A mass analyzer for use in a mass spectrometer. The mass analyzer has a set of electrodes including electrodes arranged to form at least one electrostatic sector, the set of electrodes being spatially arranged to be capable of providing an electrostatic field in a reference plane suitable for guiding ions along a closed orbit in the reference plane, wherein the set of electrodes extend along a drift path that is locally orthogonal to the reference plane and that curves around a reference axis so that, in use, the set of electrodes provide a 3D electrostatic field region. The mass analyzer is configured so that, in use, the 3D electrostatic field region provided by the set of electrodes guides ions having different initial coordinates and velocities along a single predetermined 3D reference trajectory that curves around the reference axis.