Abstract: An apparatus and method for monitoring material removal from a workpiece by a beam of energy during a material processing operation are disclosed. A detector is positioned for sensing optical emissions from the workpiece caused by removal of material when an energy beam pulse is incident upon the surface of the workpiece. A computing circuit, algorithm or artificial neural network is provided for determining a quantity of material removed from the sensed optical emissions in real-time during the material processing operation. Analysis of the optical emission pulses caused by the material removal provides an indication of the efficiency of the material processing system and provides feedback for manual or automatic adjustment of material processing parameters during the material processing operation.