EP3136418A1 - Ion-generating device with electron cyclotron resonance - Google Patents

Abstract

The invention relates to an electron cyclotron resonance ion generating device comprising: a metal tube (1) subjected to a first potential (V1) and pierced by: a first cavity forming a plasma chamber (3) intended to contain a plasma; a second cavity forming a waveguide (4) arranged to inject a high frequency wave into the plasma chamber (3), extraction means (12) comprising an upstream end (15) connected to the plasma chamber (3) and a downstream end (16) intended to be connected to an ion transport line (22), the connection flange (21) being subjected to a second potential (V 2), means for generating (8) a magnetic field, - a ceramic tube (17) in contact with the metal tube (1), the ceramic tube (17) surrounding the metal tube (1) and at least a portion of the extraction means (12).

Description

TECHNICAL AREA

The present invention relates to an electron cyclotron resonance ion generating device, and more specifically to an ECR or "electron cyclotron resonance" type ion source, for electron cyclotron resonance.

STATE OF THE PRIOR ART

In a known manner, electronic cyclotron resonance devices, also called ECR sources, are used to produce mono-charged or multicharged ions (that is, atoms to which one or more electrons have been torn off).

• une chambre plasma destinée à contenir un plasma ;
• des moyens de génération d'un champ magnétique dans la chambre plasma, la chambre plasma étant à un premier potentiel, les moyens de génération d'un champ magnétique étant à un deuxième potentiel,
• des moyens de propagation d'une onde haute-fréquence à l'intérieur de la chambre plasma,
• une structure isolante, la structure isolante présentant une extrémité amont qui est au premier potentiel et une extrémité aval qui est au deuxième potentiel, les moyens de génération d'un champ magnétique étant situés en aval de la structure isolante.

The document FR2969371 discloses an electronic cyclotron resonance device comprising:

• a plasma chamber for containing a plasma;
• means for generating a magnetic field in the plasma chamber, the plasma chamber being at a first potential, the means for generating a magnetic field being at a second potential,
• means for propagating a high-frequency wave inside the plasma chamber,
• an insulating structure, the insulating structure having an upstream end which is at the first potential and a downstream end which is at the second potential, the means for generating a magnetic field being located downstream of the insulating structure.

This device is particularly advantageous because it is very compact due to the presence of the insulating structure upstream of the plasma chamber, which reduces the total length of the device. However, it is still relatively bulky.

Furthermore, this device comprises an accelerator tube for extracting the ions from the plasma chamber. For this, the accelerator tube comprises a plurality of electrodes whose shape is simplified compared to the devices of the prior art.

However, it has been found that the extraction of the ion beam is sometimes interrupted in this device. These interruptions in the extraction of the beam could be explained by the presence of Penning type discharges in the device. Indeed, during certain favorable combinations of the electric and magnetic field lines in the plasma chamber, Penning type discharges may appear. However, because of the vacuum level in the accelerator tube, particles can then be trapped between the electrodes. These particles then acquire energy and describe circular trajectories oscillating with a greater or lesser amplitude depending on the electric and magnetic field levels. These particles generally end up striking the electrodes of the accelerator tube which creates a particle flow at the high voltage power supply of the device, which causes a voltage drop. The ion beam can no longer be removed from the plasma chamber.

Furthermore, the second electrode of this device of the prior art, also called "intermediate electrode" because it is biased to an intermediate potential, has a complex geometry to avoid electrical breakdown in the accelerator tube.

SUMMARY OF THE INVENTION

The invention aims to overcome the drawbacks of the state of the art by providing a more compact electronic cyclotron resonance ion generating device than those of the prior art.

The invention also aims to propose a device in which the risk of Penning type discharge is limited.

The invention also aims to provide a simpler device than those of the prior art, in which the risk of electrical breakdown is also reduced.

• un tube métallique, le tube métallique étant destiné à être placé à un premier potentiel, le tube métallique étant percé par :
  • o une première cavité formant une chambre plasma destinée à contenir un plasma;
  • o une deuxième cavité reliée à la première cavité, la deuxième cavité formant un guide d'onde agencé pour injecter une onde haute fréquence dans la chambre plasma,
• des moyens d'extraction agencés pour extraire des ions de la chambre plasma, les moyens d'extraction comportant une extrémité amont connectée à la chambre plasma et une extrémité avale pourvue d'une bride de connexion destinée à être connectée à une ligne de transport des ions, la bride de connexion étant destinée à être placée à un deuxième potentiel différent du premier potentiel,
• des moyens de génération d'un champ magnétique configurés pour générer un champ magnétique dans la chambre plasma,
• une structure isolante agencée pour isoler électriquement le tube métallique de l'extrémité avale des moyens d'extraction, la structure isolante comportant un tube céramique en contact avec le tube métallique, le tube céramique entourant le tube métallique et au moins une partie des moyens d'extraction.

To do this, a first aspect of the invention relates to an electronic cyclotron resonance ion generator device comprising:

• a metal tube, the metal tube being intended to be placed at a first potential, the metal tube being pierced by:
  • a first cavity forming a plasma chamber intended to contain a plasma;
  • a second cavity connected to the first cavity, the second cavity forming a waveguide arranged to inject a high frequency wave into the plasma chamber,
• extraction means arranged to extract ions from the plasma chamber, the extraction means comprising an upstream end connected to the plasma chamber and a downstream end provided with a connection flange intended to be connected to a transmission line of the ions, the connection flange being intended to be placed at a second potential different from the first potential,
• means for generating a magnetic field configured to generate a magnetic field in the plasma chamber,
• an insulating structure arranged to electrically isolate the metal tube from the downstream end of the extraction means, the insulating structure comprising a ceramic tube in contact with the metal tube, the ceramic tube surrounding the metal tube and at least a part of the 'extraction.

In this document, the terms "upstream" and "downstream" are used with respect to the direction of propagation of an ion beam at the outlet of the plasma chamber.

The electron cyclotron resonance ion generating device according to the first aspect of the invention is particularly advantageous because it is more compact than those of the prior art since the insulating structure is now in contact with the metal tube in which are hollowed out the waveguide and the plasma chamber. There is therefore no air gap between the insulating structure and the waveguide, in contrast to the devices of the prior art. In addition, this geometry makes it possible to have a limited risk of breakdown in the device, as well as a risk of limited Penning discharge. The extraction of the ion beam is therefore more reliable in the device according to the first aspect of the invention. In addition, by removing the air gap between the insulating structure and the waveguide, it eliminates the need for a pumping sleeve, which further simplifies the device.

The device according to the first aspect of the invention may also have one or more of the following features taken independently or in any technically possible combination.

• une première électrode solidaire du tube métallique, la première électrode étant destinée à être placée au premier potentiel,
• une troisième électrode en aval de la première électrode, la troisième électrode étant destinée à être placée au deuxième potentiel ;
• une quatrième électrode en aval de la troisième électrode, la quatrième électrode étant destinée à être placée à un potentiel négatif.

Advantageously, the extraction means comprise at least:

• a first electrode integral with the metal tube, the first electrode being intended to be placed at the first potential,
• a third electrode downstream of the first electrode, the third electrode being intended to be placed at the second potential;
• a fourth electrode downstream of the third electrode, the fourth electrode being intended to be placed at a negative potential.

Advantageously, the extraction means further comprise a second electrode disposed between the first and the third electrode, the second electrode being intended to be placed at a variable potential, the second electrode being able to be connected to means for adjusting the potential. .

Advantageously, the second electrode is connected to the ceramic tube, the second electrode having an annular shape. The second electrode therefore has a simpler geometry than in the devices of the prior art. This simplification of the geometry of the second electrode is made possible by the fact that the air gap between the insulating structure and the walls of the plasma chamber and the waveguide has been eliminated.

Advantageously, the device further comprises a ceramic ring interposed between the first and the second electrode. This ceramic ring keeps the first and the second electrode in place while reducing the risk of breakdown in the extraction means.

• une prise de connexion située à l'extérieur du tube céramique;
• un conduit de connexion longitudinal traversant longitudinalement le tube céramique, le conduit de connexion étant traversé par un fil métallique reliant la prise de connexion à la deuxième électrode.

Advantageously, the device comprises connection means able to connect the second electrode to means for adjusting the potential, the connection means comprising:

• a connection socket located outside the ceramic tube;
• a longitudinal connecting conduit longitudinally passing through the ceramic tube, the connecting conduit being traversed by a wire connecting the connection socket to the second electrode.

According to a first embodiment, the connection socket is located on a lateral outer wall of the ceramic tube, the connection means further comprising a radial connection duct connecting the longitudinal connection duct to the connection socket.

According to a second embodiment, the device further comprises an inlet flange, the connection socket being located on an outer wall of the inlet flange.

According to one embodiment, the ceramic tube comprises two concentric tubular parts. The longitudinal connection duct may thus be formed by a groove dug in one of the two tubular portions. The groove is preferably hollowed in the inner tubular portion. The longitudinal connection duct is thus easier to achieve, since it can be achieved by digging a groove on an outer surface of the inner tubular portion of the ceramic tube.

According to another embodiment, the ceramic tube is formed by an integral piece.

Advantageously, the extraction means further comprise a fifth electrode downstream of the fourth electrode, the fifth electrode being intended to be placed at the second potential.

Advantageously, the connection flange is fixed on the ceramic tube. Indeed, since the device is more compact than those of the prior art, an additional support flange can be dispensed with and the device can be directly attached to the ion transport line via the connection flange. The device is thus shortened and the ion transport line is brought closer to the plasma chamber, which results in a better quality ion beam in the ion transport line.

• la diminution du diamètre de la structure isolante au niveau de la chambre plasma grâce au fait que la structure isolante est maintenant en contact avec le tube formant le guide d'onde et la chambre plasma, et par
• la suppression de la manchette de pompage.

Advantageously, the device further comprises means for generating a magnetic field arranged to generate a magnetic field in the plasma chamber, the means for generating the magnetic field surrounding the ceramic tube, the magnetic field generating means being located at the level of the magnetic field. of the plasma chamber. Thus, unlike the devices of the prior art, the magnetic field generation means are no longer located at the level of the extraction means but at the level of the plasma chamber. This change was made possible by:

• the reduction of the diameter of the insulating structure at the level of the plasma chamber by virtue of the fact that the insulating structure is now in contact with the tube forming the waveguide and the plasma chamber, and by
• the removal of the pumping cuff.

• de bénéficier directement dans la chambre plasma du champ magnétique généré par les moyens de génération, au contraire des dispositifs de l'art antérieur dans lesquels on n'utilisait pas directement le champ magnétique généré mais le champ de fuite généré puisque les moyens de génération étaient décalés par rapport à la chambre plasma. La génération du champ magnétique dans le dispositif selon l'invention est donc plus efficace que dans les dispositifs de l'art antérieur ;
• de pouvoir connecter la ligne de transport des ions directement en sortie de la chambre plasma, ce qui n'était pas le cas dans les dispositifs de l'art antérieur puisque l'espace en sortie de la chambre plasma était occupé par les moyens de génération du champ magnétique. On obtient donc un faisceau de meilleure qualité dans la ligne de transport des ions puisque celle-ci est plus proche de la chambre plasma. Ainsi, le faisceau peut être dès son extraction guidée par des moyens de focalisation et de déviation.

This new position of the means for generating a magnetic field is particularly advantageous because it allows in particular:

• to benefit directly in the plasma chamber of the magnetic field generated by the generating means, in contrast to the devices of the prior art in which the generated magnetic field was not used directly but the leakage field generated since the generation means were offset from the plasma chamber. The generation of the magnetic field in the device according to the invention is therefore more efficient than in the devices of the prior art;
• to be able to connect the ion transport line directly at the outlet of the plasma chamber, which was not the case in the devices of the prior art since the space at the outlet of the plasma chamber was occupied by the generation means of the magnetic field. A beam of better quality is thus obtained in the ion transport line since it is closer to the plasma chamber. Thus, the beam can be as soon as its extraction guided by means of focusing and deflection.

Advantageously, the metal tube is pierced by a conduit arranged to allow the injection of a gas from outside the metal tube into the plasma chamber.

BRIEF DESCRIPTION OF THE FIGURES

• La figure 1, une vue en coupe d'un dispositif selon un mode de réalisation de l'invention ;
• La figure 2, une vue en perspective du dispositif de la figure 1 en coupe;
• La figure 3, une vue en coupe du dispositif de la figure 1 sur lequel on a représenté le potentiel auquel est portée chaque zone du dispositif ;
• La figure 4, une vue agrandie en coupe d'une partie du dispositif de la figure 1 ;
• La figure 5, une vue en coupe d'un dispositif selon un autre mode de réalisation de l'invention.

Other characteristics and advantages of the invention will emerge on reading the detailed description which follows, with reference to the appended figures, which illustrate:

• The figure 1 , a sectional view of a device according to one embodiment of the invention;
• The figure 2 , a perspective view of the device of the figure 1 sectional;
• The figure 3 , a sectional view of the device of the figure 1 on which is represented the potential to which each zone of the device is carried;
• The figure 4 , an enlarged sectional view of a part of the device of the figure 1 ;
• The figure 5 , a sectional view of a device according to another embodiment of the invention.

For the sake of clarity, identical or similar elements are identified by identical reference signs throughout the figures.

DETAILED DESCRIPTION OF AT LEAST ONE EMBODIMENT

An electron cyclotron resonance ion generating device according to an embodiment of the invention will now be described with reference to Figures 1 to 5 .

This device comprises a metal tube 1. The metal tube 1 extends along a reference axis 2. The metal tube 1 has a symmetry of revolution with respect to the reference axis 2. The metal tube 1 has an upstream end 5 and a downstream end 6. The metal tube 1 may for example be made of copper.

The metal tube 1 comprises a first cavity which forms a plasma chamber 3 intended to contain a plasma.

The metal tube 1 also comprises a second cavity which forms a waveguide 4. The waveguide 4 is intended to be traversed by a high frequency wave so as to inject it into the plasma chamber 3. A high-frequency wave frequency is a wave that has a frequency between 1 and 15 GHz. The waveguide 4 comprises an upstream end 10 intended to be connected to means for generating a high frequency wave and a downstream end 11 which opens into the plasma chamber 3. The plasma chamber 3 and the waveguide 4 are formed by a piece in one piece, which simplifies the structure of the device.

The metal tube 1 is also pierced by a conduit 7 which preferably connects the plasma chamber 3 to the upstream end of the metal tube. This duct 7 makes it possible to inject a gas into the plasma chamber 3 from outside the device.

The device also comprises means 8 for generating a magnetic field in the plasma chamber 3. These generation means 8 may for example comprise one or more coil (s) or permanent magnets.

In operation, the plasma chamber 3 is supplied with atoms via the conduit 7. The waveguide 4 conducts a high frequency wave in the plasma chamber 3 while the generation means 8 generate a magnetic field in the plasma chamber 3. The coupling of this high-frequency wave and this magnetic field makes it possible to obtain an electron cyclotron resonance in the plasma chamber 3. The atoms present in the plasma chamber 3 are then ionized and a plasma is obtained in the plasma chamber 3. For this purpose, , the magnetic field in the plasma chamber 3 must have a module B _ecr that satisfies the condition (1) of electronic cyclotron resonance: $$\begin{array}{l}\mathrm{<figure-callout\; id="1"\; label="condition"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">condition</figure-callout>}\left(\mathrm{1}\right)\mathrm{electronic\; cyclotron\; resonance}\\ {\mathrm{B}}_{\mathrm{ecr}}=\mathrm{f}\mathrm{.2}\mathrm{\pi m}/\mathrm{e}\end{array}$$

With e the charge of the electron, m the mass of the electron and f the frequency of the high frequency wave injected into the plasma chamber.

In addition, to allow the formation of ions in the plasma chamber 3, the plasma chamber 3 is placed at a first potential V ₁ . For this, the entire metal tube 1 is placed at this first potential V ₁ .

The device also comprises extraction means 12 configured to extract ions from the plasma chamber 3. The extraction means 12 comprise an upstream end 15 connected to the plasma chamber 3 and a downstream end 16 intended to be connected to a line The upstream end 15 of the extraction means is therefore intended to be placed at the same potential as the plasma chamber 3, that is to say at the first potential V ₁ . The downstream end 16 of the extraction means is intended to be placed at the same potential as the ion transport line 22. The downstream end 16 of the extraction means is therefore intended to be placed at a second potential V ₂ different of the first potential V ₁ . The potential difference between the first potential V ₁ and the second potential V ₂ is preferably between 1 and 200 kV. The second potential V ₂ is advantageously close to 0 V.

• Une première électrode 13a disposée au niveau de l'extrémité avale 14 de la chambre plasma 3. Plus précisément, la première électrode 13a forme de préférence un anneau métallique solidaire de l'extrémité avale 14 de la chambre plasma 3. La première électrode 13a est percée par un orifice par lequel peuvent passer les ions qui sortent de la chambre plasma 3. La première électrode 13a est destinée à être placée au premier potentiel V₁, c'est-à-dire au même potentiel que la chambre plasma 3;
• Une deuxième électrode 13b disposée en aval de la première électrode 13a. La deuxième électrode 13b est de préférence également formée d'un anneau métallique percé en son centre. La deuxième électrode 13b est destinée à être placée à un potentiel variable V_var pour ajuster finement les propriétés optiques du faisceau dès sa formation, au niveau du trou d'extraction ;
• Une troisième et une cinquième électrodes 13c, 13e disposées en aval de la deuxième électrode 13b. La troisième et la cinquième électrodes 13c, 13e sont destinées à être placées au deuxième potentiel V₂ ;
• Une quatrième électrode 13d disposées entre la troisième et la cinquième électrode 13c, 13e. La quatrième électrode 13d est destinée à être placée à un potentiel négatif V_neg par rapport au potentiel de la ligne de transport afin d'éviter que les électrons produits par ionisation du gaz résiduel dans la ligne de transport ne retournent en direction de la chambre plasma 3.

The extraction means 12 comprise:

• A first electrode 13a disposed at the downstream end 14 of the plasma chamber 3. More specifically, the first electrode 13a preferably forms a metal ring integral with the downstream end 14 of the plasma chamber 3. The first electrode 13a is pierced by an orifice through which can pass ions exiting the plasma chamber 3. The first electrode 13a is intended to be placed at the first potential V ₁ , that is to say at the same potential as the plasma chamber 3;
• A second electrode 13b disposed downstream of the first electrode 13a. The second electrode 13b is preferably also formed of a metal ring pierced at its center. The second electrode 13b is intended to be placed at a variable potential V _var to finely adjust the optical properties of the beam as soon as it is formed, at the level of the extraction hole;
• A third and a fifth electrode 13c, 13e disposed downstream of the second electrode 13b. The third and fifth electrodes 13c, 13e are intended to be placed at the second potential V ₂ ;
• A fourth electrode 13d disposed between the third and the fifth electrode 13c, 13e. The fourth electrode 13d is intended to be placed at a negative potential V _neg with respect to the potential of the transmission line in order to prevent the electrons produced by ionization of the residual gas in the transmission line from returning towards the plasma chamber. 3.

In order to isolate the parts of the device which are at different potentials, the device comprises an insulating structure. This insulating structure comprises a ceramic tube 17. This ceramic tube 17 may for example be made of alumina. The ceramic tube 17 is preferably fixed to the metal tube 1 via an annular inlet flange 28 secured to the metal tube 1. The ceramic tube 17 is preferably fixed by screws 29 to the inlet flange 28 preferably via metal inserts.

This ceramic tube 17 preferably comprises an inner tubular portion 18 which surrounds the metal tube 1. The inner tubular portion 18 is in contact with the metal tube 1, which makes it possible to have a less bulky device radially and which limits the risk breakdown in the device. The ceramic tube also has a concentric outer tubular portion 19 of the inner tubular portion 18. The outer tubular portion 19 preferably has a first cylindrical portion 19a that surrounds the inner tubular portion 18 and a second portion 19b that at least partially surrounds a portion of the electrodes of the extraction means 12. In this embodiment, the second cylindrical portion 19b surrounds the first and the second electrode 13a, 13b. The first electrode 13a is fixed on the metal tube 1. The second electrode 13b is fixed on the outer tubular part 19b. A ceramic ring 23 is interposed between the first and the second electrode 13a, 13b in order to isolate them electrically from each other and to avoid electrical breakdowns.

The device also comprises a connection flange 21 for fixing the device to an ion transport line 22. The connection flange 21 is fixed to the ceramic tube 17. The connection flange 21 preferably surrounds the third, fourth and fifth electrodes 13c, 13d, 13th. The third, fourth and fifth electrodes 13c, 13d, 13e are preferably fixed on an input flange of the transmission line 22. The third, fourth and fifth electrodes 13c, 13d, 13e can be separated from each other either by air gaps and insulated spacers, or by ceramic rings.

The device preferably comprises connection means able to connect the second electrode 13b to means for adjusting the potential. These connection means make it possible to polarize the second electrode 11b by connecting it to a high-voltage power supply.

• une prise de connexion 26 située sur une paroi extérieure latérale 27 du tube céramique 17;
• un conduit de connexion radial 36 réalisé dans le tube céramique 17 ;
• un conduit de connexion longitudinal 25 traversant longitudinalement le tube céramique 17.

According to one embodiment, the connection means comprise:

• a connection socket 26 located on a lateral outer wall 27 of the ceramic tube 17;
• a radial connection duct 36 made in the ceramic tube 17;
• a longitudinal connection duct 25 extending longitudinally through the ceramic tube 17.

• un premier orifice 33 creusé à travers l'anneau céramique 23 ;
• un deuxième orifice 31 creusé à travers une collerette 32 en saillie radiale du tube métallique 1 ;
• une rainure 30 creusée dans la paroi externe de la partie tubulaire interne 18. Le conduit de connexion est ainsi plus facile à réaliser ;

The longitudinal connection duct 25 is preferably formed by:

• a first orifice 33 dug through the ceramic ring 23;
• a second orifice 31 hollowed through a flange 32 projecting radially from the metal tube 1;
• a groove 30 dug in the outer wall of the inner tubular portion 18. The connection duct is thus easier to achieve;

The longitudinal connection duct 25 and the radial connection duct 36 are traversed by a metal wire 24 connecting the connection plug 26 to the second electrode 13b.

The wire 24 has a first end 34 pinched on the second electrode 11b by means of a screw. The wire 24 then passes successively into the first orifice 33, the second orifice 31 and the groove 30.

The wire therefore passes in particular the collar 32 of the metal tube 1. Or the wire 24 is not at the same potential as the flange 32. In fact, the wire is at the same potential as the second electrode 13b, while the flange is at the same potential as the plasma chamber. The wire is therefore at a potential between the first potential V ₁ and the second potential V ₂ while the flange 32 is at the first potential V ₁ . In order to avoid any electrical breakdown, an insulating sleeve 35 is inserted into the second orifice 31. The insulating sleeve 35 is therefore interposed between the flange 32 and the wire 24. The insulating sleeve 35 is preferably formed by a glass tube . This insulating sleeve 35 extends on either side of the second orifice 31, into the alumina parts on either side of the collar 32 to avoid any risk of contact between the wire 24 and the collar 32.

The means for generating the magnetic field 8 preferably surround the ceramic tube 17. More specifically, the means for generating the magnetic field 8 are preferably located at the plasma chamber 3. Thus, the magnetic field generation means 8 surround preferably the plasma chamber 3 in order to optimize the generation of the magnetic field at the level of the plasma chamber 3.

The device thus produced is compact longitudinally and radially. Indeed, the overall volume of the device has been divided by ten compared to the devices of the prior art. The device also has a risk of discharge type Penning and limited breakdown. In addition, it makes it possible to connect the ion transport line 22 directly at the outlet of the plasma chamber 3, which makes it possible to have a beam of better quality and more easily controllable in the ion transport line.

Naturally, the invention is not limited to the embodiments described with reference to the figures and variants could be envisaged without departing from the scope of the invention.

• une prise de connexion 26 située sur la bride d'entrée du dispositif;
• un conduit de connexion longitudinal 25 traversant longitudinalement le tube céramique 17.

So, with reference to the figure 5 , the ceramic tube 17 could be formed of an integral piece instead of being formed of two concentric tubular parts as shown in FIGS. Figures 1 to 4 . Moreover, again with reference to the figure 5 the connection means could comprise:

• a connection socket 26 located on the input flange of the device;
• a longitudinal connection duct 25 extending longitudinally through the ceramic tube 17.

Claims (14)

Ion generator device with electronic cyclotron resonance comprising: a metal tube (1), the metal tube (1) being intended to be placed at a first potential (V ₁ ), the metal tube (1) being pierced by: a first cavity forming a plasma chamber (3) intended to contain a plasma; a second cavity connected to the first cavity, the second cavity forming a waveguide (4) arranged to inject a high frequency wave into the plasma chamber (3), extraction means (12) arranged to extract ions from the plasma chamber (3), the extraction means (12) comprising an upstream end (15) connected to the plasma chamber (3) and a downstream end ( 16) provided with a connection flange (21) intended to be connected to an ion transport line (22), the connection flange (21) being intended to be placed at a second potential (V ₂ ) different from the first potential (V ₁ ), means for generating a magnetic field (8) configured to generate a magnetic field in the plasma chamber (3), an insulating structure arranged to electrically isolate the metal tube (1) from the downstream end (16) of the extraction means, the insulating structure comprising a ceramic tube (17) in contact with the metal tube (1), the tube ceramic (17) surrounding the metal tube (1) and at least a part of the extraction means (12). Device according to the preceding claim, wherein the extraction means (12) comprise at least: a first electrode (13a) integral with the metal tube (1), the first electrode (13a) being intended to be placed at the first potential (V ₁ ), a third electrode (13c) downstream of the first electrode (13b), the third electrode (13c) being intended to be placed at the second potential (V ₂ ); a fourth electrode (13d) downstream of the third electrode, the fourth electrode (13d) being intended to be placed at a negative potential (Vneg). Device according to the preceding claim, wherein the extraction means (12) further comprise a second electrode (13b) disposed between the first and the third electrode (13a, 13c), the second electrode (13b) being intended to be placed at a variable potential (V _var ), the second electrode (13b) being able to be connected to means for adjusting the potential. Device according to the preceding claim, wherein the second electrode (13b) is connected to the ceramic tube (17), the second electrode (13b) having an annular shape. Device according to one of claims 3 or 4, further comprising a ceramic ring (23) interposed between the first (13a) and the second electrode (13b). Device according to one of claims 3 to 5, the device comprising connecting means adapted to connect the second electrode (13b) to potential setting means, the connection means comprising: - a connection socket (26) located outside the ceramic tube (17); - A longitudinal connection duct (25) longitudinally passing through the ceramic tube (17), the connecting duct (25) being traversed by a wire (24) connecting the connection socket (26) to the second electrode (13b). Device according to claim 6, wherein the connection socket is located on a lateral outer wall (27) of the ceramic tube, the means for connection further comprising a radial connection duct (36) connecting the longitudinal connection duct to the connection socket (26). An apparatus according to claim 6, further comprising an inlet flange (28), the connection socket being located on an outer wall of the inlet flange. Device according to one of claims 1 to 8, wherein the ceramic tube (17) comprises two concentric tubular portions (18, 19). Device according to one of claims 1 to 8, wherein the ceramic tube (17) is formed by a piece in one piece. Device according to one of claims 2 to 10, wherein the extraction means further comprise a fifth electrode (13e) downstream of the fourth electrode (13c), the fifth electrode (13e) being intended to be placed in the second potential (V ₂ ). Device according to one of the preceding claims, wherein the connection flange (21) is fixed on the ceramic tube (17). Device according to one of the preceding claims, further comprising means for generating a magnetic field (8) arranged to generate a magnetic field in the plasma chamber (3), the means for generating the magnetic field surrounding the ceramic tube ( 17), the magnetic field generating means (8) being located at the plasma chamber (3). Device according to one of the preceding claims, wherein the metal tube (1) is pierced by a conduit (7) arranged to allow the injection of a gas from outside the metal tube (1) into the plasma chamber ( 3).

Images