Abstract: A remote ion source within an ICR mass spectrometer which provides an enhanced trapping (within an analyzer cell) of ions formed within that remote ion source. In a preferred embodiment, trapping enhancement is accomplished by means of magnetic perturbations of the magnetic field within the analyzer cell. The perturbations may be established by ferromagnetic means or electromagnetic means or by the use of permanent magnets to form a magnetic bottle. Ions formed within the remote ion source are extracted from that source by an electrostatic lens and directed toward the analyzer cell along the Z axis of the spectrometer magnetic field. Deceleration lenses, external to the analyzer cell, may be employed to further enhance the trapping capability of the analyzer cell. In some modes of operation, a ramped deceleration potential may be applied to the declaration lens for "grouping" of ions of different masses for analysis. Provision for mass selection is also made within the spectrometer disclosed herein.