How do you produce high vacuum?

Answer 1

Achieving high vacuum is difficult because all of the materials exposed to the vacuum must be carefully evaluated for their outgassing and vapor pressure properties.Ultra high vacuum generally requires custom built equipment, strict operational procedures, and a fair amount of trial and error . Ultra high vacuum systems are usually made of stainless steel with metal gasketed conflat flanges. The system is usually baked, preferably under vacuum, to temporarily raise the vapour pressure of all outgassing materials in the system and boil them off. If necessary, this outgassing of the system can also be performed at room temperature, but this takes much more time. Once the bulk of the outgassing materials are boiled off and evacuated, the system may be cooled to lower vapour pressures to minimize residual outgassing during actual operation. Some systems are cooled well below room temperature byliquid nitrogen to shut down residual outgassing and simultaneously cryopump the system.