The above URL will get you to the old BBS. Good luck. It was tough to search.
It sounds like you have done about all you can for the 1400 and 20 microns might be as low as it will go. That is about what mine did on Fusor I.
Many pumps are left running to maintain system vacuum. They are forepumps remember. If they were stopped, they would have to be brought up to air. This could in theory introduce unwanted contaminates in the system when cranked back up and valved back into the diff pump chain.
The Bussard effort at EMC2 here in VA., when I visited it, had its pumps going full bore 24 hours a day and only shut down if an automatic control system sees big problems. To get a system to 10e-10 torr, like they had, takes time and keeping it there is an art. Opening the thing to air for major changes can be a one-two week down time deal!
Richard Hull
Created on Wednesday, March 28, 2001 9:51 PM EDT by Richard Hull