US Patent 7893401 Mass spectrometer using a dynamic pressure ion source

A mass spectrometer has a pulsed ion source, a first ion trap (10) for trapping ions generated by the pulsed ion source and for locating trapped ions for subsequent ejection from the first ion trap. A pulse of cooling gas is introduced into the first ion trap (10) at a peak pressure suitable for enabling the first ion trap (10) to trap ions. A turbomolecular pump (17) reduces the pressure of cooling gas before the trapped ions are ejected from the first ion trap (1) towards a second ion trap (20) for analysis. The pulsed ion source has a sample plate (14) which forms an end wall of the first ion trap (10).