TWI Industrial Member Report Summary 165/1981
By R C Crafer and P J Oakley
Methods that are used to measure the three parameters that characterise the 10.6 µm wavelength beam of a continuous wave (cw) carbon dioxide laser are described. Beam power is measured by calorimetric techniques, using either the complete beam, or sampling a known fraction of the beam. Beam diameter and intensity distribution can be measured by heating or charring materials, and also by vaporising acrylic. However, the amount of information that can be deduced from such techniques is limited. The more sophisticated techniques that have been used to characterise high power CO2 laser beams are outlined. Particular details are given of a Welding Institute developed high intensity beam scanner. using a photon drag detector. Its principle of operation and construction are described, and results given and interpreted for 2 and 5kW fast axial flow CO2 lasers.