A mass spectrometer, comprising: an ion trap configured to eject different packets of ions in temporal succession; at least one pulsed mass analyzer for separating ions according to their mass-to-charge ratios to acquire a mass spectrum; and an ion interface device having a transport/collision region and a plurality of spatially separated ion confinement cells (230a, 230b, 230c, 230d, 230e, 230f, 230g, 230h), the ion interface device being configured to receive each packet of ions ejected from the ion trap, to cause at least a portion of the ions in the ion packet to undergo fragmentation or reaction, and to direct the ion packet to a selected one of the ion confinement cells (230a, 230b, 230c, 230d, 230e, 230f, 230g, 230h); the ion interface device being configured to release each ion packet to the at least one pulsed mass analyzer after the packet has been confined in the ion confinement cell (230a, 230b, 230c, 230d, 230e, 230f, 230g, 230h) for a prescribed confinement period, wherein the confinement and cooling of the ion packet in the ion confinement cell (230a, 230b, 230c, 230d, 230e, 230f, 230g, 230h) occurs concurrently with the receipt of at least one later ejected ion packet by the ion interface device; characterized in that the ion interface device further comprises a distribution section having an array of rod electrodes, each extending transversely to a longitudinal axis of the ion interface device and further characterized in that the confinement cells (230a, 230b, 230c, 230d, 230e, 230f, 230g, 230h) are disposed laterally outwardly of the longitudinal axis of the ion interface device. an ion trap configured to eject different packets of ions in temporal succession; at least one pulsed mass analyzer for separating ions according to their mass-to-charge ratios to acquire a mass spectrum; and an ion interface device having a transport/collision region and a plurality of spatially separated ion confinement cells (230a, 230b, 230c, 230d, 230e, 230f, 230g, 230h), the ion interface device being configured to receive each packet of ions ejected from the ion trap, to cause at least a portion of the ions in the ion packet to undergo fragmentation or reaction, and to direct the ion packet to a selected one of the ion confinement cells (230a, 230b, 230c, 230d, 230e, 230f, 230g, 230h); the ion interface device being configured to release each ion packet to the at least one pulsed mass analyzer after the packet has been confined in the ion confinement cell (230a, 230b, 230c, 230d, 230e, 230f, 230g, 230h) for a prescribed confinement period, wherein the confinement and cooling of the ion packet in the ion confinement cell (230a, 230b, 230c, 230d, 230e, 230f, 230g, 230h) occurs concurrently with the receipt of at least one later ejected ion packet by the ion interface device; characterized in that the ion interface device further comprises a distribution section having an array of rod electrodes, each extending transversely to a longitudinal axis of the ion interface device and further characterized in that the confinement cells (230a, 230b, 230c, 230d, 230e, 230f, 230g, 230h) are disposed laterally outwardly of the longitudinal axis of the ion interface device.