Patent ID: 6501074
Filing Date: 2002-12-31
Classification: H01J

Abstract:
A double-focusing mass spectrometer apparatus comprising:a first cylindrical sector electrode surface defined at a first radial distance from a cylindrical axis, the first cylindrical sector electrode surface having an upper and lower edge; a second cylindrical sector electrode surface defined at a second radial distance from the cylindrical axis, the second cylindrical sector electrode having an upper and lower edge corresponding to the upper and lower edge of the first cylindrical sector electrode, wherein an ion path is defined between the first and second cylindrical sector electrode surfaces; a first magnet pole and a second magnet pole positioned proximate the upper and lower edges of the first and second cylindrical sector electrode surfaces, respectively, for providing a magnetic field in the ion path; and a first array of electrodes positioned between the upper edges of the first and second cylindrical sector surfaces and a second array of electrodes positioned between the lower edges of the first and second cylindrical sector surfaces for use with the first and second cylindrical sector electrode surfaces to provide a desired electric field in the ion path perpendicular to the magnetic field, wherein the first and second arrays of electrodes are configured as a function of the magnetic field such that a desired ratio of magnetic field to electric field is attained in substantially the entire ion path such that mass selection using the mass spectrometer is achieved independent of ion velocity.