Electron beam unit for heat treatment by electron bombardment technique

An electron beam unit for heat treatment by the electron bombardment technique comprising a vacuum chamber with the item being processed contained therein;

• an electron beam gun disposed inside said vacuum chamber;
• said electron beam gun including an electron-emitting cathode, an accelerating electrode so disposed in relation to said cathode that said accelerating electrode in conjunction with said cathode shapes the emitted electrons to obtain an electron beam;
• insulator means electrically insulating said cathode from said accelerating electrode, said insulator means being disposed between said item being processed and said accelerating electrode for also electrically insulating said accelerating electrode from ground;
• whereby the same electrical insulator strength is provided between the cathode and accelerating electrode and between the item and the accelerating electrode, a power supply disposed in external relationship to said vacuum chamber, the positive pole of said power supply being connected to said item, while the negative pole of the power supply is connected to said cathode of said electron beam gun;
• a resistor for limiting the discharge current that arises between said cathode and said accelerating electrode, one lead of said resistor being connected to said item and said positive pole of said power supply while the other lead of said resistor is connected directly to said accelerating electrode so that, in the normal operating mode of said electron beam gun, said resistor is shunted by said electron beam whereas the onset of a discharge between said cathode and said accelerating electrode will switch-in said resistor.