| AVS 56th International Symposium & Exhibition | |
| Vacuum Technology | Wednesday Sessions |
| Session VT-WeM |
| Session: | Partical and Theoretical Aspects of Gas Dynamics |
| Presenter: | S. Giors, Varian S.p.A, Italy |
| Authors: | S. Giors, Varian S.p.A, Italy L. Campagna, Varian S.p.A, Italy E. Emelli, Varian S.p.A, Italy |
| Correspondent: | Click to Email |
The current turbo-drag pumps commercially available for high vacuum systems are based on either Gaede or Holweck molecular drag stages technology, used in series downstream axial bladed stages to extend the maximum compression ratio up to the 10 mbar foreline pressure range.
Modern Gaede molecular drag stages use a disk shaped impeller, allowing a very compact design, but their maximum compression ratio is limited by the leakage effect to about 10 per stage.
Holweck stages use a less compact drum-shaped impeller, but are able to supply a higher compression ratio per stage and can easily be designed to supply a higher pumping speed thanks to the presence of many channels in parallel.
In this paper a new spiral molecular drag stage design is presented, with the advantages of both high compression ratio and pumping speed per stage and very compact design: a stage occupying the very tiny axial room of a Gaede, can compress as much as two or three Gaede stages in series, and supply the same compression ratio and pumping speed of a Holweck stage of the same diameter and peripheral speed, in a much smaller axial room.
The new spiral drag stage allows the design of very compact, high compression ratio turbo-drag pumps. The comparison of new design turbo-drag pump in the size of 700 l/s with existing Gaede and Holweck based products of the same size is presented, showing the technology advantages of the new design.