The present invention relates to a mass spectrometer device comprising a source of ions, an electrostatic sector, a non-scanning magnetic sector arranged downstream of the electrostatic sector, for separating ions originating at the source of ions according to their mass-to-charge ratios, and a detection means. A magnetic shunt is arranged in the drift space between the electrostatic sector and the magnetic sector. The proposed position of the magnetic shunt enhances the resolving power of the mass spectrometer device.