| 摘要 |
At least one of the conductive members has a hollow storage portion that is formed at the conductive member and a communication hole through which the storage portion and the vacuum chamber communicate with each other, a getter is set inside the storage portion, and an adsorbed object such as metal particles and gas in a vacuum chamber is adsorbed by the getter. By prevent application of the electric field to the getter, even though the electric field appears in a vacuum casing, a temperature of the getter does not reach a re-release temperature, and also electron stimulus desorption phenomenon does not occur, then it is possible to prevent the metal particles and the gas etc. which have been adsorbed once by the getter from being released.
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