A type of diffusion pump that people might overlook because it doesn't look like the "typical" diff pump is the booster. These pumps are often seen paired with a mechanical pump on the same stand. They look like a small squat pot with two short stacks (one shorter than the other) coming out of the top of the pot. The longer stack is a bit bigger in diameter and is the inlet. The shorter one is the outlet. The pump may be aircooled or it may have coils for water cooling.
A common type is the CVC VMF-10 (more recently mfg by Varian). It's about 8" high x 4" diameter at the base.
The purpose of these pumps is to boost the performance (speed/base pressure) of mechanical pumps. The VMF-10 has its max pumping speed (around 10 liters/sec)at about 0.1 microns and it likes to see a forepressure of 0.1 Torr or less.
They are not that common but they come rather cheap as surplus either because no one knows what they are or because they aren't super high vacuum pumps. But, for giving that extra kick in performance that your mech pump needs for running a fusor, this might just be what you need.
Steve
Created on Friday, March 30, 2001 5:02 PM EDT by Steve Hansen