Scandate cathode fundamentals: interactions of Ba, O and Sc on W

Current developmental efforts on scandate cathodes are concentrated on improving uniformity in the emission and robustness in the performance. These endeavors require a good understanding of fundamental issues such as the emission mechanism and the Sc-replenishment mechanism associated with the cathodes. In order to help achieve this understanding, it is essential to unravel the complex chemical interactions on the scandate cathode surface, on which Ba, O, Sc and W are present. Our approach to investigate the complex interactions is to study first the interactions within the subsets, such as Ba and O on W and Sc and O on W. Aided with the knowledge gained, we then study the complete set of interactions.