The development of the first turbomolecular pump is attributed to Becker[1] in 1957 with the first commercially available units in 1958. Kruger and Shapiro published work in 1960 [2] which described the blading geometry of axial-flow molecular turbines in molecular flow. In the mid-1960s open, thin-bladed axial flow designs typical of modern day turbomolecular pumps were adopted. Subsequently, 'compound stage' turbomolecular pumps were developed (from the mid-1980s) in which Gaede or Holweck molecular drag stages were added to the blade stacks. These had significantly higher compression ratios and allowable backing pressures [3-7]. The turbomolecular pumps' bearing mechanisms have to support rotors at very high frequency typically ranging from 400 to 1500Hz. Magnetic levitation bearing turbomolecular pumps 'Maglev' are available which have active control and contact-less bearings. These pumps have applications in for example, semiconductor processes, low-vibration and radioactive duty but are significantly more expensive than conventional ball bearing pumps. This paper focuses on the recent developments in the Edwards' nEXT range of conventional ball bearing turbomolecular pumps.
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