| 摘要 |
PURPOSE:To sharply shorten a vacuum breaking time, a vacuum drawing time after maintenance or replacement, and a baking time by a method wherein a laser beam penetrating hole is shut off by a shutter at the maintenance or the replacement of an expendable mirror assembly to enable only the inside of the mirror assembly to be exposed to the air. CONSTITUTION:When a mirror assembly 33 is disassembled for maintenance or replacement, a pull 51 of a shutter 47 is pulled until a slit 53 is made to bear against a stopper 55. At this state, a laser beam penetrating hole 29 provided to plates 25a and 25b is separated from a laser beam penetrating hole 40 provided to the shutter 47, the hole 29 is blocked by the face of the shutter 47, and the mirror assembly 33 is separated from an oscillator main body 27. Thereafter, a vacuum breaking valve 35 is opened to keep the inside of the mirror assembly 33 at an atmospheric pressure. In succession, a mirror assembly 33 is dismounted from a resonator plate 3L and subjected to a maintenance operation or a replacement operation. Therefore, only the inside of a mirror assembly is subjected to a vacuum breaking process at the maintenance or the replacement of the mirror assembly 33. |
