Turbomolecular pump design for high pressure operation

A simple model of compressible Couette–Poiseuille flow is developed to describe the pressure distribution in a single Gaede stage, in viscous flow. From this a scaling law to optimize the stage design has been derived. Both model and scaling law are verified using experimental measurements of different channel geometries. A practical limit to high pressure operation is set by the power consumption of the motor. A program 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.