Turbo molecular pump for mass spectrometer

A turbo molecular pump comprising a stationary frame structure and at least one rotor stage located at a low pressure input region 204A, wherein a rotor rotates about an axis with respect to the stationary frame and has an axially aligned central shaft receiving member 202 from which a first rotor blade portion 206A extends radially outward and is connected to a second rotor blade portion 206B which extends paraxially to, and along the, central shaft receiving member towards a high pressure output region 204B, wherein the first and second rotor blade portions deflect gaseous matter paraxially and radially inwards, the pump further comprising a third rotor blade portion 206C which extends radially outward from the central shaft receiving member and connects to the second rotor blade portion at a position between the low pressure input region and high pressure output region, in order to enhance mechanical stability, wherein, during operation, the third rotor blade portion deflects gaseous matter substantially paraxially. A mass spectrometer comprising a turbomolecular pump is also claimed.