Design and operation of scroll-type dry primary vacuum pumps

Since being rediscovered three decades ago, scroll technology has been succ essfully adapted to vacuum use. Several innovations have allowed scroll-typ e pumps to produce vacuums lower than 10 mTorr; the pumps are used in many applications requiring an inexpensive, dry, long-lived pump. In this articl e, we detail the scroll design procedure, focusing on the trade offs betwee n the need for sufficient vacuum and low manufacturing cost. As an illustra tive example, we consider the design requirements for a high helium compres sion scroll design for use in leak detectors. We also present guidelines fo r proper pump operation, including the need for gas ballasting, high-water operation, and proper pump isolation schemes. (C) 2001 American Vacuum Soci ety.