WO2019020160A1 - Cyclotron compact avec électrodes en forme de trèfle - Google Patents

Cyclotron compact avec électrodes en forme de trèfle Download PDF

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Publication number
WO2019020160A1
WO2019020160A1 PCT/EP2017/068613 EP2017068613W WO2019020160A1 WO 2019020160 A1 WO2019020160 A1 WO 2019020160A1 EP 2017068613 W EP2017068613 W EP 2017068613W WO 2019020160 A1 WO2019020160 A1 WO 2019020160A1
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WO
WIPO (PCT)
Prior art keywords
cyclotron
stem
cyclotron according
clover
delta
Prior art date
Application number
PCT/EP2017/068613
Other languages
English (en)
Inventor
Pierre Mandrillon
Matthieu Conjat
Original Assignee
Aima Developpement
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Aima Developpement filed Critical Aima Developpement
Priority to PCT/EP2017/068613 priority Critical patent/WO2019020160A1/fr
Publication of WO2019020160A1 publication Critical patent/WO2019020160A1/fr

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Classifications

    • 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
    • H05H7/14—Vacuum chambers
    • H05H7/18—Cavities; Resonators
    • 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
    • H05H13/005—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
    • H05H13/00—Magnetic resonance accelerators; Cyclotrons
    • H05H13/02—Synchrocyclotrons, i.e. frequency modulated cyclotrons

Definitions

  • the present invention relates to cyclotron-type particle accelerator.
  • the cyclotron could operate either at a fixed frequency, the so-called “classical” or “isochronous cyclotron” or at modulated frequency in time, the so-called “synchro-cyclotron”.
  • the term “cyclotron” encompasses both isochronous cyclotrons and synchro-cyclotrons.
  • Cyclotrons encounter a growing interest in many applications and in particular in medical applications.
  • the acceleration of ions in a cyclotron is performed via a so-called radiofrequency (RF) electrode system maintained at high voltage and oscillating at a frequency selected in relation with the orbit revolution time of the beam being accelerated and the number of accelerating gaps.
  • RF radiofrequency
  • Known cyclotrons comprise delta shaped plate electrodes at the RF potential forming a hollow conductor enabling the transit of the beam, sometimes also called “dees", the electrodes being positioned on either side of a median plane of acceleration.
  • Each-electrode is surrounded by a grounded electrode, the so-called "liner”.
  • Accelerating gaps may then be defined between the delta shaped electrodes and the liner.
  • the electrodes are connected to supporting stems that extend either perpendicularly to the electrodes and to the median plane of acceleration or radially.
  • Each stem behave like an inductive line and the associated electrode(s) with the liner like a capacitive element and they form all together a resonant cavity tuned to a predetermined frequency.
  • the resonant cavity associated to delta shaped electrodes is independent from the other resonant cavities corresponding to the other delta shaped electrodes.
  • the independent RF cavities need an accurate phase control which is complex and costly.
  • the multiple stems contribute significantly to increase the footprint of the cyclotron, while there is a clear advantage in making cyclotrons as compact as possible in many applications.
  • the electrodes need to be positioned accurately one relative to the other, especially in the central region of the cyclotron where the particles are injected. Such adjustment is mechanically complex.
  • the invention aims at satisfying this need by providing a cyclotron comprising a multigap single RF accelerating cavity, the cyclotron comprising a pair of electrodes each on a respective side of a median plane of acceleration, called "clover shaped electrodes", each clover shaped electrode comprising at least three delta wings alternating with openings in a circumferential direction and connected mechanically and galvanically together by a connecting ring.
  • the connecting ring because it connects the delta wings together both mechanically and galvanically, solves the difficult problem of the required accuracy of the relative positioning of the delta shaped wings, in particular in the central region of the cyclotron where the particles are injected.
  • a single RF amplifier may be used, which reduces the dimensions, complexity and cost of the cyclotron.
  • cyclotron The limited number of components of the cyclotron according to the invention results in a rather compact and cost effective cyclotron, providing more room for receiving other equipment.
  • exemplary embodiments of the cyclotron comprise at least one stem connected to the clover shaped electrodes.
  • the stem is preferably fixed to the connecting ring.
  • the stem is preferably the only one stem connected to the clover shaped electrodes.
  • the stem may be radially oriented, preferably with its longitudinal axis extending in the median plane of acceleration. Such a configuration helps reduce the axial dimension of the cyclotron, in a direction perpendicular to the median plane of acceleration.
  • the stem may also be oriented otherwise, for example parallel to the axis of the cyclotron.
  • the cyclotron comprises a liner extending around the pair of clover shaped electrodes and defining with the stem a resonant cavity.
  • the stem may be short-circuited to the liner at a non-zero distance from the connecting ring, preferably at its end opposite the connecting ring.
  • the stem may be short-circuited by a short circuit plate which is fixed to the liner or in a variant which is movable axially relative to the liner in order to adjust the resonance frequency of the resonant cavity.
  • the cyclotron may operate in quarter wave mode of resonance. Other modes of operation are possible, for example three quarter wave.
  • the cyclotron may also use two stems in alignment and operate at half wave.
  • Each clover shaped electrode may comprise four delta shaped wings, and preferably has only four delta shaped wings. In a variant each clover shaped electrode only has three delta shaped wings.
  • At least one of the delta shaped wings is having a different azimuthal aperture a from at least one other delta shaped wing. This allows having different energy gains at accelerating gaps, which may serve to compensate for non- homogeneous distribution of the electrical field, taken into account the mode of operation.
  • this helps compensate for the inhomogeneous electrical field between delta shaped wing(s) proximal to the resonator delta shaped wing(s) distal to the stem.
  • the wing(s) proximal to the stem may thus have an azimuthal aperture a that is different from the azimuthal aperture ⁇ of the wing(s) distal to the stem.
  • the azimuthal aperture ⁇ of the distal wing(s) is smaller than the azimuthal aperture a of the proximal wing(s).
  • At least one delta shaped wing may have an azimuthal aperture ot(r) that varies with the radius r, and in particular that increases with the radius r.
  • the azimuthal aperture ⁇ (r) may take a first value until a radius r/, then a second value with a greater value for a radius greater than r/.
  • each clover shaped electrode is symmetrical about a plane of symmetry (OXZ).
  • the faces of the delta shaped wings facing the median plane of acceleration of the particles are preferably coplanar.
  • the cyclotron may comprise a stripping foil for extracting the accelerated particles.
  • a stripping foil may be hold by a support extending through an opening situated radially inside of the connecting ring when the cyclotron is observed from above along its axis.
  • each clover shaped electrode is made monolithically in a single piece of an electrical conductive material, preferably copper, for example by machining a plate of metal.
  • the connecting ring is made separately from the delta shaped wings and assembled to them, for example by soldering or otherwise.
  • the delta shaped wings join at a central region of the electrode.
  • a single high frequency amplifier is used for supplying RF to the clover shaped electrodes.
  • the central region of the clover shaped electrode preferably comprises an entry orifice for the particles to be accelerated.
  • the RF frequency preferably is in the order of 10 to 100 MHz.
  • the RF frequency preferably is constant, i.e. time independent, for isochronous cyclotrons.
  • the frequency is variable, and an adjustable inductance or capacitance or a wide-band RF amplifier may be used to modulate the frequency of the resonant cavity in the desired frequency range.
  • the profile of the liner advantageously follows the profile of the magnetic yoke, i.e. follows the hills and valleys.
  • the cyclotron according to the invention may accelerate a single beam or multiple beams in parallel, with one source of particles per injection line.
  • the injection may be double.
  • the median plane of acceleration of the particles may be horizontal or vertical, as the cyclotron is compact and may be more easily oriented is the desired direction.
  • the coil may be single or double.
  • the coil may be a supmconducting coil.
  • the magnetic field within the accelerating cavity may range (in absolute value) between 0 T and 8 or 10 Tesla for example.
  • the cyclotron may be with separated magnetic sectors or not In the case of separated magnetic sectors the electrodes may be located in valleys where the magnetic field is null.
  • the cyclotron according to the invention is more particularly intended for the acceleration of H 2 + ions, but the invention is not limited to a particular type of ion at the input of the accelerating cavity or at the output of the cyclotron.
  • the particles accelerated may also be H- or D- ions, for example.
  • Another object of the present invention is a method for producing a beam of accelerated particles comprising accelerating a beam of ions using a cyclotron according to the invention as defined above.
  • Another object of the invention resides in "target oriented radiotherapy” (TOR) by particles generated using a cyclotron made in accordance with the invention as defined above.
  • TOR target oriented radiotherapy
  • An example of TOR is the production of beams of neutrons for Neutron Capture Therapy (NCT).
  • a cyclotron made according to the invention may also be used as an injector for higher energy accelerators for example, in Accelerator Driven Systems (ADS) for nuclear waste transmutation or subcritical nuclear reactors (ADSR), or for radioisotope production.
  • ADS Accelerator Driven Systems
  • ADSR subcritical nuclear reactors
  • FIG. 1 is a schematic view of clover shaped electrodes of the cyclotron of figure 1
  • Figure 3 is a schematic view of the liner associated with the clover shaped electrodes of figure 2,
  • FIG. 4 is a simplified view showing geometric axes XYZ and showing where aperture angles are measured for the cross section of Figure 5
  • - Figure 5 is a vertical section along radius Rl (top) and along R2 (bottom),
  • FIG. 6 is a view similar to Figure 4 showing the location of the accelerator gaps
  • Figure 7 shows the distribution of the electrical field at the gaps
  • Figure 10 is a view similar to Figure 1 of a variant embodiment with three delta shaped wings per clover shaped electrode.
  • FIG. 1 shows a cyclotron 1 according to a first embodiment of the invention.
  • Hie cyclotron 1 comprises an accelerating cavity under vacuum visible in Figure 5, for accelerating at least one beam of ions.
  • a RF electrode system 3 comprising a pair of upper 4 and bottom 5 "clover” shaped electrodes forming a hollow conductor and a stem 6 surrounded by a grounded conductive liner 7 to form a quarter wave resonant cavity tuned to a predetennined resonance frequency.
  • the term "clover” should not be interpreted in a restricting manner and encompasses any shape of delta shaped wings and any shape of ring.
  • the term "delta shaped wing” should not be interpreted in a restricted manner either and covers any shape of wing generally enlarging with the radius increasing.
  • the accelerated ions are either positive or negative charged particles, for example H+, H2+ or H-, D- ions generated by at least one suitable source of ions and injected in a central region of the accelerating cavity.
  • the radiofrequency RF acceleration of the ions is obtained by creating a suitable RF electric field inside one or more gaps between the electrodes at RF potential and the liner at ground potential.
  • the accelerating cavity is subjected to a magnetic field generated by a coil 8 between magnetic sectors 9 of a yoke 10 called “hills", the accelerating electrodes being placed in “valleys” between the hills.
  • the accelerated ions spiral around the axis of the cyclotron under the effect of the magnetic field.
  • the stem 6 is short circuited with the liner 7 at one end and connects to a ring 12 at the other end.
  • a short circuit plate 16 may be used for short-circuiting the stem 6. Such plate
  • the 16 may be fixed or movable for adjusting the resonance frequency.
  • the clover shaped electrodes each comprise two delta shaped wings also called “leaves” 13 proximal to the stem 6 and two other delta shaped wings distal to the stem 6.
  • the connecting ring 12 holds the delta shaped wings 13 and 14 mechanically and connects them electrically.
  • the delta shaped wings 13 and 14 join at their inner end, opposite the connecting ring 12.
  • the delta shaped wings 13 and 14 alternate in the circumferential direction with openings 30.
  • the magnetic sectors 9 may be shimmed near the central region of the accelerating cavity, the shim 31 being apparent through the openings in Figure 1.
  • the delta shaped wings 13 and 14 define with the liner 7 eight accelerating gaps G1-G8 as shown in Figure 6.
  • the resonant cavity is a quarter wave resonator, which results in a voltage law which is increasing with the distance from the short-circuit plate 16 measured along axis X. Therefore the peak voltage is different on the distal delta shaped wings 14, i.e. the electrodes on the positive X side from the proximal delta shaped wings 13 on the negative X side which is closer to the short circuit plate 16.
  • FIG. 7 An example of electric field distribution on the radius R3 in the accelerating gaps G1-G8 is shown on Figure 7. As one can see, the electrical field is lower in the proximal gaps G1-G2-G7-G8 which are closer to the short-circuit plate 16 than in the distal gaps G3-G4-G5-G6.
  • the azimuthal aperture ⁇ (r) of the proximal delta shaped wings is advantageously larger than the azimuthal aperture ⁇ (r) of the distal delta shaped wings and increases with the radius r while the azimuthal aperture ⁇ (r) is kept constant for the distal delta shaped wings, as shown in the cross section of Figure 5 and in the front view of the clover shaped electrode of Figure 2.
  • Such variation has not been shown in Figure 4 for sake of clarity.
  • the azimuthal aperture ⁇ (r) increases while ⁇ (r) remains constant, as shown in Figure 5.
  • the pair of upper and bottom clover shaped electrodes present two symmetry planes which are orthogonal, i.e. the median plane OXY in which the particles are accelerated and the OXZ plane which contains the longitudinal axis X of the stem 6.
  • the space occupied by the connecting ring 12, which is at the RF potential, does not allow easily a conventional extraction system layout based on an extraction channel.
  • RF energy from a RF source may be transferred to the stem 6 by inductive coupling with an inductive loop 34 located close to the short circuit plate 16 as shown in Figure 8.
  • An isolating ring 33 could be inserted between the stem 6 and the liner 7 as shown in this Figure.
  • the number of delta shaped wings per clover shaped electrode may be different and equal to three as shown in Figure 10.
  • the harmonic on which the particles are accelerated changes with the number of delta shaped wings.
  • the harmonic is preferably four and with three delta shaped wings the harmonic is preferably three or six.
  • the external diameter of the connecting ring may range between 50 and 80 cm but other diameters are possible without departing from the scope of the invention.
  • the length of the stem depends from the resonance frequency.
  • the RF frequency is preferably ranging from 10 to 100 MHz.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Particle Accelerators (AREA)

Abstract

L'invention concerne un cyclotron (1), notamment un cyclotron isochrone ou un cyclotron synchrone, comprenant une cavité d'accélération RF unique à intervalles multiples, le cyclotron comprenant une paire d'électrodes en forme de trèfle, chacune sur un côté respectif d'un plan médian d'accélération, chaque électrode en forme de trèfle comprenant au moins trois ailes en forme de delta (13, 14) alternant avec des ouvertures (30) dans une direction circonférentielle et reliées mécaniquement et galvaniquement ensemble par une bague de liaison (12).
PCT/EP2017/068613 2017-07-24 2017-07-24 Cyclotron compact avec électrodes en forme de trèfle WO2019020160A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/EP2017/068613 WO2019020160A1 (fr) 2017-07-24 2017-07-24 Cyclotron compact avec électrodes en forme de trèfle

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PCT/EP2017/068613 WO2019020160A1 (fr) 2017-07-24 2017-07-24 Cyclotron compact avec électrodes en forme de trèfle

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113677083A (zh) * 2021-08-12 2021-11-19 中国原子能科学研究院 用于回旋加速器中心区的不对称加速间隙结构设计方法

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2872574A (en) * 1956-04-12 1959-02-03 Edwin M Mcmillan Cloverleaf cyclotron
US3389283A (en) * 1963-12-19 1968-06-18 Csf Electrode structure cyclotron having grounded coupling plates between the dee-rings
US3427557A (en) * 1965-04-22 1969-02-11 Philips Corp Device for accelerating particles
US4345210A (en) * 1979-05-31 1982-08-17 C.G.R. Mev Microwave resonant system with dual resonant frequency and a cyclotron fitted with such a system
WO2007130164A2 (fr) * 2006-01-19 2007-11-15 Massachusetts Institute Of Technology Synchrocyclotron supraconducteur à champ élevé
US20090218520A1 (en) * 2006-05-26 2009-09-03 Advanced Biomarker Technologies, Llc Low-Volume Biomarker Generator
US20170208676A1 (en) * 2016-01-14 2017-07-20 General Electric Company Radio-frequency electrode and cyclotron configured to reduce radiation exposure

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2872574A (en) * 1956-04-12 1959-02-03 Edwin M Mcmillan Cloverleaf cyclotron
US3389283A (en) * 1963-12-19 1968-06-18 Csf Electrode structure cyclotron having grounded coupling plates between the dee-rings
US3427557A (en) * 1965-04-22 1969-02-11 Philips Corp Device for accelerating particles
US4345210A (en) * 1979-05-31 1982-08-17 C.G.R. Mev Microwave resonant system with dual resonant frequency and a cyclotron fitted with such a system
WO2007130164A2 (fr) * 2006-01-19 2007-11-15 Massachusetts Institute Of Technology Synchrocyclotron supraconducteur à champ élevé
US20090218520A1 (en) * 2006-05-26 2009-09-03 Advanced Biomarker Technologies, Llc Low-Volume Biomarker Generator
US20170208676A1 (en) * 2016-01-14 2017-07-20 General Electric Company Radio-frequency electrode and cyclotron configured to reduce radiation exposure

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
E ACERBI ET AL: "DESIGN OF THE R.F. CAVITY FOR A 200 MeV PROTON SUPERCONDUCTING CYCLOTRON", PROCEEDINGS OF THE 14TH INTERNATIONAL CONFERENCE ON CYCLOTRONS AND THEIR APPLICATIONS, CAPE TOWN, SOUTH AFRICA, 1 January 1996 (1996-01-01), pages 245 - 248, XP055457953, ISSN: 1944-2556 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113677083A (zh) * 2021-08-12 2021-11-19 中国原子能科学研究院 用于回旋加速器中心区的不对称加速间隙结构设计方法

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