vapour pressure


The vapour pressure of materials in vacuum is essential for their suitability. The table below gives the temperatures at which a certain vapour pressure is reached for some elements.


Obviously, elements like Cd or Hg can never be used in a UHV system because their vapour pressure would prevent UHV to be achieved. Fe and W, on the other hand, are good candidates. In fact, most vacuum chambers are made of steel and tungsten is used as material of choice for hot filaments, for electron emission and heating.


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