Achromatic magnetic beam deflection system

Claim 2

In a method for achromatic magnetic deflection of a beam of non-monoenergetic charged particles through a bending angle Psi along a central orbital axis defined by the trajectory of a charge particle of a reference momentum PO is a bending plane between transverse beam entrance and beam exit planes the steps of: subjecting the beam of charged particles to a series of magnetic deflection forces for; focusing beam particles of the reference momentum PO which are initially radially displaced in the bending plane from the orbital axis at the beam entrance plane to first and second crossovers of the central orbital axis and also to trajectories with approximately zero slope relative to the orbital axis at a region along the orbital axis intermediate the beam entrance and beam exit planes; focusing beam particles of the reference momentum PO having trajectories which are on and angularly divergent from the orbital axis in the beam bending plane at the beam entrance plane to a crossover of the orbital axis at a region along the orbital axis intermediate the beam entrance and beam exit planes; focusing beam particles of the reference momentum PO which are initially displaced from and parallel to the orbital axis in the transverse plane at the beam entrance plane to a crossover of the central orbital axis at a region along the orbital axis intermediate the beam entrance and beam exit planes; focusing beam particles of the reference momentum PO which have initial trajectories on and angularly divergent from the orbital axis in the transverse plane at the beam entrance plane to a crossover of the orbital axis at the beam exit plane and to trajectories having zero slope relative to the orbital axis at a region along the orbital axis intermediate the beam entrance and beam exit planes; and achromatically focusing beam particles of a momentum differing from the reference momentum PO and having a trajectory initially coincident with the orbital axis at the beam entrance plane to the orbital axis at the beam exit plane.

Claim 3

The method of claim 1 wherein said beam particles initially radially displaced in the bending plane from and parallel to the orbital axis at the beam entrance plane are focused to trajectories which have approximately zero slope relative to the orbital axis at a region which is approximately midway along the orbital axis between the beam entrance plane and the beam exit plane, such mid region being in a transverse plane of symmetry occurring at a beam bending angle of Psi /2.

Claim 4

The method of claim 2 wherein said beam particles which are focused to first and second crossovers of the orbital axis have such crossovers on opposite sides of said mid-plane of symmetry.

Claim 5

The method of claim 1 wherein said beam particles initially angularly divergent in the bending plane from and on the orbital axis at the beam entrance plane are focused to the crossover of the orbital axis at a mid transveRse plane of symmetry occurring at a beam bending angle of Psi /2.

Claim 6

The method of claim 1 wherein said beam particles initially transversely displaced from the orbital axis in the transverse plane at the beam entrance plane are focused to the crossover of the orbital axis at a transverse mid-plane of symmetry occurring at beam bending angle of approximately Psi /2.

Claim 7

The method of claim 1 wherein said beam particles initially angularly divergent from and on the orbital axis in the transverse plane at the beam entrance plane are focused to trajectories having zero slope relative to the orbital axis substantially at a transverse mid plane of symmetry at a beam bending angle of approximately Psi /2.

Claim 8

The method of claim 1 wherein said beam particles initially transversely displaced from the orbital axis in the transverse plane at the beam entrance plane are focused to the crossover of the orbital axis at a transverse mid-plane of symmetry occurring at a beam bending angle of approximately Psi /2, and wherein the beam particles initially angularly divergent from and on the orbital axis in the transverse plane at the beam entrance plane are focused to trajectories having zero slope relative to the orbital axis substantially at a transverse plane of symmetry at a beam bending angle of approximately Psi /2.

Claim 9

The method of claim 1 including the step of, shaving off a radial edge of the beam at said plane of symmetry occurring at a beam bending angle of Psi /2.

Claim 10

The method of claim 1 wherein the series of magnetic beam deflecting forces are produced by applying the magnetic field of at least three pairs of magnetic poles spaced apart along the central orbital axis to direct their respective magnetic fields across said central orbital axis in the transverse direction, such magnetic poles being of a polarity such that all of the applied magnetic fields of the three pairs of magnetic poles are parallel and in the same sense.

Claim 11

The method of claim 9 wherein at least two of the three sets of magnetic pole pairs are substantially identical and each identical pole pair is energized to produce substantially equal transverse magnetic fields on the central orbital axis.

Claim 12

The method of claim 1 wherein said bending angle Psi is approximately 270*.

Claim 13

In an apparatus for achromatic magnetic deflection of a beam of non-monoenergetic charged particles through a bending angle Psi along a central orbital axis defined by the trajectory of a charged particle of a reference momentum PO in a bending plane between transverse beam entrance and beam exit planes: means for magnetically deflecting beam particles of the reference momentum PO which are initially radially displaced in the bending plane from the orbital axis and initially parallel to the orbital axis at the beam entrance plane into a trajectory having first and second crossovers of the orbital axis, and such trajectory having approximate zero slope relative to the orbital axis at a region along the orbital axis intermediate the beam entrance and beam exit planes; means for magnetically deflecting beam particles of the reference momentum PO and which are initially on and angularly divergent from the orbital axis in the beam bending plane at the beam entrance plane into trajectories having a crossover of the orbital axis at a region along the orbital axis intermediate the beam entrance and beam exit planes; means for magnetically deflecting beam particles of the reference momentum PO and which are initially displaced from and parallel to the orbital axis in the transverse plane at the beam entrance plane into trajectories having a crossover with the central orbital axis at a region along the orbital axis intermediate the beam entrance and the beam exit planes; means for magnetically deflecting beam particles of the reference momentum PO and having initial trajectories on and angularly divergent from the orBital axis in the transverse plane at the beam entrance plane into trajectories having a crossover of the central orbital axis at the beam exit plane and such trajectories having zero slope realtive to the orbital axis at a region along the orbital axis intermediate the beam entrance and beam exit planes; and means for magnetically deflecting beam particles of a momentum differing from the reference momentum PO and having trajectories initially coincident with the orbital axis at the beam entrance plane into trajectories that are achromatically focused to the orbital axis at the beam exit plane.

Claim 14

In an apparatus for achromatic magnetic deflection of a beam of non-monoenergetic charged particles through a bending angle Psi along a central orbital axis defined by the trajectory of a charged particle of a reference momentum PO in a bending plane between transverse beam entrance and beam exit planes: means for magnetically deflecting beam particles of the reference momentum PO which are initially radially displaced in the bending plane from the orbital axis and initially parallel to the orbital axis at the beam entrance plane into a trajectory having first and second crossovers of the orbital axis, and such trajectory having approximate zero slope relative to the orbital axis at a region along the orbital axis intermediate the beam entrance and beam exit planes; means for magnetically deflecting beam particles of the reference momentum PO and which are initially on and angularly divergent from the orbital axis in the beam bending plane at the beam entrance plane into trajectories having a crossover of the orbital axis at a region along the orbital axis intermediate the beam entrance and beam exit planes; means for magnetically deflecting beam particles of the reference momentum PO and which are initially displaced from and parallel to the orbital axis in the transverse plane at the beam entrance plane into trajectories having a crossover with the central orbital axis at a region along the orbital axis intermediate the beam entrance and the beam exit planes; means for magnetically deflecting beam particles of the reference momentum PO and having initial trajectories on and angularly divergent from the orBital axis in the transverse plane at the beam entrance plane into trajectories having a crossover of the central orbital axis at the beam exit plane and such trajectories having zero slope realtive to the orbital axis at a region along the orbital axis intermediate the beam entrance and beam exit planes; and means for magnetically deflecting beam particles of a momentum differing from the reference momentum PO and having trajectories initially coincident with the orbital axis at the beam entrance plane into trajectories that are achromatically focused to the orbital axis at the beam exit plane.

Claim 15

The apparatus of claim 12 wherein said means for magnetically deflecting said beam particles initially radially displaced in the beam bending plane and parallel to the orbital axis to trajectories having approximately zero slope includes, means for focusing said particles to trajectories which have approximately zero slope relative to the orbital axis at a transverse mid-plane of symmetry occurring at a bending angle of Psi /2.

Claim 16

The apparatus of claim 13 wherein said means for deflecting said beam particles to first and second crossovers of the orbital axis includes, means for focusing said particles to trajectories having crossovers of the orbital axis on opposite sides of said mid-plane of symmetry.

Claim 17

The apparatus of claim 12 wherein said means for magnetically deflecting said particles which are initially angularly divergent in the bending plane from and on the orbital axis at the beam entrance plane includes, means for focusing said particles to the crossover of the orbital axis at a mid-transverse plane of symmetry occurring at a bending angle of Psi /2.

Claim 18

The apparatus of claim 12 wherein said means for magnetically deflecting said beam particles which are initially transversely displaced from the orbital axis in the transverse plane at the beam entrance plane includes, means for deflecting said particles to the crossover of the orbital axis at a transverse mid-plane of symmetry occurring at a beam bending angle of approximately Psi /2.

Claim 19

The apparatus of claim 16 wherein said means for deflecting said beam particles initially angularly divergent from and on the orbital axis of the transverse plane at the beam entrance plane includes, means for focusing said trajectories to substantially zero slope relative to the orbital axis substantially at a transverse mid-plane of symmetry at a beam bending angle of approximately Psi /2.

Claim 20

The apparatus of claim 12 wherein said means for magnetically deflecting said beam particles initially angularly divergent from and on the orbital axis in the transverse plane at the beam entrance plane includes, means for focusing said particles to trajectories having zero slope relative to the orbital axis at a point substantially at a transverse mid-plane of symmetry at a beam bending angle of approximately Psi /2.

Claim 21

The apparatus of claim 12 including, means for shaving off a radial edge of the beam at a region which is approximately mid-way along the orbital axis between the beam entrance plane and the beam exit plane.

Claim 22

The apparatus of claim 12 wherein said means for producing a series of magnetic beam deflection forces comprises, at least three pairs of magnetic poles positioned along the central orbital axis to direct their respective magnetic fields across said central orbital axis in the transverse direction and in the same direction.

Claim 23

The apparatus of claim 20 wherein at least two of said three sets of magnetic pole pairs are substantially identical, and means for energizing each identical pole pair to produce substantially equal transverse magnetic fields on the central orbital axis.

Claim 24

The apparatus of claim 21 wherein each pair of said magnetic pole means has an input face and an output face each defining an edge extending across the orbital axis, and wherein each of said input and output edges is inclined at substantially the same angle Beta tO the central orbital axis.

Claim 25

The apparatus of claim 12 wherein said beam bending angle Psi is approximately 270*.

Claim 26

The apparatus of claim 12 including, shunt means defining a magnetically permeable body disposed in between adjacent angularly spaced sets of said pole pairs for shielding the beam from magnetic fields fringing between adjacent pole pairs, said magnetically permeable body having a passageway therein for passage of the beam therethrough.

Claim 27

The apparatus of claim 12 including, linear accelerator means for generating a beam of electrons and for feeding the beam of electrons to the beam deflection apparatus, X-ray target means disposed to receive the deflected beam of electrons for generating a lobe of X-rays, and means for directing said lobe of X-rays onto an object to be irradiated.

Claim 28

The apparatus of claim 25 including, collimator means disposed between said linear accelerator means and said beam deflection apparatus for collimating the electron beam prior to magnetic deflection thereof.

Claim 29

The apparatus of claim 12 including, wherein said magnetic deflection means includes a plurality of beam bending magnets disposed along the central orbital axis and including means for shaving off a radial edge of the beam in the beam bending plane at a region along the central orbital axis in between adjacent ones of said beam bending magnets.