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Technical Information/Glossary of Terms
|High Vacuum Equipment-Glossary of Terms 1
[Term]Baking
Gases such as oxygen and nitrogen, which have a small adsorption activation energy (E) and a short adsorption residence time (τ), are evacuated quickly. However, in the case of water, which has a high activation energy, evacuation does not progress quickly unless the temperature (T: absolute temperature) is raised to shorten residence time. This time is characterized as τ=τ0 exp(E/RT) where R is the ideal gas constant and τ0=(approx.) 10-13 sec.
Residence time of water at 20°C is 5.5 x 10-6 sec, whereas at 150°C, it is 2.8 x 10-8 sec, or about 200 times shorter. The objective of baking is to exhaust water with long adsorption residence time more quickly.