Abstract: A high-efficiency plasma confining method, and a laser oscillating method of oscillating a laser, confine a plasma generated by entering a laser beam via an entry of a superconducting cylinder within the cylinder. The methods include the step of inhibiting diffusion or expansion in the radial or axial direction of the generated plasma by reducing the inside diameter of the cylinder between the entrance and an exit thereof. A magnetic line of force may be generated in the axial direction by winding a coil around the superconducting cylinder, to thereby confine the plasma. A laser oscillator for carrying out the method includes a superconducting cylinder, a supply mechanism for supplying a gas or a solid into the cylinder, and a laser irradiating mechanism. The inside diameter of the cylinder is reduced between an entry and an exit thereof, or the inside diameter of the cylinder is reduced at the entry and the exit thereof.

Abstract: A laser beam machining device employs a laser for generating a laser beam, a chopper device for intermittently blocking the laser beam for intermittently irradiating the laser beam onto the surface of a work, and an assisting gas discharge device for injecting assisting gas toward the point, on which the laser beam is irradiated. By locating the chopper upstream of the primary condenser and away from the assist gas flow, the assist gas to be discharged toward the predetermined point of the work, on which the laser beam is irradiated, is not disturbed which otherwise would cause turbulence to degrade the precision of the laser beam machining operation. In addition, the assisting gas discharging device is so arranged as to direct the assist gas flow substantially along the axis of the laser beam to be irradiated onto the work surface.