A method and apparatus is provided including an ion source for generating ions, a vacuum chamber having an inlet aperture for receiving ions and an exit aperture for passing ions from the vacuum chamber. At least one ion guide is provided between the inlet and exit apertures, the at least one ion guide having an entrance end and an exit end. The at least one ion guide having an inner cylinder and an outer cylinder. The inner cylinder having a plurality of sections, each section having a different number of slots and the inner cylinder coaxially disposed within the outer cylinder wherein the inner cylinder is configured to generate more than one multipole field. A power supply is provided for providing an RF voltage between the outer and inner cylinders.