A method and system for producing an ion beam from an ion guide. In the method, ions are introduced into the ion guide, a radio frequency trapping field is generated in the ion guide to confine ions in a direction transverse to a longitudinal axis of the ion guide, a DC potential is generated along the longitudinal axis to direct ion motion along the longitudinal axis, a strength of the radio frequency trapping field is reduced toward an ion guide exit of the ion guide, and the ions are transmitted from the ion guide exit to form the ion beam. In the system, an ion guide is configured to transmit ions in a longitudinal axis of the ion guide and configured to trap ions in a direction transverse to the longitudinal axis via a radio frequency trapping field. The ion guide includes a segmented set of electrodes spaced along the longitudinal axis and an ion guide exit at the last of the segmented set of electrodes. A radio frequency device is configured to supply the radio frequency trapping field such that a strength of the radio frequency trapping field is reduced toward the ion guide exit.