Image Number 2 for United States Patent #5222547.
In the representative embodiment described in the specification, an electron beam furnace has an evacuation system which maintains the interior of the furnace at a pressure in the range from about 50 microns Hg to 300 microns Hg. The relatively high pressure reduces degassing time from a cold start, suppresses volatilization of constituents of metal being refined, and causes volatilized metal to condense in powder form on a condensing screen. A vibrator assists in removing the powder from the condensing screen. The electron beam gun has a series of compartments which are individually evacuated to maintain the pressure in the compartment containing the cathode at a level less than about 1 micron Hg.