High Vacuum System

The system starts with a Welch 1397 mechanical pump.

A molecular sieve foreline trap (stainless cylinder with central hole for bakeout heater) separates the roughing pump from the Balzers 330 liter/sec turbo pump that provides the high vacuum.  

A Stanford Research System residual gas analyzer provides important information both for vacuum diagnostics and  for our experimentation.  This instrument is a quadrupole mass spectrometer with 1 AMU resolution.  It is equipped with both Faraday cup and electron multiplier detectors and can detect partial pressures down to 5x10-14 torr.  It also provides a total system pressure measurement and functions as a built-in He leak detector.  For further details go to the SRS web site.

The vacuum system is mounted on a rigid steel frame that provides ample room and support for auxiliary equipment.  In addition to the RGA, we have several capacitance manometers for precise measurement of experiment pressures.  Our collection of Conflat-style hardware can be quickly assembled as needed for a particular experiment.  Our TIG welder permits the rapid fabrication of a wide variety of custom vacuum flanges with electrical feedthroughs or gas ports. 

The computer just out of the picture to the right serves as the display/control unit for the RGA.  The black bottle in the foreground is N2.  The RGA showed us that water vapor (from water molecules adhering to the walls of the system) was the #1 problem during pumpdown, so now we let the system up to atmospheric pressure with dry N2 instead of damp Austin air.

This system pumps down in minutes to 10-6 torr.  In a couple of hours it will reach 10-7 torr.  With a modest bakeout (or days and days of continuous pumping) it will reach 10-8 torr.

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