Electron gun for high radiant power

The invention is concerned with an electron gun for high radiant power. It is applicable to large irradiation plants for vacuum metallization. The electron gun has a rated capacity in the range from 60 kW to more than 1200 kW. Its electron beam results from a space-charge-limited emission current whose power can be controlled over the whole power range from 10% to 100% of rated capacity by means of an axially adjustable anode. A beam lens with a fixed focal length is used in such a way that there is no aperture enlargement. The electron gun operating with constant acceleration voltage consists of an axially adjustable anode with a conical angle from 600 to 1200, a cathode with a conical angle from 1400 to 1700, and a focussing electrode with a conical angle from 1300 to 1600. The anode-sided pole shoe of the magnetic beam lens which has no water cooling is fixed to the anode which is made of high-temperature resistant material. The unit pole shoe-anode can be moved axially. Furthermore it is advantageous to use a control valve for maintaining the pressure in the area of the anode (1 to 3 x 10-4 torr) which is necessary for gasfocussing of the electron beam