Patent ID: 6872938

Claim:
A method of injection of sample ions into an electrostatic trap, comprising the steps of: (a) generating a plurality of sample ions to be analysed, each of which has a mass-to-charge ratio m/z; (b) receiving the sample ions through a storage device entrance in an ion storage device having a plurality of storage device poles; (c) supplying a trapping voltage to the storage device so as to trap at least a proportion of the received sample ions within a volume ρ in the storage device, during at least a part of a trapping period, the thus trapped ions each having a kinetic energy E k such that there is an average kinetic energy Ē k of the ions in the volume ρ during the trapping period or the said part thereof; (d) supplying a release voltage to the storage device so as to controllably release at least some of the said sample ions contained within the said volume of the storage device from a storage device exit, the release voltage being of a magnitude such that the potential difference then experienced by the ions across the volume ρ is greater than the said average kinetic energy Ē k during the trapping period or said part thereof, and further wherein the release voltage is such that the strength of the electric field generated thereby at any first point across the volume ρ, upon application of the said release voltage, is no more than 50% greater or smaller than the strength of the electric field generated thereby at any other second point across the volume ρ; (e) receiving those sample ions released from the storage device exit according to the criteria of step (d) through an entrance of an electrostatic trap having a plurality of trapping electrodes, the ions arriving as a convolution of bunched time of flight distributions for each m/z, each distribution having a full width at half maximum (FWHM); and (f) trapping the received sample ions within the electrostatic trap by applying a potential to the electrodes such that the sample ions describe movement having periodic oscillations in at least one direction.