Time-of-flight mass spectrometer

Claim 2

Time-of-flight mass spectrometer comprising means defining an ion flight path having an entrance plane and an exit plane, a pulsed ion source beyond the entrance plane, which source emits a parcel of accelerated ions into said flight path, in which the ion parcel divides into partial parcels of ions of equal effective mass, with the ions of different partial parcels having differing effective mass, said flight path including a straight part, field generating means defining a deflection field which is traversed by the ions in substantially arcuate paths and which is dimensioned with regard to the straight part in such a way that the dispersion in the time of flight of the ions in the deflection field, caused by different initial velocities of ions of equal effective mass, is equal but reverse in sign to that in the straight path, and ion detection means located beyond the exit plane of the flight path, wherein the improvement consists in that the flight path is symmetrical with respect to a plane of symmetry mid-way between the entrance plane and the exit plane, said path including at least two said straight parts adjoining opposite boundaries of the deflection field, and an apertured stop located at an intermediate image plane in said plane of symmetry in the deflection field, said field generating means defining two deflection field areas symmetrically on opposite sides of said plane of symmetry, which areas are traversed by ions on opposite respective sides of a central arcuate path passing through said stop aperture, and means converging the ions to an image in the exit plane under conditions of both velocity and direction focusing.

Claim 3

Time-of-flight mass spectrometer according to claim 1 wherein the intermediate image is an axial image and wherein for radial image formation at the exit plane the following equation applies: gr g''r (ro/h) tg (180* - (h/2) Phi ) where gr length of the straight part of the flight path adjoining the entrance plane g''r length of the straight part of the flight path adjoining the exit plane ro radius of the central arcuate path of the ions in the deflection field h DEflection field inhomogeneity parameter Phi Angle of deflection in deflection field

Claim 4

Time-of-flight mass spectrometer according to claim 2, wherein the source supplies ions of substantially equal energies, and wherein the deflection field generating means are electrostatic means generating an electric toroid field having an inhomogeneity parameter h, the total length g of the straight parts of the ion path being given by: g/4 ro ((1/h2 - 1/4 ) Phi - sin (h Phi )/h3) where ro radius of the central arcuate path of the ions in the deflection field Phi angle of deflection in deflection field

Claim 5

Time-of-flight mass spectrometer according to claim 3 wherein the deflection field generating means comprise a toroid condenser having an aspect ratio of unity (that is, h 1) and wherein the flight path has two equal straight parts each equal to 5.9ro, where Phi 199.2*

Claim 6

Time-of-flight mass spectrometer according to claim 3, wherein the flight path has two equal straight parts each equal to 2.35ro, the deflection field generating means comprising a toroid condenser having an aspect ratio of 0.234 and defining a deflection field with a total deflection angle Phi of 163.2*

Claim 7

Time-of-flight mass spectrometer according to claim 2 wherein the ion source supplies ions with a substantially equal momentum, and wherein the deflection field generating means are magnetic and define a magnetic sector field with a central radius ro and a sector angle Phi , satisfying the equation: 2gr 2g''r ro/h ( Phi (1/h2 - 1) - sin (h Phi )/h3) the inhomogeneity parameter h being equal to 1-n where n is the inhomogeneity factor of the magnetic field.

Claim 8

Time-of-flight mass spectrometer according to claim 6, wherein the inhomogeneity factor n of the magnetic deflection field is equal to 0.5 and wherein the sector angle Phi 314* and gr g''r 3.7ro

Claim 9

Time-of-flight mass spectrometer according to claim 6, wherein inhomogeneity factor n of the magnetic field is equal to 0.5, the sector angle Phi 290* and gr g''r 1.23ro.

Claim 10

Time-of-flight mass spectrometer according to claim 6, wherein the magnetic field generating means define two magnetic sectors of equal angle Phi separated by a straight path part and arranged to deflect the beam successively in opposite directions.

Claim 11

Time-of-flight mass spectrometer according to claim 1, wherein the following equation applies for axial image formation at the exit plane: ga g''a (ro/k) tg (180* - (k/2) Phi ), ga, g''a lengths of the respective straight parts of the flight path adjoining the entrance and exit planes respectively ro radius of the central arcuate path of the ions in the deflection field Phi angle of deflection in deflection field k inhomogeneity parameter of deflection field.

Claim 12

Time-of-flight mass spectrometer according to claim 1, wherein the ion flight path includes in succession: a first straight flight part of a length gr ro/h ctn (h Phi ); a first portion of the deflection side producing a deflection angle Phi , the apertured stop being situated symmetrically in said first deflection field portion; a straight-line flight path with the length g (2r cos (h Phi ) - 1/h sin (h Phi )); a second portion of the deflection field producing the same deflection angle Phi and a third straight-line flight path of length gr, whereby the following equations are satisfied, in case of the acceleration of ions to equal momentum: 1/h ctn (h Phi ) 1/2 ( Phi (1/h2 - 1) - sin (h Phi )/h3 + 1/h sin (h Phi )) an in the case of the acceleration of ions to equal energies: 1/h ctg (h Phi ) 2 ( Phi (1/h2 - 1/4 ) - sin (h Phi )/h3 + 1/4h.sin(h Phi )) where ro radius of the central arcuate path of the ions in the deflection field h deflection field inhomogeneity parameter.

Claim 13

Time-of-flight mass spectrometer comprising means defining an ion flight path, having an entrance plane and an exit plane, a pulsed ion source beyond the entrance plane, which source emits a parcel of accelerated ions into said flight path, in which the ion parcel divides into partial parcels of ions of equal effective mass, with the ions of different partial parcels having differing effective mass, said flight path including a straight part, field generating means defining a deflection field which is traversed by the ions in substantially arcuate paths and which is dimensioned with regard to the straight part in such a way that the dispersion in the time of flight of the ions in the deflection field, causd by different initial velocities of ions of equal effective mass, is equal but reverse in sign to that in the straight path, and ion detection means located beyond the exit plane of the flight path, wherein the improvements consists in the following in combination: a. an apertured stop is located at an intermediate image plane in the flight path; b. the flight path includes a straight part and c. the field generating means are electrostatic and define an electrostatic deflection field which is traversed by the ions in substantially arcuate paths and in which the travelling time dispersion of the ions, caused by different initial velocities of equal effective mass, is equal and opposite to that in the straight path, and d. the following equations are satisfied: g 4ro ( Phi (1/h2 - 1/4 ) - sin (h Phi )/h3) ro/h tg (180* - h Phi /2) 0 where g total length of the straight part; h deflection field inhomogeneity parameter ro radius of the central arcuate path of the ions in the deflection field Phi angle of deflection in deflection field

Claim 14

Time-of-flight mass spectrometer comprising means defining an ion flight path, having an entrance plane and an exit plane, a pulsed ion source beyond the entrance plane, which source emits a parcel of accelerated ions into said flight path, in which the ion parcel divides into partial parcels of ions of equal effective mass, with the ions of different partial parcels having differing effective mass, said flight path including a straight part, field generating means defining a deflection field which is traversed by the ions in substantially arcuate paths and which is dimensioned with regard to the straight part in such a way that the dispersion in the time of flight of the ions in the deflection field, causd by different initial velocities of ions of equal effective mass, is equal but reverse in sign to that in the straight path, and ion detection means located beyond the exit plane of the flight path, wherein the improvements consists in the following in combination: a. an apertured stop is located at an intermediate image plane in the flight path; b. the flight path includes a straight part and c. the field generating means are electrostatic and define an electrostatic deflection field which is traversed by the ions in substantially arcuate paths and in which the travelling time dispersion of the ions, caused by different initial velocities of equal effective mass, is equal and opposite to that in the straight path, and d. the following equations are satisfied: g 4ro ( Phi (1/h2 - 1/4 ) - sin (h Phi )/h3) ro/h tg (180* - h Phi /2) 0 where g total length of the straight part; h deflection field inhomogeneity parameter ro radius of the central arcuate path of the ions in the deflection field Phi angle of deflection in deflection field

Claim 15

Time-of-flight mass spectrometer according to claim 12, wherein the electrostatic field generating means comprise a toroid condenser with an aspect ratio of 0.4 producing a deflection angle Phi of 284.5*, the length g of the straight part of the flight path is 1.5 ro.

Claim 16

Time-of-flight mass spectrometer according to claim 12, including an ion optical lens located in the straight part of the flight path and producing a stigmatic image at the entrance to the deflection field.