Electrostatic trap

摘要

An electrostatic trap such as an orbitrap is disclosed, with an electrode structure. An electrostatic trapping field of the form U′(r, φ, z) is generated to trap ions within the trap so that they undergo isochronous oscillations. The trapping field U′(r, φ, z) is the result of a perturbation W to an ideal field U(r, φ, z) which, for example, is hyperlogarithmic in the case of an orbitrap. The perturbation W may be introduced in various ways, such as by distorting the geometry of the trap so that it no longer follows an equipotential of the ideal field U(r, φ, z), or by adding a distortion field (either electric or magnetic). The magnitude of the perturbation is such that at least some of the trapped ions have an absolute phase spread of more than zero but less than 2 π radians over an ion detection period Tm.

主权项

1. A method of mass analyzing ions in an electrostatic trap, comprising:
applying a substantially electrostatic potential to at least a part of the electrode assembly, such that the ions undergo substantially isochronous multiple reflections and/or oscillations in a volume V; causing a perturbation of the electrostatic potential so that a phase spread for a first number of ions in the volume V increases during an ion detection period Tm, but a phase spread for a second number of ions in the volume V decreases during the ion detection period Tm.