Patent ID: 6717140
Filing Date: 2004-04-06
Classification: H01J

Abstract:
A mass spectrometer in which ions created by collision with an electron beam emitted by a heated filament, are submitted to the action of a uniform adjustable first electrical field {right arrow over (E)}1, established within a set of plane parallel electrodes a1, . . . ,ai, . . . ,an, each plane parallel electrode being fitted with slits located for a transmission of the ions there through, and to the action of a uniform magnetic induction {right arrow over (B)}1, the magnetic induction {right arrow over (B)}1 being perpendicular to the first electrical field {right arrow over (E)}1, the ions travelling in parallel travelling planes perpendicular to {right arrow over (B)}1, each travelling plane having a reference system defined by an x-axis and an y-axis, the x-axis being perpendicular to the first electrical field {right arrow over (E)}1 and the y-axis being parallel to the first electrical field {right arrow over (E)}1, an origin of the reference system being located at an average intersection of the electron beam with the travelling plane, x and y both having the value 0 at the origin of the reference system, wherein for each travelling plane, the first electrical field {right arrow over (E)}1 and the magnetic induction {right arrow over (B)}1 act together on the ions in an area of the travelling plane where y1 acts alone on the ions in a further area of the travelling plane where y>d, d being a distance separating the origin of the reference system in the travelling plane from the electrode an, a first selection slit S1 being located at coordinates x=2,1d and y=2d, and a value of the first electrical field E1 that is applied for selecting ions having a number of mass n, being defined by, E1=2&it;dn&it;em&it;B12,â€ƒ&it;wherein&it;â€ƒ&it;em&it;â€ƒis a ratio charge to mass for a mono atomic hydrogen ion H+, further wherein the ions are created by electronic bombardment only in the vicinity of a plane parallel to the magnetic induction {right arrow over (B)}1, the plane parallel to the magnetic induction {right arrow over (B)}1 having an angle of 45Â° with the first electrical field {right arrow over (E)}1, the heated filament being positioned above the electrodes a1,a2, along a line in the plane parallel to the magnetic induction {right arrow over (B)}1, the electron beam being limited by a rectangular diaphragm positioned parallel to the heated filament and between the heated filament and the electrodes a1,a2, such that a resulting collimated ion beam is substantially parallel to an xâ€”axis of the travelling beam corresponding to the ion beam when crossing the first selection slit of the travelling plane, an ion beam intensity of the ion beam corresponding to a selected number of mass n for the ions.