Roughing pump

A roughing pump is any vacuum pump (typically mechanical) used to initially evacuate a vacuum system, as a first stage towards achieving high vacuum or ultra high vacuum. Pumps that operate in the high vacuum ranges don't operate or operate inefficiently at atmospheric pressures, whereas pumps that work efficiently at atmospheric pressure usually can't produce a vacuum lower than approximately 1x10^-3 torr. The term "roughing pump" derives from the vacuum range it works in, "rough vacuum", above 1x10^-3 torr.

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One consideration for choosing a roughing pump is whether the pump uses lubricating oil that's exposed to the vacuum, which can result in oil backstreaming into the vacuum chamber.

Sources

• The Essentials of a Vacuum System, Hasina Jamal, University of Maryland