US3629576A - Accelerator tube electrode for focusing a beam of charged particles - Google Patents

Accelerator tube electrode for focusing a beam of charged particles Download PDF

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US3629576A
US3629576A US39461A US3629576DA US3629576A US 3629576 A US3629576 A US 3629576A US 39461 A US39461 A US 39461A US 3629576D A US3629576D A US 3629576DA US 3629576 A US3629576 A US 3629576A
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tube
electrode
charged particles
accordance
electrodes
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Harald A Enge
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Deltaray Corp
Sanwa Business Credit Corp
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Deltaray Corp
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Assigned to SANWA BUSINESS CREDIT CORPORATION AS COLLATERAL AGENT reassignment SANWA BUSINESS CREDIT CORPORATION AS COLLATERAL AGENT COLLATERAL ASSIGNMENT OF COPYRIGHTS, PATENTS, TRADEMARKS AND LICENSES Assignors: DATCON INSTRUMENT COMPANY, HALMAR ROBICON GROUP, INC., HIGH VOLTAGE ENGINEERING CORPORATION, HIVEC HOLDINGS, INC.
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H5/00—Direct voltage accelerators; Accelerators using single pulses
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J5/00—Details relating to vessels or to leading-in conductors common to two or more basic types of discharge tubes or lamps
    • H01J5/02—Vessels; Containers; Shields associated therewith; Vacuum locks
    • H01J5/06—Vessels or containers specially adapted for operation at high tension, e.g. by improved potential distribution over surface of vessel

Definitions

  • f(r) is a function which preferably should approximate f(r) kr for the region substantially immediately surrounding the aperture and, preferably, up to a radius of twice the aperture radius.
  • PATENTEU DEEZI n 3.629576 sum 1 0F 2 ACCELERATOR TUBE ELECTRODE FOR FOCUSING A BEAM OF CHARGED PARTICLES
  • This invention relates generally to accelerator tubes and, more particularly, to electrodes for use therein.
  • the structures thereof comprise a plurality of equipotential electrodes separated by relatively short, substantially cylindrical sections of insulator members made, for example, of glass, as is well known.
  • Such electrodes normally each comprise a disk of conductive material, such as aluminum, having a centrally located aperture, the apertures of all of said electrodes being aligned so as to permit passage of charged particles down the tube therethrough.
  • the charged particles are appropriately injected at one end of the tube and the tube has a suitable output utilization device for making use of the charged particles as they exit from the tube.
  • the electrodes are effectively cup shaped so as to shield the insulative inner surfaces of the tube located between the electrodes from bombardment by any free ions present in the tube which may be directed toward such surfaces as a result of their encounter with the charged particles being accelerated down the tube. If such bombardment is permitted to continue, an undesired charge, which cannot be appropriately drawn off, builds up on such surfaces to distort the accelerating field within the tube.
  • substantially cup shaped electrode members the inner surfaces of the insulator tube between electrodes are efi'ectively shielded from such bombardment and any ions which are directed toward the inner surfaces of the tube are intercepted by the conductive member itself and charge buildup is prevented.
  • the beam is generally caused to converge to an image, or waist, beyond the exit of the tube by virtue of the focusing power of the entrance aperture in combination with one or more lenses in the ion source or electron gun.
  • the focal length is varied by varying the injection voltage V.
  • a waist can be produced at the stripper in the terminal in the same way as explained above for single-stage accelerators.
  • the beam cross section at the exit is generally 2-4 cm. in diameter and diverging. External focusing must be provided in the form of electric or magnetic lenses, generally quadrupole lenses.
  • internal focusing is provided by appropriately shaping the electrodes within the accelerator tube so that a set of such electrodes effectively acts as either a diverging or a converging lens in a specified plane with respect to the direction of travel of the charged particles therethrough.
  • such lens action is produced essentially by providing each conductive electrode of any particular converging or diverging set thereof with a group of four protrusions, two of which protrude from the principal plane of the electrode in the direction of travel of the particles and two of which protrude from the principal plane of the electrode in the opposite direction.
  • the electrode is shaped so that the locii of points (i.e., the displacement of the electrode surface from the principal plane thereof) at fixed radial distances from the center of the centrally located aperture of the electrode varies in a sinusoidal fashion with an amplitude substantially proportional to the square of the radial distance value, at least so long as such radial distance is less than an appropriately selected value.
  • the sinusoidal relationship which is so chosen produces a first pair of positive protrusions in the electrode (i.e., displacements along the direction of travel of the particles) which are oppositely disposed from each other with reference to the aperture and a second pair of negative protrusions in the electrode (i.e., displacements in a direction opposite to such direction of travel) which are also oppositely disposed from each other with reference to the aperture and which are located intermediate the first pair of positive protrusions.
  • said protrusions are arranged essentially symmetrically about the aperture.
  • the set of electrodes then acts in specified planes as either a converging or a diverging lens depending on the orientation of such protrusions relative to such planes, as described more fully below.
  • FIG. I shows a perspective view of a typical electrode structure fabricated in accordance with the invention and which may be used in an accelerator tube;
  • FIG. 2 shows a plan view looking downwardly at the electrode of FIG. 1;
  • FIG. 3 shows a curve representative of the locii of points on the surface of the electrode structure of FIG. I at a fixed radial distance from the center thereof;
  • FIG. 4 shows a view in cross section taken along the lines 4-4 of the electrode depicted in FIG. 2;
  • FIG. 5 shows a view in cross section of a portion of an accelerator tube utilizing a set of electrodes of FIG. I oriented to provide focusing in the x-z plane and defocusing in the y-z plane;
  • FIG. 6 shows two diagrammatic views of the converging and diverging effects in an accelerator tube using the electrode configuration of the invention
  • FIG. 7 shows a view in cross section of a portion of an accelerator tube using cup-shaped embodiments of a set of electrodes of the invention oriented to provide focusing in the y-z plane and defocusing in the x-z plane;
  • FIG. 8 shows a diagrammatic view of an accelerator tube using sets of the electrode configuration of the invention in a system for producing a flared accelerated beam of charged particles
  • FIG. 9 shows diagrammatic plan views of a further embodiment of the invention depicting the orientation of a plurality of successive electrodes of the invention as used in an accelerator tube for producing a spiraled focusing effect.
  • the electrode comprises a substantially circular conductive member 10, fabricated of aluminum for example, having a centrally located aperture 11.
  • the beam of charged particles can be represented as passing through aperture ll downwardly in the positive z-direction indicated by the axis 12, as shown in the figure.
  • the orthogonal directions 1 and y perpendicular to the z direction are shown by axes I3 and 14 and the .ry plane is hereinafter referred to as the principal plane of the electrode.
  • the conductive member has a first pair of protrusions 15 and 16 projecting downwardly in the positive z-axis direction and lying on opposite sides of center aperture 11 along the x-axis direction. Further, conductive member 10 has a second pair of protrusions 17 and I8 projecting upwardly in in the negative z-axis direction, as shown, and lying on opposite sides of center aperture 11 along the y-axis direction.
  • plan view of electrode 10 looking downwardly in FIG. 2 also can be considered with reference to a cylindrical coordinate system having its origin at the center of aperture 11 and having its radial coordinate r indicated by dashed line 19, its angular coordinate 6 indicated by angle 20, both in the plane of the drawing, and a linear coordinate 2: (not specifically shown) which extends in a positive direction into the paper.
  • the surface of electrode 10 is so shaped that, if a cylindrical cut is made at a radial distance r from the center of aperture I1, indicated by the radial line 21, the locii of points in the z-direction at the surface of electrode 10 along dashed line 21a is sinusoidal in shape and has an amplitude substantially proportional to r
  • the curve representing such locii is shown as curve 22 in FIG. 3 wherein the points A, B, C and D coincide with the corresponding points shown in FIG. 2.
  • the displacement, Az, of the surface of electrode 10 in the z-direction, as represented by curve 22 can be defined in the cylindrical coordinate system by the following equation:
  • FIG. 4 a cross-sectional view taken along the lines 44 of FIG. 2 (Le, a view in the y-z plane), provides another viewpoint for expressing the desired shape of the protruding surfaces involved with reference to an x-y-z coordinate system.
  • the electrode has a. principal plane shown by dashed line 27 and surfaces 24 and 26 displaced therefrom conform to a selected portion of a parabolic curve, denoted by dashed line 28 in the y-z plane, which curve has its apex 29 substantially at the center of the aperture 11 as shown.
  • dashed line 28 denoted by dashed line 28 in the y-z plane
  • the parabolic shape shown is maintained for a distance r and thereafter departs from such paraboidal shape.
  • a similar conformity exits with reference to the protruding shapes in the x-z plane.
  • FIG. 5 shows a portion of a section of an accelerator tube 30 which utilizes electrodes in accordance with the invention to provide a desired lens operation.
  • a plurality of successive adjacent electrodes identically oriented with respect to each other in any given converging or diverging section of the tube, are used.
  • a set of such electrodes 31 in a section 32 of the tube are oriented in the manner shown in FIG.
  • Such a section of the tube may contain, for example, as many as IO, 20 or 30 identically oriented electrodes, or even more, the number depending upon the electrode spacing, the total length of the tube, and upon what focusing properties are desired.
  • the electrodes of such a section are oriented orthogonally with respect to the electrodes 31 shown in FIG. 5 with their positive protrusions on the y-axis and their negative protrusions on the x-axis.
  • FIG. 6 shows two simplified diagrammatic views of an accelerator tube consisting of a number of such converging or diverging sections, alternately focusing and defocusing the charged particle beam in given planes, as shown by the exemplary analogous converging and diverging lenses 36 and 37, respectively.
  • the net effect of such an arrangement of alternately focusing and defocusing elements is to provide an overall focusing, i.e., a diverging beam will be made to converge again.
  • Such operation for example, may be considered analogous to the focusing effect in an alternating gradient synchrotron.
  • FIG. 7 shows a cross-sectional view of such an arrangement wherein a portion of a section of an accelerator tube 40 utilizes a set of electrodes 41 each formed in a generally cupshaped fashion having a bottom cup portion 42, an upwardly extending portion 43, and a flange portion 44 for suitable attachment to the tube as shown.
  • the surfaces at the bottom cup portions 42 have protrusions of the type previously discussed above for producing the lens effects desired. In this case they are shown as having an orientation so that in the section, of which FIG. 7 shows only a portion, a diverging lens sheet is produced in the x-z plane and a converging lens effect in the y-z plane. In such a configuration utilizing cup-shaped electrodes, prevention of a charge buildup on the inner surfaces 46 of tube 40 is more effectively assured.
  • FIG. 8 depicts an alternative embodiment of an accelerator tube structure utilizing the principles of the invention, wherein a tube 47 utilizes at its entrance end an upper section 48 having a set of identically oriented electrodes fabricated in accordance with the invention, which set effectively provides a converging lens effect in the y-z plane'(shown) and a diverging lens effect in the x-z plane (not shown), as shown diagrammatically by the analogous lens 49 at the entrance end.
  • Tube 47 further utilizes a lower section 50 having a set of identically oriented electrodes, which electrodes, however, are orthogonally oriented with respect to the set of electrodes in upper section 48 so as to provide a diverging lens effect in the y-z plane, with a corresponding converging effect in the x-z plane, at the exit end of tube 47 as shown diagrammatically by the analogous lens 51.
  • a flared beam 52 of charged particles (which particles are injected at the entrance end through an appropriately slotted entrance member 53) is focused in the y-z plane by converging section 48 at an internal focal plane represented by reference numeral 54 as shown and, thence, diverges with the divergence enhanced by section 50 so as to produce at the exit end of the tube an accelerated flared beam 55 in the y-z plane, which beam can be used in an appropriate beam processing system.
  • a material 56 which is to be processed by the accelerated particles can be appropriately passed under the flared particle beam 55 which is produced at the exit end of the tube.
  • Such a system can be used, for example, as a substitute for a conventional beam scanning system wherein an accelerator tube produces an effective pencil beam which must be appropriately oscillated to produce a fanned scanning effect in a beam bombardment process.
  • the embodiment of FIG. 8 using the principles of the invention eliminates the necessity for an oscillating beam system and effectively produces a fixed flared beam which is more easily obtained and made available for such processing.
  • E Ez+G/2(x y
  • G the gradient of the quadrupole.
  • E the electric field strength in the axial direction of the tube
  • G the gradient of the quadrupole.
  • the electric field will have one polarity, while for negatively charged particles the electric field polarity will accordingly be reversed.
  • the rate of change of the potential i.e., ND
  • the rate of change of the surface dimension in the z-direction i.e., Az
  • A1 may be more generally expressed as:
  • each tube section which uses a set of identically oriented electrodes made in accordance with the invention, is arranged so that such electrode set is orthogonally oriented with respect to the electrode set of adjacent sections of the tube so that alternating converging-diverging combinations are achieved.
  • I has an orientation such that its protrusions 58 in the negative z-direction lie along the x-axis and its protrusions 59 in the positive z-direction lie along the y-axis, as shown.
  • the next adjacent electrode 60 is oriented so that its negative protrusions 61 (and its positive protrusions 62) lie at a fixed angle, A0, with reference to the corresponding protrusions of electrode 57.
  • Each successive electrode is thereupon rotated through the same fixed angle A0 with respect to its adjacent preceding electrode, as shown by subsequent electrodes 63-66, with still further electrodes (not shown) continuing the same sequence along the length of the tube. Accordingly, in such an arrangement, an effective spiraled focusing effect of the charged particle beam can be achieved, if desired.
  • An electrode for use in an accelerator tube comprising a conductive member adapted to be attached to said tube and having a centrally located aperture for permitting the passage of charged particles therethrough;
  • said conductive member being shaped such that the displacement of the surface thereof from the principal plane of said conductive member at fixed radial distances from the center of said aperture varies sinusoidally and has amplitudes which vary as an increasing function of the value of said radial distance when said radial distance is less than a preselected value.
  • An accelerator tube for accelerating charged particles passing therethrough said tube utilizing electrodes in accordance with claim 1, wherein said tube comprises one or more first sections, each said first sections including a set of said electrodes substantially identically oriented with respect to each other for producing a converging lens effect with respect to said charged particles in a first plane and a diverging lens effect with respect to said charged particles in a second plane; and
  • each said second sections ineluding a set of electrodes substantially orthogonally oriented with respect to the set of electrodes of said first sections for producing a diverging lens effect with respect to said charged particles in said first plane and a converging lens effect in said second plane with respect to said charged particles;
  • said electrodes in each said first and said second sections being spaced at specified distances from each other to form a plurality of spaced equipotential surfaces along the length ofsaid tube.
  • An accelerator tube in accordance with claim 10 wherein said further sections are positioned at the: entrance and exit end portions of said tube and said first and second sections are positioned in the central portion of said tube.
  • An accelerator tube utilizing electrodes in accordance with claim 1 wherein said electrodes are positioned along the length of said tube and each successive electrode is oriented at an angle less than 90 from its adjacent preceding electrode.
  • a processing system utilizing an accelerating system in accordance with claim 14 and further including means for supplying material to be processed by the impingement of charged particles thereon; and means for moving said processing material into the path of said output flared beam of charged particles whereby said material is processed by the impingement of said charged particles thereon.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Electron Tubes For Measurement (AREA)
  • Particle Accelerators (AREA)
US39461A 1970-05-21 1970-05-21 Accelerator tube electrode for focusing a beam of charged particles Expired - Lifetime US3629576A (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1990005931A1 (en) * 1988-11-18 1990-05-31 Geoffrey Francis Le Maistre Prevention of condensation on a mirror
US5557178A (en) * 1994-11-01 1996-09-17 Cornell Research Foundation, Inc. Circular particle accelerator with mobius twist
US5612588A (en) * 1993-05-26 1997-03-18 American International Technologies, Inc. Electron beam device with single crystal window and expansion-matched anode

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3253144A (en) * 1963-05-27 1966-05-24 Tektronix Inc Electron lens having means for correcting astigmatism
US3328618A (en) * 1965-09-13 1967-06-27 High Voltage Engineering Corp High-voltage acceleration tube with inserts for the electrodes
US3519868A (en) * 1967-07-17 1970-07-07 Peter Schwarz Color television tube shadow mask provided with concave mirrors surrounding each aperture and facing the phosphor screen

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3253144A (en) * 1963-05-27 1966-05-24 Tektronix Inc Electron lens having means for correcting astigmatism
US3328618A (en) * 1965-09-13 1967-06-27 High Voltage Engineering Corp High-voltage acceleration tube with inserts for the electrodes
US3519868A (en) * 1967-07-17 1970-07-07 Peter Schwarz Color television tube shadow mask provided with concave mirrors surrounding each aperture and facing the phosphor screen

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1990005931A1 (en) * 1988-11-18 1990-05-31 Geoffrey Francis Le Maistre Prevention of condensation on a mirror
GB2242831A (en) * 1988-11-18 1991-10-16 Maistre Geoffrey Francis Le Prevention of condensation on a mirror
GB2242831B (en) * 1988-11-18 1992-07-29 Maistre Geoffrey Francis Le Prevention of condensation on a mirror
US5612588A (en) * 1993-05-26 1997-03-18 American International Technologies, Inc. Electron beam device with single crystal window and expansion-matched anode
US5557178A (en) * 1994-11-01 1996-09-17 Cornell Research Foundation, Inc. Circular particle accelerator with mobius twist

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GB1307658A (en) 1973-02-21
NL7106995A (cs) 1971-11-23

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AS Assignment

Owner name: MARINE MIDLAND BANK, N.A.

Free format text: SECURITY INTEREST;ASSIGNOR:HIGH VOLTAGE ENGINEERING CORPORATION;REEL/FRAME:005009/0952

Effective date: 19880801

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Owner name: SANWA BUSINESS CREDIT CORPORATION AS COLLATERAL AG

Free format text: COLLATERAL ASSIGNMENT OF COPYRIGHTS, PATENTS, TRADEMARKS AND LICENSES;ASSIGNORS:HIGH VOLTAGE ENGINEERING CORPORATION;DATCON INSTRUMENT COMPANY;HALMAR ROBICON GROUP, INC.;AND OTHERS;REEL/FRAME:008013/0660

Effective date: 19960509