Issues in Cathode Performance Part 2 - Cathode Mounting Design

Extract

LaB₆ and CeB₆ cathodes are widely used as high-brightness, highstability, long-lifetime cathodes in a variety of electron beam appiications. Two of these factors - stability and lifetime - are critically dependent on proper cathode-mounting design.

When the benefits of LaB₆ as an emitter material were first investigated, the LaB₆ was indirectly heated by an electron bombardment coil. This design was cumbersome and did not perform well. Wire mounts, such as those used for tungsten emitters, were developed (and are stili used today); however, they have many drawbacks. Their stability and lifetime are limited because the thin wire mount moves easily and will eventually break under the changing temperature conditions encountered during operation.