(19)
(11)EP 3 314 988 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
17.06.2020 Bulletin 2020/25

(21)Application number: 16813365.0

(22)Date of filing:  21.06.2016
(51)Int. Cl.: 
B29C 64/205  (2017.01)
(86)International application number:
PCT/AU2016/000214
(87)International publication number:
WO 2016/205857 (29.12.2016 Gazette  2016/52)

(54)

PLASMA DRIVEN PARTICLE PROPAGATION APPARATUS AND PUMPING METHOD

PLASMAANGETRIEBENE PARTIKELAUSBREITUNGSVORRICHTUNG UND PUMPVERFAHREN

APPAREIL DE PROPAGATION DE PARTICULES ENTRAÎNÉES PAR PLASMA ET PROCÉDÉ DE POMPAGE


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 23.06.2015 AU 2015902421

(43)Date of publication of application:
02.05.2018 Bulletin 2018/18

(73)Proprietor: Aurora Labs Ltd
Bibra Lake, WA 6163 (AU)

(72)Inventor:
  • BUDGE, David
    Applecross, Western Australia 6153 (AU)

(74)Representative: Aronova 
Aronova S.A. BP 327 12, avenue du Rock'n'Roll
4004 Esch-sur-Alzette
4004 Esch-sur-Alzette (LU)


(56)References cited: : 
WO-A1-2014/096755
JP-A- H09 223 474
US-A- 5 821 705
US-A1- 2014 158 047
JP-A- H0 817 377
US-A- 5 578 831
US-A1- 2009 288 773
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description

    FIELD OF INVENTION



    [0001] The present invention relates to a plasma driven particle propagation apparatus and pumping method.

    BACKGROUND ART



    [0002] Three-dimensional (3D) printed parts result in a physical object being fabricated from a 3D digital image by laying down consecutive thin layers of material.

    [0003] Typically these 3D printed parts can be made by a variety of means, such as selective laser melting or sintering, which operate by having a powder bed onto which an energy beam is projected to melt the top layer of the powder bed so that it welds onto a substrate or a substratum. This melting process is repeated to add additional layers to the substratum to incrementally build up the part until completely fabricated.

    [0004] These printing methods are significantly time consuming to perform and it may take several days, or weeks, to fabricate a reasonable sized object. The problem is compounded for complex objects comprising intricate component parts. This substantially reduces the utility of 3D printers and is one of the key barriers currently impeding large-scale adoption of 3D printing by consumers and in industry.

    [0005] Power is also a significant limiting factor for existing 3D printing methods and devices.

    [0006] Whilst selective electron beam melting can be used as a powerful material fabrication method, this must typically be performed in a vacuum because interaction between charged particle beams and air molecules at atmospheric pressure causes dispersion and attenuation of the beams, significantly impairing their power. It is, therefore, known to use an assembly comprising a high-powered electron gun (for example, a 150kW electron gun) contained inside a first vacuum housing that is adjoined to a second vacuum housing containing a workpiece to be operated on. Such assemblies, however, result in low productivity rates due to the required pumping time for evacuating the housings. The practical size of the workpiece that may be contained inside the second housing is also substantially limited.

    [0007] It is, therefore, also known to use a plasma window in conjunction with a high-powered electron gun to perform material fabrication work. Such an assembly comprises an electron gun contained in a vacuum chamber, wherein the vacuum chamber is adjoined to a region of higher pressure (such as atmospheric pressure) containing a workpiece. A beam of charged particles is discharged from within the vacuum chamber and out of the chamber via a beam exit disposed in a wall of the chamber.

    [0008] A plasma interface is disposed at the beam exit comprising an elongate channel for bonding a plasma. A plasma-forming gas, such as helium, argon or nitrogen, that is highly ionized, is injected into the channel. Electrical currents are applied to a cathode and an anode disposed at opposite ends of the channel which causes a plasma to form and bond statically between the cathode and anode. The plasma serves to prevent pressure communication between the higher pressure region and the vacuum chamber whilst permitting substantially unhindered propagation of charged particles from the vacuum chamber to the higher pressure region, via the channel, and onto the workpiece.

    [0009] Whilst plasma interfaces constructed in the above manner also serve to pump down the vacuum chamber, this pumping action is weak and of limited effectiveness only. In practice, both the vacuum chamber and the plasma interface's channel must be pumped such that they are substantially in vacuum prior to the formation of the plasma. This is time consuming and, to implement effectively, requires equipment that is costly and mechanically cumbersome. Particle gun assemblies that comprise plasma interfaces constructed in this manner are, therefore, not well suited for 3D printing apparatuses, where the gun assembly is required to be dexterous and flexible in operation.

    [0010] One example of such a device is that disclosed in US Patent Number 5,578,831 (Hershcovitch). The Hershcovitch device discloses a plasma interface but requires a mechanical pump to pump down the low pressure region, while the plasma interface serves to maintain the pressure but does not provide significant pump down effect.

    OBJECT OF THE INVENTION



    [0011] It is an object of the present invention to provide a charged particle propagation apparatus having a vacuum chamber and plasma interface, wherein the plasma interface serves to pump down the vacuum chamber effectively.

    SUMMARY OF THE INVENTION



    [0012] In accordance with one further aspect of the present invention, there is provided a charged particle propagation apparatus according to claim 1.

    [0013] The sequence of electrical currents may be configured to cause a plurality of plasmas to move concurrently from the first end to the second end of the plasma channel.

    [0014] A non-plasma region may be formed between two successive plasmas moving concurrently from the first end to the second end of the plasma channel.

    [0015] The, or each, non-plasma region may contain residual gas from the vacuum chamber.

    [0016] The sequence of electrical currents may be a repeating sequence that causes the beam exit to be pumped down continuously.

    [0017] Each insulator may be made of aluminium oxide.

    [0018] Each insulator may be made of high-density polyethylene.

    [0019] Each insulator may be made of mica.

    [0020] Each insulator may be made of polytetrafluoroethylene.

    [0021] The higher pressure region may be maintained at atmospheric pressure.

    [0022] The charged particle propagation apparatus may further comprise an injection means for injecting a plasma-forming gas into the plasma channel.

    [0023] The injection means may comprise a supply tube and mechanical gas pump.

    [0024] The plasma-forming gas may be a inert or non-inert plasma-forming gas.

    [0025] The plasma-forming gas may be helium.

    [0026] The plasma-forming gas may be argon.

    [0027] The plasma-forming gas may be nitrogen.

    [0028] The charged particle propagation apparatus may further comprise a means for stabilizing the, or each, plasma in the plasma channel, the stabilizing means comprising a plurality of stacked annular cooling plates collectively having a central bore defining the plasma channel there through, and means for circulating cooling fluid through the cooling plates to remove heat therefrom.

    [0029] In accordance with one further aspect of the present invention, there is provided a pumping method for pumping down a vacuum chamber according to claim 16.

    [0030] The sequence of electrical currents used in the pumping method may cause a non-plasma region to be formed between two successive plasmas moving concurrently from the first end to the second end of the plasma channel.

    [0031] Residual gas from the vacuum chamber may be contained in the, or each, non-plasma region formed when the pumping method is executed.

    [0032] The sequence of electrical currents used in the pumping method may be repeated causing the exit to be pumped down continuously.

    BRIEF DESCRIPTION OF DRAWINGS



    [0033] The present invention will now be described, by way of example, with reference to the accompanying drawings, in which Figure 1 is a schematic view of a charged particle propagation apparatus according to a preferred embodiment of the invention.

    DETAILED DESCRIPTION OF THE DRAWINGS



    [0034] Referring to Figure 1, there is shown a charged particle propagation apparatus 64 according to a preferred embodiment of the invention.

    [0035] The particle propagation apparatus 64 comprises a generator 66 comprising a vacuum chamber 68. Inside the vacuum chamber 68, there is disposed a gun 70 for discharging a charged particle beam 72. The gun 70 may, for example, comprise a high-powered 150kW electron beam gun.

    [0036] As shown in the Figure, the charged particle beam 72 is discharged from within the vacuum chamber 68 and out of the vacuum chamber 68 through a beam exit 74 disposed in a wall 76 of the vacuum chamber 68.

    [0037] A region of higher pressure 78 adjoins the vacuum chamber 68 which is maintainable at a pressure greater than a pressure of the vacuum chamber 68. Preferably, the region of higher pressure 78 is maintained at atmospheric pressure.

    [0038] A plasma interface 80 is disposed at the beam exit 74 that comprises a plasma channel 82. The plasma channel 82 is substantially aligned with the beam exit 74 such that the particle beam 72 may pass through an elongate length of the plasma channel 82.

    [0039] The plasma channel 82 has a first end 84 and second end 86 and a plurality of electrode plates 88 are disposed between the first end 84 and the second end 86. Each electrode plate 88 has a central aperture (not shown) coaxially aligned with the plasma channel 82 which the particle beam 72 may pass there through.

    [0040] Each electrode plate 88 is, separated from the others in the plurality by an insulator 89 disposed between adjacent electrode plates 88. Each insulator 89 also has a central aperture (not shown) coaxially aligned with the plasma channel 82 which the particle beam 72 may also pass there through.

    [0041] Each insulator 89 is made from a material having electrical insulating properties such as, for example, aluminium oxide, high-density polyethylene, mica or polytetrafluoroethylene. The dimensions of each insulator 89 is adapted to minimise the distance between adjacent electrodes plates 88 while preventing electrical interference between the electrodes plates 88.

    [0042] In the exemplary embodiment shown in the Figure, the plasma channel 82 comprises a total of nine electrode plates 88. However, it will be appreciated that an alternative number of plates may be used, provided always that a minimum of three plates must be used.

    [0043] A plasma-forming gas, such as helium, argon or nitrogen, that is highly ionized and contains positive ions and electrons, is injected into the plasma channel 82 using an injection means known in the art such as, for example, a supply tube and mechanical gas pump (not shown).

    [0044] Once the gas has sufficiently filled the plasma channel 82, electrical currents are applied to the electrode plates 88 using a control system that is incorporated into the particle propagation apparatus 64. The electrical currents cause a first plasma to form at the first end 84 of the plasma channel 82 and be maintained at a high pressure, which may be atmospheric pressure, for example. This is achieved by supplying a high voltage, low current power supply to a first plate 90, thus causing the first plate 90 to form a cathode, followed by supplying a low voltage, high current power supply to a second plate 92, thus causing the second plate 92 to form an anode. The opposing cathode and anode causes a plasma to form and bond between the first plate 90 and the second plate 92.

    [0045] The control system then selectively applies a pre-determined sequence of electrical currents to the other electrode plates 88 in the channel 82. The sequence of electrical currents is configured to cause the first plasma to move from the low pressure region at the first end 84 of the plasma channel 82 to the high pressure region at the second end 86 of the plasma channel 82.

    [0046] After the first plasma has propagated through the plasma channel 82 towards its second end 86 by a sufficient distance, further electrical currents are then applied to the first and second electrode plates 90,92 causing a second plasma to form at the first end 84 of the plasma channel 82. The second plasma is then, similarly, propagated through the plasma channel 82 towards its second end 86 by a sequence electrical currents being selectively applied to the other electrode plates 88.

    [0047] This process is, preferably, repeated thereby causing further plasmas to be generated and travel simultaneously along the elongate length of the plasma channel 82 in succession.

    [0048] The movement of the, or each, plasma through the plasma channel 82 towards its second end 86 in this manner advantageously causes a substantial pumping down to occur at the beam exit 74. This process is used to create the vacuum in the vacuum chamber 68 rapidly and maintain the vacuum once formed.

    [0049] Further, the sequence of electrical currents that is applied to the electrode plates 88 is, preferably, configured such that a non-plasma region is formed between each pair of plasmas traveling concurrently along the elongate length of the plasma channel 82.

    [0050] In embodiments of the invention wherein the plasma channel 82 comprises a high number of electrode plates 88, it will be appreciated that a high number of plasmas, and corresponding non-plasma regions, will be caused to travel simultaneously along the elongate length of the plasma channel 82.

    [0051] The, or each, non-plasma region travelling along the plasma channel 82, preferably, contains residual gas from the vacuum chamber. This substantially increases the power and effectiveness of the pumping down that is performed at the beam exit 74.

    [0052] In use, the particle beam 72 propagates from the vacuum chamber 68, through the beam exit 74 and through the, or each, plasma that may be present in the plasma channel 82, without dispersion or attenuation, and onto a workpiece 94 disposed in the region of higher pressure 78. This arrangement provides for substantially unhindered transmission of charged particles from the gun 70 to the workpiece 94.

    [0053] Each plasma that is formed within, and propagating through, the plasma channel 82 may reach a high temperature of approximately 15,000° K. Stabilizing means are, therefore, used to stabilize each plasma preferably by providing a lower temperature boundary around each plasma. The stabilizing means, preferably, comprises a plurality of coaxially stacked together annular cooling plates 96 with the plates 96 collectively having a central bore which defines the plasma channel 82 therethrough.

    [0054] Cooling fluid or gas is circulated under pressure through each of the cooling plates 96 for removing heat therefrom for establishing a lower temperature boundary around each plasma. During operation, heat is transmitted radially outwardly by conduction through the cooling plates 96 and is removed by the cooling fluid circulating therethrough. Accordingly, by circulating the cooling fluid or gas around the plasma channel 82, heat is removed therefrom for stabilising each plasma.

    [0055] Modifications and variations as would be apparent to a skilled addressee are deemed to be within the scope of the present invention. The scope of the invention is defined by the claims.

    [0056] In the claims that follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" are used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.


    Claims

    1. A charged particle propagation apparatus (64) comprising:

    a generator (66) comprising a vacuum chamber (68) with a gun (70) therein for discharging a charged particle beam (72) from within the vacuum chamber (68) and out of the vacuum chamber (68) through a beam exit (74) disposed in a wall (76) of the vacuum chamber (68);

    a higher pressure region (78) adjoining the vacuum chamber (68) at the beam exit (74) that is maintainable at a pressure greater than a pressure of the vacuum chamber (68);

    a plasma interface (80) disposed at the beam exit (74) comprising a plasma channel (82),

    wherein the plasma channel (82):

    is aligned with the beam exit (74);

    has a first end (84) and a second end (86);

    has at least three electrode plates (88)

    disposed between the first end (84) and the second end (86), and characterised in that the plasma channel (82) has a plurality of insulators (89), each insulator (89) being disposed between a pair of adjacent electrode plates (88) in the plasma channel (82), each electrode plate (88) and

    insulator (89) having a central aperture coaxially aligned with the plasma channel (82)

    which the charged particle beam (72) may pass there through,

    and a control system adapted to apply a sequence of electrical currents to the electrode plates (88) causing each plate (88) to behave selectively as either an anode or cathode thereby causing a plurality of plasmas to move concurrently from the first end (84) to the second end (86) of the plasma channel (82) thereby pumping down the beam exit (74), and,

    in use, the charged particle beam (72) is propagated from the vacuum chamber (68) through each plasma in the plasma channel (82) and into the higher pressure region (78).


     
    2. The charged particle propagation apparatus (64) according to claim 1, wherein the sequence of electrical currents is configured to cause a non-plasma region to be formed between two successive plasmas moving concurrently from the first end (84) to the second end (86) of the plasma channel (82).
     
    3. The charged particle propagation apparatus (64) according to claim 2, wherein the, or each, non-plasma region contains residual gas from the vacuum chamber (68).
     
    4. The charged particle propagation apparatus (64) according to any one of the preceding claims, wherein the sequence of electrical currents is a repeating sequence that causes the beam exit (74) to be pumped down continuously.
     
    5. The charged particle propagation apparatus (64) according to any one of the preceding claims, wherein each insulator (89) is made of aluminium oxide.
     
    6. The charged particle propagation apparatus (64) according to any one of the preceding claims, wherein each insulator (89) is made of high-density polyethylene.
     
    7. The charged particle propagation apparatus (64) according to any one of the preceding claims, wherein each insulator (89) is made of mica.
     
    8. The charged particle propagation apparatus (64) according to any one of the preceding claims, wherein each insulator (89) is made of polytetrafluoroethylene.
     
    9. The charged particle propagation apparatus (64) according to any one of the preceding claims, wherein the higher pressure region (78) is maintained at atmospheric pressure.
     
    10. The charged particle propagation apparatus (64) according to any one of the preceding claims, further comprising an injection means for injecting a plasma-forming gas into the plasma channel (82).
     
    11. The charged particle propagation apparatus (64) according to claim 10, wherein the injection means comprises a supply tube and mechanical gas pump.
     
    12. The charged particle propagation apparatus (64) according to claim 10, wherein the plasma-forming gas is helium.
     
    13. The charged particle propagation apparatus (64) according to claim 10, wherein the plasma-forming gas is argon.
     
    14. The charged particle propagation apparatus (64) according to claim 10, wherein the plasma-forming gas is nitrogen.
     
    15. The charged particle propagation apparatus (64) according to any one of the preceding claims, further comprising a means for stabilizing the, or each, plasma in the plasma channel (82), the stabilizing means comprising a plurality of stacked annular cooling plates (96) collectively having a central bore defining the plasma channel (82) there through, and means for circulating cooling fluid through the cooling plates (96) to remove heat therefrom.
     
    16. A pumping method for pumping down a vacuum chamber (68) comprising the steps of:

    disposing a plasma interface (80) at an exit (74) of the vacuum chamber (68) comprising a plasma channel (82), wherein the plasma channel (82):

    is aligned with the exit (74);

    has a first end (84) and a second end (86);

    has at least three electrode plates (88) disposed between the first end (84) and the second end (86); and characterised in that the plasma channel (82) has a plurality of insulators (89), each insulator (89) being disposed between a pair of adjacent electrode plates (88) in the plasma channel (82), each electrode plate (88) and

    insulator (89) having a central aperture coaxially aligned with the plasma channel (82)

    which the charged particle beam (72) may pass there through,

    and applying a sequence of electrical currents to the electrode plates (88), wherein the sequence of electrical currents is configured to cause each plate (88) to behave selectively as either an anode or cathode thereby causing a plurality of plasmas to move concurrently from the first end (84) to the second end (86) of the plasma channel (82) thereby pumping down the exit (74).


     
    17. The pumping method according to claim 16, wherein the sequence of electrical currents used in the pumping method are repeated thereby causing the exit (74) to be pumped down continuously.
     


    Ansprüche

    1. Vorrichtung (64) zur Ausbreitung geladener Teilchen, umfassend:

    einen Generator (66), der eine Vakuumkammer (68) mit einer Pistole (70) darin zum Ausstoßen eines Strahls geladener Teilchen (72) von innerhalb der Vakuumkammer (68) und aus der Vakuumkammer (68) durch einen Strahlausgang (74) umfasst, der in einer Wand (76) der Vakuumkammer (68) angeordnet ist;

    eine Region höheren Drucks (78), die am Strahlausgang (74) an die Vakuumkammer (68) grenzt und die auf einem Druck gehalten werden kann, der größer als ein Druck der Vakuumkammer (68) ist;

    eine Plasmaschnittstelle (80), die am Strahlausgang (74) angeordnet ist und einen Plasmakanal (82) umfasst, wobei der Plasmakanal (82)

    mit dem Strahlausgang (74) ausgerichtet ist; ein erstes Ende (84) und ein zweites Ende (86) aufweist;

    mindestes drei Elektrodenplatten (88) aufweist, die zwischen dem ersten Ende (84) und dem zweiten Ende (86) angeordnet sind, und dadurch gekennzeichnet, dass der Plasmakanal (82) aufweist:
    eine Mehrzahl von Isolatoren (89), wobei jeder Isolator (89) zwischen einem Paar von benachbarten Elektrodenplatten (88) im Plasmakanal (82) angeordnet ist, jede Elektrodenplatte (88) und jeder Isolator (89) eine mittige Öffnung koaxial ausgerichtet mit dem Plasmakanal (82) aufweisen, durch welche der Strahl geladener Teilchen (72) durchtreten kann,

    und ein Steuersystem, das so ausgelegt ist, dass es eine Folge von elektrischen Strömen an die Elektrodenplatten (88) anlegt, die bewirkt, dass jede Platte (88) sich selektiv entweder als eine Anode oder Kathode verhält, um dadurch zu bewirken, dass eine Mehrzahl von Plasmen sich gleichzeitig vom ersten Ende (84) zum zweiten Ende (86) des Plasmakanals (82) bewegt, wodurch der Strahlausgang (74) abgepumpt und in Verwendung der Strahl geladener Teilchen (72) aus der Vakuumkammer (68) durch jedes Plasma im Plasmakanal (82) und in die Region höheren Drucks (78) ausgebreitet wird.


     
    2. Vorrichtung (64) zur Ausbreitung geladener Teilchen nach Anspruch 1, wobei die Folge von elektrischen Strömen so ausgelegt ist, dass sie bewirkt, dass zwischen zwei aufeinanderfolgenden Plasmen, die sich gleichzeitig vom ersten Ende (84) zum zweiten Ende (86) des Plasmakanals (82) bewegen, eine Nicht-Plasmaregion gebildet wird.
     
    3. Vorrichtung (64) zur Ausbreitung geladener Teilchen nach Anspruch 2, wobei die oder jede Nicht-Plasmaregion Restgas aus der Vakuumkammer (68) enthält.
     
    4. Vorrichtung (64) zur Ausbreitung geladener Teilchen nach einem der vorhergehenden Ansprüche, wobei die Folge von elektrischen Strömen eine sich wiederholende Folge ist, die bewirkt, dass der Strahlausgang (74) kontinuierlich abgepumpt wird.
     
    5. Vorrichtung (64) zur Ausbreitung geladener Teilchen nach einem der vorhergehenden Ansprüche, wobei jeder Isolator (89) aus Aluminiumoxid hergestellt ist.
     
    6. Vorrichtung (64) zur Ausbreitung geladener Teilchen nach einem der vorhergehenden Ansprüche, wobei jeder Isolator (89) aus Polyethylen hoher Dichte hergestellt ist.
     
    7. Vorrichtung (64) zur Ausbreitung geladener Teilchen nach einem der vorhergehenden Ansprüche, wobei jeder Isolator (89) aus Glimmer hergestellt ist.
     
    8. Vorrichtung (64) zur Ausbreitung geladener Teilchen nach einem der vorhergehenden Ansprüche, wobei jeder Isolator (89) aus Polytetrafluorethylen hergestellt ist.
     
    9. Vorrichtung (64) zur Ausbreitung geladener Teilchen nach einem der vorhergehenden Ansprüche, wobei die Region höheren Drucks (78) auf atmosphärischem Druck gehalten wird.
     
    10. Vorrichtung (64) zur Ausbreitung geladener Teilchen nach einem der vorhergehenden Ansprüche, ferner umfassend ein Injektionsmittel zum Injizieren eines Plasma bildenden Gases in den Plasmakanal (82).
     
    11. Vorrichtung (64) zur Ausbreitung geladener Teilchen nach Anspruch 10, wobei das Injektionsmittel ein Zufuhrrohr und eine mechanische Gaspumpe umfasst.
     
    12. Vorrichtung (64) zur Ausbreitung geladener Teilchen nach Anspruch 10, wobei das Plasma bildende Gas Helium ist.
     
    13. Vorrichtung (64) zur Ausbreitung geladener Teilchen nach Anspruch 10, wobei das Plasma bildende Gas Argon ist.
     
    14. Vorrichtung (64) zur Ausbreitung geladener Teilchen nach Anspruch 10, wobei das Plasma bildende Gas Stickstoff ist.
     
    15. Vorrichtung (64) zur Ausbreitung geladener Teilchen nach einem der vorhergehenden Ansprüche, ferner umfassend ein Mittel zum Stabilisieren des oder jedes Plasmas im Plasmakanal (82), wobei das Stabilisierungsmittel eine Mehrzahl von gestapelten ringförmigen Kühlplatten (96) umfasst, die zusammen eine mittige Bohrung aufweisen, die den Plasmakanal (82) dadurch definiert, und Mittel zum Zirkulierenlassen von Kühlfluid durch die Kühlplatten (96) zum Entfernen von Wärme daraus.
     
    16. Pumpverfahren zum Abpumpen einer Vakuumkammer (68), umfassend die folgenden Schritte:

    Anordnen einer Plasmaschnittstelle (80), die einen Plasmakanal (82) umfasst, an einem Ausgang (74) der Vakuumkammer (68), wobei der Plasmakanal (82)

    mit dem Ausgang (74) ausgerichtet ist;

    ein erstes Ende (84) und ein zweites Ende (86) aufweist;

    mindestes drei Elektrodenplatten (8) aufweist, die zwischen dem ersten Ende (84) und dem zweiten Ende (86) angeordnet sind; und dadurch gekennzeichnet, dass der Plasmakanal (82) aufweist:
    eine Mehrzahl von Isolatoren (89), wobei jeder Isolator (89) zwischen einem Paar von benachbarten Elektrodenplatten (88) im Plasmakanal (82) angeordnet ist, jede Elektrodenplatte (88) und jeder Isolator (89) eine mittige Öffnung koaxial ausgerichtet mit dem Plasmakanal (82) aufweisen, durch welche der Strahl geladener Teilchen (72) durchtreten kann,

    und Anlegen einer Folge von elektrischen Strömen an die Elektrodenplatten (88), wobei die Folge von elektrischen Strömen so ausgelegt ist, dass sie bewirkt, dass jede Platte (88) sich selektiv entweder als eine Anode oder Kathode verhält, um dadurch zu bewirken, dass eine Mehrzahl von Plasmen sich gleichzeitig vom ersten Ende (84) zum zweiten Ende (86) des Plasmakanals (82) bewegt, wodurch der Strahlausgang (74) abgepumpt wird.


     
    17. Pumpverfahren nach Anspruch 16, wobei die Folge von elektrischen Strömen, die im Pumpverfahren verwendet wird, wiederholt wird, um dadurch zu bewirken, dass der Ausgang (74) kontinuierlich abgepumpt wird.
     


    Revendications

    1. Appareil de propagation de particules chargées (64) comprenant :

    un générateur (66) comprenant une chambre à vide (68) équipée d'un canon (70) en son sein pour décharger un faisceau de particules chargées (72) depuis l'intérieur de la chambre à vide (68) et hors de la chambre à vide (68) à travers une sortie (74) de faisceau disposée dans une paroi (76) de la chambre à vide (68) ;

    une région à pression supérieure (78) accolée à la chambre à vide (68) au niveau de la sortie (74) de faisceau qui peut être maintenue à une pression supérieure à une pression de la chambre à vide (68) ;

    une interface plasmatique (80) agencée au niveau de la sortie (74) de faisceau comprenant un canal (82) de plasma,

    dans lequel le canal (82) de plasma :

    est aligné sur la sortie (74) de faisceau ;

    possède une première extrémité (84) et une seconde extrémité (86) ;

    comporte au moins trois plaques d'électrode (88) disposées entre la première extrémité (84) et la seconde extrémité (86), et caractérisé en ce que le canal (82) de plasma possède

    une pluralité d'isolateurs (89), chaque isolateur (89) étant disposé entre deux plaques d'électrode (88) adjacentes dans le canal (82) de plasma, chaque plaque d'électrode (88) et chaque isolateur (89) possédant une ouverture centrale alignée coaxialement sur le canal (82) de plasma au travers duquel peut passer le faisceau de particules chargées (72),

    et un système de commande conçu pour appliquer une séquence de courants électriques aux plaques d'électrode (88), ce qui amène chaque plaque (88) à se comporter sélectivement soit comme une anode, soit comme une cathode, ce qui amène une pluralité de plasmas à se déplacer simultanément depuis la première extrémité (84) vers la seconde extrémité (86) du canal (82) de plasma, ce qui permet de descendre en vide la sortie (74) de faisceau, et, lors de l'utilisation, le faisceau de particules chargées (72) est propagé depuis la chambre à vide (68) à travers chaque plasma dans le canal (82) de plasma et vers la région à pression supérieure (78).


     
    2. Appareil de propagation de particules chargées (64) selon la revendication 1, dans lequel la séquence de courants électriques est conçue pour amener une région sans plasma à être formée entre deux plasmas successifs se déplaçant simultanément depuis la première extrémité (84) vers la seconde extrémité (86) du canal (82) de plasma.
     
    3. Appareil de propagation de particules chargées (64) selon la revendication 2, dans lequel la, ou chaque, région sans plasma contient un gaz résiduel provenant de la chambre à vide (68).
     
    4. Appareil de propagation de particules chargées (64) selon l'une quelconque des revendications précédentes, dans lequel la séquence de courants électriques est une séquence de répétition qui amène la sortie (74) de faisceau à être descendue en vide de manière continue.
     
    5. Appareil de propagation de particules chargées (64) selon l'une quelconque des revendications précédentes, dans lequel chaque isolateur (89) est en oxyde d'aluminium.
     
    6. Appareil de propagation de particules chargées (64) selon l'une quelconque des revendications précédentes, dans lequel chaque isolateur (89) est en polyéthylène haute densité.
     
    7. Appareil de propagation de particules chargées (64) selon l'une quelconque des revendications précédentes, dans lequel chaque isolateur (89) est en mica.
     
    8. Appareil de propagation de particules chargées (64) selon l'une quelconque des revendications précédentes, dans lequel chaque isolateur (89) est en polytétrafluoroéthylène.
     
    9. Appareil de propagation de particules chargées (64) selon l'une quelconque des revendications précédentes, dans lequel la région à pression supérieure (78) est maintenue à la pression atmosphérique.
     
    10. Appareil de propagation de particules chargées (64) selon l'une quelconque des revendications précédentes, comprenant en outre un moyen d'injection pour injecter un gaz plasmagène dans le canal (82) de plasma.
     
    11. Appareil de propagation de particules chargées (64) selon la revendication 10, dans lequel le moyen d'injection comprend un tube d'alimentation et une pompe à gaz mécanique.
     
    12. Appareil de propagation de particules chargées (64) selon la revendication 10, dans lequel le gaz plasmagène est l'hélium.
     
    13. Appareil de propagation de particules chargées (64) selon la revendication 10, dans lequel le gaz plasmagène est l'argon.
     
    14. Appareil de propagation de particules chargées (64) selon la revendication 10, dans lequel le gaz plasmagène est l'azote.
     
    15. Appareil de propagation de particules chargées (64) selon l'une quelconque des revendications précédentes, comprenant en outre un moyen pour stabiliser le, ou chaque, plasma dans le canal (82) de plasma, le moyen de stabilisation comprenant une pluralité de plaques de refroidissement annulaires empilées (96) ayant collectivement un alésage central délimitant le canal (82) de plasma à travers celles-ci, et des moyens pour faire circuler un fluide de refroidissement à travers les plaques de refroidissement (96) afin d'éliminer la chaleur de celles-ci.
     
    16. Procédé de pompage pour descendre en vide une chambre à vide (68) comportant les étapes consistant à :

    disposer une interface plasmatique (80) au niveau d'une sortie (74) de la chambre à vide (68) comprenant un canal (82) de plasma, dans lequel le canal (82) de plasma :

    est aligné sur la sortie (74) ;

    possède une première extrémité (84) et une seconde extrémité (86) ;

    comporte au moins trois plaques d'électrode (88) disposées entre la première extrémité (84) et la seconde extrémité (86) ; et caractérisé en ce que le canal (82) de plasma

    possède une pluralité d'isolateurs (89), chaque isolateur (89) étant disposé entre deux plaques d'électrode (88) adjacentes dans le canal (82) de plasma, chaque plaque d'électrode (88) et chaque isolateur (89) possédant une ouverture centrale alignée coaxialement sur le canal (82) de plasma au travers duquel peut passer le faisceau de particules chargées (72),

    et appliquer une séquence de courants électriques aux plaques d'électrode (88), la séquence de courants électriques étant conçue pour amener chaque plaque (88) à se comporter sélectivement soit comme une anode, soit comme une cathode, ce qui amène une pluralité de plasmas à se déplacer simultanément depuis la première extrémité (84) vers la seconde extrémité (86) du canal (82) de plasma, ce qui permet de descendre en vide la sortie (74).


     
    17. Procédé de pompage selon la revendication 16, dans lequel la séquence de courants électriques utilisée dans le procédé de pompage est répétée, ce qui amène la sortie (74) à être descendue en vide de manière continue.
     




    Drawing






    REFERENCES CITED IN THE DESCRIPTION



    This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

    Patent documents cited in the description