US2572414A - Magnetic induction accelerator - Google Patents

Magnetic induction accelerator Download PDF

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Publication number
US2572414A
US2572414A US790912A US79091247A US2572414A US 2572414 A US2572414 A US 2572414A US 790912 A US790912 A US 790912A US 79091247 A US79091247 A US 79091247A US 2572414 A US2572414 A US 2572414A
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orbit
poles
electron
tube
path
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Expired - Lifetime
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US790912A
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English (en)
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Wideroe Rolf
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BBC Brown Boveri AG Germany
BBC Brown Boveri France SA
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BBC Brown Boveri France SA
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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
    • H05H11/00—Magnetic induction accelerators, e.g. betatrons
    • H05H11/04—Biased betatrons

Definitions

  • This invention relates in general to devices for accelerating charged particles such as a stream of electrons to high velocity and hence high potential on a circular orbit and in particular to an improved arrangement for improving the stabilization of the electron stream at the time when the stream is first injected into the device, at the time that the stream is. removed after it has reached its final velocity, or both.
  • Fig. I is a view in central vertical section through an electron accelerator embodying the present invention
  • Fig. 2 is a diagrammatic view illustrating a conventional arrangement for shifting the electron orbit of an induction type accelerator
  • Fig. 3 is a diagrammatic view illustrating the approximate electron orbit and the orbitalshift effected by the arrangement of Fig. 2
  • Figs. 4-6 are explanatory curves relating to the type of orbit shift provided by the Fig. 2' arrangement
  • Figs. 7 and 7a are diagrammatic views illustrating the approximate electron orbitand type of orbital shift provided. by the present invention
  • Fig. 8 is: a diagrammatic view illustrating the arrangement of the auxiliary, orbit shifting coils included inthe Fig. 1- construction
  • FIG. 9 and1l0 are fragmentary viewsin vertical central section illustrating modified forms of the invention.
  • Fig. 1 1 is aschematic wiringdiagram of the control circuit for energizing the auxiliary coils in Fig. 1 bywhich the shift in the electron orbit is effected.
  • the invention is applicable to various types of electron accelerators but in this application is illustrated and described in its relation toan accelerator operating on the magnetic induction principle.
  • the latter are now generally known as betatrons or ray transformers and a typical. construction is illustrated in the diametral section view of Fig. 1.
  • the betatron is comprised of a magnetic field structure I!) made up from steel-laminations of appropriate contour to provide a pair of cylindrical poles Hl l separated by air gap l2 and located concentrically along axis a.a, and a pair of concentric annular poles l3l3' facing one another and separated by air gap l4.
  • Yoke members complete the magnetic' circuit for a cyclically varying flux set up in the annular and cylindrical poles.
  • l and l3-l3 are surrounded by an annular winding preferably split into two coil sections Iii-16 connected in series for energization from a source of alternating current of suitable frequency as for example 100 cycles/sec. applied to terminals H.
  • a condenser 31 is also connected in shunt with the coils
  • An annular evacuated glass tube l8 rests in the air gap [4 between the poles
  • the electron stream to be accelerated is of course produced at the cathode 20 and after it hasbeen accelerated to its final velocity along the circular orbit 7c which occurs when the current reaches its maximum value the stream can be caused to impinge upon a target anode 2
  • cathode 20 is located radially inward from the circular orbit is and the target anode 2
  • the cathode 20 is energized periodically in timed relation with the alternating current wave applied to the coil sections I6, I6 to produce a stream of electrons at just about the instant that the wave passes through zero.
  • the stream upon reaching the circular orbit is undergoes a constant acceleration under the influence of the magnetic field produced in the field structure [8- by'the applied alternating current.
  • This field divides into essentially two operating components.
  • the inducing field component acting axially through poles IlH may be Viewed as being responsible for the acceleration of the electron stream;.
  • the other component commonly referred to as the control field which acts axially through the annular poles l3l3' produces a centripetal efiect upon the electron stream to ofiset the centrifugal forces of the electrons caused by their motion along the circularorbit k.
  • the centripetal force which likewise increases substantially matches the centrifugal forces of the electrons with the result that the stream isv confined to a circular orbit of constant radius. This is the orbit k.
  • the stabilizing force on the electron stream produced by the magnetic control field component previously discussed functions in such a manner that any radiall inward or outward deviations of equal magnitude of the electrons from the equilibrium orbit give rise to equal stabilizing forces.
  • the conditions at the points A and B of Fig. 3 will be represented by the graph shown in Fig. 4 from which it will be seen that the deviations of orbit k from its prescribed radius 1'0 in the positive and negative sense, respectively, will give rise to oppositely directed but like varying stabilizing forces tending to force the electrons back" into theoriginal orbit.
  • Stabilizing force conditions of the character shown by the graphs of Figs. 5 and 6 are highly undesirable because the maximum stabilizing force available in one direction from To may be exceeded upon the occurrence of a relatively small deviation of the electrons from the circular orbit in that direction whereupon such electrons will no longer be restored to the radius 10.
  • the foregoing undesirable operating characteristics are eliminated and satisfactory stabilizing conditions obtained upon injection of the electron stream into the tube [8, upon its ejection following acceleration thereof, or both.
  • the improved result is obtained by effecting -a change in the radius of the equilibrium orbit simultaneously with the displacement of its center such that the old and new orbits pass at least approximately through the same point at one place in tube l8.
  • the old orbit in Fig. 7 is designated ICE. and the new i. e. displaced orbit by kb.
  • can then be located in or adjacent to the point E while at the point F the stabilizing conditions are the same for both orbits he. and kb.
  • orbit kb would represent the old orbit and orbit ka the new or displaced orbit.
  • FIG. 8 One constructional form of the invention is illustrated schematically in Fig. 8.
  • the control poles I3, I 3 are seen to be surrounded by an auxiliary coil 30.
  • This winding is energized through conventional controls, as exemplified by Fig. 11, at the proper instant when displacement of the electron orbit is desired and the turns of the winding are varied circumferentially of the orbit 76a in such manner that the strength of the magnetic field produced thereby and which is superimposed upon the main control field acting through the control poles varies along the circumference of the orbit ks. approximately in accordance with the equation where a is a positive or negative constant, and $0 the azimuth angle.
  • the constant a is equal to unit.
  • Fig. 1 illustrates the position of the turns of coils on the control poles l3-l3 assuming the vertical section there shown were to be taken along the line YY of Fig. 8.
  • Fig. 11 use can be made of conventional control circuits for energizing coils 30 at the proper instant, and one such control is shown in Fig. 11.
  • the coils 39 are seen to be connected in series with a variable resistor 36 and a thyratron type of switching tube 33 to terminals 38 to Which a source of direct current designated by the conventional and symbols is applied.
  • the voltage between the grid 33a, and cathode 331) the amplitude of which determines the instant at which the tube fires i. e. reduces the impedance across the cathode33b, anode330 to a nil value so that current can flow freely therethrough, is supplied from the secondary of transformer 34.
  • the primary of this transformer is connected across the alternating current terminals I!
  • phase shifting device 35 The circuit is so arranged that when the alternating current through coils I6I6' reaches its maximum value, at which time the electron stream has also reached its maximum energy level and must be removed, the voltage impressed upon the con trol grid 33a will have. likewise and simultaneously attained a value sufficient to fire the tube thus causing a flow of current through the coils 39.
  • the amplitude of the current in coils 30 can be adjusted by means of the Variable resistor 3E.
  • the phase-shifting device 35 is of course needed because the current wave in coils i6l6 lags substantially 9O electrical degrees behind the alternating voltage wave at terminals ll due to the cross-wound coil 25 of Fig. 2 can be used in con-- junction with one of the known betatron constructions in which provision is made for changing the diameter of the orbit at the desired instant such as for example at the time when the fully accelerated electron stream'is to be ejected from the orbit.
  • the desired result is obtained by varying the coil current so that oppositely directed fields are created at diametrically opposite points of the circular path while simultaneously altering the radius of the path. Two constructions for accomplishing the latter are illustrated respectively in Figs. 9 and 10.
  • Fig. 9 the coils 25 are shown applied to the control poles l3l3 in the manner illustrated schematically in Fig. 2, it being assumed that the vertical section of Fig. 9 is taken in a plane coincident with the diameter R in Fig. 2.
  • These poles are each seen to include a section 3! of reduced cross-section such that the control poles will begin to saturate towards the end of the accelerating period.
  • the normal ratio between the control and inducing field which has been maintained up to that instant to confine the circling electron stream to an orbit of constant radius likewise begins to change.
  • the inducing field now begins to increase at a greater rate than does the control field with the result that the radius of the electron path begins to enlarge.
  • Fig. illustrates another practical arrangement.
  • the cross-wound coil of Fig. 2 is applied to each of the control poles
  • a short-circuited conductor ring 32 imbedded in the face of pole l I will serve this purpose as explained more in detail in U. S. Patent No. 2,297,305 issued to D. W. Kerst, September 29, 1942.
  • Displacement in phase between the control and inducing fields is also discussed in Swiss Patent No. 254,937.
  • the principles underlying the present invention are not limited in application to electron accelerators operating wholly on the magnetic induction principle.
  • the invention can be applied equally as well for'similarly changing the electron orbit in the well known synchrotron type of electron accelerator Where initial acceleration of the electron stream to an energy level of .the order of two million electron volts is effected through use of the magnetic induction principle and further electron acceleration is produced by high frequency electrostatic fields.
  • the desired change in the orbit radiusiincrease or decrease) can be obtained by reducing or increasing the frequency of the accelerating voltage relative to its original value.
  • a charged particle accelerator of the type wherein at least an initial acceleration of the particles is effected through magnetic induction said accelerator including an annular tube within which the particles may follow an orbital path, meansproviding charged particles within said tube, a magnetic structure comprising inducing field pole means extending axially through said tube and a pair of annular control field poles arranged in confronting relation at and on opposite sides of said tube, and a magnetizing winding on said structure adapted to be energized by a cyclic, time varied current to produce a corresponding time varied magnetic field in said poles and which causes said particles to be accelerated around said tube along a path of substantially constant radius; of means including cross wound coil means disposed on said control poles and which are energized at a predetermined instant in the cycle of said time varied magnetic field for eifecting a change in radius of said path and simultaneously displacing the path center along a diameter thereof.
  • a charged particle accelerator of the type wherein at least an initial acceleration of the particles is efiected through magnetic induction said accelerator including an annular tube within which the particles may follow an orbital path, means providing charged particles within said tube, a magnetic structure comprising inducing field pole means extending axially through said tube and a pair of annular control field poles arranged in confronting relation at and on opposite sides of said tube, and a magnetizing winding on said structure adapted to be energized by a cyclic, time varied current to produce a corresponding time varied magnetic field in said poles and which causes said particles to be accelerated around said tube along a path of substantially constant radius; of coil means disposed on said control poles and which when energized produces an auxiliary magnetic field varying in the circumferential direction of said path and having maximum and minimum values,
  • Afi represents the varying field strength, Aflm and a constants, and go the polar angle.
  • a charged particle accelerator of the type wherein at least an initial acceleration of the particles is effected through magnetic induction said accelerator including an annular tube within which the particles may follow an orbital path, means providing charged particles within said tube, a magnetic structure comprising inducing field pole means extending axially through said tube and a pair of annular control field poles arranged in confronting relation at and on opposite sides of said tube, a magnetizing winding on said structure adapted to be energized by a cyclic, time varied current to produce a corresponding time varied magnetic field in said poles and which causes said particles to be continuously accelerated around said tube along a path of substantially constant radius; of means operating in timed relation with said magnetic field for changing the radius of said path,
  • said center displacing means including cross-wound coils on said control poles which when energized produce auxiliary magnetic fields of opposite directions at the two points where the path diameter coincident with the direction of its displacement intersects the path, and means operating in timed relation with said time varied magnetic field for energizing said auxiliary field producing coils.
  • An accelerator for charged particles as defined in claim 4 wherein the center of said path is displaced through a distance substantially equal to the change in radius whereby the initial and changed paths coincide at one point in said tube.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Particle Accelerators (AREA)
US790912A 1946-12-11 1947-12-10 Magnetic induction accelerator Expired - Lifetime US2572414A (en)

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CH253828T 1946-12-11

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US (1) US2572414A (de)
CH (1) CH253828A (de)
DE (1) DE858587C (de)
FR (1) FR957169A (de)
GB (1) GB645758A (de)
NL (1) NL73372C (de)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2669652A (en) * 1948-12-15 1954-02-16 Gail D Adams Means for improving the yield from betatron x-ray generators
US2736799A (en) * 1950-03-10 1956-02-28 Christofilos Nicholas Focussing system for ions and electrons
US2738420A (en) * 1950-12-28 1956-03-13 Gen Electric Injection into charged particle accelerators
US2935691A (en) * 1952-10-18 1960-05-03 Bbc Brown Boveri & Cie Process and apparatus to conduct out particles accelerated in an induction accelerator
US2942106A (en) * 1955-11-21 1960-06-21 Willard H Bennett Charged particle accelerator
US20090153279A1 (en) * 2007-12-14 2009-06-18 Schlumberger Technology Corporation Single drive betatron
US20090268872A1 (en) * 2006-10-28 2009-10-29 Bermuth Joerg Betatron with a contraction and expansion coil
US20090267542A1 (en) * 2006-10-28 2009-10-29 Bermuth Joerg Betatron with a variable orbit radius
US20090267543A1 (en) * 2006-10-28 2009-10-29 Bermuth Joerg Betatron with a removable accelerator block
US20090290684A1 (en) * 2006-11-28 2009-11-26 Bermuth Joerg Circular accelerator with adjustable electron final energy
US20100148705A1 (en) * 2008-12-14 2010-06-17 Schlumberger Technology Corporation Method of driving an injector in an internal injection betatron

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8153997B2 (en) 2009-05-05 2012-04-10 General Electric Company Isotope production system and cyclotron
US8106370B2 (en) 2009-05-05 2012-01-31 General Electric Company Isotope production system and cyclotron having a magnet yoke with a pump acceptance cavity
US8106570B2 (en) 2009-05-05 2012-01-31 General Electric Company Isotope production system and cyclotron having reduced magnetic stray fields
US8374306B2 (en) 2009-06-26 2013-02-12 General Electric Company Isotope production system with separated shielding

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2297305A (en) * 1940-11-13 1942-09-29 Gen Electric Magnetic induction accelerator
US2394070A (en) * 1942-06-02 1946-02-05 Gen Electric Magnetic induction accelerator

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2297305A (en) * 1940-11-13 1942-09-29 Gen Electric Magnetic induction accelerator
US2394070A (en) * 1942-06-02 1946-02-05 Gen Electric Magnetic induction accelerator

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2669652A (en) * 1948-12-15 1954-02-16 Gail D Adams Means for improving the yield from betatron x-ray generators
US2736799A (en) * 1950-03-10 1956-02-28 Christofilos Nicholas Focussing system for ions and electrons
US2738420A (en) * 1950-12-28 1956-03-13 Gen Electric Injection into charged particle accelerators
US2935691A (en) * 1952-10-18 1960-05-03 Bbc Brown Boveri & Cie Process and apparatus to conduct out particles accelerated in an induction accelerator
US2942106A (en) * 1955-11-21 1960-06-21 Willard H Bennett Charged particle accelerator
US20090267543A1 (en) * 2006-10-28 2009-10-29 Bermuth Joerg Betatron with a removable accelerator block
US20090268872A1 (en) * 2006-10-28 2009-10-29 Bermuth Joerg Betatron with a contraction and expansion coil
US20090267542A1 (en) * 2006-10-28 2009-10-29 Bermuth Joerg Betatron with a variable orbit radius
US7994740B2 (en) * 2006-10-28 2011-08-09 Smiths Heimann Gmbh Betatron with a removable accelerator block
US8013546B2 (en) * 2006-10-28 2011-09-06 Smiths Heimann Gmbh Betatron with a variable orbit radius
US8073107B2 (en) * 2006-10-28 2011-12-06 Smiths Heimann Gmbh Betatron with a contraction and expansion coil
RU2516293C2 (ru) * 2006-10-28 2014-05-20 Смитс Хайманн Гмбх Бетатрон с катушкой сжатия и расширения
US20090290684A1 (en) * 2006-11-28 2009-11-26 Bermuth Joerg Circular accelerator with adjustable electron final energy
US7983393B2 (en) * 2006-11-28 2011-07-19 Smiths Heimann Gmbh Circular accelerator with adjustable electron final energy
US20090153279A1 (en) * 2007-12-14 2009-06-18 Schlumberger Technology Corporation Single drive betatron
US7638957B2 (en) * 2007-12-14 2009-12-29 Schlumberger Technology Corporation Single drive betatron
US20100148705A1 (en) * 2008-12-14 2010-06-17 Schlumberger Technology Corporation Method of driving an injector in an internal injection betatron
US8362717B2 (en) 2008-12-14 2013-01-29 Schlumberger Technology Corporation Method of driving an injector in an internal injection betatron

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Publication number Publication date
FR957169A (de) 1950-02-16
CH253828A (de) 1948-03-31
GB645758A (en) 1950-11-08
DE858587C (de) 1952-12-08
NL73372C (de)

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