EP0199625B1 - Elektronzyklotronresonanzquelle negativer Ionen - Google Patents

Elektronzyklotronresonanzquelle negativer Ionen Download PDF

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Publication number
EP0199625B1
EP0199625B1 EP86400726A EP86400726A EP0199625B1 EP 0199625 B1 EP0199625 B1 EP 0199625B1 EP 86400726 A EP86400726 A EP 86400726A EP 86400726 A EP86400726 A EP 86400726A EP 0199625 B1 EP0199625 B1 EP 0199625B1
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EP
European Patent Office
Prior art keywords
enclosure
negative ion
ion source
ions
extraction
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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
Application number
EP86400726A
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English (en)
French (fr)
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EP0199625A1 (de
Inventor
Göran Hellblom
Claude Jacquot
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Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
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Commissariat a lEnergie Atomique CEA
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J27/00—Ion beam tubes
    • H01J27/02—Ion sources; Ion guns
    • H01J27/16—Ion sources; Ion guns using high-frequency excitation, e.g. microwave excitation
    • H01J27/18—Ion sources; Ion guns using high-frequency excitation, e.g. microwave excitation with an applied axial magnetic field
    • 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
    • G21K1/14—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating using charge exchange devices, e.g. for neutralising or changing the sign of the electrical charges of beams
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J27/00—Ion beam tubes
    • H01J27/02—Ion sources; Ion guns
    • H01J27/028—Negative ion sources

Definitions

  • the present invention relates to a source of negative ions with electronic cyclotron resonance. It is advantageously applied in the production of high intensity H- ion beams (greater than 1 A) or of its D- or T- isotopes, these beams being mainly used for the production of beams of energetic neutral atoms ( intensity of several tens of amps and energy from 200 to 500 KeV) used in particular as efficient means of heating thermonuclear plasmas produced in fusion devices with magnetic confinement. Furthermore, high intensity H-, D- or T- ion beams can also be used in nuclear physics and in particular in accelerators of the Van de Graaf-Tandem type or in the medical field using accelerators of the type variable energy cyclotron.
  • volume ionization One of the techniques currently known for producing beams of negative ions and in particular of H-, D- and T- ions is volume ionization. This technique is based on the formation, from a gas or a vapor contained in a closed enclosure, of a plasma constituted mainly in the case of hydrogen of H-, H + ions and electrons .
  • This technique consists first of all of creating molecules of hydrogen, deuterium or tritium depending on the starting gas used, vibrational excited by hot or energetic electrons, that is to say whose kinetic energy is higher at 20 eV, according to the following reaction scheme (1), in the case of hydrogen:
  • H-, D- or T- ions are formed by the following dissociative attachment reaction (2), in the case of hydrogen:
  • the intermediate compound is unstable.
  • the effective cross-sections of attachment are high for so-called cold electrons having a kinetic energy at most equal to 1 eV.
  • This dissociative attachment phenomenon has in particular been described in an article by M. BA-CAL et al., Phys. Rev. Letters, 42, 1538 (1979).
  • the difficulty in such a technique for producing negative ions is to create in the closed enclosure of the ion source a population of energetic or hot electrons and a population of cold electrons, spatially separated so that the hot electrons do not destroy the negative ions formed by a collision in the case of hydrogen, of the type:
  • the destruction of the negative ions formed by reaction with the hot electrons of the plasma is relatively large, which is detrimental to the production of a beam of intense negative ions.
  • the number of negative ions constituting the plasma created in the enclosure represents only 10% of the number of positive ions.
  • the object of the present invention is precisely a source of negative ions making it possible to remedy the various drawbacks above.
  • it makes it possible to produce an intense negative ion beam, in particular of H-, D- or T- ions, using as physical phenomena the dissociative attachment technique as well as electronic cyclotron resonance.
  • This resonance phenomenon is generally used to produce multi-charged positive ions.
  • the European patent application No. 0,127,523 filed in the name of applicant describes a positive ion source operating on the principle of electron cyclotron resonance.
  • This condition of electronic cyclotron resonance makes it possible to create energetic or hot electrons, of kinetic energy greater than 20 eV, in a direction perpendicular to the magnetic field.
  • These hot electrons by collision on the molecules of gas or vapor contained in the source, generate other electrons which will also be accelerated by cyclotronic resonance.
  • the hot plasma of electrons thus formed makes it possible, according to the reaction mechanism (1), to excite the molecules of the gas or of the vapor.
  • the electrons formed by the interaction of the electromagnetic wave and gas or vapor molecules, have a lower energy, for example at most equal to 1 eV. These cold electrons interact with the unexcited neutral molecules of gas or vapor, creating positive ions and other cold electrons, thus forming a cold plasma of electrons. Given the profile of the amplitude of the magnetic field, this cold electron plasma is mainly located in the extraction zone of negative ions. According to the reaction mechanism (2), this cold plasma of electrons formed allows the formation of negative ions.
  • the source of negative ions according to the invention allows the formation of a hot electron plasma and a cold electron plasma well separated spatially, thus making it possible to form negative ions, and in particular H- ions, D- or T-, by dissociative attachment and by electronic cyclotron resonance, while avoiding the destruction of negative ions formed by collisions with energetic electrons, according to the reaction mechanism (3).
  • the negative ions thus formed and extracted from the plasma can advantageously be accelerated using appropriate means located downstream of the extraction means.
  • This final acceleration of the ions can for example be obtained by using an electrode, pierced with one or more openings to allow the passage of the ions, brought to a positive potential relative to that of the extraction means.
  • means for reducing the amplitude of the magnetic field at the level of the ion extraction means can be provided.
  • This local cancellation of the amplitude of the magnetic field can advantageously be carried out using as means of extraction of the negative ions an electrode or plate made of a ferromagnetic substance, pierced with slots or holes to allow the passage of the negative ions formed.
  • This cancellation of the amplitude of the magnetic field at the level of the extraction of the ions traps the electrons which have not reacted with the gas or vapor molecules, thus making it possible to avoid their acceleration between the means of extraction and of acceleration, and therefore their output from the source.
  • the means for injecting the electromagnetic field comprise a waveguide whose end, mounted on the enclosure, is equipped with a window in a dielectric material.
  • the source of negative ions comprises a containment vacuum enclosure 2 constituting a resonant cavity which can be excited by a microwave electromagnetic field.
  • This enclosure 2 has an axis of symmetry Z, which in the case of a cylindrical enclosure represents the axis of revolution.
  • the electromagnetic wave produced by a source 4 such as a klystron is introduced into the resonant cavity 2 by means of a waveguide 6, of circular or rectangular section, comprising at its end mounted on the enclosure a window 8 made of a dielectric material such as A1 2 0 3 .
  • This wave can be continuous or pulsed and have a frequency between 1 and 100 GHz.
  • a pipe 10 makes it possible to introduce a gas or a vapor of a material inside the cavity 2 intended to form a plasma in said cavity.
  • this introduction of gas is carried out near the introduction of the electromagnetic wave.
  • the enclosure 2 can for example be filled with hydrogen, deuterium or tritium at a pressure of 1 to 10 mtorr (0.134 to 1.34 Pa).
  • Means not shown, such as a diffusion or cryogenic pump, mounted on the cavity 2 allow the maintenance of a high vacuum inside the cavity.
  • the cavity 2 is brought to an electrostatic potential -V with respect to the mass.
  • it is surrounded by two coils 12 and 14, the coil 12 being supplied in counter-field, making it possible to create a magnetic field of axial symmetry.
  • the axis of symmetry of this magnetic field can be merged with the axis of symmetry Z of the cavity 2.
  • the arrows 16 represent the field lines of the magnetic field. This magnetic field can be either continuous or pulsed.
  • the source of negative ions according to the invention further comprises means making it possible to extract the ions formed.
  • These means consist for example of a conductive plate 18 brought to a positive potential with respect to the enclosure 2, for example to a potential -V + AV. They are mounted on one end of the enclosure and isolated from them by means of an insulating ring 19.
  • These means 18 are equipped with at least one hole or a slot 20 allowing the passage of ions negative. This extrac orifice tion 20 is for example located on the axis of symmetry Z of the microwave cavity.
  • V and of V can be between -1500 V and -2000 V and A V between 5 and 20 volts.
  • the extraction electrode 18, negative ions can be followed by another electrode 22 brought to a positive potential with respect to the extraction electrode 18, and for example to the ground potential, in order to accelerate negative ions formed to their final value.
  • This electrode 22 is of course equipped with at least one opening 24, located in particular on the axis of symmetry Z of the cavity, allowing the exit of the negative ions formed, outside the source.
  • the positions of the extraction 18 and acceleration 20 electrodes are advantageously adjustable along the Z axis.
  • the electromagnetic waveguide 6 and the extraction 18 and acceleration 22 electrodes of the ion source are arranged at the two opposite ends of the resonant cavity 2; the axis of symmetry of the waveguide 6 and those of the openings 20 and 24, reciprocally made in the electrodes 18 and 22, coincide with the axis of symmetry Z of the cavity.
  • the coils 12 and 14 surrounding the cavity 2 make it possible, as shown in FIG. 2, to create a magnetic field of axial symmetry in the enclosure whose amplitude B increases from the window 8 of the injector of the electromagnetic wave at the extraction electrode 18.
  • This magnetic field has, at a point Z R taken on the axis of symmetry of the cavity 2, and approximately at the center of said cavity, an amplitude B R satisfying the condition of electronic cyclotronic resonance (4), thus allowing the formation of energetic electrons used for the vibrational excitation of the molecules of the gas contained in enclosure 2.
  • this magnetic field has a maximum amplitude B M just upstream of l extraction electrode 18, the position of which is marked by the dimension Z e .
  • the electrons acquire a strong kinetic energy, perpendicular to the magnetic field.
  • these electrons undergo a mirror effect and are subjected to a force.
  • ⁇ being the magnetic moment of the electron. They are therefore accelerated towards window 8 of the electromagnetic injector; the direction of movement of these electrons is illustrated by the arrow F.
  • the energetic electrons entrain, by electrostatic or ambipolar effect, the positive ions such as H + , D + or T + formed during the ionization of the hydrogen gas, deuterium or tritium contained in the enclosure 2.
  • the positive ions such as H + , D + or T + formed during the ionization of the hydrogen gas, deuterium or tritium contained in the enclosure 2.
  • This more positive potential is responsible for the self-acceleration of the H- ions, represented by the arrow F ', these ions being created in the ion extraction zone, that is to say near and upstream of the electrode 18.
  • Negative ions and, for example, H-, D- or T- ions are created preferentially in the region of extraction of the ions, because the molecules of gas vibratively excited, equation (1), are insensitive to the magnetic field; they can therefore diffuse isotropically.
  • the amplitude of the magnetic field can advantageously cancel out at the level of the extraction electrode 18, that is to say at the Ze dimension, in order to carry out a trapping of the electrons of the plasma. thus making it possible to avoid their acceleration between the extraction electrode 18 and the electrode 22.
  • This cancellation of the magnetic field can for example be obtained by using an extraction electrode 18 made of a ferromagnetic substance.
  • the source of negative ions according to the invention allowed the production of a beam of H- ions having an energy of 2 KeV per nucleon and an intensity of 10 mA using an average microwave power of 1 kW, a cyclotronic frequency. 10 GHz electronics and a magnetic field whose amplitude increases from 0.2 to 0.45 T.
  • the ion source had a cylindrical cavity 10 cm in diameter and 15 cm in length; it was brought to a negative potential of -2000 volts and the extraction electrode 18 to a potential of 2 volts higher than that of the cavity, ie -1998 V.
  • the pressure of the hydrogen gas contained in the enclosure was 0 , 2 Pa.
  • the magnetic field with axial symmetry can be produced by ferrites instead of the use of two coils supplied in counter-field and surrounding the microwave cavity.
  • the cavity may have a shape other than a cylindrical shape, for example a parallelepiped shape.
  • the source according to the invention can produce other types of negative ions and in particular oxygen, sodium, lithium and iodine ions.

Claims (7)

1. Quelle negativer lonen, enthaltend einen geschlossenen Behälter (2), der ein Gas oder einen Dampf aus einem Material enthält, das zur Bildung eines Plasmas bestimmt ist, dadurch gekennzeichnet, daß sie enthält:
Injektionseinrichtungen (6, 8) in dem Behälter (2) für ein elektromagnetisches Feld hoher Frequenz, das durch Ionisation des Gases oder des Dampfes Elektronen bildet,
Einrichtungen (12, 14) zum Erzeugen eines Magnetfeldes in dem Behälter (2) in axialer Symmetrie, dessen Amplitude (B) längs der Symmetrieachse (Z) zunimmt, wobei diese Amplitude, die nahe und stromaufwärts der Extraktionszone der negativen Ionen maximal (BM) ist, im mittleren Bereich (ZR) des Behälters (2) einen Wert (BR) zeigt, für den die Elektroncyclotronresonanzbedingung erfüllt ist, und
Extraktionseinrichtungen (18) für die gebildeten negativen lonen, die auf einem gegenüber dem Behälter (2) positiven Potential (+AV) gehalten sind.
2. Quelle für negative Ionen nach Anspruch 1, dadurch gekennzeichnet, daß sie stromabwärts der Extraktionseinrichtungen (18) Beschleunigungseinrichtungen (22) für die gebildeten negativen Ionen aufweist.
3. Quelle für negative Ionen nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß sie Annulierungseinrichtungen (18) für die Amplitude des Magnetfeldes in Höhe der lonenextraktionseinrichtungen (18) enthält.
4. Quelle für negative Ionen nach Anspruch 3, dadurch gekennzeichnet, daß die Annulierungseinrichtungen und die Extraktionseinrichtungen zusammenfallen, wobei diese Einrichtungen (18) von einer Platte aus ferromagnetischem Material gebildet sind, die von wenigstens einer Öffnung (20) durchdrungen ist, um den Durchgang von Ionen zu ermöglichen.
5. Quelle für negative tonen nach einem der Ansprüche 2 bis 4, dadurch gekennzeichnet, daß die Beschleunigungseinrichtungen (22) von einer Elektrode gebildet sind, die auf einem gegenüber den Extraktionseinrichtungen positiven Potential gehalten ist und die mit wenigstens einer Öffnung (24) für den Durchgang von Ionen versehen ist.
6. Quelle für negative Ionen nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, daß die Injektionseinrichtungen (6, 8) für das elektromagnetische Feld einen Wellenleiter (6) umfassen, dessen auf dem Behälter (2) montiertes Ende mit einem Fenster (8) aus einem dielektrischen Material versehen ist.
7. Quelle für negative Ionen nach einem der Ansprüche 1 bis 6, dadurch gekennzeichnet, daß das Gas Wasserstoff oder seine Isotope ist.
EP86400726A 1985-04-11 1986-04-04 Elektronzyklotronresonanzquelle negativer Ionen Expired EP0199625B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8505461 1985-04-11
FR8505461A FR2580427B1 (fr) 1985-04-11 1985-04-11 Source d'ions negatifs a resonance cyclotronique des electrons

Publications (2)

Publication Number Publication Date
EP0199625A1 EP0199625A1 (de) 1986-10-29
EP0199625B1 true EP0199625B1 (de) 1989-03-22

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EP86400726A Expired EP0199625B1 (de) 1985-04-11 1986-04-04 Elektronzyklotronresonanzquelle negativer Ionen

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US (1) US4757237A (de)
EP (1) EP0199625B1 (de)
JP (1) JPS61239546A (de)
DE (1) DE3662576D1 (de)
FR (1) FR2580427B1 (de)

Families Citing this family (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4859908A (en) * 1986-09-24 1989-08-22 Matsushita Electric Industrial Co., Ltd. Plasma processing apparatus for large area ion irradiation
US4845364A (en) * 1988-02-29 1989-07-04 Battelle Memorial Institute Coaxial reentrant ion source for surface mass spectroscopy
JPH0216732A (ja) * 1988-07-05 1990-01-19 Mitsubishi Electric Corp プラズマ反応装置
US5107170A (en) * 1988-10-18 1992-04-21 Nissin Electric Co., Ltd. Ion source having auxillary ion chamber
US5051557A (en) * 1989-06-07 1991-09-24 The United States Of America As Represented By The Secretary Of The Department Of Health And Human Services Microwave induced plasma torch with tantalum injector probe
US5106570A (en) * 1990-08-02 1992-04-21 The United States Of America As Represented By The Secretary Of The Air Force Intense negative ion source
FR2668642B1 (fr) * 1990-10-25 1993-11-05 Commissariat A Energie Atomique Source d'ions fortement charges a sonde polarisable et a resonance cyclotronique electronique.
KR0158234B1 (ko) * 1992-03-02 1999-02-18 이노우에 아키라 이온 주입 시스템
JP2693899B2 (ja) * 1992-10-09 1997-12-24 栄電子工業株式会社 Ｅｃｒプラズマ加工方法
DE19929278A1 (de) * 1998-06-26 2000-02-17 Nissin Electric Co Ltd Verfahren zum Implantieren negativer Wasserstoffionen und Implantierungseinrichtung
US6441569B1 (en) 1998-12-09 2002-08-27 Edward F. Janzow Particle accelerator for inducing contained particle collisions

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2475798A1 (fr) * 1980-02-13 1981-08-14 Commissariat Energie Atomique Procede et dispositif de production d'ions lourds fortement charges et une application mettant en oeuvre le procede
US4447773A (en) * 1981-06-22 1984-05-08 California Institute Of Technology Ion beam accelerator system
US4486665A (en) * 1982-08-06 1984-12-04 The United States Of America As Represented By The United States Department Of Energy Negative ion source
FR2546358B1 (fr) * 1983-05-20 1985-07-05 Commissariat Energie Atomique Source d'ions a resonance cyclotronique des electrons
US4602161A (en) * 1985-03-04 1986-07-22 The United States Of America As Represented By The United States Department Of Energy Negative ion source with low temperature transverse divergence optical system

Also Published As

Publication number Publication date
DE3662576D1 (en) 1989-04-27
FR2580427A1 (fr) 1986-10-17
EP0199625A1 (de) 1986-10-29
JPS61239546A (ja) 1986-10-24
US4757237A (en) 1988-07-12
FR2580427B1 (fr) 1987-05-15

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