Multiple port vacuum pump system

A mass spectrometer system comprising:

• an ion source;
• a mass analyzer;
• an ion optical arrangement for transporting ions from the ion source to the mass analyzer;
• and
• a vacuum pump system for evacuating at least 5 volumes of the mass spectrometer, the vacuum pump system comprising a forevacuum pump and a turbomolecular pump arrangement, the system arranged so that the forevacuum pump pumps an output of the turbomolecular pump arrangement to atmosphere, and wherein the turbomolecular pump arrangement comprises multiple pumping ports corresponding to different pumping stages and is configured so that:
• there are at least 5 pumping stages, each connected to a respective volume;
• each pumping stage is separated by at least one set of rotor blades and at least one set of stator blades;
• not more than 3 pumping stages have pumping speeds in excess of ⅓ of the highest pumping speed of a pumping stage when under vacuum and/or a pumping port cross section in excess of ⅓ of the biggest pumping port cross section;
• at least 2 pumping stages have pumping speeds less than ¼ of the highest pumping speed of a pumping stage when under vacuum and/or a pumping port cross section of less than ¼ of the biggest pumping port cross section;
• wherein when under vacuum the total range of pressures across all volumes pumped by the turbomolecular pump arrangement spans at least 8 orders of magnitude and the volume at the lowest pressure is maintained below 1×10−9 mbar.