Abstract: Stability of the optical path in a laser resonator cavity is achieved by means of two reflective surfaces mounted orthogonally with respect to each other, serving as the reflector at one end of the resonator cavity. Return and feedback mirrors are rigidly mounted at the opposite end of the aforementioned resonator cavity. Changes in relative orientation not self-compensated by the use of orthogonally-mounted mirrors are corrected by means of a real-time servomechanism. A typical servomechanism comprises an auxiliary laser mounted rigidly to one end of the laser resonator cavity reflecting a collimated light beam from a reflector mounted rigidly to the opposite end of the resonator cavity. The reflected spot is detected by a detector, sensitive to positional changes in the reflected light, rigidly mounted with respect to the auxiliary laser. The positional changes of this reflected spot are used to drive a linear translator to correct the relative orientation in real-time.

Abstract: An apparatus is described for cooling the inner circumference of an annular laser window. A cylinder, conductive to heat, is inserted in the central opening of the annular window. Compliant metal wires are used to maintain good thermal contact between the cooling cylinder and the inner circumference of the annular window. A spring compression device is used to maintain constant pressure on the compliant metal wires. The portion of the cooling cylinder outside the window, in the region external to the laser, is slotted. A cooling fluid, typically refrigerated air, is passed through the slots to provide effective heat exchange with the metal cylinder.

Abstract: A method and apparatus for welding a first workpiece which is to be joined to a second workpiece, with said first workpiece extending within or through the second workpiece. The apparatus includes a rotatable workpiece drive member, a workpiece holding fixture for securing at least one other workpiece in position relative to the first workpiece and a radial support for the first workpiece that is separate and spaced from the drive member. Among the preferred embodiments disclosed for providing the radial support are a tailstock supporting sleeve arrangement, collet chucking, and roller type steady rests.