US2510448A - Magnetic induction accelerator - Google Patents

Magnetic induction accelerator Download PDF

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Publication number
US2510448A
US2510448A US793501A US79350147A US2510448A US 2510448 A US2510448 A US 2510448A US 793501 A US793501 A US 793501A US 79350147 A US79350147 A US 79350147A US 2510448 A US2510448 A US 2510448A
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United States
Prior art keywords
tube
electron
orbit
cathode
lens
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Expired - Lifetime
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US793501A
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English (en)
Inventor
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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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
    • F16K31/00—Actuating devices; Operating means; Releasing devices
    • F16K31/44—Mechanical actuating means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
    • F16K17/00—Safety valves; Equalising valves, e.g. pressure relief valves
    • F16K17/20—Excess-flow valves
    • F16K17/22—Excess-flow valves actuated by the difference of pressure between two places in the flow line
    • F16K17/24—Excess-flow valves actuated by the difference of pressure between two places in the flow line acting directly on the cutting-off member
    • F16K17/28—Excess-flow valves actuated by the difference of pressure between two places in the flow line acting directly on the cutting-off member operating in one direction only
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
    • F16K31/00—Actuating devices; Operating means; Releasing devices
    • F16K31/44—Mechanical actuating means
    • F16K31/56—Mechanical actuating means without stable intermediate position, e.g. with snap action
    • 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

Definitions

  • This invention relates in general to accelerators for charged particles and in particular to those of the high speed type.
  • the present invention is applicable to any of the known types of particle accelerators where a stream of charged particles is accelerated along a closed orbital path, such as devices known as synchrotrons or betatrons, it will be described and illustrated in connection with an accelerator of the magnetic induction type.
  • These betatrons or ray transformers are comprised generally of an evacuated annular tube into which electrons are introduced from an electron emissive cathode and a magnetic system which produces a magnetic field varying with time and having a space distribution such that the injected electrons are accelerated by the field along a circular orbit.
  • the magnetic system is so designed that a part of the magnetic field threads the tube in such a manner as to create a compensating centripetal force upon the electrons thus confining the latter to a circular orbit of substantially constant radius during their entire accelerating period.
  • the part of the magnetic field from which the centripetal force is derived is commonly referred to as the control or guiding field while the field producing the electron acceleration is known as the inducing field. It has been established that the centrifugal and centripetal forces will theoretically balance out to maintain the electrons in a circular orbit of constant radius r (often referred to as the equilibrium circle) when the following relationship is established:
  • the desired field relationship according to the above equation can in general be attained by making the reluctance of the magnetic path greater by an appropriate amount at the orbit than its average reluctance within the orbit.
  • the gradient of the magnetic field in a radial direction at the control field poles can be so designed that any tendency on the part of the electrons to deviate from the prescribed equilibrium orbit either in an axial or radial direction or a combination of both instantly gives rise to stabilizing forces which drive the errant electrons back into the orbit.
  • the desired field gradient is attained by tapering the control field poles outwardly so that the gap between them increases in a radially outward direction.
  • the electron stream completes many thousands of revolutions on the acceleration orbit between the time it is first introduced and the time when it reaches its final velocity, and thus undergoes a periodically changing stabilizing force during each revolution as it passes through that portion of the lens way where the lens diameter varies. Since the stabilizing force, viewed in the direction of electron travel, diminishes abruptly at the place where the electron stream enters the main tube body and thereafter gradually increases as the tube and lens diameters decrease, the periodic curve of the force contains not only a fundamental wave caused by the period of electron rotation but also very much higher harmonies.
  • the electrons can also be thought of as describing oscillatory movements with respect to the axis of the equilibrium circle since the lens force directed radially towards the axis is zero at the equilibrium circle itself and increases with distance from the circle. Stabilization of the electron stream can therefore be viewed as a constant oscillation of the electron in a direction transverse to the circumference of the acceleration orbit.
  • the characteristic frequency of the electrons oscillating in this manner coincides with the fundamental wave above referred to or with one of the hormonics of the varying stabilizing force, a condition of resonance will obtain which may result in such a great increase in the oscillation amplitude that a great part of the electron stream will be lost by impingment of electrons against the walls of the tube.
  • the object of the present invention is to provide an improved construction for the lens way in which the stabilizing forces remain uniform throughout the entire circumference of the tube.
  • the new arrangement which also entails a redesign of the electron emissive cathode thus avoids the undesirable periodic change in stabilizing force inherent with the arrangement described in my prior application and materially improves the overall stability of the electron stream during its acceleration.
  • the new construction consists of an annular tube of substantially uniform diameter throughout its entire circumference. Stabilizing fields alternating 'in polarity surround the tube and these are arranged concentrically with respect to the tube center i. e. the axis of each field coincides with a tangent at equilibrium orbit in the same manner as described in the previously mentioned co-pending application.
  • the cathode for producing the electron streams at the proper point in the cycle of the current Wave that provides the cyclically varying inducing and control fields is, however, quite different and consists of one or more annular bodies placed in the tube perpendicular to a tangent to the equilibrium orbit and equidistant between two adjacent stabilizing fields. The center of the cathode coincides with the equilibrium orbit.
  • the new construction includes in addition a tubular electrode also concentric with the orbit and placed directly in front of the cathode so as to form with the latter an electrostatic immersion lens for properly guiding the emitted electrons into the prescribed equilibrium orbit.
  • FIG. 1 is a vertical view in diametrical section taken on line ll of Fig. 2;
  • Fig. 2 is a plan view of the tube and part of the magnetic field structure and
  • Fig. 3 is-a-n enlarged sectional View in development of that portion of the tube containing the cathode to more clearly show structural details.
  • the electron accelerator is seen to include a central inducing core comprised of upper and lower magnetizable poles ll-l l of cylindrical form coaxial with the axis a-a of an evacuated annular glass electron tube II) which surrounds it, and the control field is produced by annular magnetizable poles 8-8 which confront one another at the electron orbit k in the tube, one of the control field poles being located above tube IE3 and the other below it.
  • the magnetic circuit is completed by yokes ,7 interconnecting the induction field poles Ill l" and the control field poles 88, and the varying magnetic field required for accelerating the particles around orbit is is furnished by upper and lower annular coils 6'-8' which surround the control field poles and are connected to a suitable source of relatively low frequency alternating current applied to terminals 5.
  • stabilizing fields are, in the illustrated construction, produced electromagnetically by a plurality of coils I2 surrounding the tube Ill in spaced relation. These coils are connected in series for energization from a suitable source of power such as battery l3 and it will be seen from the directional arrows in the figure that adjacent coils are wound in opposite directions so that the magnetic fields produced thereby are oppositely poled.
  • Fig. tube ii] at a point midway between two of the field coils I2 is enlarged to provide a bulbous cavity iiia within which is placed an annular metallic cathode body It.
  • this body is arranged perpendicular to a tangent to the electron orbit is and its geometrical center coincides with the orbit.
  • the electrons themselves are emitted in the direction of the arrows from a concave inner annular surface portion I5 of the body is coated with an electron emissive material it.
  • an electron emissive filament in annular form may be placed at the concave annular surface l5.
  • Tube ll functions as an anode for the emitted electron stream and thus has a potential applied thereto from a source it that is positive with respect of the potential applied to the cathode coating [6.
  • the potential at anode ll can be 0 kv. with the cathode coating it at -30 kv.
  • This conductive coating 23 extends almost along the entire inner surface and ends shortly before the cathode It as shown in Fig. 2.
  • Anode H in conjunction with the cathode coating l6 constitutes an immersion lens, and with the cathode coating it, at a negative potential with respect to anode, El, the paths taken by the annular electron discharge from coating I6 will be substantially as indicated by the dashed lines 26.
  • the electron discharge appears to originate from an imaginary annular cathode body 21 located radially inward from and in back of the real cathode l6 and thus makes it possible to introduce the electron stream into the tube H] for acceleration along the circular orbit 7c in the direction indicated by the arrow and at the same time maintain a uniform diameter of the magnetic lens way that assures uniform and alternately poled magnetic stabilizing fields around the complete circumference of the tube l0.
  • the immersion lens formed by the cathode coating It and anode l7, will efiect a retarding force on the stream each time the latter passes through it but the initial magnitude of this disturbance can be kept low by making the cathode coating l6 narrow in the direction of the orbit 7c and placing the mouth I8 of the anode I! close to the coating such that the distance therebetween as well as the width of the coating is small in relation to the radius 1' of the tube I0. Furthermore it should be noted that the magnitude of the disturbance due to the presence of the immersion lens diminishes rapidly as the speed of the electron stream increases.
  • the potential on the cathode coating it can normally be maintained at that of the anode l1 and brought to its negative value only for a brief period each time that an electron stream is discharged from the coating is into the circular orbit k.
  • This can be accomplished as shown in Fig. 2 by means of a switch 22 which when thrown from the dashed line position to the solid line position indicated in the drawing raises the potential on coating It from its negative value to ground level which is also the fixed potential of anode ll.
  • the disturbance due to the immersion lens can be limited to about 1 microsecond or less, i. e. for at most the first hundred or less revolutions of the electron stream.
  • the switch 22 has been shown schematically only. In actual practice, the switch would be controlled electronically through conventional timing circuits properly correlated with the current wave of the alternating current source that supplies the main inducing and control field components.
  • the new construction permits the safe use of a very high negative potential between the annular cathode coating l6 and the anode il thereby assuring a rapid and accurate run for the electron stream from the coating into the equilibrium orbit k.
  • anode ll need not be limited to a single tube but can be divided up axially into a plurality of tube sections each of which would be carried at a different positive potential with respect to that of the cathode.
  • the invention has been described with respect to its application to an induction accelerator of the half wave type in which an electron stream is injected into the tube and accelerated in one direction (clockwise) around the tube once for each complete cycle of the applied alternating current wave.
  • an induction accelerator of the half wave type in which an electron stream is injected into the tube and accelerated in one direction (clockwise) around the tube once for each complete cycle of the applied alternating current wave.
  • To adapt the invention for use on a full wave type of accelerator wherein separate electron streams would be accelerated in opposite directions of rotation about the tube on successive half cycles of the current wave it would be necessary to provide a like annular electron emissive coating or filament to the opposite face of the annular cathode carrier and a second anode like anode I! associated therewith to form the immersion lens for introducing the other electron stream.
  • an accelerator for charged particles of the type comprising a tube within which charged particles such as electrons may follow an orbital path and means including spaced pole pieces for producing a cyclically varying magnetic field of such space distribution as to confine the electrons to a fixed orbit while continuously accelerating them along said orbit, of a uniformly sized annular lens way enclosing said orbit for stabilizing the particles during their acceleration.
  • said lens way having its axis coincident with said orbit and comprising a plurality of circumferentially spaced electric lenses alternating in polarity, an annular emissive surface for said particles located interiorly of said tube midway between an adjacent pair of said lenses, and a tubular anode within said tube and spaced from said surface in the direction of particle emission, the respective axes of said surface and said anode being coincident with said orbit to thereby form an electrostatic immersion lens through which said particles are led into said orbit from said surface.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Electron Beam Exposure (AREA)
  • Particle Accelerators (AREA)
US793501A 1944-10-04 1947-12-23 Magnetic induction accelerator Expired - Lifetime US2510448A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE260982X 1944-10-04

Publications (1)

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US2510448A true US2510448A (en) 1950-06-06

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US793501A Expired - Lifetime US2510448A (en) 1944-10-04 1947-12-23 Magnetic induction accelerator

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US (1) US2510448A (ru)
CH (1) CH260982A (ru)
FR (1) FR956808A (ru)
GB (1) GB659739A (ru)
NL (1) NL71533C (ru)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2665392A (en) * 1949-10-31 1954-01-05 Gund Konrad Magnetic induction accelerator
US2825833A (en) * 1953-06-03 1958-03-04 Machlett Lab Inc Electron tube for magnetic induction accelerator
US2928019A (en) * 1957-03-11 1960-03-08 Itt Traveling wave electron discharge device
US2932797A (en) * 1956-01-03 1960-04-12 Research Corp Imparting energy to charged particles
US3170841A (en) * 1954-07-14 1965-02-23 Richard F Post Pyrotron thermonuclear reactor and process
DE1188221B (de) * 1958-07-15 1965-03-04 Atomic Energy Commission Verfahren zum Erzeugen einer energiereichen hochtemperierten Gasentladung
US3441756A (en) * 1965-04-05 1969-04-29 Avco Corp Electrical devices
US20090267543A1 (en) * 2006-10-28 2009-10-29 Bermuth Joerg Betatron with a removable accelerator block
US20090267542A1 (en) * 2006-10-28 2009-10-29 Bermuth Joerg Betatron with a variable orbit radius

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2245670A (en) * 1938-02-16 1941-06-17 Telefunken Gmbh Oscillation generator
US2297305A (en) * 1940-11-13 1942-09-29 Gen Electric Magnetic induction accelerator

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2245670A (en) * 1938-02-16 1941-06-17 Telefunken Gmbh Oscillation generator
US2297305A (en) * 1940-11-13 1942-09-29 Gen Electric Magnetic induction accelerator

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2665392A (en) * 1949-10-31 1954-01-05 Gund Konrad Magnetic induction accelerator
US2825833A (en) * 1953-06-03 1958-03-04 Machlett Lab Inc Electron tube for magnetic induction accelerator
US3170841A (en) * 1954-07-14 1965-02-23 Richard F Post Pyrotron thermonuclear reactor and process
US2932797A (en) * 1956-01-03 1960-04-12 Research Corp Imparting energy to charged particles
US2928019A (en) * 1957-03-11 1960-03-08 Itt Traveling wave electron discharge device
DE1188221B (de) * 1958-07-15 1965-03-04 Atomic Energy Commission Verfahren zum Erzeugen einer energiereichen hochtemperierten Gasentladung
US3441756A (en) * 1965-04-05 1969-04-29 Avco Corp Electrical devices
US20090267543A1 (en) * 2006-10-28 2009-10-29 Bermuth Joerg Betatron with a removable accelerator block
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

Also Published As

Publication number Publication date
GB659739A (en) 1951-10-24
CH260982A (de) 1949-04-15
FR956808A (ru) 1950-02-08
NL71533C (ru)

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