| 摘要 |
PURPOSE:To prevent the whole part of a preliminary discharge electrode from warping, by providing a retaining part formed in the manner in which a part of the outer part of an insulating pipe of the preliminary discharge electrode is exposed, along an optical axis, on the discharge surface of a main discharge electrode, and this insulating pipe does not penetrate the other side of the main discharge electrode, and holding the preliminary discharge electrode in the state where it is inserted in the retainer. CONSTITUTION:On the discharge surface 21 side of a cathode 20, a groove type retainer 22 is formed in a body, which, from a sectional view, has a section surrounding the other periphery more than a semi-circle of the insulating pipe 11 of a preliminary discharge electrode 6, and making a part of the outer side surface of the insulating pipe 11 along a laser optical axis expose. When the preliminary discharge electrode 6 is retained by the retainer 22 like this, the insertion from the discharge surface 21 side is physically impossible, so that the electrode 6 is inserted from the one end of the retainer 22 toward the other end, and retained. Although the preliminary electrode 6 vibrates almost in a body with a cathode 20 at the time of main discharge, the electrode is totally retained, so that it can be prevented from warping toward the side of an anode 20. |
