EP0295981B1 - Beschleuniger für einen Elektronenteppich - Google Patents

Beschleuniger für einen Elektronenteppich Download PDF

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Publication number
EP0295981B1
EP0295981B1 EP88401255A EP88401255A EP0295981B1 EP 0295981 B1 EP0295981 B1 EP 0295981B1 EP 88401255 A EP88401255 A EP 88401255A EP 88401255 A EP88401255 A EP 88401255A EP 0295981 B1 EP0295981 B1 EP 0295981B1
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EP
European Patent Office
Prior art keywords
cavity
electrons
axis
cathode
median plane
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.)
Expired - Lifetime
Application number
EP88401255A
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English (en)
French (fr)
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EP0295981A1 (de
Inventor
Jean-Pierre Gueguen
Annick N'guyen
Jacques Pottier
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
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Commissariat a lEnergie Atomique CEA
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Publication of EP0295981A1 publication Critical patent/EP0295981A1/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
    • H05H9/00—Linear accelerators
    • H05H9/04—Standing-wave linear accelerators
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21K—TECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
    • G21K1/00—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating
    • G21K1/08—Deviation, concentration or focusing of the beam by electric or magnetic means
    • G21K1/093—Deviation, concentration or focusing of the beam by electric or magnetic means by magnetic means
    • 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 present invention relates to a sheet electron accelerator. It finds an application in the irradiation of various substances and in particular in the polymerization or crosslinking of materials in the form of sheets or strips.
  • a vacuum bell 2 comprises, at its lower part, an outlet window 3, grounded, and at its upper part, a cathode K supported by an insulator 4.
  • the cathode is connected to the negative pole of a HT source high voltage, a few hundred thousand volts.
  • An electric field E directed towards the cathode accelerates the electrons emitted by this one until the exit window. An electron sheet is thus formed and accelerated. It bombs a band 5 which passes under the bell.
  • Such a device has many drawbacks.
  • the use of a voltage of a few hundred kilovolts means that the cathode has to be supported by high quality insulators. It is also necessary to provide a sealed crossing supporting such a voltage.
  • the cathode is made emissive by heating, it is necessary that the source of heating current is itself at high voltage which is not very convenient. This drawback can possibly be remedied by making the cathode emissive by ion bombardment using an ion source located at the window. But the complexity of the device is increasing.
  • the object of the present invention is precisely to remedy these drawbacks. To this end, it offers an electron accelerator which uses a cavity whose original shape, in this application, makes it possible to obtain the same uniform accelerating field without deviating magnetic field. This result is obtained by the use of a general structure of coaxial shape.
  • the subject of the present invention is a sheet electron accelerator, comprising a linear cathode emitting a sheet-like electron beam, a accelerating structure in which there is an electric field directed in the plane of the sheet, characterized in that the accelerating structure is a resonant coaxial cavity having a fundamental resonance mode consisting of an outer cylindrical conductor and an inner cylindrical conductor having the same axis, this cavity being closed by two flanges perpendicular to the axis, this cavity being excited by a high frequency source at the resonance frequency of the fundamental mode, and by the fact that the cathode is contained in the median plane of the perpendicular cavity at the axis, the electron beam emitted by the cathode being injected into the cavity in this median plane, the outer and inner cylinders being pierced with openings, in the form of arcs of a circle centered on the axis of the cavity for the passage of the beam.
  • the accelerating structure is a resonant coaxial cavity having a fundamental resonance mode
  • FIG. 2 we see a coaxial cavity CC constituted by an external cylindrical conductor 10, an internal cylindrical conductor 20 and two flanges 31 and 32.
  • a cavity has an axis A and a median plane Pm, perpendicular to the axis.
  • the resonance modes possible of such a cavity there is one, said to be fundamental, of transverse electric type, for which the electric field E is purely radial in the median plane. This field decreases on either side of this plane to come to cancel on the flanges 31, 32.
  • the magnetic field is maximum along the flanges and is canceled in the median plane by changing direction.
  • Such a mode can be designated, according to conventional conventions, by TE001, the initials TE recalling that it is a mode where the electric field is transverse, where the first index "0" indicates that the field has symmetry of revolution, the second index "0” indicates that there is no field cancellation along a radius of the cavity, and the third index of value "1" indicates that there is a half -alternation of the field in a direction parallel to the axis.
  • Such a cavity can be supplied by a high frequency source SHF coupled to the cavity by a loop 34.
  • the electron sheet is injected into the coaxial cavity in the median plane thereof. It is indeed in this plane that there is no parasitic field capable of deflecting the beam. As this point is essential we can stop there.
  • the cavity is seen in cross section in the median plane.
  • the electric fields E1 and E2 are equal along two separate radii.
  • a contour 17 is defined by these two radii and by two arcs of a circle along which the electric field is radial.
  • the circulation of the electric field (that is to say the integral of this field) is zero along this contour. Consequently, the flux of magnetic induction through a surface resting on this contour is also zero. In other words, there is no magnetic component perpendicular to the median plane.
  • Figure 4 shows, schematically, a sheet accelerator according to the invention.
  • Part a is a longitudinal section and part b is a section in the median plane of the cavity.
  • the device comprises a cathode K, a coaxial cavity CC, formed of an external cylindrical conductor 10 and an internal cylindrical conductor 20 having the same axis A.
  • the cathode is in the form of an arc of a circle centered on the axis A of the cavity and it is located in the median plane Pm thereof.
  • the operation of this device is as follows.
  • the cathode K emits a beam of electrons Fe directed in the median plane Pm of the coaxial cavity CC.
  • the beam enters the cavity through an opening 11, in the form of a slit, pierced in the external conductor.
  • the inner conductor 20 is pierced with two openings 21 and 22, which are also in the form of slots and symmetrical with respect to the axis.
  • the electron beam is accelerated by the electric field prevailing in the coaxial cavity, if certain phase conditions are satisfied.
  • the beam leaves the cavity through an opening 12, in the form of a slot, pierced in the external conductor and diametrically opposite to the opening 11.
  • the accelerated beam irradiates the strip 5 which passes under the cavity.
  • the coaxial nature of the acceleration structure means that, at each instant, the electric field does not have the same direction in the first and in the second half of the path taken by the electrons, in other words along rays which go from the outer conductor to inner conductor, then along the spokes from the inner conductor to the conductor outside. But the field is at high frequency (a few hundred MHz). It reverses periodically. The electron beam is therefore injected in such a way that the electric field is canceled out and changes direction when the electrons pass through the central conductor. the time taken by the electrons to pass from one conductor to another must therefore be less than the half-period of the field; the time taken by the electrons to cross the entire cavity is therefore less than the field period.
  • the dose is strictly speaking homogeneous only if the strip is arranged so as to follow the shape of a cylinder coaxial with the cavity (by a system of rollers for example).
  • part a is a section perpendicular to the median plane and part b is a section in the median plane, therefore in the plane of the electron beam.
  • the pole pieces 41-42, on the one hand, and 43-44, on the other hand, define two air gaps with parallel edges.
  • the magnets have a thickness which increases as one moves away from the median plane Pm (part b).
  • the path traveled by the electrons between the pole pieces is therefore longer for the electrons which follow trajectories distant from the median plane than for the trajectories close to this plane.
  • the action of the magnetic field is therefore prolonged for the former and abridged for the latter.
  • the strongly inclined paths are therefore more curved than the others, which gives the beam parallel paths.
  • FIG. 7 illustrates another variant of these deflection means.
  • the pole pieces 51-52, on the one hand, and 53-54, on the other hand, define air gaps which tighten when moving away from the axis.
  • the magnetic field between such pole pieces increases as one moves outward. We thus find a greater deflection for the trajectories located far from the median plane than for the trajectories close to this one.
  • the calculation shows that, for a 400 keV machine, the optimum is obtained for R2 ⁇ 0.265 ⁇ and R1 ⁇ (R2 / 5), ⁇ being the wavelength.
  • the shunt impedances obtained in practice are somewhat lower (typically 30%) than the calculated values.
  • the power dissipated in the cavity would be close to 33 kW for a 400 keV machine.

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

Claims (3)

  1. Elektronenbeschleuniger für flächenhaften Elektronenstrahl, bestehend aus einer linearen Kathode (K), die einen flächenhaften Elektronenstrahl (Fe) aussendet, und einer Beschleunigerstruktur, die von einem elektrischen Feld (E) erfüllt ist, das in die Ebene des flächenhaften Strahls gerichtet ist, dadurch gekennzeichnet, daß die Beschleunigerstruktur ein koaxialer Hohlraumresonator ist, der eine fundamentale Schwingungsmode hat und der gebildet wird von einem äußeren zylindrischen Leiter (10) und einem inneren zylindrischen Leiter (20) mit derselben Achse (A), wobei der Hohlraum von zwei zur Achse senkrechten Wangen (31,32) geschlossen wird und durch eine Hochfrequenzquelle (SHF) auf die Resonanzfrequenz der Fundamentalmode angeregt wird, und dadurch, daß die Kathode (K) in der zur Achse senkrechten Mittelebene (Pm) des Hohlraums enthalten ist, wobei der von der Kathode (K) emittierte Elektronenstrahl (Fe) in dieser Mittelebene in den Hohlraum injiziert wird und der äußere (10) und der innere (20) Zylinder für den Durchtritt des Strahls (Fe) Öffnungen (11, 12, 21, 22) in Form von auf der Hohlraumachse zentrierten Kreisbögen haben.
  2. Elektronenbeschleuniger nach Anspruch 1, dadurch gekennzeichnet, daß der innere Leiter (20) kegelstumpfförmige Enden (33, 35) besitzt mit dem größeren Durchmesser an den Enden des inneren Leiters (20).
  3. Beschleuniger nach Anspruch 1, dadurch gekennzeichnet, daß er darüber hinaus an der Austrittstelle des Strahls eine magnetische Einrichtung (M1, M2) zur Ablenkung der Elektronen besitzt, die aus zwei symmetrischen magnetischen Kreisen mit einem Luftspalt (41, 42, 43, 44 und 51, 52, 53, 54) besteht, wobei die seitlichen Ränder des Strahls jeweils die beiden Luftspalte durchqueren und die Luftspalte derart sind, daß die Wirkung des Magnetfeldes auf die Elektronen um so stärker ist, je weiter die Elektronen von der Mitte des Strahls entfernt sind.
EP88401255A 1987-05-26 1988-05-24 Beschleuniger für einen Elektronenteppich Expired - Lifetime EP0295981B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8707379A FR2616033B1 (fr) 1987-05-26 1987-05-26 Accelerateur d'electrons a nappe
FR8707379 1987-05-26

Publications (2)

Publication Number Publication Date
EP0295981A1 EP0295981A1 (de) 1988-12-21
EP0295981B1 true EP0295981B1 (de) 1993-01-13

Family

ID=9351458

Family Applications (1)

Application Number Title Priority Date Filing Date
EP88401255A Expired - Lifetime EP0295981B1 (de) 1987-05-26 1988-05-24 Beschleuniger für einen Elektronenteppich

Country Status (6)

Country Link
US (1) US4893058A (de)
EP (1) EP0295981B1 (de)
JP (1) JP2587270B2 (de)
CA (1) CA1291568C (de)
DE (1) DE3877427T2 (de)
FR (1) FR2616033B1 (de)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2637122A1 (fr) * 1988-09-23 1990-03-30 Thomson Csf Dispositif correcteur de trajectoires pour tube electronique
BE1004879A3 (fr) * 1991-05-29 1993-02-16 Ion Beam Applic Sa Accelerateur d'electrons perfectionne a cavite coaxiale.
CN115529710B (zh) * 2022-09-28 2024-02-20 中国原子能科学研究院 一种电子帘加速器

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2452561A (en) * 1940-02-06 1948-11-02 Standard Telephones Cables Ltd Electron discharge apparatus using velocity modulated beams
US2405612A (en) * 1941-03-05 1946-08-13 Bell Telephone Labor Inc Ultra high frequency resonant cavities
NL90056C (de) * 1952-03-20
FR1136936A (fr) * 1954-10-18 1957-05-21 Procédé et appareil pour accélérer des particules chargées d'électricité
US3307194A (en) * 1963-05-21 1967-02-28 Sheleg Boris High speed microwave phase shifter using a positionable electron beam to cause electromagentic-wave reflection
US3833814A (en) * 1973-06-20 1974-09-03 Energy Sciences Inc Apparatus for simultaneously uniformly irradiating a region using plural grid controlled electron guns
FR2574978B1 (fr) * 1984-12-14 1987-01-16 Commissariat Energie Atomique Dispositif d'irradiation de matiere par un faisceau electronique

Also Published As

Publication number Publication date
FR2616033B1 (fr) 1989-08-04
FR2616033A1 (fr) 1988-12-02
CA1291568C (en) 1991-10-29
JPS646400A (en) 1989-01-10
DE3877427D1 (de) 1993-02-25
DE3877427T2 (de) 1993-06-24
EP0295981A1 (de) 1988-12-21
US4893058A (en) 1990-01-09
JP2587270B2 (ja) 1997-03-05

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