US3459988A - Cyclotron having charged particle and electron beams - Google Patents

Cyclotron having charged particle and electron beams Download PDF

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Publication number
US3459988A
US3459988A US607480A US3459988DA US3459988A US 3459988 A US3459988 A US 3459988A US 607480 A US607480 A US 607480A US 3459988D A US3459988D A US 3459988DA US 3459988 A US3459988 A US 3459988A
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cyclotron
cavities
electron
energy
cavity
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US607480A
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English (en)
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Francis Michael Russell
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Science Research Council
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Science Research Council
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K21/00—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets
    • H02K21/12—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets with stationary armatures and rotating magnets
    • H02K21/14—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets with stationary armatures and rotating magnets with magnets rotating within the armatures
    • H02K21/16—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets with stationary armatures and rotating magnets with magnets rotating within the armatures having annular armature cores with salient poles
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K19/00—Synchronous motors or generators
    • H02K19/16—Synchronous generators
    • H02K19/36—Structural association of synchronous generators with auxiliary electric devices influencing the characteristic of the generator or controlling the generator, e.g. with impedances or switches
    • 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
    • H05H13/00—Magnetic resonance accelerators; Cyclotrons
    • 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
    • H05H7/00—Details of devices of the types covered by groups H05H9/00, H05H11/00, H05H13/00
    • H05H7/02—Circuits or systems for supplying or feeding radio-frequency energy

Definitions

  • This invention relates to cyclotrons, and more particularly to separated orbit cyclotrons.
  • a beam of charged particles moves in a spiral path under the influence of a steady magnetic field and an electric field of unvarying, radio-frequency, these fields focussing, accelerating and confining the beam.
  • the magnetic and electric fields are normally provided by an alternating series of magnets and excited cavities which are disposed in a closed ring and which are of such dimensions that all the turns of the spiral path pass between the poles of the magnets and through the cavities.
  • radio-frequency energy to excite the cavities and hence accelerate the beam of charged particles is provided by a power amplifier using thermionic valves, and is supplied to the cavities over transmission lines.
  • the efiiciency with which such amplifiers generate the required large quantities of radio-frequency power is, however, not very great.
  • a method of exciting the cavities of a separated orbit cyclotron comprises passing a pulsed beam of electrons through the cavities in such a phase relationship with the pulsed beam of charged particles being accelerated that energy is coupled from the electron beam to the cavities and thence to the charged particles, the energy of the electrons being such that they circulate in an orbit outside the outermost turn of the spiral path followed by the beam of charged particles.
  • a separated orbit cyclotron comprises a series of magnets and cavities disposed in a closed ring, a beam tube within which a pulsed beam of charged particles is arranged to be focussed, accelerated and confined by the magnetic and electric fields associated with the magnets and cavities, respectively, the beam following a spiral path the radius of which increases as the energy of the charged particles increases, and means to excite the cavities with radio-frequency energy by passing a pulsed beam of high energy electrons through the cavities in such a phase relationship with the beam of charged particles being accelerated that energy is coupled from the electron beam to the cavities so that the charged particles are accelerated, the energy of the electrons being such that they circulate in an orbit outside the outermost turn of the spiral path followed by the beam of charged particles.
  • each such electron beam then passes through a fraction of the total number of cavities and is diverted out of the cyclotron at a point in the periphery just prior to the point where the next electron beam enters.
  • FIGURE 1 shows a first diagrammatic plan view of the cyclotron
  • FIGURE 2 shows a second diagrammatic plan view of the cyclotron
  • FIGURES 3 to 6 show diagrammatically parts of the arrangement for generating radio-frequency electric energy which is to be supplied to the cyclotron.
  • the cyclotron to be described is a separated orbit cyclotron for accelerating intense pulsed beams of protons to high energies.
  • the cyclotron comprises an alternating series of electro-magnets 1 and radio-frequency excited cavities 2 disposed in a closed ring.
  • the proton beam 3 is focussed, accelerated and confined by a steady magnetic field associated with the magnets 1 and an electric field of unvarying, radio-frequency associated with the cavities 2, such that it moves in a spiral path the radius of which increases as the energy of the protons increases.
  • the spiral path lies within an evacuated beam tube (not indicated) which passes between the poles of the magnets 1 and through the cavities 2.
  • FIGURE 2 This figure shows the magnets I and cavities 2 making up half the cyclotron, and part of the path of the beam 3, the confines of which are indicated by the broken lines 4.
  • beams 5 of high energy electrons enter the beam tube and circulate through several cavities 2 before being diverted out of the cyclotron at points in the periphery just prior to points where the next electron beam 5 enters.
  • the energy of the electron beams 5 is such that the orbit in which they move is outside the outermost turn of the spiral path followed by the proton beam 3. To achieve this the electrons will normally have to be relativistic initially, having an energy of say 4.2 million electron volts. In passing through the cavities 2 the electron beams 5 couple energy to the cavities 2. Some of this energy is lost in the metallic walls of the cavities 2, but assuming the correct phase relationship is maintained between the electron beams 5 and the proton beam 3, the remainder of the energy is absorbed by the proton beam 3, so bringing about the desired acceleration.
  • the cavities 2 are detuned slightly to accommodate the reactance introduced by the proton beam 3.
  • each cavity 2 has a portion 6 of restricted width in the region where the electron bear 5 is to pass through the cavity 2.
  • the width of each portion 6 is the same, so that the resonant frequency and voltage distribution with radius are substantially independent of the exact location in azimuth of the portion 6.
  • each portion 6 can be calculated, it is preferable to arrange that some adjustment of the positions can be made during setting-up.
  • V l /C1 V02 +16 V l where k andk are constants.
  • the principal effect of a finite cavity transit time on the electron beams 5 is to introduce a dispersion in the energy of the pulses following deceleration. Such dispersion is of little consequence if the electrons remain relativistic in energy, but tends to dominate the behaviour of the pulses during the final stages of deceleration. As loss of an electron beam 5 in the last cavity 2 must be avoided if the cavity voltages are to be maintained contant, then a minimum requirement is that all electrons in a pulse should leave the last cavity 2 with finite energy. If there is an appreciable energy dispersion then the overall efiiciency of the system is reduced, because the energy of the electron beam 5 emerging from the last cavity 2 is lost. Added disadvantages of dispersion are a progressive increase in emittance of the electron beams 5 and a tendency to redistribute particles within apulse.
  • the electron beams 5 are coupled to the cavities 2 at zero phase angle relative to the electric field.
  • the residual dispersion for an elec- Cal tron beam 5 of reasonable phase-spread is still unacceptably large, and so the electron beams 5 are arranged to pass through a small cavity resonator 8 following each deceleration.
  • These correction cavities 8 are operated at a high harmonic (say the eighth) of the frequency of the main cavities 2, and reduce the dispersion in energy to an acceptable amount.
  • the high frequency and low amplitude of the signal needed in the correction cavities 8 leads to quite modest power requirements for their excitation. Further, most of the energy given to the electron beams 5 in the cavities 8 is usefully coupled into the main cavities 2.
  • the average energy of the electron beam 5 emerging from the last cavity 2 before being diverted out of the cyclotron can be as low as 0.2 million electron volts, and with a phase spread of In FIGURE 2 the electron beams 5 are shown as being absorbed by blocks 9 of metal after leaving the cyclotron.
  • (l) proton linear accelerator 0 to 10 million electron volts (2) first cyclotronlO to 70 million electron volts (3) second cyclotron 70 to 350 million electron volts (4) third cyclotron 350 to 1000 million electron volts
  • Each of the three cyclotrons would be generally similar to the one described above and suitable beam transport systems would be provided to convey the proton beam 3 from the linear accelerator to the first cyclotron and from one cyclotron to the next.
  • the electron beams 5 in those cyclotrons are arranged to circulate at half the synchronous radius, and the cavities are spaced such that the proton beam 3 is accelerated once every two cycles of the radio-frequency.
  • the electron beams 5 are generated, as it will be appreciated that they are of large intensity and high energy; approximately 1 amp and 4.2 million electron volts respectively in the example quoted above.
  • the electron beams 5 are generated by a device comprising the combination of electron sources 10, a high voltage generator 11 and linear accelerators 12.
  • the whole device is housed in a containing vessel 13 filled with a gas, such as sulphur hexafiuoride, at high pressure.
  • the electron sources 10 are mounted near the top of the vessel 13, and each one is formed by an electron gun 14 and a modulating grid 15.
  • large numbers of electrons are emitted by the guns 14 and the velocity of these electrons is modulated by sinusoidally-varying radio-frequency signals supplied to the grids 15 such that the electrons emerge from the guns 10 in bunches or pulses.
  • the bunched electrons pass into the accelerators 12 where they are accelerated to 4.2 million electron volts and the resulting high energy pulsed electron beams 5 are passed by way of suitable beam transport systems including the bending magnets 16 to the desired points on the periphery of the cyclotron (FIGURE 2).
  • shaft 17 is made up of a series of generally flat, permanent magnet sections 20, each of which has 18 pole pieces 21 of alternate polarity projecting from its periphery.
  • the outer face of each pole piece 21 is some 15 cms. square and the gap between adjacent pole pieces 21 is also some 15 cms.
  • discs 22 having alternately castellated edges are interposed betweeneach adjacent pair of sections 20, a portion of a disc 22 being shown in FIGURE 6.
  • the discs 22 are made of a non-magnetic metal such as titanium or stainless steel.
  • the selections 20 and the discs 22 are bonded together but maintained electrically-insulated from one another by being embedded in epoxy resin, the outer surface of the resin being smoothly cylindrical to minimise viscosity losses as the shaft 17 rotates.
  • the shaft 17 rotates within a stator 23 formed by a number of stator sections 24 equal in number to, and adjacent in position to, the magnet sections 20.
  • Each stator section 24 has a number of inwardly-projecting projections 25, equal in number to the pole pieces 21 on a magnet section 20 and similarly disposed.
  • On each projection 25 is wound a coil 26, only two of which are shown in FIGURE 4.
  • Across each coil 26 is connected a bridge rectifier 27 and a smoothing capacitor 28.
  • the discs 29 have aligned apertures through which pass evacuated glass tubes 30 down which the electron beams 5 pass.
  • the successively increasing potentials of the discs 29 which may amount to 100 kilo volts per disc 29 over the range to 4.2 megavolts results in the required acceleration of the electron beams 5.
  • Some at least of the discs 29 have quadrapo'le focusing magnets 31.
  • the generator 11 has associated with it 6 accelerator 12, so that six electron beams can be produced simultaneously.
  • accelerators 12 may be provided, either associated with the same generator 11 or associated with a further, similar generator.
  • a method of exciting the cavities of a separated orbit cyclotron comprising passing a pulsed beam of electrons through the cavities in such a phase relationship with the pulsed beam of charged particles being accelerated that power is coupled from the electron beam to the cavities and thence to the charged particles, guiding the beam of electrons so that it passes through the cavities, the electrons circulating in an orbit outside the outermost turn of the spiral path followed by the beam of charged particles.
  • a separated orbit cyclotron comprising a series of magnets and cavities disposed in a closed ring, a beam tube within which a pulsed beam of charged particles is focussed, accelerated and confined by the magnetic and electric fields associated with the magnets and cavities, respectively, the beam following a spiral path the radius of which increases as the energy of the charged particles increases, an electron beam source for producing a pulsed beam of high energy electrons, and guide means for guiding the beam of electrons so that it passes through the cavities in such a phase relationship with the beam of charged particles being accelerated that power is coupled from the electron beam to the cavities so that the charged particles are accelerated, the energy of the electrons being such that they circulate in a orbit outside the outermost turn of the spiral path followed by the beam of charged particles.
  • each cavity has a portion of restricted width formed by closing together parts of two opposite walls of the cavity, the electron beam crossing the cavity in this portion of restricted width so that the cavity transit time of the electron beam is reduced.
  • a cyclotron in accordance with claim 4 wherein magnets are provided between each adjacent pair of cavities such that the electron beam passes through each cavity at the same radius, this radius being less than the synchronous radius for the electron beam.
  • a cyclotron in accordance with claim 6 wherein more than one such beam of electrons supplied to the cyclotron, the electron beams entering the cyclotron at symmetrically disposed points around the periphery, and each electron beam passing through a plurality of consecutive cavities before being diverted out of the cyclotron at a point in the periphery just prior to the point where the next electron beam enters.
  • the high voltage generator comprises a rotor formed by an electrically insulating shaft made up of a plurality of magnet sections having outwardly projecting pole pieces, adjacent pole pieces having opposite magnetic polarity, a stator having a similar number of correspondingly disposed inwardly-projecting projections on each of which is wound a coil, means to drive the rotor, means to rectify the alternating currents developed in the coils as the rotor rotates, and means to apply the resulting direct current potentials to the electrodes of said accelerator to produce the required acceleration of the electron beam.
  • An accelerator for accelerating a beam of charged particles comprising at least one electrically resonant cavity for providing an electric field to act upon the beam of charged particles, an electron beam source for producing a pulsed beam of high energy electrons, and guide means for guiding the beam of electrons so that it passes through the cavity or cavities in such a phase relationship with the beam of charged particles being accelerated that power is coupled from the electron beam to the cavities so that the charged particles are accelerated, the

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Power Engineering (AREA)
  • Permanent Magnet Type Synchronous Machine (AREA)
  • Particle Accelerators (AREA)
  • Iron Core Of Rotating Electric Machines (AREA)
  • Connection Of Motors, Electrical Generators, Mechanical Devices, And The Like (AREA)
US607480A 1966-01-14 1967-01-05 Cyclotron having charged particle and electron beams Expired - Lifetime US3459988A (en)

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Application Number Priority Date Filing Date Title
GB0976/66A GB1165181A (en) 1966-01-14 1966-01-14 Improvements in or relating to Accelerators for Charged Particles

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US607965A Expired - Lifetime US3504209A (en) 1966-01-14 1967-01-09 Electric generators

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US (2) US3459988A (de)
CH (1) CH468112A (de)
DE (1) DE1638537B2 (de)
FR (1) FR1509331A (de)
GB (1) GB1165181A (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4010396A (en) * 1973-11-26 1977-03-01 Kreidl Chemico Physical K.G. Direct acting plasma accelerator
US4197510A (en) * 1978-06-23 1980-04-08 The United States Of America As Represented By The Secretary Of The Navy Isochronous cyclotron
US5256938A (en) * 1992-02-28 1993-10-26 The United States Of America As Represented By The Department Of Energy ECR ion source with electron gun

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NO783310L (no) * 1977-10-06 1979-04-09 Ass Elect Ind Synkronmaskin.
DE3332533A1 (de) * 1983-09-09 1985-03-28 Layh Hans Dieter Wechselstromtachogenerator
GB2296372A (en) * 1994-12-23 1996-06-26 Atomic Energy Authority Uk Bending accelerated charged particle beams
JP4796674B2 (ja) * 2005-06-24 2011-10-19 日立ビアメカニクス株式会社 スキャナ
JP4767765B2 (ja) * 2006-06-19 2011-09-07 愛三工業株式会社 回転角センサと回転角センサの回転体の成形方法とスロットル開度制御装置

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2882396A (en) * 1953-10-30 1959-04-14 Ernest D Courant High energy particle accelerator
US2890348A (en) * 1957-07-08 1959-06-09 Ohkawa Tihiro Particle accelerator
US2979635A (en) * 1959-07-15 1961-04-11 Richard J Burleigh Clashing beam particle accelerator
US3328708A (en) * 1965-03-04 1967-06-27 Bob H Smith Method and apparatus for accelerating ions of any mass

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US908097A (en) * 1905-02-13 1908-12-29 Adolf Herz Magneto alternating-current generator.
US2293951A (en) * 1939-09-20 1942-08-25 Westinghouse Electric & Mfg Co Induction apparatus and method of core construction therefor
US2516114A (en) * 1946-12-30 1950-07-25 Duncan Electric Mfg Co Alternator
US3139547A (en) * 1961-06-30 1964-06-30 Thompson Ramo Wooldridge Inc Rotary digital actuator

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2882396A (en) * 1953-10-30 1959-04-14 Ernest D Courant High energy particle accelerator
US2890348A (en) * 1957-07-08 1959-06-09 Ohkawa Tihiro Particle accelerator
US2979635A (en) * 1959-07-15 1961-04-11 Richard J Burleigh Clashing beam particle accelerator
US3328708A (en) * 1965-03-04 1967-06-27 Bob H Smith Method and apparatus for accelerating ions of any mass

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4010396A (en) * 1973-11-26 1977-03-01 Kreidl Chemico Physical K.G. Direct acting plasma accelerator
US4197510A (en) * 1978-06-23 1980-04-08 The United States Of America As Represented By The Secretary Of The Navy Isochronous cyclotron
US5256938A (en) * 1992-02-28 1993-10-26 The United States Of America As Represented By The Department Of Energy ECR ion source with electron gun

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DE1638537B2 (de) 1971-11-04
CH468112A (de) 1969-01-31
DE1638537A1 (de) 1971-02-11
US3504209A (en) 1970-03-31
FR1509331A (fr) 1968-01-12
GB1165181A (en) 1969-09-24

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