applied on opposite electrodes boundary electrodes can be manufactured as shown in fig5 the ends of every electrode 11 5 12 5 etc is joint directly with end plates to corresponding opposite electrodes 11 51 12 51 etc without a zero potential boundary electrode and in such case two electrodes on the opposite side are united as one rectangle frame or even ellipsoid frame electrode fig5 b it will be understood that the potential applied to opposite electrodes of the top and bottom array can be different for example a dipole excitation voltage can be applied between them to eject or excite ions fig6 shows another method of ejecting and detecting ions in the y direction there is a slit 41 in each electrode in the electrode array and these slits are parallel to the electrodes outside the slits there is an ion detector 8 6 which has an area big enough to cover all the slits a reticulate electrode 40 may be placed between the ion detector 8 6 and slits to shield interference from a high frequency signal after ions are captured and selected with a dipole excitation signal applied on the electrodes the ions accelerated in the y direction and pass through the slits 41 and reticulate electrode 40 and then hit the ion detector 8 6 similar to other linear quadrupole ion traps ions in the stability region can be trapped if the potential applied on the electrodes are pure alternative current signal v u2212 v ions will be trapped mass selectively and a low mass to charge ratio cut off will exist this means ions with a mass to charge ratio lower than a particular value low mass limit will hit the electrodes and be lost for.