Method of assessing vacuum conditions in a mass spectrometer

摘要

A method is proposed for assessing the vacuum conditions in a mass spectrometer (10) such as an ion cyclotron resonance or orbital trapping mass spectrometer. Such mass spectrometers generate a transient detection signal resulting from ions of one or species in an ion trap (80). The parameters of the trap and/or introduced ions are adjusted so as to cause the decay rate of the transient in respect of the ion species to be dominated by collisional effects. Typically this can be achieved by introducing ions into the trap (80) in quantities such that ion clouds of a particular ion species self bunch. The rate of decay of the transient signal in that case is determined and compared with one or more threshold decay rates. This in turn can provide an indication of vacuum conditions within the trap (80).