Patent ID: 8822918

Claim:
An ion guide, comprising: a) an electrode unit including a number N (where N is an integer not less than 6) of rod-shaped or plate-shaped electrodes arranged so as to surround an ion optical axis, the electrode unit transports ions to a subsequent stage while focusing ions by action of a high frequency electric field formed in a space surrounded by said N electrodes, b) a voltage generator configured to generate a first square wave voltage of predetermined frequency and predetermined amplitude and a second square wave voltage of opposite phase to said first square wave voltage as voltages for forming the high frequency electric field in the space surrounded by said N electrodes; and c) a connection switch configured to switch the electrode unit between a first state and a second state; wherein in the first state, the electrodes are grouped in a number 2M of sets (where M is an integer not less than 2), and in the second state, the electrodes are grouped in a number 2L of sets (where L is an integer not less than 3 and greater than M); in both said first and second states, each of the sets includes either only one of the electrodes or a plurality of circumferentially adjacent electrodes electrically connected to one another; and the connection switch causes an electrical connection to be established between electrodes of said voltage generator and said electrode unit such that the first square wave voltage is applied to one of the sets and the second square wave voltage is applied to another of the sets which is circumferentially adjacent to the one of the sets.