FAST PUMP-DOWN ALUMINUM ULTRAHIGH-VACUUM SYSTEM

An extremely fast pump-down aluminum ultrahigh vacuum system has been developed, with an evacuation time of less than 5 min from atmosphere to pressures in the 10(-9) Torr range. Key elements of the system are: (1) a moisture trap (three-stage sintered metal filter) to produce super-dry nitrogen gas, with a water content of about 10 parts per billion, and (2) a cryogenic aluminum alloy panel. A 50 l/s turbomolecular pump is initially used to evacuate the chamber, followed by a 300 l/s turbomolecular pump as the main pump, which immediately operates with normal its full speed. The system can be vented to atmospheric pressure, with the use of super-dry nitrogen gas at a flow rate of 10 l/min, without degradation of the fast pump-down time.