| 摘要 |
A turbo molecular pump which can prevent the lowering in vacuum property while maintaining the increased throughput of the gas to be discharged during a normal operation. An axial interval between a rotor vane and a stator vane provided close to a inlet port is set so that the gas can be dealt as molecular flow under a condition that the pressure in the inlet port during the normal operation is not less than 10 mTorr. Since whether or not the gas can be dealt as the molecular flow is delimited by a mean free path of gas molecular, the above axial interval is set based on the mean free path. With this arrangement, the gas can be dealt as the molecular flow under the condition of pressure not less than 10 mTorr during the normal operation, and thus sufficient discharge performance can be obtained. Consequently, even if the throughput of the gas supplied to a vacuum chamber during the normal operation is increased, it is possible to ensure the required pressure (vacuum property) while maintaining the increased throughput.
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