The invention relates to devices and methods for the acquisition of
mass spectra with very high
mass resolution in
ion cyclotron resonance mass spectrometers and methods to produce the devices. The invention presents cylindrical ICR measuring cells with special
electrode geometries to generate
harmonic trapping potentials for orbiting ions up to the walls of the
cell. Only a single DC
trapping voltage has to be applied to create the
harmonic trapping potential distribution. The sheath of the cylindrical
cell is divided by longitudinal gaps into a multitude of sheath electrodes, which either have to carry
layers with resistance profiles able to generate parabolic
voltage profiles along the sheath electrodes, or which form sheath electrodes of varying width by parabolic gaps, able to create complicated potential distributions which are
harmonic on average for orbiting ions. Orbiting ions of a given mass m / z can oscillate harmonically in axial direction with exactly the same oscillation frequency, independent of the
radius of their
orbit and of their axial
oscillation amplitude. Ideally, the cylinders are closed by endcaps with rotationally hyperbolic form, divided into partial electrodes like in infinity cells. The ions can then be excited to their
cyclotron motions by dipolar excitation fields also uniformly filling the ICR
cell up to the endcaps. The
ion clouds orbiting on their
cyclotron trajectory are kept together for much longer periods than was possible hitherto, even if they
orbit near the sheath electrodes. The image currents thus give rise to minute-long transients, from which mass spectra with ultrahigh mass resolution can be obtained.