The rotary probe device allows detailed examination of the electron beam and is particularly useful for determining the focus position, the focal spot size and the beam convergence angle. These are the most important beam characteristics which govern the welding performance. Degradation of beam quality will occur if an electron gun cathode is incorrectly set-up, damaged by ions during use or distorted due to thermal cycling. Monitoring beam parameters improves quality assurance and, in addition, enables more rapid development of welding conditions for new applications.
The monitoring equipment consists of a lightweight arm fitted with tungsten wires which is rotated at 3000rpm or higher. As the wires move through the beam some current is collected which is displayed as an oscilloscope signal. The beam width can be readily found from this signal, which also gives an indication of the intensity and angle of convergence. Any critical changes in the gun set-up or elsewhere in the electron column can cause these parameters to change - this will generally disrupt machine performance and can lead to inconsistent welding results.
Rotary probe devices are available to measure beams of up to 15kW power and have proved to be a useful diagnostic tool.
If you have any questions regarding beam monitoring equipment please contact us.