US3691374A - Stigmatic and achromatic system for deflecting a particle beam - Google Patents

Stigmatic and achromatic system for deflecting a particle beam Download PDF

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Publication number
US3691374A
US3691374A US66849A US3691374DA US3691374A US 3691374 A US3691374 A US 3691374A US 66849 A US66849 A US 66849A US 3691374D A US3691374D A US 3691374DA US 3691374 A US3691374 A US 3691374A
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Prior art keywords
deflector
magnetic
plane
input
face
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US66849A
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Hubert Leboutet
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Thales SA
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Thomson CSF SA
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/46—Arrangements of electrodes and associated parts for generating or controlling the ray or beam, e.g. electron-optical arrangement
    • H01J29/70—Arrangements for deflecting ray or beam
    • H01J29/72—Arrangements for deflecting ray or beam along one straight line or along two perpendicular straight lines
    • H01J29/76—Deflecting by magnetic fields only
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21K—TECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
    • G21K1/00—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating
    • G21K1/08—Deviation, concentration or focusing of the beam by electric or magnetic means
    • G21K1/093—Deviation, concentration or focusing of the beam by electric or magnetic means by magnetic means

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  • the System according to the invention comprises four deflecting elements arranged in pairs symmetrically 8 "250/495 B ag/ 8 with respectthto a flllanef pfh peracdicular 1t: th; Plane O n o I q a n e e e n u u a no. e c I c n n a I e o e m e [58] held of searchmzsolflg 3 g 6 between the faces of the deflecting elements is adjusted so that the energy conjugates of the two intermediate deflecting element coincide with the energy [56] References Cited foci of the terminal deflecting elements.
  • the device is UNITED STATES PATENTS thus achromatic- 3,405,363 10/1968 Brown ..328/230 8 Claims, 7 Drawing Figures PATENTEU SEP 12 I972 SHEET 1 BF 3 PATENTEU SEP 12' m2 SHEEI 3 [1F 3 STIGMATIC AND ACI-IROMATIC SYSTEM FOR DEFLECTING A PARTICLE BEAM
  • the present invention relates to devices for directing and focussing a beam of particles such as electrons, i.e. fundamental material particles. Such devices are to be found in particular in the field of particle accelerators for nuclear research purposes and for industrial and medical gammaradiography applications. Frequently, recourse is had to the action of a magnetic field created between pole-pieces, the latter determining an air-gap crossed by said beam.
  • the magnetic field used has a direction perpendicular to the paths of the particles, they are deflected.
  • The, present invention relates to a system by which the same results can be achieved for larger deflection angles, for example lying between 90 and 360.
  • the system essentially being of such design that a straight path at entry to the system is converted at the exit therefrom into another straight path whose position and direction are independent of the energies of said particles.
  • An object of the present invention is a stigmatic and achromatic magnetic deflection device for deflecting, within a plane, a beam of charged particles, said deflection device comprising first and second identical magnetic deflectors and intermediate deflector means crossed by said beam and positioned symmetricallywith respect to a further plane perpendicular to said plane said further plane being a plane of symmetry of said intermediate deflector means said beam being subjected to magnetic field vectors parallel to each other and perpendicular to said plane the direction of said field vectors being selected for bending said beam, along a mean path crossing successively the first magnetic deflector, said intermediate deflector means and the second magnetic deflector which is identical to said first said mean path having rectilinear segments separated by substantially curvilinear segments, said rectilinear segments including on both sides of the first deflector a first and a second rectilinear segment at an angle a and a third and a fourth rectilinear segment at said angle a said second and on both sides of the
  • FIG. 1 illustrates an electromagnet forming'a part of the device in accordance with the invention.
  • FIG. 2 illustrates a device in accordance with the invention.
  • FIG. 3 illustrates schematically the magneto-optical properties of the device of FIG. 2.
  • FIG. 4 illustrates another device in accordance with the invention.
  • FIG. 5 illustrates a device in which respectively the input and output faces of the first and second magnetic deflectors are no longer perpendicular to the beam.
  • FIG. 6 illustrates the same device as FIG. 5, this time however the two intermediate magnets being separated.
  • FIG. 7 illustrates a practical embodiment of the device in accordance with the invention.
  • Typical particle paths have been illustrated in FIGS. 2, 3, 4, 5 and 6, namely the path A for particles of medium energy and central position, path B for particles of medium energy but with incident path parallel to A, and path C for particles of central position but having energies differing from the mean value.
  • FIG. 1 schematically illustrates a deflection electromagnet and is designed to indicate that known property of this type of apparatus, upon which the invention is based.
  • the electromagnet is composed of a yoke plate 1 with its two arms 2, two electrical coils 3, and two polepieces 4 which define an air-gap 5, crossed by a particle beam for the purpose of deflection.
  • the input faces 6 and output faces 7 of these pole-pieces have an intersection 8 at which the center of curvature of the mean path 9 of the deflected particles, is located.
  • the physical laws which govern the electron-optical system show that the electromagnet has an infinite number of pairs of particular points, such as M and M, located in the mean path plane of the air-gap and symmetrically in relation to the plane of symmetry of the magnet perpendicular to said mean path plane, such that particles falling with a certain energy band or energy spread" and passing through one such point, also pass through the other. These points are the energy conjugates" of the deflec tion system.
  • the positions of these pairs of particular points depend upon the characteristic operating parameters of the electromagnet, being linked by relationships including factors such as the angle of input and output faces of the electro magnet pole-pieces, the respective intervals of the points in question from the faces located opposite them, the mean radius of the paths, the distance of the extreme paths of the beam from the mean path, and the energy spread in the beam.
  • geometric focus the focus relating to the plane of deflection, the system in accordance with theinvention, and its variant embodiments, being convergent or afocal in the plane perpendicular to this plane, but never divergent.
  • FIG. 2 illustrates by way of example a-device in accordance with the invention.
  • the magnetic deflection system comprises a first magnetic deflector which is a first electromagnet l and a second identical magnetic deflector which is a second electromagnet 11 such as those illustrated in FIG. 1, having a sectoral pole-pieces at an angle a and an intermediate deflector means formed by an electromagnet 12 having sectoral pole-pieces at an angle 20.
  • These electromagnets are arranged in succession in such a way that one of the energy conjugate points of one of the electromagnet coincides with one of the energy focii of another of the electromagnets in the system.
  • FIG. 3 schematically illustrates the paths of the particles through the devicedescribed hereinbefore. Calculation shows that it is possible in this fashion to produce a system which is totally insensitive to differences in particle energy, i.e. by analogy with conventional optics where the wavelength of light is replaced by the particle energy, is non-dispersive" or achromatic in the energy sense". Another way of putting it is to say that the system is afocal in the energy sense.
  • the respective magnetic fiels are parallel vectors perpendicular to the plane of the figure, the air-gaps being symmetrically positioned with respect to the plane containing the mean path of the beam.
  • the arrangement of the first and second magnetic deflectors is such that the assembly has a plane of symmetry P, which is the plane of symmetry of the intermediate magnetic deflector means represented by the electromagnet 12.
  • the input face 6 and output face 7 of pole pieces 4 of the first electromagnet l0 and second electromagnet 11 are at an angle a and the input and output faces 6 and 7 of the electromagnet 12, are at an angle 20 the latter faces are respectively parallel to output face 7 of electromagnet 10 and input face 6 of the electromagnet 11.
  • the direction of magnetic field H is indicated by an arrow.
  • the rectilinear segments 1, II, III and IV are separated by curvilinear segments.
  • the beam enters the sectoral pole piece perpendicularly to the input face 6 of the sectoral pole piece 4 and emerges from said sectoral pole piece perpendicularly to the output face 7.
  • the angle of the sectoral pole piece of electromagnet 10 is the angle a formed by the rectilinear segment I and II of said mean path A.
  • the angle of segments III and IV and of the sectoral pole piece of electromagnet 11 has a same value a.
  • FIG. 3 schematically illustrates the trajectories of the particles through the device described hereinbefore.
  • the geometric focus of the first electromagnet will coincide at H with the geometric focus of half the intermediate magnetic deflector of angle 26.
  • FIG. 4 illustrates a variant embodiment of the device in accordance with the invention in which the intermediate deflector means if formed by two electromagnets of angle 0, substituted to the intermediate electromagnet having an angle 20 this possibility already having been referred to hereinbefore, said electromagnets having the mutually opposite faces of their polepieces at equal distances from the plane of symmetry P.
  • FIG. 5 illustrates another variant embodiment of the device in accordance with the invention in which the input face 6 of said first electromagnet l0 and the output face 7 of said second electromagnet 11, make an angle y different from zero.
  • the intermediate deflector means being one electromagnet 12 at an angle 20.
  • the angle y is such that the angle of the planes of the input and output faces of said first electromagnet .is smaller than the initial angle a, the effect produced in the plane of the drawing is equivalent to that of a divergent lens and the geometric focus thus displaces towards the intermediate deflector means 12.
  • FIG. 6 illustrates an advantageous variant embodiment of the device shown in FIG. 5, in which the intermediate magnetic deflector of angle 20 is remplaced by two electromagnets at an angle 0 separated by a .distance 2L.
  • FIG. 7 illustrates an embodiment of the device in accordance with the invention, viewed in section in the plane of symmetry of the air-gap.
  • the device comprises a yoke plate 22 and two yoke arms 23, common to the three electromagnets described hereinbefore, these latter being distinguished simply by their pole-pieces 24, 25 and 26.
  • the terminal faces 27 and 28 of the intermediate magnet have a cylindrical curvature produced in accordance with a conventional method in order to correct the spherical aberration of the system.
  • a magnetic coil 29, with its leads 30 and 31, surrounds the set of pole-pieces.
  • a stigmatic and achromatic magnetic deflection device for deflecting, within a plane, a beam of charged particles, said deflection device comprising first and second identical magnetic deflectors and intermediate deflector means crossed by said beam and positioned symmetrically with respect to a further plane perpendicular to said plane said further plane being a plane of symmetry of said intermediate deflector means said beam being subjected to magnetic field vectors parallel to each other and perpendicular to said plane the direction of said field vectors being selected for bending said beam, along a mean path crossing successively the first magnetic deflector, said intermediate deflector means and the second magnetic deflector said mean path having rectilinear segments separated by substantially curvilinear segments, said rectilinear segments including on both sides of the first deflector, a first and second rectilinear segment and, on both sides of the second deflector, a third and a fourth rectilinear segment: said second and third rectilinear segments situated on both sides of said intermediate
  • said intermediate deflector means comprise a third deflector having sectoral pole-pieces at an angle 20, the input and output faces of said third deflector being symmetrically positioned with respect to said further plane.
  • said intermediate deflector means comprise a third and a fourth magnetic deflector having sectoral pole-pieces symmetrically positioned with respect to said further plane the input and output faces of said pole-pieces being at an angle 0 the input face of said fourth deflector being parallel to the output face of said third deflector.
  • a device as claimed in claim 6 wherein in front of the input face of said first deflector and beyond the out- 2 sin 1x Sin 2(9-l-sin 2oz

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  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Particle Accelerators (AREA)
  • Electron Tubes For Measurement (AREA)
US66849A 1969-09-10 1970-08-25 Stigmatic and achromatic system for deflecting a particle beam Expired - Lifetime US3691374A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR6930797A FR2058485A1 (enrdf_load_stackoverflow) 1969-09-10 1969-09-10

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US (1) US3691374A (enrdf_load_stackoverflow)
JP (1) JPS519120B1 (enrdf_load_stackoverflow)
CH (1) CH519838A (enrdf_load_stackoverflow)
FR (1) FR2058485A1 (enrdf_load_stackoverflow)
GB (1) GB1301493A (enrdf_load_stackoverflow)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3867635A (en) * 1973-01-22 1975-02-18 Varian Associates Achromatic magnetic beam deflection system
DE2533347A1 (de) * 1974-08-15 1976-02-26 Atomic Energy Of Canada Ltd Magnetisches buendelablenksystem
US3956634A (en) * 1974-02-04 1976-05-11 C.G.R.-Mev. Linear particle accelerator using magnetic mirrors
US4134017A (en) * 1976-07-09 1979-01-09 C.G.R.-Mev Radiation device using a beam of charged particles
DE3120301A1 (de) * 1980-06-04 1982-04-29 Atomic Energy of Canada Ltd., Ottawa, Ontario Asymmetrisches zweifach-achromatisches zweimagnet-strahlablenksystem
FR2516695A1 (fr) * 1981-11-19 1983-05-20 Varian Associates Dispositif de deflexion achromatique avec focalisation par un seul quadripole, notamment pour appareil d'irradiation therapeutique
US4687936A (en) * 1985-07-11 1987-08-18 Varian Associates, Inc. In-line beam scanning system
EP0790622A1 (en) * 1996-02-16 1997-08-20 Mitsubishi Jukogyo Kabushiki Kaisha Magnetic beam deflection system and method

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2423951A1 (fr) * 1978-04-21 1979-11-16 Cgr Mev Miroir magnetique pour faisceaux de particules chargees, et accelerateur de particules muni d'un tel miroir
FR2453492A1 (fr) * 1979-04-03 1980-10-31 Cgr Mev Dispositif de deviation magnetique achromatique d'un faisceau de particules chargees et appareil d'irradiation utilisant un tel dispositif
DE3532699A1 (de) * 1985-09-13 1987-03-26 Zeiss Carl Fa Elektronenenergiefilter vom omega-typ
DE3532698A1 (de) * 1985-09-13 1987-03-26 Zeiss Carl Fa Elektronenenergiefilter vom alpha-typ
JP3518271B2 (ja) * 1997-08-28 2004-04-12 株式会社日立製作所 エネルギーフィルタおよびこれを備えた電子顕微鏡
DE19860988B4 (de) * 1997-08-28 2007-12-13 Hitachi, Ltd. Elektronenmikroskop mit Energiefilter

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3867635A (en) * 1973-01-22 1975-02-18 Varian Associates Achromatic magnetic beam deflection system
US3956634A (en) * 1974-02-04 1976-05-11 C.G.R.-Mev. Linear particle accelerator using magnetic mirrors
DE2533347A1 (de) * 1974-08-15 1976-02-26 Atomic Energy Of Canada Ltd Magnetisches buendelablenksystem
US3967225A (en) * 1974-08-15 1976-06-29 Atomic Energy Of Canada Limited Magnetic beam deflector system
US4134017A (en) * 1976-07-09 1979-01-09 C.G.R.-Mev Radiation device using a beam of charged particles
DE3120301A1 (de) * 1980-06-04 1982-04-29 Atomic Energy of Canada Ltd., Ottawa, Ontario Asymmetrisches zweifach-achromatisches zweimagnet-strahlablenksystem
US4389572A (en) * 1980-06-04 1983-06-21 Atomic Energy Of Canada Limited Two magnet asymmetric doubly achromatic beam deflection system
FR2516695A1 (fr) * 1981-11-19 1983-05-20 Varian Associates Dispositif de deflexion achromatique avec focalisation par un seul quadripole, notamment pour appareil d'irradiation therapeutique
US4687936A (en) * 1985-07-11 1987-08-18 Varian Associates, Inc. In-line beam scanning system
EP0790622A1 (en) * 1996-02-16 1997-08-20 Mitsubishi Jukogyo Kabushiki Kaisha Magnetic beam deflection system and method
US5705820A (en) * 1996-02-16 1998-01-06 Mitsubishi Jukogyo Kabushiki Kaisha Magnetic beam deflection system and method

Also Published As

Publication number Publication date
JPS519120B1 (enrdf_load_stackoverflow) 1976-03-24
DE2044879B2 (de) 1976-10-28
CH519838A (fr) 1972-02-29
GB1301493A (enrdf_load_stackoverflow) 1972-12-29
FR2058485A1 (enrdf_load_stackoverflow) 1971-05-28
DE2044879A1 (de) 1971-03-11

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