An electron source includes a vacuum chamber within which a vacuum is maintained
by a vacuum pump. An insulated receptacle is mounted within the vacuum chamber
and has a receptacle mounting flange. The receptacle mounting flange is used to
establish a coordinate system having an electron beam axis and a lateral plane,
wherein the lateral plane is transverse to the electron beam axis. An adapter is
mounted to the receptacle and is adjustable in five degrees of freedom with respect
to the coordinate system. A cathode and focus electrode are adjustable in at least
four degrees of freedom and are pre-aligned with respect to one another prior to
being installed on the adapter. An anode is mounted in the vacuum chamber and is
aligned at a predetermined distance from the cathode with respect to the coordinate system.
