Abstract: A method for the removal of embedded contamination from a metallic surface in which a laser beam is directed on to the contaminated surface. The laser beam has sufficient power density to cause direct ejection of laser-generated melt pool liquid from the metallic surface thereby removing a metallic surface layer containing the embedded contamination. Means are provided for the collection of laser ejected material in order to prevent recontamination of the metallic surface or contamination of previously uncontaminated surfaces.

Abstract: In a method of detecting the spatial position of a laser beam relative to a body locatable in the path of the laser beam by detecting an acoustic signal produced by the beam in the body, wherein the laser beam carries a power modulation signal and the body has a plurality of acoustic sensors for detecting the acoustic signal produced in the body by the laser beam, the method includes detecting in the outputs of the acoustic sensors signals corresponding to the power modulation of the incident laser beam and detecting any difference in phase between the detected signals. A processor may be provided for processing the outputs of the acoustic sensors, the processor including a sensor for sensing in the respective outputs signals corresponding to the power modulation of the output beam of the laser and a phase sensitive detector for detecting differences in phase between the detected signals.

Abstract: A method of treating a concrete or other non-metallic surface contaminated with embedded radionuclides to reduce the total level of radioactivity in a concrete or other hydraulically bonded material body is described. The method comprises the steps of producing relative mutual movement between the surface to be removed and a laser heat source such that a layer adjacent the surface is caused to be detached from said concrete body. The surface may be detached as a vapour, in flakes or as a sheet.

Abstract: In a method of treating a surface 12 of an object 10 contaminated with radionuclides 14, a laser source 16 is directed at the surface 12 to apply a local area 18 of intense heat to the surface 12. The laser source 16 is arranged to pass in a raster manner to cause local melting of the surface 12, surface 12 subsequently solidifying and fixing the radionuclides 14 therein. At least one layer of a coating material be applied before or after the application of the intense heat to fix and seal the radionuclides on or in the object.

Abstract: Apparatus and method for monitoring laser materials processing, such as laser welding and laser drilling, wherein an indication of the quality of the processing is obtained by monitoring the plasma generated spaced charge distribution near the melt pool. A metal electrode, or electrodes, is disposed near the melt pool but not in contact with the workpiece, nor necessarily in contact with the hot plasma. The electric charge distribution (one dimensional or multi-dimensional) is monitored between the electrode or electrodes and the workpiece or between the electrodes themselves. The existing laser processing nozzle (insulated from the workpiece) can be used for this purpose, multi-probes such as a quadrant nozzle, can identify the focused laser beam position in real time.

Abstract: A gas shroud comprises a chamber having a beam inlet, a gas inlet and an outlet portion. A shroud having an inner surface and an outer surface is operably associated with the outlet portion and is rotatable relative to the chamber. A drive system is operably connected to the shroud for rotating the shroud. A plurality of fins are positioned about the outer surface of the shroud and are rotatable therewith so that rotation of the shroud causes the environment surrounding the shroud to be expelled radially away therefrom.

Abstract: A beam monitor comprises a mirror for reflecting an incident beam of radiation to a target and for receiving a reflected beam from the target and has a surface on which the beams impinge. Incident and reflected beam channels are orthogonally disposed within the mirror. Each of the channels has an opening disposed in the surface for admitting the associated beam thereto. First and second detectors are operably associated with the mirror and each generates a signal indicative of a selected characteristic of the beam illuminating the associated channel. A controller compares the generated signals and thereby monitors at least one selected characteristic of the target or of the beam.

Abstract: A screw powder feeder has a rotary screw (12) disposed at the base of a hopper (10). The screw (12) comprises a twist drill bit. Powder is discharged into a chamber (18) and picked-up by a flow of gas. The pressure in chamber (18) is varied relative to the pressure in hopper (10) to control the feed rate for a given screw speed. Ultra-low feed rates are made possible by feeding gas into the hopper (10) through the screw (12) and controlling the relative gas pressures such that the pressure in the chamber (18) exceeds the pressure in hopper (10).

Abstract: A predetermined characteristic of a laser beam is detected by disposing a reflector (11) in the path of the beam and coupling an electromechanical transducer (12) to the reflector to detect a mechanical response of the reflector to the incident beam.

Abstract: Non-conductive workpieces present a problem where laser treatment of a workpiece is to be augmented by the application of an arc, since the arc cannot be struck to the workpiece. In the present invention a laser beam is augmented by an arc struck between two electrodes typically on opposite sides of the workpiece. The arc usually either penetrates the workpiece, or two arcs are formed on respective sides of the workpiece.

Abstract: Methods and apparatuses for cutting, welding, drilling or surface treating a workpiece are described. A laser beam is directed towards a workpiece and an arc is struck between an electrode and the heat affected zone created by the laser beam in the workpiece.