EP0136216A2 - Selbstfokussierende, lineare beschleunigende Struktur für geladene Teilchen - Google Patents

Selbstfokussierende, lineare beschleunigende Struktur für geladene Teilchen Download PDF

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Publication number
EP0136216A2
EP0136216A2 EP84401699A EP84401699A EP0136216A2 EP 0136216 A2 EP0136216 A2 EP 0136216A2 EP 84401699 A EP84401699 A EP 84401699A EP 84401699 A EP84401699 A EP 84401699A EP 0136216 A2 EP0136216 A2 EP 0136216A2
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EP
European Patent Office
Prior art keywords
cavity
accelerating
length
face
accelerator
Prior art date
Legal status (The legal status 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 status listed.)
Granted
Application number
EP84401699A
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English (en)
French (fr)
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EP0136216A3 (de
EP0136216B1 (de
Inventor
Dominique Tronc
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CGR MEV SA
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CGR MEV SA
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Publication date
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Publication of EP0136216A3 publication Critical patent/EP0136216A3/xx
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Publication of EP0136216B1 publication Critical patent/EP0136216B1/de
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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
    • 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

Definitions

  • the invention relates to a self-focusing linear accelerating structure of charged particles, intended to equip a linear electron accelerator.
  • Linear accelerators of charged particles are used in many fields such as, scientific, medical, and even industrial. Depending on their application, these accelerators produce beams of particles, of electrons for example, having energies often between one and several tens of MeV.
  • Linear electron accelerating structures are generally formed by a succession of resonant cavities, the dimensions of which are related to the frequency of an electromagnetic wave injected into the structure to accelerate the electrons, and to the speed of the electrons.
  • the accelerating structures are optimized as regards the longitudinal dynamics: one chooses the lengths of the resonant cavities, which constitute accelerating cavities, so as to constantly accelerate in each of them the electrons.
  • the accelerating part of the electromagnetic wave is at most equal to its half period, and to benefit from a maximum mum of energy given up by this wave to the electrons, that is to say a high value of the so-called "transit angle" coefficient, these cavities commonly have a length 1 substantially equal to the product of a quarter to a third of the length ⁇ o of the electromagnetic wave by the relative speed ⁇ of the electrons, according to the following relation: where / 3 is the quotient of the average speed V of the electrons by the speed C of light ( ), and n is between 3 and 4. This length, defined within the framework of the calculation of a conventional cavity, is called accelerating length.
  • This defocusing of the beam is generally compensated for by adding solenoids arranged concentrically around the accelerating structure, to create a corrective magnetic field, which increases the cost and the complexity.
  • the present invention relates to an accelerating structure of self-focusing charged particles, in which the defocusing effect of the beam is avoided by the cancellation of one of its causes, unlike structures according to the prior art where this effect is only compensated.
  • the accelerating structure according to the invention is obtained thanks to a simple and inexpensive arrangement of the single or the first accelerating cavity of this structure, and particularly strictly applicable in the case where, in this cavity, the beam exit hole has a diameter less than the previously mentioned accelerating length; this arrangement is remarkable in that it makes it possible, in the latter case, to take account of the fact that the radial component of the electric field in the accelerating cavity constitutes one of the main causes of the divergence of peripheral charged particles of the beam, and that this radial component is located near the entry and exit faces of the cavity and has effects contrary to the entry and exit of this cavity.
  • a self-focusing linear accelerating structure of charged particles comprising a first accelerating cavity of a succession of accelerating cavities, making it possible to accelerate a beam of charged particles under the effect of an electromagnetic wave of given frequency F injected in said structure, said first cavity having an axis coincident with a longitudinal axis of said structure and the axis of said beam, and comprising an inlet face and an outlet face provided respectively with an inlet hole and a exit hole of said beam, is characterized in that the distance between the entry and exit faces of said first cavity is formed by an accelerating length, plus an additional length intended to delay the instant of arrival of the particles at the exit face.
  • the particles are not subjected to the defocusing action of the radial component located near the face output, this radial component being either in the process of disappearing, has even become focusing; the only minor drawback is a slight deceleration of these particles, before they have passed the exit hole.
  • FIG. 1 partially shows a linear accelerating structure 1 in accordance with the invention, comprising a first accelerating cavity CA followed by n accelerating cavities C 1 , ..., C n , n being in the example described equal to 2.
  • n did not include any so-called coupling cells, which constitute conventional elements arranged between the cavities C 1 , ..., C in a known manner.
  • the structure 1 has a longitudinal axis Z, coincident with the axis of the first cavity CA, and which also constitutes the axis of a particle beam (not shown) propagating in the direction of the arrow 2; this particle beam is accelerated by the energy of an electromagnetic wave (not shown in FIG. 1) conventionally injected into the structure 1 by a coupling hole 4.
  • the first cavity CA of cylindrical shape, has an inlet face 3 and an outlet face 5 normal to the axis of the beam Z, and spaced from one another by a distance D; the inlet face 3 is provided with an inlet hole 7, the outlet face 5 is provided with an outlet hole 8, these two holes being centered on the axis Z of the beam.
  • the particle beam coming for example, in a known manner, from an electron gun followed by a sliding element (not shown), enters the first accelerating cavity CA by the inlet hole 7, and emerges from this cavity CA through the outlet hole 8, propagating in the structure 1 in the direction shown by the arrow 2.
  • This relative speed of the electrons is calculated by taking the average between the speed of entry into the first cavity CA, and the maximum speed reached in this cavity at the exit of the accelerating length L 1 . It should be noted that certain electrons are decelerated at the very beginning of their trajectory, which is not taken into account in the approximation of the accelerating length L 1 .
  • these same charged particles having crossed the first accelerating length L 1 do not undergo the influence of this diverging radial component Er 2 , from which they are still separated by an additional length L 2 ; the distance D between the inlet and outlet faces being formed by the addition of these two lengths L 1 + L 2 , and the additional length L 2 being equal to or greater than twice the radius r of the outlet hole 8 ( L 2 ⁇ 2 r).
  • the inlet and outlet holes 7,8 generally have spouts, not shown in FIG. 1 which is schematic, and the radius r represents an approximate mean radius of the outlet hole 8.
  • the additional length L 2 is such that the electromagnetic wave is canceled, or even reversed when these particles have crossed the distance D, they leave the first cavity CA through the outlet hole 8 without diverging; they can even, if the phase of the electromagnetic wave is reversed, undergo a convergent action and a weak deceleration, the radial component then being also reversed. It is noted that this additional length L 2 , of the first cavity CA, also promotes the converging action at the entry of the following accelerating cavity CI which constitutes the second cavity.
  • the distance D 1 between the exit face 5 of the first cavity CA and the entry plane 15 of the second cavity C 1 is less than the accelerating length L 1 , and thus ensures convergence sensitive to the input of this second cavity C 1 , taking into account the phase shift of the electromagnetic wave between cavities CA, C 1 , C 2 .
  • the energy gain is such that the effect of the output from the second cavity C 1 is (almost) negligible.
  • L 2 L 1 .K, where K is a coefficient between 0.5 and 1.
  • the distribution of the electric field being symmetrical with respect to the axis Z of the beam, it is not represented in the lower part of the first cavity CA.
  • This distribution of the electric field in the first accelerating cavity CA corresponds to the existence in the latter of an accelerating field.
  • Figure 2 shows the electromagnetic wave OE of which half a period determines this accelerating field and of which the part of the OE wave comprised on the one hand between an instant to and the instant tl, and on the other hand between an instant t3 and an instant t4 determines a decelerating field; the instant t2 corresponding to the peak value of the half period x where the accelerator field Zo is maximum.
  • this electron undergoes a decelerating field near the input face 3 until time tl when the OE wave reverses and the field becomes accelerator; the action of the radial component Er 1 , located near the entry face 3, is therefore first divergent then convergent when the field becomes accelerator, and its action is globally convergent.
  • This slowed down electron is joined by electrons that entered the CA cavity after it.
  • the arrangement of the first cavity CA of the structure 1 according to the invention makes it possible to avoid the defoca-jisation effect at the output for a wide range of values of arrival phase ⁇ o, for example between - 45 ° and - 190 ° relative to Zo or the instant tl.
  • FIG. 3 illustrates the trajectory of a peripheral electron of the beam, and shows the field components Er, Ez seen at different times, taking into account the finite speed of the electron.
  • the exit face 5 would have occupied the position of the line 11 in dotted lines and, the field to which the electron would then have been subjected at its exit from the first cavity CA is represented in dotted lines by the components Er 2 and Ez; the trajectory of the electron would have been modified according to arrow 12 represented in dotted lines, which tends to diverge from the axis Z of the beam.
  • the accelerating structure 1 according to the invention eliminates the defocusing effect of the charged peripheral particles of the beam, at the exit of an accelerating cavity. This elimination of the divergence effect is obtained by a simple, economical arrangement, which makes it possible to increase the efficiency of a linear accelerator of charged particles.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Particle Accelerators (AREA)
EP84401699A 1983-09-02 1984-08-21 Selbstfokussierende, lineare beschleunigende Struktur für geladene Teilchen Expired EP0136216B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8314090 1983-09-02
FR8314090A FR2551617B1 (fr) 1983-09-02 1983-09-02 Structure acceleratrice lineaire autofocalisante de particules chargees

Publications (3)

Publication Number Publication Date
EP0136216A2 true EP0136216A2 (de) 1985-04-03
EP0136216A3 EP0136216A3 (de) 1985-05-02
EP0136216B1 EP0136216B1 (de) 1988-06-08

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ID=9291964

Family Applications (1)

Application Number Title Priority Date Filing Date
EP84401699A Expired EP0136216B1 (de) 1983-09-02 1984-08-21 Selbstfokussierende, lineare beschleunigende Struktur für geladene Teilchen

Country Status (4)

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US (1) US4639641A (de)
EP (1) EP0136216B1 (de)
DE (1) DE3472053D1 (de)
FR (1) FR2551617B1 (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2587164A1 (fr) * 1985-09-10 1987-03-13 Cgr Mev Dispositif de pregroupement et d'acceleration d'electrons
EP0336850A1 (de) * 1988-04-08 1989-10-11 Cgr Mev Linearbeschleuniger mit selbstfokussierenden Kavitäten und hohen Elektronen-Einfangraten bei niedrigen Injektions-Vorbeschleunigungsspannungen

Families Citing this family (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4782303A (en) * 1987-04-06 1988-11-01 Linlor William I Current guiding system
US4906896A (en) * 1988-10-03 1990-03-06 Science Applications International Corporation Disk and washer linac and method of manufacture
US5014014A (en) * 1989-06-06 1991-05-07 Science Applications International Corporation Plane wave transformer linac structure
FR2679727B1 (fr) * 1991-07-23 1997-01-03 Cgr Mev Accelerateur de protons a l'aide d'une onde progressive a couplage magnetique.
US7098615B2 (en) * 2002-05-02 2006-08-29 Linac Systems, Llc Radio frequency focused interdigital linear accelerator
US6777893B1 (en) 2002-05-02 2004-08-17 Linac Systems, Llc Radio frequency focused interdigital linear accelerator
US6864633B2 (en) * 2003-04-03 2005-03-08 Varian Medical Systems, Inc. X-ray source employing a compact electron beam accelerator
US10398018B2 (en) * 2017-08-30 2019-08-27 Far-Tech, Inc. Coupling cancellation in electron acceleration systems
DE102020119875B4 (de) * 2020-07-28 2024-06-27 Technische Universität Darmstadt, Körperschaft des öffentlichen Rechts Vorrichtung und Verfahren zum Führen geladener Teilchen

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2770775A (en) * 1951-12-21 1956-11-13 Westinghouse Air Brake Co Wayside vehicle speed determining means
US2770755A (en) * 1954-02-05 1956-11-13 Myron L Good Linear accelerator
US2925522A (en) * 1955-09-30 1960-02-16 High Voltage Engineering Corp Microwave linear accelerator circuit
FR2110799A5 (de) * 1970-10-30 1972-06-02 Thomson Csf
FR2374815A1 (fr) * 1976-12-14 1978-07-13 Cgr Mev Perfectionnement aux accelerateurs lineaires de particules chargees
FR2386232A1 (fr) * 1977-03-31 1978-10-27 Cgr Mev Structure acceleratrice pour accelerateur lineaire de particules chargees fonctionnant en regime d'ondes stationnaires
FR2386231A1 (fr) * 1977-03-31 1978-10-27 Cgr Mev Structure acceleratrice pour accelerateur lineaire de particules chargees
US4211954A (en) * 1978-06-05 1980-07-08 The United States Of America As Represented By The Department Of Energy Alternating phase focused linacs

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2587164A1 (fr) * 1985-09-10 1987-03-13 Cgr Mev Dispositif de pregroupement et d'acceleration d'electrons
EP0336850A1 (de) * 1988-04-08 1989-10-11 Cgr Mev Linearbeschleuniger mit selbstfokussierenden Kavitäten und hohen Elektronen-Einfangraten bei niedrigen Injektions-Vorbeschleunigungsspannungen
FR2629976A1 (fr) * 1988-04-08 1989-10-13 Cgr Mev Accelerateur lineaire muni de cavites autofocalisantes a fort taux de capture electronique pour des tensions d'injections moderes
US4975652A (en) * 1988-04-08 1990-12-04 Cgr Mev Linear accelerator provided with self-focusing cavities having high electron capture efficiency in respect of moderate injection voltages

Also Published As

Publication number Publication date
EP0136216A3 (de) 1985-05-02
US4639641A (en) 1987-01-27
FR2551617B1 (fr) 1985-10-18
FR2551617A1 (fr) 1985-03-08
EP0136216B1 (de) 1988-06-08
DE3472053D1 (en) 1988-07-14

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