Electron beam gun for use in an electron beam evaporation source

In an electron beam gun for use in an electron beam evaporation source including:

• a split cathode block having two electrically conductive sides;
• a filament located between the two sides of the cathode block and connected to the two sides of the cathode block so that an electric current applied to the sides of the cathode block causes the filament to emit electrons;
• an anode having a top section of inverted U shaped cross-section passing over the filament and terminating in a front edge located in front of the filament;
• and a beam former having a top section of inverted U shaped cross-section, located between the anode and the filament and configured so that the filament is shielded from the anode and the electrons are constrained to pass beneath the top section of the beam former and toward the front edge of the top section of the anode in a ribbon shaped electron beam, the improvement comprising:
• the beam former having two sections with a vertical gap between the sections;
• the two sections separately connected to the two sides of the cathode block so that the two sections of the beam former are in good thermal contact with the two sides of the cathode block and the two sides of the cathode block act as heat sinks for the two sections of the beam former to prevent a non-uniform thermal gradient from being produced within the beam former and consequent thermal warpage and movement of the beam former;
• and
• the gap between the two sections of the beam former sized such that electrons cannot pass through the gap to the anode.