EBOGEN
The main item of any EB system is the generator.
In the beam generator the electrons are emitted from a wolfram cathode accelerated by 60 to 175 kV to about 2/3 of the speed of light and then focused on the work piece into a beam with high power intensity. The electrons are slowed down here and the beam energy is converted into heat.
Power flux intensities of approximately more than 1 kW/mm2 lead to spontaneous vaporization of the material with the corresponding deep weld effect. PTR electron beam generators reach power flux densities of more than 100 kW/mm2 and therefore feature another field of application for electron beam technology.
The most important subassemblies are:
Beam head
This contains an insulator, which is equipped with a high voltage cable connector. The so-called beam generating system, which consists of the cathode, bias cup and the anode, is integrated in the insulator.
Wolfram – strip-type harmonic cathode
High emission density with long working life of the cathode. Easy cathode exchange.
Wehnelt cylinder (corresponds to a negative control grid)
Powerless, high dynamic control of the beam energy.
Column valve
This subassembly contains the connection for a vacuum system that is required for the EB generator, the column valve, which separates the beam generating system from the chamber by means of a vacuum.
Turbo molecular pump stand
High vacuum free from hydrocarbons for a long cathode life.
Viewing system
Amongst other purposes, the viewing system is used to adjust the beam’s focus point on the work piece in the chamber. Furthermore, the welding process inside the chamber can be watched. Whereas telescopic systems were previously used, camera systems are mainly employed now. Electron optical viewing systems are the most up-to-date development.
Electromagnetic system
The electromagnetic lens for beam focusing, as well as the deflection system are housed in this section.