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.

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Plasma processes are a very popular method to produce high‐grade quality thin films on many different substrates. There are a large variety of different coating systems. Such systems go from small‐scale machines (i.e. Optical coating systems for ophthalmic lenses and filters), through mid‐size machines (such as systems for deposition on flexible substrates used in the food, electronics and packaging industry or systems used for producing optical and magnetic data storage media), up to large‐area systems (i.e. used for architectural glass coating or in the flat panel display industry). Even if all of these systems look very different, there are few common specific points that characterize most of these applications. The plasma is normally based on Argon, Oxygen, Nitrogen (and more recently Krypton) mixtures in the mid 10–3 mbar range. The base pressure is generally over the mid 10–7 mbar range. The deposition rate is very high and so the demand for gas throughput is high as well. (i.e. a glass coater can ionize more than 2000 sccm of Argon per cathode segment). There is a high probability of debris and particle generation within the process; roughing and venting cycles are fast and sometimes uncontrolled (they can be described as air‐in rushes in some cases). Uptime and reliability are not an option, but a must in industrial production environments. It is therefore difficult to believe that turbo molecular pumps originally designed to reach the 10–10 mbar range with a high number of pumping stages and very tight clearances, are capable to work reliability in this demanding environment. We are keener to think that if we want a reliable and performing pumping solution the design of the turbomolecular pump must be specific and dedicated to the application. Ideally this development process is done side by side with the ultimate equipment users, matching at best process requirements and turbomolecular pump design know‐how. As Varian Vacuum Technologies, we have followed that process and this article is sharing the results.