Hi All,

      We have a Delta Plus XL Mass Spectrometer that we vented last week to 
replace one of the quartz spacers in the source. While all the parts we 
laid on the table overnight (we had to order the spacer), the cooling unit 
in our building failed and the lab temp got up to 85 degrees. We had 
inadvertently left our cooling water turned after venting the instrument. 
When we reassembled the source and tried to pump down, the source vacuum 
will only pump down to 5X10-5. Thermo said that the source flange clamps 
were overtightened and the knife edge seal that seals the source housing 
needed to be replaced. Well we finally got the source flange clamps (from a 
secondary source), and replaced the knife edge seal and see that the source 
vacuum is still 10-5. The forevac vacuum is normal (2X10-3). My 
question(s): Could the temperature difference between the cooling water (15 
degrees) and the air temperature (85 degrees) cause problems in the vented 
source housing and/or exposed flight tube?  Could the high vacuum gauge be 
faulty? Do I suddenly not know how to tighten a source gasket to get the 
proper vacuum?

Any ideas will be very much appreciated.

Bernie Genna
NCSU