Patent ID: 8729470
Filing Date: 2014-05-20
Classification: H01J

Abstract:
1. An electron microscope, comprising: an electron emitter configured to provide an electron beam in response to heating associated with an electrical current passed through the electron emitter at least during operation of the electron microscope; a housing having an inside wall that defines a cavity that at least partially encloses the electron emitter and the electron beam during the operation of the electron microscope; and a vacuum-generating mechanism, mechanically coupled to the housing, configured to provide a reduced pressure greater than or equal to a medium vacuum in the cavity at least during the operation of the electron microscope when the electron beam is present, wherein the electron emitter is exposed to the reduced pressure while the electron emitter provides the electron beam, wherein the electron emitter has an operating lifetime at the reduced pressure exceeding that of a tungsten emitter, wherein the electron emitter is a ceramic that forms a surface-protective layer having a rate of a phase transition less than that of the tungsten emitter at the reduced pressure, and wherein the phase transition is one of: evaporation and sublimation.