A device for manipulating charged particles using an axial electric field as they travel along a longitudinal axis of the device is disclosed. The method comprises providing an outer electrode for generating an electric field and providing a plurality of inner electrodes that are separated by gaps of different lengths. The electric field generated by the outer electrode penetrates the gaps between the inner electrodes and the gaps are selected such that the desired potential profile is arranged along the longitudinal axis in order to manipulate the charged particles in the desired manner.