The invention relates to measuring devices of an electrostatic
Fourier transform mass spectrometer and measurement methods for the acquisition of
mass spectra with high
mass resolution. The measuring device includes electrostatic measuring cells according to the Kingdon principle, in which ions can, when appropriate voltages are applied,
orbit on circular trajectories around the cylinder axis between two concentric cylindrical surfaces, which are composed of specially shaped sheath electrodes, insulated from each other by parabolic gaps, and can harmonically oscillate in the axial direction, independently of their orbiting motion. In the longitudinal direction, the two cylindrical surfaces of the measuring
cell are divided by the parabolic separating gaps into different types of double-angled and tetragonal sheath
electrode segments. Appropriate voltages at the sheath
electrode segments generate a potential distribution between the two concentric cylindrical surfaces which forms a parabolic
potential well in the axial direction for orbiting ions. The
ion clouds oscillating harmonically in the axial direction in this
potential well induce image currents in suitable electrodes, from which the oscillation frequencies can be determined by Fourier analyses.