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
Any ideas will be very much appreciated.