EP0514255A1 - Elektronzyklotronresonanz-Ionenquelle - Google Patents

Elektronzyklotronresonanz-Ionenquelle Download PDF

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Publication number
EP0514255A1
EP0514255A1 EP92401292A EP92401292A EP0514255A1 EP 0514255 A1 EP0514255 A1 EP 0514255A1 EP 92401292 A EP92401292 A EP 92401292A EP 92401292 A EP92401292 A EP 92401292A EP 0514255 A1 EP0514255 A1 EP 0514255A1
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EP
European Patent Office
Prior art keywords
enclosure
source
point
resonance
cyclotron resonance
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
EP92401292A
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English (en)
French (fr)
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EP0514255B1 (de
Inventor
Bernard Jacquot
Marc Delaunay
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 EP0514255A1 publication Critical patent/EP0514255A1/de
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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 present invention relates to an improvement of an ion source with electronic cyclotron resonance (ECR) allowing, in particular the production of multicharged ions.
  • ECR electronic cyclotron resonance
  • the ions are obtained by ionization, in a closed enclosure, such as a microwave cavity, of a gaseous medium consisting of one or more gases or metallic vapors, by means of electrons strongly accelerated by electronic cyclotron resonance.
  • HF high frequency electromagnetic field
  • the quantity of ions that can be produced results from the 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, during a collision of the latter with a neutral atom; this neutral atom can come from the gas not yet ionized or else be produced on the walls of the enclosure by impact of an 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 so-called "equimagnetic" surface, having no contact with the walls of the enclosure and on which the condition of electronic cyclotron resonance is satisfied.
  • This surface has the shape of a rugby ball. The closer this equimagnetic surface is to the walls of the enclosure, the greater its efficiency because it makes it possible to limit the volume of presence of neutral atoms and therefore the amount of collisions between ions and neutral atoms.
  • This surface also makes it possible to confine the ions and the electrons produced by ionization of the gas. Thanks to this confinement, the electrons created have the time to bombard the same ion several times and fully ionize it.
  • FIG. 1 there is shown schematically an ion source according to the prior art.
  • This source includes an enclosure 1 constituting a resonant cavity which can be excited by a high frequency electromagnetic field (HF).
  • HF high frequency electromagnetic field
  • This electromagnetic field is produced by a generator 3 of electromagnetic waves; it is introduced inside the enclosure 1 via a waveguide 5 and a transition cavity 20.
  • This source also includes an externally shielded magnetic structure (7, 9, 11), the shielding 11 of which makes it possible to magnetize only the volume useful for electronic cyclotron resonance in the enclosure 1.
  • This magnetic structure comprises, in addition to the shielding 11, permanent magnets 7 and solenoids 9, arranged around the enclosure 1 and respectively creating a radial magnetic field and an axial magnetic field. These two magnetic fields are superimposed and distributed throughout the enclosure; they thus form a resulting magnetic field which defines a resonant equimagnetic surface 13 inside the enclosure 1.
  • First and second dielectric lines 23 connect the opening 19 of the shield 11 to respective openings 25 and 27 of the transition cavity 20, these openings being located on the lateral faces of the cavity 20 which has the shape of a cube .
  • the ratio of the diameters of these two pipes 21, 23 is such that it is possible to assimilate the latter to a coaxial line of characteristic impedance of the order of 85 ⁇ .
  • a coaxial line preferably propagates an electromagnetic Transverse Electro-Magnetic (TEM) mode in which the electromagnetic field is transverse to the direction of propagation of the waves and perpendicular to the surface of the conductors, that is to say pipes 21, 23.
  • TEM Transverse Electro-Magnetic
  • said gas is introduced into the enclosure 1 via a gas pipeline 30 connected to the opening 27 of the transition cavity 20.
  • the gas and the electromagnetic waves introduced into the cavity 20 are transmitted to enclosure 1 by the first and second pipes 21 and 23, the role of which is to enable said waves to be transmitted to said enclosure and to inject them there along the longitudinal axis 15.
  • enclosure 1 the combination of the axial magnetic field and the electromagnetic field makes it possible to strongly ionize the gas introduced.
  • the electrons produced are then strongly accelerated by electronic cyclotron resonance, which leads to the formation of a plasma of hot electrons confined in the volume limited by the equimagnetic surface 13.
  • the ions then formed in enclosure 1 are extracted therefrom by an electric extraction field generated by a potential difference applied between an electrode 31 and enclosure 1.
  • the electrode 31 and enclosure 1 are all two connected to a source 33 of electrical supply, the electrode 31 being positioned outside the opening 17 of the enclosure 1.
  • a pulse generator 35 itself located upstream of a power source 37 connected to the generator d 'electromagnetic waves.
  • Said pulse generator 35 controls said power source 37 by adjusting the useful cycle, namely the ratio between the duration of a pulse and the period of the pulses.
  • means 39 for measuring total pressure are connected to an input of a comparator 41, the output of which is itself connected to a valve 43 of the gas pipe 30.
  • a comparator 41 On a second input of comparator 41, a reference voltage R is applied and compared with the measured value of the ion current to give, at the output of the comparator, the value to be transmitted to valve 43.
  • This valve 43 acts on the quantity of gas to be introduced into enclosure 1, so as to automatically regulate the ion current.
  • an adaptation piston 45 connected to a third lateral opening 29 of the cavity 20, makes it possible to adjust the internal volume of said cavity 20.
  • the adjustment of said piston 45 is used to tune all of the internal volumes of the cavity 20 on the frequency of the electromagnetic waves in order to obtain a minimum of reflected waves, that is to say waves which return to the wave generator 3.
  • these internal volumes are tuned to the frequency of the electromagnetic waves , the waves injected into the cavity 20 by the generator 3 are almost completely transmitted, via the pipes 21 and 23, to the enclosure 1 containing the plasma, then absorbed by the equimagnetic surface 13.
  • the second pipe 23 is transparent to electromagnetic waves at its end 23a, end close to the opening 19 of the enclosure 1, located opposite the shielding 11.
  • this transparent part 23a there is an axial magnetic field from the solenoids, an electromagnetic field and a high gas pressure.
  • the electromagnetic field comes from electromagnetic waves transmitted between the first pipe 21 and a non-transparent part 23b of the second pipe 23, and which pass through the transparent part 23a of the second pipe 23. Therefore, an electronic cyclotronic resonance can take place at inside the end 23a of the second pipe 23 in a volume where there is a high gas pressure.
  • the denser the plasma produced by electronic cyclotron resonance inside the end 23a the better the transmission of electromagnetic waves, this dense plasma cord itself becoming conductive.
  • this plasma cord has the same outside diameter as the part 23b of the second pipe. The characteristic impedance of the coaxial line is therefore not modified, which makes it possible to avoid the reflection of electromagnetic waves.
  • This end transparent to electromagnetic waves therefore constitutes a self-regulated pre-ionization stage, where the excess of incident power of the electromagnetic waves is transmitted without reflection to the zone of electronic cyclotron resonance formed by the equimagnetic surface 13.
  • the subject of the present invention is precisely a source of RCE ions comprising a device making it possible to rationally optimize said source.
  • the means for moving the resonance point comprise a tubular part placed around the second pipe at the level of the transparent part and capable of being translated parallel to the pipes.
  • the tubular part comprises, on its external peripheral part, a thread so as to form, with the shielding, a screw / nut system.
  • the points A and B represent the ends of the equimagnetic surface 13, also called closed resonant surface, located in the confining plasma.
  • the point C is located in the second dielectric line 23, in the preionization plasma, that is to say at the level of the shielding 11 magnetic, said shielding 11 causing the sudden drop in magnetic induction.
  • the part of the pipes 21, 23 located at the level of the shield 11 is an area of strong magnetic gradient, that is to say an area where the magnetic induction varies greatly.
  • the RCE resonance is optimized at point C, when the electric field reaches its maximum value, that it is perpendicular to the resonant induction field and that it is on a cylinder of small radius, that is to say on the second pipe 23 of small radius.
  • the preionization plasma created in the dielectric lines 21, 23 is so dense that it becomes practically conductive, flourishing up to the equimagnetic surface 13, thus reaching point B.
  • This equimagnetic surface 13 also contains a dense plasma which is capable of absorbing and reflecting electromagnetic waves, thus making said surface 13 semi-conductive, from point B to point A.
  • the RCE ion source behaves like a coaxial line up to point A of the magnetic axis 15. This open line is then the seat of standing waves between point A and piston 45.
  • the distances between two points A and B, B and C, or C and A are equal to an integer (n or m) of times the half-wavelength ⁇ of the electromagnetic waves introduced into the source.
  • Figure 3 is a schematic representation of the ion source comprising the device according to the invention for optimizing the position of points A, B and C.
  • the RCE source represented in FIG. 3 is the same as the RCE source of the prior art, to which the optimization device of the invention has been added, said RCE source having been described at the beginning of the description. All the elements, cited during the description of Figure 1, retain the same references in Figure 3, which will be described.
  • the device for optimizing an RCE source is shown in FIG. 4. It consists of a tubular piece 47, also called a magnetic screw, this screw 47 being placed around the first pipe 21, with a clearance of approximately 0.5 mm, in order to avoid any friction with said pipe 21, when the latter is moved in translation relative to the shield 11.
  • This tubular part 47 of the same thickness as the shield 11, comprises, on its periphery, a thread 47a suitable to be screwed onto the threaded part (11a) of the shielding 11.
  • the screwing / unscrewing of the magnetic screw 47 on the shielding 11 ensures the displacement of said magnetic screw 47.
  • This magnetic screw 47 is made of iron. Therefore, there is a strong magnetic gradient at the level of the shielding which makes it possible to act on the position of the point C of resonance. In fact, point C almost follows the movement of said tubular part 47 relative to the shield 11.
  • the displacement of the tubular part 47 is carried out using a special tool provided with two nipples which come to engage in two of the four holes 47b included in the tubular part 47. These four holes 47b are regularly distributed over the outer surface of the magnetic screw 47 and are each on an axis parallel to the magnetic axis 15.
  • the special tool provided with its two pins comes s '' Engage in two diametrically opposite holes, thus making it possible to turn the screw 47.
  • the translation of the magnetic screw 47 is carried out in the absence of a magnetic field, that is to say when the RCE source is stopped. In the presence of the magnetic field created by the solenoids 9, an interaction is established between the magnetic screw 47 and the shielding 11. In fact, a large magnetic force then opposes the translation of the screw 47, the thread 47a of the screw 47 then pressing strongly on the thread 11a of the shield 11 thus ensuring magnetic continuity in the shield of the RCE source.
  • the optimum electric field at point C is obtained, at high gas pressure, so as to optimize the source on low states of ionic charge. This optimum is assessed by adjusting the screw 47 on the one hand and the position of the piston 45 on the other hand. There is then a first position of the point C. According to prior knowledge of the axial magnetic profile of the RCE source, the points A and B are positioned by adjusting the intensity of the current in the two solenoids 9, this intensity being controlled by external power supplies which provide, for example, a current varying from 0 to 1000 amps.
  • the diameter of the enclosure 1 is approximately 6 centimeters and the wavelength ⁇ of the waves introduced is three centimeters, ie a frequency f of 10 GHz.
  • the wavelength ⁇ of the waves introduced is three centimeters, ie a frequency f of 10 GHz.
  • all of the adjustments must be made for an electromagnetic wave power of less than 100 Watts.
  • a knowledgeable experimenter is able to optimize this source in five or six operations, that is to say in a few minutes.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Combustion & Propulsion (AREA)
  • Particle Accelerators (AREA)
  • Electron Sources, Ion Sources (AREA)
EP92401292A 1991-05-14 1992-05-12 Elektronzyklotronresonanz-Ionenquelle Expired - Lifetime EP0514255B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9105803 1991-05-14
FR9105803A FR2676593B1 (fr) 1991-05-14 1991-05-14 Source d'ions a resonance cyclotronique electronique.

Publications (2)

Publication Number Publication Date
EP0514255A1 true EP0514255A1 (de) 1992-11-19
EP0514255B1 EP0514255B1 (de) 1996-01-17

Family

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Family Applications (1)

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EP92401292A Expired - Lifetime EP0514255B1 (de) 1991-05-14 1992-05-12 Elektronzyklotronresonanz-Ionenquelle

Country Status (5)

Country Link
US (1) US5336961A (de)
EP (1) EP0514255B1 (de)
JP (1) JPH06103943A (de)
DE (1) DE69207641T2 (de)
FR (1) FR2676593B1 (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1996025755A1 (fr) * 1995-02-16 1996-08-22 Plasmion Dispositif a resonance cyclotron electronique pour creer un faisceau d'ions
WO2010001036A2 (fr) * 2008-07-02 2010-01-07 Commissariat A L'energie Atomique Dispositif générateur d'ions à résonance cyclotronique électronique

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4868330B2 (ja) * 2004-10-08 2012-02-01 独立行政法人科学技術振興機構 多価イオン発生源およびこの発生源を用いた荷電粒子ビーム装置

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0238397A1 (de) * 1986-03-13 1987-09-23 Commissariat A L'energie Atomique Elektronenzyklotronresonanz-Ionenquelle mit koaxialer Injektion elektromagnetischer Wellen

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4788473A (en) * 1986-06-20 1988-11-29 Fujitsu Limited Plasma generating device with stepped waveguide transition
JP2515810B2 (ja) * 1987-07-10 1996-07-10 東京エレクトロン東北株式会社 プラズマ処理装置
US5132597A (en) * 1991-03-26 1992-07-21 Hughes Aircraft Company Hollow cathode plasma switch with magnetic field

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0238397A1 (de) * 1986-03-13 1987-09-23 Commissariat A L'energie Atomique Elektronenzyklotronresonanz-Ionenquelle mit koaxialer Injektion elektromagnetischer Wellen

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
JOURNAL OF VACUUM SCIENCE AND TECHNOLOGY: PART A. vol. 8, no. 3, Juin 1990, NEW YORK US pages 2900 - 2903; CC TSAI ET AL: 'POTENTIAL APPPLICATIONS OF AN ELECTRON CYCLOTRON RESONANCE MULTICUSP PLASMA SOURCE' *
PATENT ABSTRACTS OF JAPAN vol. 13, no. 196 (E-755)(3544) 10 Mai 1989 & JP-A-1 017 399 ( TERU SAGAMI K. K. ) 20 Janvier 1989 *

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1996025755A1 (fr) * 1995-02-16 1996-08-22 Plasmion Dispositif a resonance cyclotron electronique pour creer un faisceau d'ions
FR2730858A1 (fr) * 1995-02-16 1996-08-23 Plasmion Dispositif a resonance cyclotron electronique pour creer un faisceau d'ions
WO2010001036A2 (fr) * 2008-07-02 2010-01-07 Commissariat A L'energie Atomique Dispositif générateur d'ions à résonance cyclotronique électronique
FR2933532A1 (fr) * 2008-07-02 2010-01-08 Commissariat Energie Atomique Dispositif generateur d'ions a resonance cyclotronique electronique
WO2010001036A3 (fr) * 2008-07-02 2010-02-25 Commissariat A L'energie Atomique Dispositif générateur d'ions à résonance cyclotronique électronique
US8760055B2 (en) 2008-07-02 2014-06-24 Commissariat A L'energie Atomique Et Aux Energies Alternatives Electron cyclotron resonance ion generator

Also Published As

Publication number Publication date
DE69207641T2 (de) 1996-09-05
JPH06103943A (ja) 1994-04-15
EP0514255B1 (de) 1996-01-17
DE69207641D1 (de) 1996-02-29
US5336961A (en) 1994-08-09
FR2676593A1 (fr) 1992-11-20
FR2676593B1 (fr) 1997-01-03

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