Abstract
Turbomolecular pumps (TMPs) are fully grown products. There are four points to say so. First, hydrodynamic designing method is well established because there is no change in the pumping speed in the last ten years. Second, ultimate pressures of the order of 10−10 Pa are achieved. This corresponds to the lowest outgassing rate developed for metals. Third, they have extended operating range to pressures as high as 100 Pa with combination of turbo-drag pumps. Fourth, TMPs with electro-magnetic bearings produce perfectly clean vacuum with clean roughing pumps. For further development TMPs might focus on special usages.
