TURBOMOLECULAR PUMP DESIGN FOR HIGH-PRESSURE OPERATION

A simple model of compressible. Couette-Poiseuille flow is developed t o describe the pressure distribution in a single Gaede stage, in visco us flow. From this a scaling law to optimize the stage design has been derived. Both model and scaling law are verified using experimental m easurements of different channel geometries. A practical limit to high pressure operation: is set by the power consumption of the motor. A p rogram has been developed to optimize the design of a multistage Gaede pump and the results of it suggests that a pump with an axial height of only 3 cm can exhaust at pressures up to 100 mbar. (C) 1998 America n Vacuum Society.