EP0483004B1 - Quelle starkgeladener Ionen mit polarisierbarer Probe und mit Elektronzyklotronresonanz - Google Patents

Quelle starkgeladener Ionen mit polarisierbarer Probe und mit Elektronzyklotronresonanz Download PDF

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Publication number
EP0483004B1
EP0483004B1 EP19910402829 EP91402829A EP0483004B1 EP 0483004 B1 EP0483004 B1 EP 0483004B1 EP 19910402829 EP19910402829 EP 19910402829 EP 91402829 A EP91402829 A EP 91402829A EP 0483004 B1 EP0483004 B1 EP 0483004B1
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EP
European Patent Office
Prior art keywords
cavity
probe
source
ions
voltage
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Expired - Lifetime
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EP19910402829
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English (en)
French (fr)
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EP0483004A1 (de
Inventor
Paul Briand
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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

Definitions

  • the subject of the present invention is a source of highly charged positive ions with probe polarizable and electron cyclotron resonance (RCE). It finds many applications, in function of the different values of kinetic energy ions extracted, in the fields of implantation ionic, microgravure, and more particularly in the equipment of particle accelerators, used both in the scientific field than medical.
  • RCE probe polarizable and electron cyclotron resonance
  • the ions are obtained by ionizing, in a closed cavity-like enclosure microwave, a gas, consisting for example of metallic vapors, using an electron plasma strongly accelerated by cyclotronic resonance electronic.
  • HF high electromagnetic field frequency
  • the amount of ions that can be produced results from competition between two processes: on the one hand the formation of ions by electronic impact on neutral atoms constituting the gas to be ionized and on the other hand the destruction of these same ions by recombination, single or multiple, in a collision of these last with a neutral atom; this neutral atom can come from gas not yet ionized or be produced on the walls of the enclosure by impact of a ion on said walls.
  • This drawback is avoided by confining, in the enclosure constituting the source, the ions formed as well as the electrons used for their ionization. This is achieved by creating inside the enclosure radial and axial magnetic fields, defining a closed tablecloth called "equimagnetic", having no contact with the walls of the enclosure and on which the electronic cyclotronic resonance condition is satisfied.
  • This tablecloth is shaped like a balloon rugby. The closer this equimagnetic sheet walls of the enclosure, the more effective it is great because it limits the volume of attendance neutral atoms and therefore the amount of collision neutral atom-ions.
  • This tablecloth also allows confine the ions and electrons produced by gas ionization. Thanks to this confinement, the created electrons have time to bomb several times the same ion and totally ionize it.
  • This source contains two stages.
  • the role of the first stage A is largely part of providing an electron flow in the axis X of the source.
  • This first stage A has a cavity 2a with symmetry of revolution of the solenoidal coils 14a arranged at the two ends of the cavity 2a, creating an axial magnetic field, this field being plus 18a soft iron shielding located at the entrance from the source.
  • the gas or vapor to be ionized is introduced through a conduit 6 inside the cavity 2a. When it comes to steam, it can be introduced into the cavity in the form of a rod suitable for vaporizing.
  • An electromagnetic field is created inside the cavity 2a by a first high frequency input 4a.
  • This stage B consists of a cylindrical cavity multimode 2 of high order, i.e. of dimension large compared to the dimension of the length of the electromagnetic field. Its axis of symmetry bears the reference X. This electromagnetic field is introduced radially by a second entry high frequency 4.
  • Cavity 2 is joined at its end 5 to a vacuum pump 10b, by means of a pipe in which electrodes are housed 10a.
  • a power source 9 allows to apply a potential difference at these electrodes.
  • This pump, pipe and electrodes constitutes the extraction means 10 of ions.
  • the ions thus extracted from cavity 2 can then be selected according to their degree ionization using any known means using a magnetic field and / or an electric field.
  • coils 14 creating an axial magnetic field and a set 16 of permanent magnets creating a field magnetic radial, generally of the hexapolar type. These axial and radial magnetic fields are superimposed one over the other and distributed throughout the cavity; they thus form a resulting magnetic field which defines at least one equimagnetic surface to inside the cavity 2.
  • the first problem in this type of source is the importance of clutter; to this problem there is also the manufacturing difficulty and therefore the cost of such a source.
  • the subject of the present invention is a ion source with cyclotron resonance allowing to remedy these drawbacks by simplifying including this type of source.
  • the main feature of the invention is to replace the first stage of the source Minimafios by a voltage polarizable probe.
  • the invention allows a lower cost than that existing sources such as Minimafios, the manufacturing the probe being easier than that from the first floor of Minimafios.
  • the voltage supply means consist of a variable voltage source suitable for supplying said probes a negative voltage compared to the potential of the cavity thus ensuring an increase in the current ions.
  • This negative voltage has an absolute value at least equal to about 100 volts for a increased charge of ions.
  • the probe is arranged along the axis of the cavity, at a from its ends and from the side opposite to the means extraction. It is also possible to arrange it laterally.
  • the probe is made of tantalum.
  • any other electron-emitting metal can be considered and, in particular, tungsten and molybdenum.
  • the probe includes a rod of this electron emitting metal and a disc of this same metal attached to one end of this rod. It is possible to use a probe whose rod is made of a metal different from that of the disc.
  • the introduction of gas takes place along the axis of the cavity, parallel to the probe. This increases the ionization of neutral atoms.
  • the introduction of the high frequency is done along the axis of the cavity, on the probe side. However, it is possible to introduce the high frequency radially. This source allows in particular the obtaining of a current seventeen times positively charged argon ions.
  • Figure 2 shows the ion source according to the invention.
  • This source includes, like that of the prior art, a stage B equipped with the cavity 2 RCE almost identical to the second stage B of the source of figure 1.
  • the first floor A from the source in Figure 1 has disappeared and has been replaced by a 20 polarizable probe, powered in voltage by a variable power source 8.
  • this source includes, at the entry of the HF cavity, an element of soft iron 18 and a other element of soft iron 12 at the outlet of the cavity HF, downstream of the electrodes 10a.
  • element 18 The role of element 18 is identical to that of element 18a of the source of the figure 1. Element 12, meanwhile, allows the reduction of the axial magnetic field downstream of the electrodes output 10a.
  • gas or steam supply 6 metallic is carried out along the X axis of the cavity HF and no longer radially in order to increase the quantity ions.
  • the probe 20 is supplied by the source 8 of variable voltage (0 - 200 V) including connection electric is such that the probe 20 receives a voltage negative compared to the potential of the cavity which is a few kilovolts higher (10 to 20 kV) relative to mass.
  • the probe 20 is made up of a rod 20a of an electron emitting metal at end of which is fixed a disc 20b of the same metal. This disc has a diameter about ten times larger than that of the rod 20a in order to improve the emission electrons.
  • This metal is in particular tantalum.
  • the probe 20 is placed at the end 3 of the cavity 2, end opposite to that of the ion extraction means 10. In addition, it is placed along the X axis of the cavity 2, parallel to the high frequency input 4 and when the gas is introduced 6.
  • the probe is fixed in this position using a shutter 22, insulating electric fitted with holes for passage, respectively, of the rod 20a, of the introduction gas 6 and high frequency input 4.
  • FIG 3 there is shown schematically part of the source according to the invention and, in particular, the interior of the microwave cavity 2.
  • the probe 20 located at the end 3 of the cavity 2 has no contact with this surface equimagnetic S in order to best avoid possibilities of recombination of an ion with one or several electrons.
  • FIG. 4 represents the ionization spectra of krypton, that is to say the variations of the ion current I i of krypton, in microamperes, as a function of the state of charge Q of the krypton ion.
  • the first spectrum a is obtained for a non-polarized probe and therefore for a zero probe voltage.
  • the second spectrum b is obtained for a probe polarized by a negative voltage of -180 volts.
  • the inventors have found that the probe, powered by a positive voltage compared to the HF cavity, has the effect of decreasing the ion current and increase the weak states dump.
  • the curve in Figure 5 represents the variations in the quantity N of argon ions seventeen times positively charged, expressed as a number pulses per second, based on potential U of the probe, expressed in volts.
  • This curve was plotted by increasing the intensity of the K ⁇ ray emitted by an Ar ion beam 17+ intercepted by a solid target.
  • the ion beam is extracted from the source with a potential of 15 kV applied to the cavity relative to the mass and is deflected by a magnet, relative to the X axis, to be analyzed.
  • the line K ⁇ (2.957 KeV) is observed with a hyper-pure germanium detector which looks at the target from a solid 4.10 -5 steradian angle through a Kapton® window.
  • This measurement technique does not directly give the intensity of the Ar 17+ ion current but makes it possible to follow its evolution without ambiguity.
  • the intensity of the line being proportional to the current of Ar 17+ ions falling on the target.
  • the energy of the X-rays being characteristic of this ion, one thus avoids any confusion with the states of charge having a close Q / M such as the nitrogen ion six times charged.
  • the growth factor for the number of Ar 17+ ions is approximately 100 for a potential of the probe passing from -5 volts to -150 volts.
  • the curve in FIG. 6 represents the variations in the current I s of the probe in milliamps as a function of the potential U of this same probe in volts.
  • U 0, the tantalum probe current is negative, with an absolute value greater than 3 milliamps; this current corresponds to a capture of electrons.
  • the probe current is positive; it is then emission of electrons by the probe or else of an ion current of tantalum collected or else emission of electrons and of an ion current of tantalum collected.
  • the ion source according to the invention is simpler to manufacture than two sources known floors and makes it possible to reach at least the same performance as a two-stage source for lower cost.

Claims (7)

  1. Quelle stark geladener positver Ionen mit Elektronzyklotronresonanz, umfassend:
    einen Ultrahochfrequenzresonator (2) mit einer Symmetrieachs (X);
    einen Hochfrequenzeingang (4), der in dem Resonator mündet, um dort ein elektromagnetisches Hochfreqenzfeld zu erzeugen;
    eine Gaseinleitung (6) in den Resonator;
    Einrichtungen (14), um in dem genannten Resonator ein Magnetfeld in Achsrichtung zu erzeugen;
    Einrichtungen (16), um in diesem Resonator ein multipolares radiales Magnetfeld zu erzeugen, wobei durch die Überlagerung dieser axialen und radialen Magnetfelder ein resultierendes Magnetfeld entsteht, das in dem gesamten Resonator verteilt ist und wenigstens eine vollständig ins Innern des Resonators eingeschlossene äquimagnetische Fläche (S) bildet;
    Ionenextraktionseinrichtungen (10) am Ende (5) des Resonators.
    dadurch gekennzeichnet, daß sie umfaßt:
    eine spannungspolarisierbare bzw. vorspannbare Sonde (20), um die Ionisierung des Gases zu verbessern und derart den Fluß der extrahierten Ionen zu erhöhen, hergestellt aus elektronenemittierendem Metall, vor den Extraktionseinrichtungen angeordnet, wobei sie keinen Kontakt mit der äquimagnetischen Fläche hat; und
    Spannungsversorgungseinrichtungen (8) der Sonde.
  2. Quelle nach Anspruch 1, dadurch gekennzeichnet, daß die Spannungsversorgungseinrichtungen durch eine verstellbare Spannungsquelle (8) gebildet werden, die der genannten Sonde zur Erhöhung des Ionenstroms eine bezüglich des Potentials des Resonators negative Spannung liefern kann.
  3. Quelle nach Anspruch 2, dadurch gekennzeichnet, daß diese negative Spannung einen Absolutwert von wenigstens ungefähr 100 Volt hat, um die Ladung der Ionen zu erhöhen.
  4. Quelle nach einem der vorangehenden Ansprüche, dadurch gekennzeichnet, daß die Sonde entsprechend der Achse (X) des Resonators und an einem seiner Enden angeordnet ist.
  5. Quelle nach einem der vorangehenden Ansprüche, dadurch gekennzeichnet, daß die Sonde (20) eine Stange (20a) aus einem elektronenemittierenden Material und eine an einem der Enden der Stange befestigte Scheibe (20b) aus demselben Material umfaßt.
  6. Quelle nach einem der vorangehenden Ansprüche, dadurch gekennzeichnet, daß die Gaseinleitung in der Richtung der Achse des Resonators erfolgt, parallel zu der Sonde.
  7. Elektronzyklotronresonanz-Quelle um siebzehnfach positiv geladene Argonionen zu erhalten, dadurch gekennzeichnet, daß die Quelle gebildet wird nach einem der Ansprüche 1 bis 6, und dadurch, daß das in den Resonator eingeleitete Gas Argon enthält.
EP19910402829 1990-10-25 1991-10-23 Quelle starkgeladener Ionen mit polarisierbarer Probe und mit Elektronzyklotronresonanz Expired - Lifetime EP0483004B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9013232A FR2668642B1 (fr) 1990-10-25 1990-10-25 Source d'ions fortement charges a sonde polarisable et a resonance cyclotronique electronique.
FR9013232 1990-10-25

Publications (2)

Publication Number Publication Date
EP0483004A1 EP0483004A1 (de) 1992-04-29
EP0483004B1 true EP0483004B1 (de) 1999-02-24

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EP (1) EP0483004B1 (de)
JP (1) JPH0589792A (de)
DE (1) DE69130913T2 (de)
FR (1) FR2668642B1 (de)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4419970A1 (de) * 1994-06-08 1995-12-21 Juergen Prof Dr Andrae Vorrichtung zur Erzeugung von Strahlen hochgeladener Ionen
FR2757310B1 (fr) * 1996-12-18 2006-06-02 Commissariat Energie Atomique Systeme magnetique, en particulier pour les sources ecr, permettant la creation de surfaces fermees d'equimodule b de forme et de dimensions quelconques
FR2757881B1 (fr) * 1996-12-31 1999-04-09 Univ Paris Curie Procede de traitement d'une surface d'un semi-conducteur, dispositif correspondant et semi-conducteur associe
FR2933532B1 (fr) * 2008-07-02 2010-09-03 Commissariat Energie Atomique Dispositif generateur d'ions a resonance cyclotronique electronique
RU2538764C2 (ru) * 2013-01-09 2015-01-10 Федеральное государственное бюджетное учреждение "Государственный научный центр Российской Федерации-Институт Теоретической и Экспериментальной Физики" Лазерно-плазменный генератор ионов с большим зарядом

Family Cites Families (2)

* 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
FR2580427B1 (fr) * 1985-04-11 1987-05-15 Commissariat Energie Atomique Source d'ions negatifs a resonance cyclotronique des electrons

Also Published As

Publication number Publication date
FR2668642B1 (fr) 1993-11-05
FR2668642A1 (fr) 1992-04-30
EP0483004A1 (de) 1992-04-29
DE69130913D1 (de) 1999-04-01
DE69130913T2 (de) 1999-09-09
JPH0589792A (ja) 1993-04-09

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