Patent ID: 7582861

Claim:
A mass spectrometer comprising: an ion source for ionizing sample atoms or molecules; a mass separator section for separating ions on a mass number basis; and an ion optical system disposed on an ion transit path between said ion source and said mass separator section and adapted to form a high-frequency electric field and/or an electrostatic field so as to converge ions and transport the ions to a subsequent stage, said ion optical system including a number n of metal plate members each serving as an electrode (wherein n is an even number of four or more), each of said metal plate members being disposed to extend along an ion optical axis, in such a manner that respective thin edge surfaces of said metal plate members face and surround said ion optical axis, wherein each of said metal plate members constituting said ion optical system is disposed such that the edge surface thereof facing the ion optical axis is inclined to come close to or get away from said ion optical axis toward a traveling direction of the ions.