| 摘要 |
Apparatus for establishing and controlling a low pressure gas mixture in a vacuum enclosure ( 8 ) comprises at least one secondary pump ( 9 ) of the molecular, turbomolecular, or hybrid type, followed by at least one primary pump ( 10 ), with first control and adjustment means ( 22 ) such as a regulation valve ( 24 ) for controlling and adjusting the total gas pressure of the mixture of gases in the vacuum enclosure ( 8 ) as a function of a total pressure setpoint ( 27 ). The apparatus further comprises second control and adjustment means ( 28 ) such as a second regulation valve ( 29 a) downstream from the secondary pump ( 9 ). The second regulation valve ( 29 a) is controlled as a function of a delivery pressure setpoint ( 32 ) to modify the delivery pressure of the secondary pump ( 9 ) and thus to adapt its pumping capacity in selective manner. This makes it possible to adjust the proportions of the gases in the mixture of gases in the vacuum enclosure, independently of the total pressure which is controlled by the first regulation valve ( 24 ).
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