Electron beam generated in low pressure noble gas atmosphere – compact device construction and applications

Abstract

Simple and compact design of prototype electron beam welding machine is presented. The instrument allows welding of typical materials as metals and alloys. It can be used also for surface melting of insulators like glass and ceramic. Electron beam source uses hollow cathode of 20 mm diameter and operates in the pressure between 0.001 to 0.1 Torr of noble gas, with the work-piece positioned at 30 mm distance from the cathode. Focussing of the electron beam is provided by curvature and shape of the cathode surface. No magnetic focussing is provided. Applied voltage to the cathode is in the range 1 – 3 kV, so the energy of electrons is much lower than in conventional electron beam welders. The presence of working gas in the chamber and the occurrence of accompanying glow discharge allows for surface charge neutralization. This causes that the electron beam can bombard insulating materials. The prototype construction of welder does not require complicated and expensive pumping system. In order to obtain a necessary vacuum, sufficient is rotary vane pump. A simple construction of the electron gun design makes it very cheap. We will present some examples of the use of the welder for making of wire thermocouples, welds of small pieces up to 0.4 mm thick sheet metals like as: Al, Cu, Ag, Ni, Fe or their alloys. In addition, we will show the results of bombarding the surface of different types of glass (sodium borosilicate and quartz) and alundum ceramic