Contact-free exhaust system for vacuum compatible gas bearing guides

Using linear gas bearing guides in a high vacuum environment, the common method to keep the vacuum quality is to exhaust the gas emitted by the bearing pads before leaking into the vacuum chamber. Thereby the exhaust tubes between the guide and the exhaust pumps should interfere with the guide as little as possible while maintaining a flexible connection and a highly effective exhaustion rate. A novel exhaust system that implements these requirements is described within this paper. The major achievement was the realization of two exhaust tubes slidable into one another combined with the known method of non-contact clearance seals, thus enabling an highly efficient and yet disturbance free exhaustion. This setup was developed and characterized at static and dynamic conditions. An analytical model for dimensioning the non-contact seal was worked out and experimentally verified. The number of seal stages and the clearance height were identified as the major impact factors on the leakage rate of the setup. It is concluded that the investigated approach is very suitable for vacuum compatible gas bearing guides since a vacuum level in the order of 10-4 Pa was maintained during the experiments.