An ion focusing and conveying device 10 comprises a plurality of electrodes 12 in series. Means is provided to apply a first alternating voltage waveform to each electrode 12, the phase of the alternating voltage in the first waveform is applied to each electrode 12 in the series being ahead of the phase of the first alternating voltage waveform applied to the preceding electrode 12 in the series by less than 180°, preferably by 90° or less, such that ions are focused onto an axis of travel and impelled along the series of electrodes 12.