| 摘要 |
PURPOSE:To prevent discharge energy from being scattered to the outside of a core tube and to make use of it effectively by a method wherein a cylindrical discharge shock-resistant plasma cup having an opening part in a axial center direction of the core tube is installed between a heat-insulating layer keeping discharge heat of the core tube and a plasma electrode. CONSTITUTION:A torus-shaped stepped part is formed at an electrode-supporting flange 6 composed of an SUS material or the like; a plasma cup 24 is fixed to the support part in such a way that it is coupled to the stepped part; this plasma cup 24 is constituted of a metal having a discharge shock-resistant characteristic such as Mo, Ta, W or the like. Thereby, discharge paths A, B can be formed easily during an operation to oscillate a laser beam. On the other hand, when an electric discharge is generated into a heat-insulating layer 9 from the neighborhood of the tip of a cathode electrode 4a (an anode electrode 3a), a discharge path C to the heat-insulating layer 9 is generated from the plasma cup 24 and prevents that the electrode-supporting flange 6 which is damaged easily by the electric discharge is damaged by the electric discharge. Thereby, it is possible to prevent the electric discharge from the electrode- supporting flange to the heat-insulating layer; as a result, a large part of discharge energy can be injected into a discharge part of a core tube. |
