductor emission characteristic.