Patent ID: 7763849

Claim:
An FTICR mass analyzer having an ICR cell located in a homogeneous magnetic field having a field direction, the mass analyzer comprising: a plurality of detection electrodes, each of which is positioned symmetrically about an axis which is aligned with the magnetic field direction; a plurality of excitation electrodes, each of which is positioned symmetrically about the axis and arranged relative to the detection electrodes so that together, the detection electrodes and the excitation electrodes define a volume around the axis; a trapping plate positioned symmetrically on said axis on either side of said excitation and detection electrodes, such that an application of repulsive electrical potentials to the trapping plates traps ions in the volume defined by the detection and excitation electrodes; and a set of reflecting electrodes positioned symmetrically on said axis adjacent to each trapping plate so that electric potentials applied to the reflecting electrodes form a homogeneous electrostatic field with substantially no radial component for reflecting ions into the volume defined by the detection and excitation electrodes.