Molecular Seive for making vacuum tubes

  • Thread starter Y2keddie
  • Start date
im trying to jog my memory back 30years when I worked with vacuum tubes. I worked with manufacturing of image tubes. I remember the vacuum systems used vac-ion pumps to achieve -12 power torr. I alsoo remember first using a molecular seive for roughing,pumping to 10 microns.
The seive was a canister filled with a zeonolite which was cooled with liquid nitrogen.
I believe it worked as an adosorbtion process where water molecules would adhere to the zenolite surface thus removing water molecules from air in the beginning stages of vacuum.
What my memory is fuzzy about: is the seive used just for water,or other gas molecules?
My recall is not that good. I’m guessing the process sequence was:

Use Mechanical pump ( to 10 microns).
Then molecular Seive (to ?? Torr) The decrease in pressure would indicate the oil molecules had decreased?
Then Vac Ion pump to 10x-14 torr

That would make sense. The oil contaminants would destroy the tubes cathode properties.

Want to reply to this thread?

"Molecular Seive for making vacuum tubes" You must log in or register to reply here.

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving