Magnetic mass spectrometer with shaped, uniformly saturating magnetic poles

Claim 2

A scanning mass spectrometer comprising: a source of ions; a detector of ions; a deflecting and focusing magnetic analyzing sector interposed between the ion source and ion detector along the path of ions from the source, the magnetic analyzing sector including a pair of shaped pole pieces of a magnetic material, the pole pieces being spaced a predetermined distance apart and having a predetermined thickness and width, the shaping of said pole pieces being chosen such that the magnetic material magnetizes substantially uniformly and the magnetic flux distribution in the magnetic material remains substantially constant at all magnetic field strengths; and means for varying the magnetic field in the magnetic analyzing sector for bringing ions of any one of a plurality of different predetermined masses into register at the detector.

Claim 3

A mass spectrometer according to claim 1 wherein the shape of the pole pieces is substantially defined by the expression where a is the minimum spacing between the pole pieces and y is the ordinate axis passing perpendicularly through the pole pieces and gap spacing and x is the abscissa axis passing perpendicularly to the y axis.

Claim 4

A mass spectrometer according to Claim 1 wherein the pole pieces are provided with rounded edges and outwardly tapering faces at the ends and sides thereof, the edges being rounded to a radius approximately 1.25 times the pole pieces spacing distance, the faces having a slope of approximately 11.5* with respect to an axis passing perpendicularly through the pole pieces and gap spacing.

Claim 5

A mass spectrometer according to claim 3 including magnetic shunting means located adjacent the ends of the pole pieces, the spacing of the shunting means relative to the ends being chosen such that the condition of constant flux distribution in the magnetic field of the analyzing sector is not altered.

Claim 6

A mass spectrometer according to claim 4 wherein the shunting means are spaced from the ends of the pole pieces a distance approximately equal to 3.333 times the pole piece spacing.

Claim 7

A mass spectrometer according to claim 1 including magnetic shunting means located adjacent the ends of the pole pieces, the spacing of the shunting means relative to the ends being chosen such that the condition of substantially constant flux distribution in the magnetic field of the analyzing sector is not appreciably altered.

Claim 8

A mass spectrometer according to claim 6 wherein the shunting means are spaced from the ends of the pole pieces a distance approximately equal to 3.333 times the pole piece spacing.

Claim 9

A scanning double focusing mass spectrometer comprising: a source of ions; an electrostatic lens disposed along the path of ions from the source; a deflecting and focusing magnet disposed along a path of ions from the source at a predetermined spacing from the lens, the focusing magnet having a pair of opposed shaped pole pieces of a magnetic material spaced a predetermined gap distance apart and having a predetermined thickness and width, the shaping of the pole pieces being such that the magnetic material of the pole pieces saturates substantially uniformly and the flux distribution in the magnetic material remains substantially constant at all magnetic field strengths; a detector of ions disposed along the path of ions from the source located on the side of the magnet and lens opposite the source, the source, lens, magnet and detector being spaced and oriented relative to each other such that ions are focused on the detector for both angular divergence and energy divergence from the source; and means for varying the strength of the magnetic field in the magnet for bringing ions of any one of a plurality of different predetermined masses into register at the detector.

Claim 10

A scanning double focusing mass spectrometer comprising: a source of ions; an electrostatic lens disposed along the path of ions from the source; a deflecting and focusing magnet disposed along a path of ions from the source at a predetermined spacing from the lens, the focusing magnet having a pair of opposed shaped pole pieces of a magnetic material spaced a predetermined gap distance apart and having a predetermined thickness and width, the shaping of the pole pieces being such that the magnetic material of the pole pieces saturates substantially uniformly and the flux distribution in the magnetic material remains substantially constant at all magnetic field strengths; a detector of ions disposed along the path of ions from the source located on the side of the magnet and lens opposite the source, the source, lens, magnet and detector being spaced and oriented relative to each other such that ions are focused on the detector for both angular divergence and energy divergence from the source; and means for varying the strength of the magnetic field in the magnet for bringing ions of any one of a plurality of different predetermined masses into register at the detector.

Claim 11

A mass spectrometer according to claim 8 wherein the shape of the pole pieces is substantially defined by the expression where a is the minimum spacing between the pole pieces and y is the ordinate axis passing perpendicularly through the pole pieces and gap spacing and x is the abscissa axis passing perpendicularly to the y axis.

Claim 12

A mass spectrometer according to claim 8 wherein the pole pieces are provided with rounded edges and outwardly tapering faces at the ends and sides thereof, the edges being rounded to a radius approximately 1.25 times the gap distance, the faces having a slope of approximately 11.5* with respect to an axis passing perpendicularly through the pole pieces and gap spacing.

Claim 13

A mass spectrometer according to claim 10 including first magnetic shunting means located adjacent the pole pieces between the lens and the magnet; and second magnetic shunting means located adjacent the pole pieces between the magnet and the detector, the spacing of the first and second shunting means relative to the pole pieces being chosen such that the constant flux distribution in the magnetic field of the analyzing sector is not altered.

Claim 14

A mass spectrometer according to claim 11 wherein the first and second shunting means are each spaced from the pole pieces a distance approximately equal to 3.333 times the gap distance.

Claim 15

A mass spectrometer according to claim 12 wherein the pole pieces are elongated in the direction of ion travel such that ions pass through an entrance and exit side of the pole pieces and move approximately parallel to the remaining sides of the pole pieces.

Claim 16

A mass spectrometer according to claim 13 wherein the thickness of the pole piece is at least about 3.333 times the gap distance, and the width of the pole pieces is at least about 2.50 times the gap distance.

Claim 17

A mass spectrometer according to claim 8 including first magnetic shunting means located adjacent the pole pieces between the lens and the magnet; and second magnetic shunting means located adjacent the pole pieces between the magnet and the detector, the spacing of the first and second shunting means relative to the pole pieces being chosen such that the substantially constant flux distribution in the magnetic field of the analyzing sector is not appreciably altered.

Claim 18

A mass spectrometer according to claim 15 wherein the first and second shunting means are each spaced from the pole pieces a distance approximately equal to 3.333 times the gap distance.