Scanning electron microscope

An electron microscope comprising:

• a gun assembly producing an electron beam, wherein said gun assembly includes an electron beam emitter assembly, said electron beam emitter assembly including
• a back plate;
• a front plate;
• clamping means extending between said front plate and said back plate;
• a filament means including a cathode means supported between a pair of electrodes, said electrodes supported by an insulating base, said insulating base being clamped between said back plate and said front plate by said clamping means;
• a grid adjustably held against said front plate by said clamping means, whereby said grid may be adjustably positioned relative to said front plate and said filament means;
• a column assembly coupled to said gun assembly;
• an electromagnetic lens means positioned within said column assembly for focusing, Shaping and deflecting said electron beam;
• and
• a beam passage means positioned within said column assembly extending through a central portion of said electromagnetic lens means for forming an evacuated path for said electron beam, said beam passage means including
• an outer sealing jacket forming a seal with said column assembly sufficient to maintain a vacuum within said outer sealing jacket, and
• a conductive inner liner tube positioned substantially within said outer sealing jacket adapted to have said electron beam pass therethrough, said inner liner tube supporting beam modifying means for modifying said electron beam passing through said inner liner tube.

An electron microscope comprising:

• a gun assembly producing an electron beam;
• a column assembly coupled to said gun assembly;
• an electromagnetic lens means positioned within said column assembly for focusing, shaping and deflecting said electron beam;
• and
• a removable beam tube assembly positioned within said column assembly extending through a central portion of said electromagnetic lens means for forming an evacuated path for said electron beam, said removable beam tube assembly including
• an anode means incorporated in an end of said removable beam tube assembly adjacent said gun assembly whereby said beam tube assembly may be removed as a single integrated unit including said anode means.

An electron beam emitter assembly comprising:

• a back plate;
• a front plate;
• clamping means extending between said front plate and said back plate;
• a filament means including a cathode means supported between a pair of electrodes, said electrodes supported by an insulating base, said insulating base being clamped between said back plate and said front plate by said clamping means;
• and
• a grid adjustably held against said front plate by said clamping means, whereby said grid may be adjustably positioned relative to said front plate and said filament means.