In a simple diff pumped system, which uses silicon oil or pentavac or similar fuild, there is no need for a cold trap above the diff pump.
I have a full block diagram of a simple fusor system on my website which shows all traps, valves, etc. A three page discussion on it follows the diagram.
http://www.richmond.infi.net/~rhull
The diff pump would go between the fusor and the valve near the trap. Another valve between the diff pump and the fusor would be nice. Thus, I would only add those two components to my diagram to make it a full fledged diff pumped system.
Richard Hull
Created on Wednesday, March 21, 2001 2:13 PM EDT by Richard Hull