| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a particle optical device having a predetermined final vacuum pressure. <P>SOLUTION: A pressure chamber of this device is connected to a volume where steam or gas is present at known pressure through a first throttle valve, and connected to a vacuum pump through a second throttle valve. By converting a ratio of two conductance values related to the throttle valves to a calibrated ratio, the final pressure of a vacuum chamber is set at predetermined final pressure. Thereby, for instance, the need of a vacuum gage and a control system is obviated, whereby such a device can be designed in a small size. <P>COPYRIGHT: (C)2007,JPO&INPIT</p> |
