Abstract: A mass spectrometer comprises an ion source which provides a beam of ions; a mass filter comprising a pair of electrodes and a drive circuit, the drive circuit operable to apply a time varying voltage to the electrodes having a profile that accelerates the ions to equal velocities irrespective of their mass: charge ratios; and an ion detector for detecting the proportions of ions according to their mass-to-charge ratios. In one embodiment, the voltage profile is exponential. In another embodiment, the voltage profile is a sequence of constant amplitude and increasing repetition frequency pulses. The novel mass filter thus imparts equal velocities to all ion species irrespective of their mass. This allows the ion species to be discriminated at the detector by energy, enabling simple and compact detection schemes to be used.

Abstract: A mass spectrometer comprises an ion source which provides a beam of ions; a mass filter comprising a pair of electrodes and a drive circuit, the drive circuit operable to apply a time varying voltage to the electrodes having a profile that accelerates the ions to equal velocities irrespective of their mass: charge ratios; and an ion detector for detecting the proportions of ions according to their mass-to-charge ratios. In one embodiment, the voltage profile is exponential. In another embodiment, the voltage profile is a sequence of constant amplitude and increasing repetition frequency pulses. The novel mass filter thus imparts equal velocities to all ion species irrespective of their mass. This allows the ion species to be discriminated at the detector by energy, enabling simple and compact detection schemes to be used.