| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for reducing vibration of a structure contained in a vessel, in a system in which the structure is cooled by a liquid refrigerant introduced into the vessel. SOLUTION: At least three pieces of balloons 6 are disposed rotation- symmetrically with respect to the central axis of a lens. As a replacement for the balloons provided separately, a toroidal balloon many also be employed. A large difference exists in the rigidities of the refrigerant and air. Air exhibits a father more softness than the refrigerant. Accordingly, when the balloons 6 are sunk under the refrigerant 4 as shown (b), the balloons 6 relax pressure fluctuation of the refrigerant 4. When the balloons 6 are placed in the vicinity of the structure of an electromagnetic lens 2, the vibration is relaxed in those parts, and the vibration can be prevented from being transferred to the lens 2.
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