EP0241362B1 - Device, particularly a duoplasmatron, for ionizing a gas, and method of using this device - Google Patents

Device, particularly a duoplasmatron, for ionizing a gas, and method of using this device Download PDF

Info

Publication number
EP0241362B1
EP0241362B1 EP87400738A EP87400738A EP0241362B1 EP 0241362 B1 EP0241362 B1 EP 0241362B1 EP 87400738 A EP87400738 A EP 87400738A EP 87400738 A EP87400738 A EP 87400738A EP 0241362 B1 EP0241362 B1 EP 0241362B1
Authority
EP
European Patent Office
Prior art keywords
cathode
electrodes
gas
filament
anode
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
EP87400738A
Other languages
German (de)
French (fr)
Other versions
EP0241362A1 (en
Inventor
Bruno Blanchard
Pierre Juliet
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
Original Assignee
Commissariat a lEnergie Atomique CEA
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Commissariat a lEnergie Atomique CEA filed Critical Commissariat a lEnergie Atomique CEA
Publication of EP0241362A1 publication Critical patent/EP0241362A1/en
Application granted granted Critical
Publication of EP0241362B1 publication Critical patent/EP0241362B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J27/00—Ion beam tubes
    • H01J27/02—Ion sources; Ion guns
    • H01J27/022—Details
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J27/00—Ion beam tubes
    • H01J27/02—Ion sources; Ion guns
    • H01J27/08—Ion sources; Ion guns using arc discharge
    • H01J27/10—Duoplasmatrons ; Duopigatrons

Definitions

  • the present invention relates to a device usable for ionizing a gas and comprising a cathode serving as a hot or cold cathode and a method of using this device.
  • the invention applies to all devices used in particular for ionizing a gas such as electric arcs, unoplasmatrons and duoplamatrons.
  • a gas such as electric arcs, unoplasmatrons and duoplamatrons.
  • the invention will be described from a duoplasmatron used for example in surface analysis apparatus as an ion source for abrading samples.
  • a duoplasmatron comprises either a cold cathode or a hot cathode.
  • Figure 1 shows schematically in longitudinal section a duoplasmatron with cold cathode of known type.
  • This duoplasmatron comprises a hollow cathode 1 of cylindrical shape, the upper part of which is mounted on a generally conductive support 2, an intermediate electrode 3 surrounding the cathode 1 and comprising in its lower part an opening 4 and an anode 5 surrounding the intermediate electrode 3 , provided opposite the opening 4 of this electrode, with an opening 6 of divergent shape towards the outside.
  • the cathode 1 is made of nickel and the intermediate electrode 3 and the anode 5 are made of soft iron.
  • the cathode 1 mounted on the support 2, the intermediate electrode 3 and the anode 5 are electrically isolated. These three elements are arranged one inside the other so as to define three chambers 11, 13, 15 communicating with each other, seals 8, 9 ensuring the tightness of these chambers with the outside.
  • the chamber 11 is defined by the internal cylindrical walls of the cathode, the chamber 13 by the space provided between the cathode 1 and the intermediate electrode 3 and the chamber 15 by the space defined between the intermediate electrode 3 and the anode 5.
  • a magnetic coil 21 surrounds the chambers 11, 13, 15; this coil is located around the upper part of the anode 5 and rests on both the lower part of the anode 5 and the upper part of the intermediate electrode 3.
  • a voltage generator 23 connected for example to the lower part of the anode 5 and to the conductive support 2 of the cathode 1 makes it possible to apply a potential difference Va-Vc of the order of 300 to 500 volts between the anode and the cathode, Va represents the voltage applied to the anode and Vc the voltage applied to the cathode.
  • This voltage Vi can also be obtained from the voltage generator 23 via a divider bridge connected to the intermediate electrode and to the voltage generator 23. In this case, the generator 25 is omitted.
  • Means for making the vacuum ensure the evacuation for example by the opening 6 of any gas present in the chambers 11, 13 and 15 before the introduction of the gas to be ionized into the duoplasmatron .
  • the gas to be ionized is stored for example in a bottle 16 connected by a pipe 17 to the support 2 of the cathode 1, said support comprising a passage 10 connected to the chamber 11. Opening and closing means such as a valve 17 ′ arranged for example on the pipe 17, makes it possible to introduce a regulated flow of gas into the duoplasmatron, from the bottle 16.
  • gas is introduced into the duoplasmatron by opening the valve 17 '.
  • the gas will circulate in the chamber 11 where it will be ionized by the electrons emitted by the cathode 1 on which the potential Vc is applied.
  • a plasma of ions and electrons is then formed which will be entrained towards the intermediate electrode 3, by the electric field 1 induced by the potential difference Vi-Vc between the cathode 1 and the electrode 3.
  • This plasma will pass through the opening 4 driven by an electric field 2 induced by the potential difference Va-Vi between the electrode 3 and the anode 5 as well as by a magnetic field between the electrode 3 and the anode 5.
  • This field circulates in a closed loop between the magnetic coil 21, the intermediate electrode 3 on which the coil rests, the part of the chamber 15 defined between the lower part of the intermediate electrode 3 and the upper part of the anode 5 and finally the anode 5 on which also rests the magnetic coil.
  • the plasma is therefore confined by the electric field 2 and the magnetic field between the intermediate electrode 3 and the anode 5. This plasma then passes through the opening 6 formed in the anode 5, driven by an electric field 3 induced by the potential difference between the anode and the surface 20 to be abraded generally to ground.
  • this duoplasmatron To operate as a hot cathode, this duoplasmatron must be dismantled to replace the cylindrical cathode 1 by a filament wound in a helix following a cylinder whose axis is perpendicular to the direction of the gas flow.
  • This filament is connected by each of its ends to a separate conductive tab mounted on the support 2, the gas to be ionized passing between these tabs and through the filament.
  • voltages Vc, Va and Vi are applied respectively to the support 2, to the anode 5 and to the intermediate electrode 3. Furthermore, a voltage Vs is applied between the two ends of the filament by a voltage generator; this voltage Vs allows the circulation of a current in the filament and consequently the heating of the filament by Joule effect.
  • the electronic emission is produced in particular by the bombardment of this one by the ions and electrons of the plasma; this emission therefore depends on the conditions prevailing in the duoplasmatron such as pressure, electric fields and the nature of the gas.
  • the electronic emission of a hot cathode due to the heating of the filament, is determined in particular by its temperature and therefore by the intensity of the current 1 which it is easy to regulate.
  • the hot cathode therefore allows a more stable electronic emission, the intensity of which can generally be adjusted greater than that provided by a cold cathode. Therefore, in operation in hot cathode, a potential difference Va-Vc of the order of a few tens of volts is sufficient.
  • a cold cathode or a hot cathode is used with reactive gases such as oxygen which would attack a filament (hot cathode), on the other hand, for inert gases such as argon, xenon, etc., it is more advantageous to use a hot cathode.
  • the hot cathode allows operation of the duoplasmatron with a lower pressure of the order of 10- 4 Pa and gives, because the electronic emission serving to ionize the gas is more stable, better stability of the current. ions extracted.
  • duoplasmatron With a duoplasmatron of known type, to pass from an operation in hot cathode to an operation in cold cathode, it is necessary to disassemble the duoplasmatron, which means in particular the stop of the use of the duoplasmatron and the rupture of the vacuum.
  • the object of the present invention is precisely to remedy these drawbacks by providing a device which can be used to ionize a gas operating as a cold cathode or a hot cathode without dismantling the device.
  • the invention relates to a device usable for ionizing a gas comprising a cathode and an opposite anode, the gas to be ionized successively passing through the cathode and the anode, characterized in that the cathode is formed of a first and a second facing electrodes, the gas to be ionized passing between said electrodes and a conductive filament connected by a first end to the first electrode and by a second end to the second electrode and located between said electrodes.
  • the first and second electrodes are half-cylinders arranged opposite so as to form a split cylinder according to two opposite generatrices and the filament is connected to the outlet ends of the gas to be ionized from the first and second electrodes.
  • the filament is wound in a helix along a cone, the axis of which coincides with the longitudinal axis of the cylinder created by the first and second electrodes, the gas to be ionized passing through this cone from its top.
  • This cone has an angle at the top ranging for example from 7 to 15 °.
  • the first and second electrodes are made of titanium and the filament is of tantalum.
  • the invention also relates to a duoplasmatron comprising a device as described above.
  • the invention also relates to a method of using the device which can be used to ionize a gas, this method is characterized in that this device operating as a cold cathode, a potential difference is applied between the anode and the first and second electrodes .
  • a first potential difference is applied between the anode and the first and second electrodes, and a second potential difference is applied between the first and second ends of the filament.
  • the cathode 30 shown in FIG. 2 is made up of two opposite electrodes 31, 33 and a conductive filament 35 connected by one of its ends 32 to the electrode 31 and by its other end 34 to the electrode 33.
  • the two electrodes 31 and 33 are respectively constituted by a half-cylinder opposite one another so as to form a split cylinder according to two opposite generatrices, the gas to be ionized passing through this cylinder.
  • This cylinder has for example a diameter of 40 mm and a length of 70 mm.
  • the filament 35 is wound in a helix (see FIG. 3) along a cone with an angle at the apex comprised between values of the order of 7 to 15 ° and a length for example of 15 mm. This filament is located at the gas outlet ends of the first and second electrodes and it is traversed by the gas from the top of the cone that it forms.
  • the two electrodes are preferably made of titanium.
  • titanium makes it possible to obtain a purer ion beam than the nickel used in the prior art.
  • the filament is advantageously in tantalum, the latter having a lifetime of 5 to 10 times longer than that of a tungsten filament used under the same conditions.
  • the wear of the filament is essentially due to sputtering, or the sputtering of tungsten is greater than that of tantalum.
  • the resistivity of tantalum being greater than that of tungsten, a filament with a diameter of approximately 0.7 mm is used instead of 0.5 mm for a tungsten filament of the prior art.
  • the axis of the cone formed by the filament coincides with the longitudinal axis of the cylinder created by the two electrodes 31, 33; this particular arrangement also makes it possible to increase the life of the filament by a factor of the order of 4 to 5.
  • the lifetime of the filament exceeds one month.
  • a voltage generator 37 and a switch 39 in series are connected between the two ends of the filament.
  • this cathode 30 in a duoplasmatron, it is mounted on the support 2 of FIG. 1 in place of the cathode 1.
  • the lower part of the electrodes 31 and 33 being connected to the filament 35.
  • the first and second electrodes and the support are preferably made in a single piece but of course the first and second electrodes can also be attached to the support.
  • This support is also advantageously made of titanium.
  • a potential difference Va-Vc is applied between the electrodes 31 and 33 and the anode 5 by the voltage generator 23 and a voltage Vi is applied as previously to the intermediate electrode 3.
  • the duoplasmatron When the switch 39 is closed, a voltage Vs is applied to the ends of the filament by the generator 37.
  • Vs a voltage applied to the ends of the filament by the generator 37.
  • the duoplasmatron operates as a hot cathode. Indeed, the filament traversed by a current gives off heat by the Joule effect. This filament then emits electrons which will ionize gas atoms. The ions formed will be confined as described above in electric and magnetic fields before being extracted from the duoplasmatron.
  • the potential difference Va-Vc applied between the first and second electrodes and the anode is of the order of a few tens of volts, the voltage Vs applied between the two ends of the filament is of the order of some 0.1 volts and the current flowing in the filament is of the order of a few amperes.
  • the electrons are mainly emitted by the filament.
  • the quantity of electrons emitted by the first and second electrodes is very small due to the small potential difference Va-Vc.
  • the duoplasmatron When the switch 39 is open, the voltage applied to the filament 35 is zero, no current flows in the filament: the duoplasmatron operates as a cold cathode. In this case, so that the first and second electrodes emit enough electrons to ionize the gas, a different potential Va-Vc of the order of 300 to 500 volts is applied between the anode and the first and second electrodes .
  • cathode according to the invention serving as a cold cathode or a hot cathode in a duoplasmatron, but of course, the invention applies to all ion sources using a cold or hot cathode .

Description

La présente invention concerne un dispositif utilisable pour ioniser un gaz et comprenant une cathode servant de cathode chaude ou froide ainsi qu'un procédé d'utilisation de ce dispositif.The present invention relates to a device usable for ionizing a gas and comprising a cathode serving as a hot or cold cathode and a method of using this device.

L'invention s'applique à tous les dispositifs utilisés en particulier pour ioniser un gaz tel que les arcs électriques, les unoplasmatrons et les duopla- smatrons. Pour plus de clarté dans la description, on décrira l'invention à partir d'un duoplasmatron utilisé par exemple dans des appareils d'analyse de surface comme source d'ions pour abraser des échantillons.The invention applies to all devices used in particular for ionizing a gas such as electric arcs, unoplasmatrons and duoplamatrons. For clarity in the description, the invention will be described from a duoplasmatron used for example in surface analysis apparatus as an ion source for abrading samples.

De façon connue, un duoplasmatron comprend soit une cathode froide, soit une cathode chaude.In known manner, a duoplasmatron comprises either a cold cathode or a hot cathode.

La figure 1 représente schématiquement en coupe longitudinale un duoplasmatron à cathode froide de type connu.Figure 1 shows schematically in longitudinal section a duoplasmatron with cold cathode of known type.

Ce duoplasmatron comprend une cathode creuse 1 de forme cylindrique dont la partie supérieure est montée sur un support 2 généralement conducteur, une électrode intermédiaire 3 entourant la cathode 1 et comportant dans sa partie inférieure une ouverture 4 et une anode 5 entourant l'électrode intermédiaire 3, munie en regard de l'ouverture 4 de cette électrode, d'une ouverture 6 de forme divergente vers l'extérieur.This duoplasmatron comprises a hollow cathode 1 of cylindrical shape, the upper part of which is mounted on a generally conductive support 2, an intermediate electrode 3 surrounding the cathode 1 and comprising in its lower part an opening 4 and an anode 5 surrounding the intermediate electrode 3 , provided opposite the opening 4 of this electrode, with an opening 6 of divergent shape towards the outside.

Généralement, la cathode 1 est en nickel et l'électrode intermédiaire 3 et l'anode 5 sont en fer doux.Generally, the cathode 1 is made of nickel and the intermediate electrode 3 and the anode 5 are made of soft iron.

Les termes de "partie supérieure " et "partie inférieure" de chaque élément sont définies dans ce texte par rapport au sens de déplacement du gaz à ioniser à travers le duoplasmatron.The terms "upper part" and "lower part" of each element are defined in this text with respect to the direction of movement of the gas to be ionized through the duoplasmatron.

La cathode 1 montée sur le support 2, l'électrode intermédiaire 3 et l'anode 5 sont isolées électriquement. Ces trois éléments sont agencés les uns dans les autres de façon à définir trois chambres 11, 13, 15 communiquant entre elles, des joints 8, 9 assurant l'étanchéité de ces chambres avec l'extérieur. La chambre 11 est définie par les parois cylindriques internes de la cathode, la chambre 13 par l'espace ménagé entre la cathode 1 et l'électrode intermédiaire 3 et la chambre 15 par l'espace défini entre l'électrode intermédiaire 3 et l'anode 5.The cathode 1 mounted on the support 2, the intermediate electrode 3 and the anode 5 are electrically isolated. These three elements are arranged one inside the other so as to define three chambers 11, 13, 15 communicating with each other, seals 8, 9 ensuring the tightness of these chambers with the outside. The chamber 11 is defined by the internal cylindrical walls of the cathode, the chamber 13 by the space provided between the cathode 1 and the intermediate electrode 3 and the chamber 15 by the space defined between the intermediate electrode 3 and the anode 5.

D'autre part, une bobine magnétique 21 entoure les chambres 11, 13, 15 ; cette bobine est située autour de la partie supérieure de l'anode 5 et repose à la fois sur la partie inférieure de l'anode 5 et la partie supérieure de l'électrode intermédiaire 3.On the other hand, a magnetic coil 21 surrounds the chambers 11, 13, 15; this coil is located around the upper part of the anode 5 and rests on both the lower part of the anode 5 and the upper part of the intermediate electrode 3.

Par ailleurs, un générateur de tension 23 relié par exemple à la partie inférieure de l'anode 5 et au support conducteur 2 de la cathode 1 permet d'appliquer une différence de potentiel Va-Vc de l'ordre de 300 à 500 volts entre l'anode et la cathode, Va représente la tension appliquée à l'anode et Vc la tension appliquée à la cathode. De plus, un générateur de tension 25 est relié à l'électrode intermédiaire, par exemple à la partie supérieure de cette électrode et à une masse. Ce générateur de tension 25 permet d'appliquer une tension Vi à l'électrode intermédiaire, cette tension Vi est généralement telle que Vi = (Va-Vc)/2. Cette tension Vi peut être obtenue également à partir du générateur de tension 23 par l'intermédiaire d'un pont diviseur relié à l'électrode intermédiaire et au générateur de tension 23. Dans ce ces, le générateur 25 est supprimé.Furthermore, a voltage generator 23 connected for example to the lower part of the anode 5 and to the conductive support 2 of the cathode 1 makes it possible to apply a potential difference Va-Vc of the order of 300 to 500 volts between the anode and the cathode, Va represents the voltage applied to the anode and Vc the voltage applied to the cathode. In addition, a voltage generator 25 is connected to the intermediate electrode, for example to the upper part of this electrode and to a ground. This voltage generator 25 makes it possible to apply a voltage Vi to the intermediate electrode, this voltage Vi is generally such that Vi = (Va-Vc) / 2. This voltage Vi can also be obtained from the voltage generator 23 via a divider bridge connected to the intermediate electrode and to the voltage generator 23. In this case, the generator 25 is omitted.

Des moyens pour faire le vide non représentés tels qu'une pompe à vide, assurent l'évacuation par exemple par l'ouverture 6 de tout gaz présent dans les chambres 11, 13 et 15 avant l'introduction du gaz à ioniser dans le duoplasmatron.Means for making the vacuum, not shown, such as a vacuum pump, ensure the evacuation for example by the opening 6 of any gas present in the chambers 11, 13 and 15 before the introduction of the gas to be ionized into the duoplasmatron .

Le gaz à ioniser est stocké par exemple dans une bouteille 16 reliée par une canalisation 17 au support 2 de la cathode 1, ledit support comportant un passage 10 relié à la chambre 11. Des moyens d'ouverture et de fermeture tels qu'une vanne 17' disposée par exemple sur la canalisation 17, permet d'introduire un débit régulé de gaz dans le duoplasmatron, à partir de la bouteille 16.The gas to be ionized is stored for example in a bottle 16 connected by a pipe 17 to the support 2 of the cathode 1, said support comprising a passage 10 connected to the chamber 11. Opening and closing means such as a valve 17 ′ arranged for example on the pipe 17, makes it possible to introduce a regulated flow of gas into the duoplasmatron, from the bottle 16.

Le reste de la description permet de comprendre le fonctionnement du duoplasmatron à cathode froide.The rest of the description helps to understand how the cold cathode duoplasmatron works.

Après réalisation du vide dans les chambres 11, 13 et 15, on introduit du gaz dans le duoplasmatron en ouvrant la vanne 17'. Le gaz va circuler dans la chambre 11 où il va être ionisé par tes électrons émis par la cathode 1 sur laquelle le potentiel Vc est appliqué. Il se forme alors un plasma d'ions et d'électrons qui va être entraîné vers l'électrode intermédiaire 3, par le champ électrique 1 induit par la différence de potentiel Vi-Vc entre la cathode 1 et l'électrode 3. Ce plasma va traverser l'ouverture 4 entraîné par un champ électrique 2 induit par la différence de potentiel Va-Vi entre l'électrode 3 et l'anode 5 ainsi que par un champ magnétique entre l'électrode 3 et l'anode 5.After completion of the vacuum in the chambers 11, 13 and 15, gas is introduced into the duoplasmatron by opening the valve 17 '. The gas will circulate in the chamber 11 where it will be ionized by the electrons emitted by the cathode 1 on which the potential Vc is applied. A plasma of ions and electrons is then formed which will be entrained towards the intermediate electrode 3, by the electric field 1 induced by the potential difference Vi-Vc between the cathode 1 and the electrode 3. This plasma will pass through the opening 4 driven by an electric field 2 induced by the potential difference Va-Vi between the electrode 3 and the anode 5 as well as by a magnetic field between the electrode 3 and the anode 5.

Ce champ circule en boucle fermée entre la bobine magnétique 21, l'électrode intermédiaire 3 sur laquelle repose la bobine, la partie de la chambre 15 définie entre la partie inférieure de l'électrode intermédiaire 3 et la partie supérieure de l'anode 5 et enfin l'anode 5 sur laquelle repose également la bobine magnétique.This field circulates in a closed loop between the magnetic coil 21, the intermediate electrode 3 on which the coil rests, the part of the chamber 15 defined between the lower part of the intermediate electrode 3 and the upper part of the anode 5 and finally the anode 5 on which also rests the magnetic coil.

Le plasma est donc confiné par le champ électrique 2 et le champ magnétique entre l'électrode intermédiaire 3 et l'anode 5. Ce plasma passe ensuite par l'ouverture 6 ménagée dans l'anode 5, entraîné par un champ électrique 3 induit par la différence de potentiel entre l'anode et la surface 20 à abraser généralement à la masse.The plasma is therefore confined by the electric field 2 and the magnetic field between the intermediate electrode 3 and the anode 5. This plasma then passes through the opening 6 formed in the anode 5, driven by an electric field 3 induced by the potential difference between the anode and the surface 20 to be abraded generally to ground.

Ces champs électriques et magnétique 1,These electric and magnetic fields 1,

2, 3 et ont la même direction et le même sens que le flux gazeux. 2 , 3 and have the same direction and the same direction as the gas flow.

Pour fonctionner en cathode chaude, ce duoplasmatron doit être démonté pour remplacer la cathode cylindrique 1 par un filament enroulé en hélice suivant un cylindre dont l'axe est perpendiculaire à la direction du flux gazeux. Ce filament est relié par chacune de ses extrémités à une patte conductrice distincte montée sur le support 2, le gaz à ioniser passant entre ces pattes et à travers le filament.To operate as a hot cathode, this duoplasmatron must be dismantled to replace the cylindrical cathode 1 by a filament wound in a helix following a cylinder whose axis is perpendicular to the direction of the gas flow. This filament is connected by each of its ends to a separate conductive tab mounted on the support 2, the gas to be ionized passing between these tabs and through the filament.

Comme précédemment, des tensions Vc, Va et Vi sont appliquées respectivement au support 2, à l'anode 5 et à l'électrode intermédiaire 3. Par ailleurs, une tension Vs est appliquée entre les deux extrémités du filament par un générateur de tension ; cette tension Vs permet la circulation d'un courant dans le filament et par conséquent l'échauffement du filament par effet Joule.As before, voltages Vc, Va and Vi are applied respectively to the support 2, to the anode 5 and to the intermediate electrode 3. Furthermore, a voltage Vs is applied between the two ends of the filament by a voltage generator; this voltage Vs allows the circulation of a current in the filament and consequently the heating of the filament by Joule effect.

Pour une cathode froide, l'émission électronique est produite notamment par le bombardement de celle-ci par les ions et électrons du plasma ; cette émission dépend donc des conditions qui règnent dans le duoplasmatron telles que la pression, les champs électriques et la nature du gaz. L'émission électronique d'une cathode chaude, due à l'échauffement du filament, est déterminée en particulier par sa température et donc par l'intensité du courant 1 qu'il est facile de réguler. La cathode chaude permet donc une émission électronique plus stable dont on peut régler l'intensite généralement plus importante que celle fournie par une cathode froide. De ce fait, en fonctionnement en cathode chaude, une différence de potentiel Va-Vc de l'ordre de quelques dizaines de volts est suffisante.For a cold cathode, the electronic emission is produced in particular by the bombardment of this one by the ions and electrons of the plasma; this emission therefore depends on the conditions prevailing in the duoplasmatron such as pressure, electric fields and the nature of the gas. The electronic emission of a hot cathode, due to the heating of the filament, is determined in particular by its temperature and therefore by the intensity of the current 1 which it is easy to regulate. The hot cathode therefore allows a more stable electronic emission, the intensity of which can generally be adjusted greater than that provided by a cold cathode. Therefore, in operation in hot cathode, a potential difference Va-Vc of the order of a few tens of volts is sufficient.

Suivant le type de gaz à ioniser, il est plus intéressant d'utiliser une cathode froide ou une cathode chaude. La cathode froide est employée avec des gaz réactifs tels que l'oxygène qui attaquerait un filament (cathode chaude), en revanche, pour des gaz inertes tels que l'argon, le xénon, etc., il est plus intéressant d'utiliser une cathode chaude. En effet, la cathode chaude permet un fonctionnement du duoplasmatron avec une pression moindre de l'ordre de 10-4 Pa et donne, du fait que l'émission électronique servant à ioniser le gaz est plus stable, une meilleure stabilité du courant d'ions extrait.Depending on the type of gas to be ionized, it is more advantageous to use a cold cathode or a hot cathode. The cold cathode is used with reactive gases such as oxygen which would attack a filament (hot cathode), on the other hand, for inert gases such as argon, xenon, etc., it is more advantageous to use a hot cathode. Indeed, the hot cathode allows operation of the duoplasmatron with a lower pressure of the order of 10- 4 Pa and gives, because the electronic emission serving to ionize the gas is more stable, better stability of the current. ions extracted.

Avec un duoplasmatron de type connu, pour passer d'un fonctionnement en cathode chaude à un fonctionnement en cathode froide, il faut démonter le duoplasmatron, ce qui signifie en particulier l'arrêt de l'utilisation du duoplasmatron et la rupture du vide.With a duoplasmatron of known type, to pass from an operation in hot cathode to an operation in cold cathode, it is necessary to disassemble the duoplasmatron, which means in particular the stop of the use of the duoplasmatron and the rupture of the vacuum.

La présente invention a justement pour but de remédier à ces inconvénients en réalisant un dispositif utilisable pour ioniser un gaz fonctionnant en cathode froide ou en cathode chaude sans démontage du dispositif.The object of the present invention is precisely to remedy these drawbacks by providing a device which can be used to ionize a gas operating as a cold cathode or a hot cathode without dismantling the device.

De façon plus précise, l'invention a pour objet un dispositif utilisable pour ioniser un gaz comprenant une cathode et une anode en regard, le gaz à ioniser traversant successivement la cathode et l'anode, caractérisé en ce que la cathode est formée d'une première et d'une deuxième électrodes en regard, le gaz à ioniser passant entre lesdites électrodes et d'un filament conducteur relié par une première extrémité à la première électrode et par une deuxième extrémité à la deuxième électrode et situé entre lesdites électrodes.More specifically, the invention relates to a device usable for ionizing a gas comprising a cathode and an opposite anode, the gas to be ionized successively passing through the cathode and the anode, characterized in that the cathode is formed of a first and a second facing electrodes, the gas to be ionized passing between said electrodes and a conductive filament connected by a first end to the first electrode and by a second end to the second electrode and located between said electrodes.

De façon avantageuse, les première et deuxième électrodes sont des demi-cylindres disposés en regard de façon à former un cylindre fendu selon deux génératrices opposées et le filament est relié aux extrémités de sortie du gaz à ioniser des première et deuxième électrodes.Advantageously, the first and second electrodes are half-cylinders arranged opposite so as to form a split cylinder according to two opposite generatrices and the filament is connected to the outlet ends of the gas to be ionized from the first and second electrodes.

De préférence, le filament est enroulé en hélice suivant un cône dont l'axe est confondu avec l'axe longitudinal du cylindre créé par les première et deuxième électrodes, le gaz à ioniser parcourant ce cône à partir de son sommet. Ce cône a un angle au sommet allant par exemple de 7 à 15°.Preferably, the filament is wound in a helix along a cone, the axis of which coincides with the longitudinal axis of the cylinder created by the first and second electrodes, the gas to be ionized passing through this cone from its top. This cone has an angle at the top ranging for example from 7 to 15 °.

Selon un mode préféré de réalisation de l'invention, les première et deuxième électrodes sont en titane et le filament est en tantale.According to a preferred embodiment of the invention, the first and second electrodes are made of titanium and the filament is of tantalum.

L'invention a aussi pour objet un duoplasmatron comportant un dispositif tel que décrit précédemment.The invention also relates to a duoplasmatron comprising a device as described above.

L'invention a également pour objet un procédé d'utilisation du dispositif utilisable pour ioniser un gaz, ce procédé est caractérisé en ce que ce dispositif fonctionnant en cathode froide, une différence de potentiel est appliquée entre l'anode et les première et deuxième électrodes.The invention also relates to a method of using the device which can be used to ionize a gas, this method is characterized in that this device operating as a cold cathode, a potential difference is applied between the anode and the first and second electrodes .

Selon une variante du procédé d'utilisation du dispositif utilisable pour ioniser un gaz, celui-ci fonctionnant en cathode chaude, une première différence de potentiel est appliquée entre l'anode et les première et deuxième électrodes, et une deuxième différence de potentiel est appliquée entre les première et deuxième extrémités du filament.According to a variant of the method of using the device which can be used to ionize a gas, the latter operating as a hot cathode, a first potential difference is applied between the anode and the first and second electrodes, and a second potential difference is applied between the first and second ends of the filament.

D'autres caractéristiques et avantages de l'invention ressortiront mieux de la description qui va suivre, donnée à titre purement illustratif et non limitatif en référence aux figures annexées dans lesquelles :

  • - la figure 1, déjà décrite, représente schématiquement en coupe longitudinale un duoplasmatron à cathode froide de type connu,
  • - la figure 2 représente schématiquement une cathode conforme à l'invention utilisable en cathode chaude ou en cathode froide, et
  • - la figure 3 représente le filament de la cathode conforme à l'invention enroulée en hélice suivant un cône.
Other characteristics and advantages of the invention will emerge more clearly from the description which follows, given purely by way of nonlimiting illustration with reference to the appended figures in which:
  • FIG. 1, already described, schematically represents in longitudinal section a duoplasmatron with a cold cathode of known type,
  • FIG. 2 schematically represents a cathode according to the invention usable as a hot cathode or as a cold cathode, and
  • - Figure 3 shows the filament of the cathode according to the invention wound in a helix following a cone.

La cathode 30 représentée figure 2 est constituée de deux électrodes 31, 33 en regard et d'un filament conducteur 35 relié par une de ses extrémités 32 à l'électrode 31 et par son autre extrémité 34 à l'électrode 33.The cathode 30 shown in FIG. 2 is made up of two opposite electrodes 31, 33 and a conductive filament 35 connected by one of its ends 32 to the electrode 31 and by its other end 34 to the electrode 33.

Les deux électrodes 31 et 33 sont constituées respectivement par un demi-cylindre en regard l'un de l'autre de façon à former un cylindre fendu selon deux génératrices opposées, le gaz à ioniser traversant ce cylindre. Ce cylindre a par exemple un diamètre de 40 mm et une longueur de 70 mm.The two electrodes 31 and 33 are respectively constituted by a half-cylinder opposite one another so as to form a split cylinder according to two opposite generatrices, the gas to be ionized passing through this cylinder. This cylinder has for example a diameter of 40 mm and a length of 70 mm.

Le filament 35 est enroulé en hélice (voir figure 3) suivant un cône d'angle au sommet compris entre des valeurs de l'ordre de 7 à 15° et une longueur par exemple de 15 mm. Ce filament est situé aux extrémités de sortie du gaz des première et deuxième électrodes et il est parcouru par le gaz à partir du sommet du cône qu'il forme.The filament 35 is wound in a helix (see FIG. 3) along a cone with an angle at the apex comprised between values of the order of 7 to 15 ° and a length for example of 15 mm. This filament is located at the gas outlet ends of the first and second electrodes and it is traversed by the gas from the top of the cone that it forms.

Les deux électrodes sont de préférence en titane. En effet, le titane permet d'obtenir un faisceau d'ions plus pur que le nickel employé dans l'art antérieur.The two electrodes are preferably made of titanium. In fact, titanium makes it possible to obtain a purer ion beam than the nickel used in the prior art.

D'autre part, le filament est de façon avantageuse en tantale, celui-ci ayant une durée de vie de 5 à 10 fois supérieure à celle d'un filament en tungstène employé dans les mêmes conditions. En effet, l'usure du filament est essentiellement due à la pulvérisation cathodique, or la pulvérisation cathodique du tungstène est supérieure à celle du tantale. Par ailleurs, la résistivité du tantale étant supérieure à celle du tungstène, on utilise un filament de diamètre environ 0,7 mm au lieu de 0,5 mm pour un filament en tungstène de l'art antérieur.On the other hand, the filament is advantageously in tantalum, the latter having a lifetime of 5 to 10 times longer than that of a tungsten filament used under the same conditions. Indeed, the wear of the filament is essentially due to sputtering, or the sputtering of tungsten is greater than that of tantalum. Furthermore, the resistivity of tantalum being greater than that of tungsten, a filament with a diameter of approximately 0.7 mm is used instead of 0.5 mm for a tungsten filament of the prior art.

L'axe du cône constitué par le filament est confondu avec l'axe longitudinal du cylindre créé par les deux électrodes 31, 33 ; cette disposition particulière permet d'augmenter également la durée de vie du filament d'un facteur de l'ordre de 4 à 5.The axis of the cone formed by the filament coincides with the longitudinal axis of the cylinder created by the two electrodes 31, 33; this particular arrangement also makes it possible to increase the life of the filament by a factor of the order of 4 to 5.

Ainsi, par exemple, pour un filament en tantale parcouru par du xénon qui est un gaz ayant un fort taux de pulvérisation la durée de vie du filament dépasse un mois.Thus, for example, for a tantalum filament traversed by xenon which is a gas having a high sputtering rate, the lifetime of the filament exceeds one month.

D'autre part, un générateur de tension 37 et un interrupteur 39 en série sont connectés entre les deux extrémités du filament.On the other hand, a voltage generator 37 and a switch 39 in series are connected between the two ends of the filament.

Dans le cas de l'utilisation de cette cathode 30 dans un duoplasmatron, elle est montée sur le support 2 de la figure 1 à la place de la cathode 1. La partie inférieure des électrodes 31 et 33 étant reliée au filament 35.In the case of the use of this cathode 30 in a duoplasmatron, it is mounted on the support 2 of FIG. 1 in place of the cathode 1. The lower part of the electrodes 31 and 33 being connected to the filament 35.

Les première et deuxième électrodes et le support sont réalisés de préférence en une pièce unique mais bien entendu les première et deuxième électrodes peuvent être également rapportées sur le support. Ce support est de façon avantageuse également en titane.The first and second electrodes and the support are preferably made in a single piece but of course the first and second electrodes can also be attached to the support. This support is also advantageously made of titanium.

Une différence de potentiel Va-Vc est appliquée entre les électrodes 31 et 33 et l'anode 5 par le générateur de tension 23 et une tension Vi est appliquée comme précédemment à l'électrode intermédiaire 3.A potential difference Va-Vc is applied between the electrodes 31 and 33 and the anode 5 by the voltage generator 23 and a voltage Vi is applied as previously to the intermediate electrode 3.

Lorsque l'interrupteur 39 est fermé, une tension Vs est appliquée aux extrémités du filament par le générateur 37. Dans ce cas, le duoplasmatron fonctionne en cathode chaude. En effet, le filament parcouru par un courant dégage de la chaleur par effet Joule. Ce filament émet alors des électrons qui vont ioniser des atomes de gaz. Les ions formés vont être confinés comme décrit précédemment dans des champs électriques et magnétique avant d'être extraits du duoplasmatron.When the switch 39 is closed, a voltage Vs is applied to the ends of the filament by the generator 37. In this case, the duoplasmatron operates as a hot cathode. Indeed, the filament traversed by a current gives off heat by the Joule effect. This filament then emits electrons which will ionize gas atoms. The ions formed will be confined as described above in electric and magnetic fields before being extracted from the duoplasmatron.

La différence de potentiel Va-Vc appliquée entre les première et deuxième électrodes et l'anode est de l'ordre de quelques dizaines de volts, la tension Vs appliquée entre les deux extrémités du filament est de l'ordre de quelque 0,1 volt et le courant circulant dans le filament est de l'ordre de quelques Ampères.The potential difference Va-Vc applied between the first and second electrodes and the anode is of the order of a few tens of volts, the voltage Vs applied between the two ends of the filament is of the order of some 0.1 volts and the current flowing in the filament is of the order of a few amperes.

En fonctionnement en cathode chaude, les électrons sont émis essentiellement par le filament. La quantité d'électrons émis par la première et la deuxième électrodes est très faible du fait de la différence de potentiel Va-Vc faible.In operation as a hot cathode, the electrons are mainly emitted by the filament. The quantity of electrons emitted by the first and second electrodes is very small due to the small potential difference Va-Vc.

Lorsque l'interrupteur 39 est ouvert, la tension appliquée au filament 35 est nulle, aucun courant ne circule dans le filament : le duoplasmatron fonctionne en cathode froide. Dans ce cas, pour que les première et deuxième électrodes émettent suffisamment d'électrons pour ioniser le gaz, une différente de potentiel Va-Vc de l'ordre de 300 à 500 volts est appliquée entre l'anode et la première et la deuxième électrodes.When the switch 39 is open, the voltage applied to the filament 35 is zero, no current flows in the filament: the duoplasmatron operates as a cold cathode. In this case, so that the first and second electrodes emit enough electrons to ionize the gas, a different potential Va-Vc of the order of 300 to 500 volts is applied between the anode and the first and second electrodes .

On a décrit l'utilisation d'une cathode conforme à l'invention servant de cathode froide ou de cathode chaude dans un duoplasmatron, mais bien entendu, l'invention s'applique à toutes les sources d'ions utilisant une cathode froide ou chaude.We have described the use of a cathode according to the invention serving as a cold cathode or a hot cathode in a duoplasmatron, but of course, the invention applies to all ion sources using a cold or hot cathode .

Par ailleurs, les dispositifs électriques associés au duoplasmatron et en particulier à la cathode conforme à l'invention décrits précédemment sont très simplifiés, d'autres dispositifs plus complexes peuvent être utilisés sans sortir du cadre de l'invention tel que défini dans la revendications.Furthermore, the electrical devices associated with the duoplasmatron and in particular with the cathode according to the invention described above are very simplified, other more complex devices can be used without departing from the scope of the invention as defined in the claims.

Claims (9)

1. Apparatus usable for ionizing a gas comprising a facing cathode (30) and anode (5), the gas to be ionized successively traversing the cathode and the anode, characterized in that the cathode (30) is formed from first and second electrodes (31, 33), which are semi-cylinders arranged in facing manner so as to form a cylinder slit along two of its opposite generatrixes, the gas to be ionized passing between the said electrodes in a direction essentially parallel to the axis of the cylinder, and a conductive filament (35) connected by a first end (32) to the first electrode (31) and by a second end (34) to the second electrode (33) and positioned between said electrodes, and in that the apparatus comprises a first voltage source (23) connected on the one hand to the anode (5) and on the other to the first and second electrodes (31, 33) of the cathode (30) and a second voltage source (37) connected by a switch (39) to the first and second electrodes (31, 33).
2. Apparatus according to claim 1, characterized in that the filament (35) is connected to the outlet ends for the gas to be ionized of the first and second electrodes (31, 33).
3. Apparatus according to either of the claims 1 and 2, characterized in that the filament (35) is helically wound to form a cone, whose axis coincides with the longitudinal axis of the cylinder, the gas to be ionized traversing said cone from its apex.
4. Apparatus according to claim 3, characterized in that the cone has an apex angle of 7 to 15°.
5. Apparatus according to any one of the claims 1 to 4, characterized in that the first and second electrodes (31, 33) are made from titanium.
6. Apparatus according to any one of the claims 1 to 5, characterized in that the filament (35) is made from tantalum.
7. Duoplasmatron, characterized in that it incorporates an apparatus according to any one of the claims 1 to 6.
8. Process for the use of the apparatus usable for ionizing a gas in accordance with any one of the claims 1 to 6, characterized in that the apparatus functions as a cold cathode, a potential difference being applied between the anode (5) on the one hand and the first and second electrodes (31, 33) on the other.
9. Process for the use of the apparatus usable for ionizing a gas according to any one of the claims 1 to 6, characterized in that the apparatus functions as a hot cathode and a first potential difference is applied between the anode on the one hand and the first and second electrodes (31, 33) on the other and a second potential difference is applied between the first and second ends of the filament (32, 34).
EP87400738A 1986-04-09 1987-04-03 Device, particularly a duoplasmatron, for ionizing a gas, and method of using this device Expired - Lifetime EP0241362B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8605064 1986-04-09
FR8605064A FR2597286B1 (en) 1986-04-09 1986-04-09 DEVICE AND PARTICULARLY DUOPLASMATRON FOR USE IN IONIZING A GAS COMPRISING A CATHODE AS A HOT OR COLD CATHODE AND METHOD OF USING THE SAME

Publications (2)

Publication Number Publication Date
EP0241362A1 EP0241362A1 (en) 1987-10-14
EP0241362B1 true EP0241362B1 (en) 1992-07-29

Family

ID=9334059

Family Applications (1)

Application Number Title Priority Date Filing Date
EP87400738A Expired - Lifetime EP0241362B1 (en) 1986-04-09 1987-04-03 Device, particularly a duoplasmatron, for ionizing a gas, and method of using this device

Country Status (4)

Country Link
US (1) US4752667A (en)
EP (1) EP0241362B1 (en)
DE (1) DE3780675T2 (en)
FR (1) FR2597286B1 (en)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5257500A (en) * 1992-07-27 1993-11-02 General Electric Company Aircraft engine ignition system
DE102006027853B4 (en) * 2006-06-16 2012-06-14 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Method and apparatus for generating a plasma and use thereof
US7550741B2 (en) * 2006-10-18 2009-06-23 Sanns Jr Frank Inertial electrostatic confinement fusion
CA2836816C (en) 2011-05-23 2018-02-20 Schmor Particle Accelerator Consulting Inc. Particle accelerator and method of reducing beam divergence in the particle accelerator
US20160133426A1 (en) 2013-06-12 2016-05-12 General Plasma, Inc. Linear duoplasmatron

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3164739A (en) * 1960-07-20 1965-01-05 Vakutronik Veb Ion source of a duo-plasmatron
US3513351A (en) * 1968-06-26 1970-05-19 Atomic Energy Commission Duoplasmatron-type ion source including a gas reservoir
GB1243483A (en) * 1969-06-12 1971-08-18 Hughes Aircraft Co An ion source
US3705998A (en) * 1972-01-27 1972-12-12 Us Army Negative ion generator
US4596945A (en) * 1984-05-14 1986-06-24 Hughes Aircraft Company Modulator switch with low voltage control
US4659899A (en) * 1984-10-24 1987-04-21 The Perkin-Elmer Corporation Vacuum-compatible air-cooled plasma device

Also Published As

Publication number Publication date
DE3780675D1 (en) 1992-09-03
US4752667A (en) 1988-06-21
FR2597286B1 (en) 1988-06-10
EP0241362A1 (en) 1987-10-14
FR2597286A1 (en) 1987-10-16
DE3780675T2 (en) 1993-02-04

Similar Documents

Publication Publication Date Title
EP0200651B1 (en) Triode-type ion source with a single high frequency ionization chamber and with multiple magnetic confinement
EP1496727B1 (en) Closed electron drift plasma accelerator
EP3344873B1 (en) Gridded ion thruster with integrated solid propellant
FR2501725A1 (en) PROCESS AND DEVICE FOR EVAPORATING A VACUUM MATERIAL
FR2797372A1 (en) PROCESS FOR PRODUCING ELEMENTARY PLASMAS WITH A VIEW TO CREATING A UNIFORM PLASMA FOR A USING SURFACE AND DEVICE FOR PRODUCING SUCH A PLASMA
FR2887072A1 (en) IMPROVED SPECTOGRAPHIC SYSTEM WITH PLASMA SOURCE
FR2691834A1 (en) Method for producing and initiating a low voltage discharge, vacuum treatment plant and cathode chamber therefor, and uses of the method.
EP0238397A1 (en) Electronic cyclotron resonance ion source with coaxial injection of electromagnetic waves
EP0241362B1 (en) Device, particularly a duoplasmatron, for ionizing a gas, and method of using this device
WO2009027156A1 (en) System for analysing a low pressure gas by optical emission spectroscopy
FR2660999A1 (en) IMPROVED IONIZATION MANOMETER FOR VERY LOW PRESSURES.
WO2006024775A1 (en) Ion trap with longitudinal permanent magnet and mass spectrometer using same
FR2637725A1 (en) DEVICE FOR EXTRACTING AND ACCELERATING IONS LIMITING THE REACCELERATION OF SECONDARY ELECTRONS IN A HIGH-FLOW SEALED NEUTRONIC TUBE
FR2637726A1 (en) SEALED NEUTRON TUBE EQUIPPED WITH A MULTICELLULAR ION SOURCE WITH MAGNETIC CONTAINMENT
FR2641899A1 (en) ELECTRON GUN WITH AN ACTIVE DEVICE PRODUCING A MAGNETIC FIELD IN THE VICINITY OF THE CATHODE
FR2468203A1 (en) ELECTRIC DISCHARGE APPARATUS WITH HOLLOW CATHODE
EP0532411B1 (en) Electron cyclotron resonance ion source with coaxial injection of electromagnetic waves
EP0350358A1 (en) Electron gun and electron tube including such an electron gun
EP0104973A1 (en) Apparatus for ionizing a material by high-temperature heating
EP0362953A1 (en) Sealed neutron tube provided with an ion source with electrostatic confinement
EP0483004B1 (en) Electron cyclotron resonance ion source for highly charged ions with polarisable probe
EP2311061B1 (en) Electron cyclotron resonance ion generator
FR2714966A1 (en) Ionization gauge with a microtip cathode.
EP0300932B1 (en) Electron source
EP0002406B1 (en) Ion source, in particular for an ion implantation device

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): CH DE GB LI

17P Request for examination filed

Effective date: 19880316

17Q First examination report despatched

Effective date: 19891117

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): CH DE GB LI

REF Corresponds to:

Ref document number: 3780675

Country of ref document: DE

Date of ref document: 19920903

GBT Gb: translation of ep patent filed (gb section 77(6)(a)/1977)
PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Effective date: 19930403

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: LI

Effective date: 19930430

Ref country code: CH

Effective date: 19930430

PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed
GBPC Gb: european patent ceased through non-payment of renewal fee

Effective date: 19930403

REG Reference to a national code

Ref country code: CH

Ref legal event code: PL

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Effective date: 19940101