WO2012101472A1

WO2012101472A1 - Process for manufacturing a plasma source, and plasma source obtained from this manufacturing process

Info

Publication number: WO2012101472A1
Application number: PCT/IB2011/000551
Authority: WO
Inventors: Peter Choi
Original assignee: Nano-Uv
Priority date: 2011-01-24
Filing date: 2011-01-24
Publication date: 2012-08-02

Abstract

The invention concerns a process for manufacturing a plasma source (103), said plasma source comprising a first electrode (2), a second electrode (3), a conduit (7) linking the two electrodes (2, 3) and going at least partially through at least one of the electrodes (2, 3), said conduit (7) being arranged for guiding a gas (4) inside the conduit (7), the process being characterized in that it comprises a step of placing an electrically insulating material (52) in a hydrostatic state around the conduit such that said insulating material (52) surrounds at least a part of the conduit (7), and a step of solidifying at least a part of the hydrostatic insulating material (52). When the insulating material is hydrostatic between the electrodes, it wets the surfaces it is in contact with, before the solidification step. This avoids the presence of an empty space linking the electrodes (2, 3) between the electrodes. The invention also relates to a plasma source obtained from this manufacturing process.

Description

« Process for manufacturing a plasma source, and plasma source obtained from this manufacturing process »

Technical field

The present invention relates to a process for manufacturing a plasma source.

The invention also relates to a plasma source obtained from the manufacturing process according to the invention.

State of the Art

The arc discharge plasma source and the capacitively coupled plasma source (CCP) are two common types of industrial plasma sources. A discharge plasma source 100 as illustrated in figure 1 is already known. This is the common configuration of a discharge tube, such as a neon light or a gas laser discharge tube where the plasma radiation is emitted longitudinally through the discharge axis, defined by the electrodes. This source 100 comprises a first electrode 200 and a second electrode 300, a conduit 700 linking the two electrodes 200 and 300 and arranged for guiding a gas 400 inside the conduit 700, and an electric power supply (not shown) connected to the electrodes and arranged for generating an electric field between the two electrodes, said electric field being arranged for ionizing the gas 400 guided inside the conduit. The plasma source 100 generally comprises an electrically insulating material 500 between the two electrodes.

Figure 2 is a view of a part 1000 of figure 1. Space 903 is an intermediate space 903 between the conduit 700 and the insulating material 500. Space 902 is an intermediate space between the electrodes 200, 300 and the insulating material 500. The sum of spaces 902 and 903 form an empty space or channel located between the electrodes and linking the electrodes 200, 300. The plasma source often needs to be compact, i.e. with a small separation between the anode and the cathode, such that air insulation between the anode and the cathode is not sufficient to prevent gas breakdown and loss of insulation. Such a compact plasma source 100 can have a quite short life time, i.e a quite short period after which the performances of the plasma source 100 are not as good as when it was new. This can be due to corona and High Voltage tracking shorting the two electrodes.

The goal of the invention is to present a process for manufacturing a plasma source having improved isolating properties between its electrodes, and a plasma source obtained from this manufacturing process.

Summary of the Invention

An aspect of the invention concerns a process for manufacturing a plasma source, said plasma source comprising a first electrode, a second electrode, a conduit linking the two electrodes and going at least partially through at least one of the electrodes, said conduit being arranged for guiding a gas inside the conduit, the process being characterized in that it comprises:

- a step of placing an electrically insulating material in a hydrostatic state around the conduit such that said insulating material surrounds at least a part of the conduit, and

- a step of solidifying at least a part of the hydrostatic insulating material .

When the insulating material is in its hydrostatic state, it can wet the surfaces it is in contact with, before the solidification step, preferably in order to avoid the presence of an empty space linking the electrodes between the electrodes. The insulating material preferably wets:

- the conduit: between the electrodes and/or for each electrode to be isolated in a intermediate space between the conduit and this electrode to be isolated, and/or

- the inner side of each electrode to be isolated (that is one of the electrodes or each electrode), and/or the surface of each electrode to be isolated in a intermediate space between the conduit and this electrode to be isolated.

In this document, it is meant that a conduit goes "at least partially through an electrode" if the conduit goes inside the electrode through a first face of the electrode but does not necessary go up to a second face of the electrode opposite to the first face. In this document, it is meant that a conduit goes "through an electrode" if the conduit goes inside the electrode through a first face of the electrode and up to or even further than a second face of the electrode opposite to the first face.

The process according to the invention can comprise, after the step of placing an electrically insulating material in a hydrostatic state, and for each of the electrodes to be isolated, an infiltration of the insulating material in its hydrostatic state into an intermediate space between the conduit and this electrode to be isolated .

The process according to the invention can be characterized in that: it comprises, after the step of placing an electrically insulating material in a hydrostatic state around the conduit, and for each one of the electrodes to be isolated, an infiltration of at least a part of the insulating material in its hydrostatic state into an intermediate space between the conduit and this electrode to be isolated, and in that

- the solidification comprises, for each one of the electrodes to be isolated, a solidification of at least a part the insulating material infiltrated into the intermediate space.

The step of placing an electrically insulating material in a hydrostatic state can comprise :

- a step of placing the electrically insulating material in a solid state around the conduit such that said insulating material surrounds at least a part of the conduit, and

- a step of changing the insulating material from its solid state to its hydrostatic state.

The step of changing the insulating material from its solid state to its hydrostatic state can comprise a step of exerting a pressure on the insulating material in its solid state up to reaching the hydrostatic state of the insulating material. The pressure is preferably maintained during all the lifetime of the plasma source.

The process according to the invention can be characterized in that: it comprises, after the step of placing an electrically insulating material in a hydrostatic state around the conduit, and for each one of the electrodes to be isolated, an infiltration of only a part the insulating material in its hydrostatic state into an intermediate space between the conduit and this electrode to be isolated, and

- the solidification comprises, for each one of the electrodes to be isolated, a solidification of at least a part the insulating material infiltrated into the intermediate space while the pressure exerted on the part of insulating material staying between the electrodes in its hydrostatic state is maintained . The pressure can be exerted by pressing the insulating material between the two electrodes.

In a variant, the insulating material can surrounds all the part of the conduit comprised between the electrodes.

In an other variant, the conduit can be immovably attached to a plate extending between the two electrodes, the step of changing the insulating material from its solid state to its hydrostatic state comprising pressing at least a part of the insulating material between one of the electrodes and the plate up to reaching the hydrostatic state of this at least a part of the insulating material, said at least a part of the insulating material being in contact with a face of the plate. The at least a part of the insulating material can surround all the part of the conduit comprised between this electrode and this face of the plate. The at least a part of the insulating material can comprise at least one ring of insulating material slipped onto the conduit, or at least two superposed rings of insulating material slipped onto the conduit. The step of changing the insulating material from its solid state to its hydrostatic state can further comprise pressing an other part of the insulating material between the other electrode and the plate up to reaching the hydrostatic state of the other part of the insulating material, said other part of the insulating material being in contact with an other face of the plate. One can start to press those two parts of the insulating material simultaneously or one after the other. The other part of the insulating material can surround all the part of the conduit comprised between the other electrode and the other face of the plate. The other part of the insulating material can comprise at least one ring of insulating material slipped onto the conduit, or at least two superposed rings of insulating material slipped onto the conduit..

Preferably, there is no empty space, in particular no air space, between the insulating material and the conduit after the solidification.

Preferably, for each one of the electrodes to be isolated, there is no empty space, in particular no air space, between the insulating material and this electrode after the solidification.

The insulating material can comprise (or, more restrictively, can consist of) a material able to pass from a solid state to a hydrostatic state:

- by increasing pressure, like rubber, and/or

by increasing temperature.

The insulating material can comprise at least one ring of insulating material slipped onto the conduit before being put into its hydrostatic state. The insulating material can comprise at least two superposed rings of insulating material slipped onto the conduit.

The insulating material has preferably an electrical resistivity ^ of at least 10 dm in its solid state, more preferably of at least 10⁴ Vim , even more preferably of at least 10⁷ Vim .

The process according to the invention can further comprise connecting the electrodes to means for generating an electric field between the two electrodes, said electric field being arranged for ionizing the gas guided inside the conduit.

An other aspect of the invention concerns a plasma source obtained from the manufacturing process according to the invention

More generally, an other aspect of the invention concerns a plasma source comprising :

- a first electrode,

- a second electrode,

- a conduit linking the two electrodes and going at least partially through at least one of the electrodes, said conduit being arranged for guiding a gas inside the conduit, and - an electrically insulating material, said insulating material surrounding a least a part of the conduit,

characterized in that there is no empty space linking the electrodes between the electrodes.

Said insulating material can comprise:

- a surrounding part located around the conduit such that said surrounding part of the insulating material surrounds a least a part of the conduit, and/or

- for each one of the electrodes to be isolated, an infiltrated part of the insulating material, infiltrated from the surrounding part of the insulating material into an intermediate space between the conduit and this electrode to be isolated .

The surrounding part of the insulating material can be in its hydrostatic state. The surrounding part of the insulating material can be maintained in its hydrostatic state thanks to an exerted pressure.

For each one of the electrodes to be isolated, at least a part of the infiltrated part of the insulating material can be in its solid state. For each one of the electrode to be isolated, at least a part of the infiltrated part of the insulating material is preferably in its solid state due to a pressure into the intermediate space inferior to the pressure exerted on the first part of the insulating material .

The conduit can be immovably attached to a plate extending between the two electrodes. The surrounding part of the insulating material can comprise a first part of the insulating material located between one of the electrode and the plate. The surrounding part of the insulating material can comprise a second part of the insulating material located between the other electrode and the plate.

The insulating material is preferably a material able to pass from a solid state to a hydrostatic state by increasing pressure, like rubber.

Preferably, there is no empty space, in particular no air space, between the insulating material and the conduit.

Preferably, there is no empty space, in particular no air space, between the insulating material and each isolated electrode. The insulating material is preferably in contact with the inner side of each one of the electrodes to be isolated .

In a first embodiment, the insulating material can surround all the part of the conduit comprised between the electrodes

In a second embodiment, the conduit can be immovably attached to a plate extending between the two electrodes. A first part of the insulating material can be in contact with the inner side of the first electrode and/or with a first face of the plate. The first part of the insulating material can surround all the part of the conduit comprised between the first electrode and the first face of the plate. A second part of the insulating material can be in contact with the inner side of the second electrode and/or with a second face of the plate. The second part of the insulating material can surround all the part of the conduit comprised between the second electrode and the second face of the plate. Each of the first and second part of the insulating material can comprise at least one ring of insulating material slipped onto the conduit.

The insulating material can comprise at least one ring of insulating material slipped onto the conduit.

The electrodes can be connected to means for generating an electric field between the two electrodes, said electric field being arranged for ionizing the gas guided inside the conduit.

Detailed description of the figures

and of realization modes of the invention

Other advantages and characteristics of the invention will appear upon examination of the detailed description of embodiments which are in no way limitative, and of the appended drawings in which :

- Figure 1 illustrates a plasma source according to prior art,

- Figure 2 illustrates a part 1000 of figure 1,

- Figure 3 is a schematic cross sectioned side view of a first embodiment of a plasma source according to the invention, - Figures 4 and 5 are schematic cross sectioned side views of a part 11 of figure 3 during two successive steps of a process for manufacturing this first embodiment of a plasma source according to the invention,

- Figure 6 is a schematic cross sectioned side view of a second embodiment of a plasma source according to the invention,

- Figures 7 and 8 are schematic cross sectioned side views of a part 110 of figure 6 during two successive steps of a process for manufacturing this second embodiment of a plasma source according to the invention,

- Figure 9 is a simplified phase diagram of polymer poly-4-methyl pentene-1 (P4MP1),

- Figure 10 is a schematic cross sectioned side view of a third embodiment of a plasma source 103 according to the invention, this third embodiment being the best realization mode of a plasma source according to the invention, and

- Figure 11 is a schematic cross sectioned side view of a part 1103 of figure 10 of this third embodiment of a plasma source according to the invention.

General description of the three illustrated embodiments: improvement of the electrical insulation.

By "hydrostatic material" or "hydrostatic" or "hydrostatic state", it is meant preferably a material in a state for which the internal pressure of this material is hydrostatic.

A hydrostatic material is preferably a fluid, and is more preferably a liquid (even very viscous) or a gel, but preferably not a gas.

Each one of the three illustrated embodiments of plasma source 1, 10, 103 according to the invention comprises:

- a first electrode 2 (anode),

- a second electrode 3 (cathode),

- a conduit 7 linking the two electrodes 2, 3 and going at least partially through at least one of the electrodes 2, 3, and

- a housing 18.

The conduit 7 goes at least partially through each one of the electrodes to be isolated among electrodes 2, 3. Only one of the electrodes 2, 3 can be intended to be isolated, or both of the electrodes 2, 3 can be intended to be isolated.

Advantageously, the conduit 7 goes at least partially through each one of the electrodes to be isolated among electrodes 2, 3, in order to create, for each of the electrodes to be isolated, an intermediate space 9 between the conduit 7 and this electrode to be isolated .

The conduit goes through an electrode if it goes through all the thickness of this electrode. In this case, the conduit can protrude and extend beyond the outer side of this electrode, or not.

The conduit goes only partially through an electrode if it goes through only a part of the thickness of this electrode, and stops inside the thickness of this electrode.

Preferably, in order to improve the lifetime of a plasma source according to the invention, the conduit 7 goes through and extend beyond at least one electrode, preferably the anode 2.

Each one of the three illustrated embodiments of plasma source 1, 10, 103 further comprises electrically insulating material 5, 6, 51, 52, 61, and/or 62 between the two electrodes 2, 3.

The electrodes 2, 3, the conduit 7, the insulating material 5, 6, 51, 52, 61, and/or 62 and the housing 18 have a revolution symmetry around the arrow 4, i.e. around the middle axis of the cylindrical conduit 7.

Each electrode 2, 3 comprises an inner side 16, 17 oriented towards the other electrode and an outer side oriented in a direction substantially opposed to the other electrode.

Each electrode 2, 3 is a plate having a disk shape and two substantially parallel faces. For each electrode 2, 3, a hole connects its inner side to its outer side, is centered in the middle of the disk shape of the electrode 2 or 3, and the conduit 7 goes through this hole or open onto this hole.

Each electrode is made of a material conducting electricity, preferably comprising a metal or an alloy.

The typical diameter of each electrode 2, 3 is five centimeters, and the typical thickness of each electrode is five millimeters. The two electrodes plates 2, 3 are substantially parallel. The conduit 7 is arranged for guiding a gas 4 inside the conduit 7 and through the electrodes 2, 3. The gas flux is injected inside the conduit 7 through the hole 60 of the second electrode 3. In the figures, this gas flux is symbolized by an arrow 4.

Finally, the electrodes 2, 3 are connected to means (power supply) 9 for generating an electric field between the two electrodes 2, 3, said electric field being arranged for ionizing the gas guided inside the conduit 7. When the gas is ionized, it creates a plasma inside the conduit 7, electrons are flowing from the cathode 3 to the anode 2, and positive ions are flowing from the anode 2 to the cathode 3. The electrodes 2, 3 are connected to the power supply 9 like a capacitor that can supply a high current in a short time to heat up the plasma to the necessary conditions to provide the wanted radiation.

The conduit 7 is made of an electrical insulating material like ceramic, otherwise the conduit 7 would electrically connect the two electrodes, no electric field or very small electric field would be created in the interelectrode region, and no plasma would be created. The conduit 7 has a rectilinear shape, more precisely a cylindrical shape. The conduit 7 has an inner wall located inside the conduit and in contact with the gas flowing and guided in the conduit, and an outer wall located at the periphery of the conduit and not in contact with the gas flowing in the conduit. The inner wall delimits the internal volume of the conduit in which the gas is guided and is flowing . The walls have both a cylindrical shape. The diameter of the inner cylindrical wall of the conduit has a typical value between 0.5 millimeter and 5 millimeters.

The insulating material 5, 6, 51, 52, 61, and/or 62 is in contact with the inner side of at least one of the electrode 2, 3. More exactly, the insulating material 5, 6, 51, 52, 61, and/or 62 is in contact with the inner side 16, 17 of each one of the electrodes 2 and/or 3 to be isolated .

The insulating material 5, 6, 51, 52, 61, and/or 62 surrounds a least a part of the conduit 7.

The insulating material 5, 6, 51, 52, 61, and/or 62 comprises: - a surrounding part 21 located around the conduit such that said surrounding part of the insulating material surrounds a least a part of the conduit 7, and

- for each one of the electrodes 2 and/or 3 to be isolated, an infiltrated part 22 of the insulating material, infiltrated from the surrounding part of the insulating material into an intermediate space 9 between the conduit 7 and this electrode to be isolated .

The surrounding part 21 of the insulating material is in its hydrostatic state. The surrounding part 21 of the insulating material is maintained in its hydrostatic state thanks to a pressure exerted on this surrounding part. This pressure is exerted by a mechanical force, typically by screws 23 screwing on the plasma source (on housing 18) each electrode to be isolated and pressing each electrode to be isolated on the insulating material.

For each one of the electrodes 2 and/or 3 to be isolated, at least a part 24 (cross hatched in figures 5, 8 and 11) of the infiltrated part 22 of the insulating material is in its solid state, and creates this way a plug avoiding that the hydrostatic part 21 of the insulating material escapes from the plasma source. For each one of the electrodes 2 and/or 3 to be isolated, the at least a part 24 of the infiltrated part 22 of the insulating material is in its solid state due to a pressure into the intermediate space inferior to the pressure exerted on the part 21 of the insulating material between the electrodes.

The process for manufacturing the plasma source 1 or 10 or 103 comprises:

1) a step of placing the electrically insulating material 5, 6, 51, 52, 61, and/or 62 in a hydrostatic state around the conduit 7 and between the two electrodes 2, 3, said hydrostatic insulating material 5, 6, 51, 52, 61, and/or 62 being in contact with the inner side of each electrode 2 and/or 3 to be isolated and surrounding a least a part of the conduit 7, this step of placing a hydrostatic electrically insulating material comprising :

l.a) as illustrated in figures 4 and 7, a step of placing the electrically insulating material 5, 6, 51, 52, 61, and/or 62 in a solid state around a portion of the conduit 7 designed for being between the two electrodes 2, 3; said insulating material 5, 6, 51, 52, 61, and/or 62 is preferably in contact with the inner side of each one of the electrodes 2 and/or 3 to be isolated and surrounds a least a part of the conduit 7; then

l.b) as illustrated in figures 5 and 8, a step of changing the insulating material 5, 6, 51, 52, 61, and/or 62 from its solid state to its hydrostatic state by exerting a pressure on the solid insulating material 5, 6, 51, 52, 61, and/or 62 up to reaching the hydrostatic state of the insulating material 5, 6, 51, 52, 61, and/or 62 and preferably (but not necessarily) while keeping the complete plasma source under vacuum to remove the air trapped in space 9; this pressure is then exerted during all the lifetime of the plasma source; this pressure is typically exerted by the screws 23 as explained previously; The step of exerting a pressure can be preceded by increasing the temperature of the insulating material in order to facilitate the step of changing the insulating material from its solid state to its hydrostatic state.

2) after step 1), a step of solidifying only a part of the hydrostatic insulating material 5, 6, 51, 52, 61, and/or 62.

3) a step of connecting the electrodes 2, 3 to the means 9 for generating an electric field between the two electrodes 2, 3.

In step la), (i.e. before solidification step 2) ) there is as illustrated in figures 4 and 7 :

- for each electrode to be isolated, an empty space 9 between this electrode and the conduit 7, because the surfaces of the electrodes and of the conduit are not perfectly smooth, because the outside diameter of the cylindrical conduit 7 is not perfectly equal to the diameter of the hole made in the electrodes, and

- an empty space 12 between the insulating material 5, 6, 51, 52, 61, and/or 62 and the conduit 7, because the surfaces of the insulating material and of the conduit are not perfectly smooth, and - an empty space 13, 14 between the insulating material 5, 6, 51, 52, 61, and/or 62 and each electrode 2 and/or 3 to be isolated, because the surfaces of the insulating material and of the electrodes are not perfectly smooth .

By empty space, it is meant a space that does not comprise any liquid or solid, but that can be filled with gas or that can be vacuumed or evacuated .

The insulating material is hydrostatic between the electrodes and wets the surfaces it is in contact with, before the solidification step 2). This avoids the presence of an open empty space or channel linking the electrodes 2, 3 between the electrodes.

By "open empty space" between two elements, it is meant a space that is open such that something (gas or plasma for example) can flow between these two elements through this open space. A closed air bubble is not an "open space".

The insulating material is in contact with the part of the conduit 7 that it is surrounding, in its hydrostatic state and after the solidification step 2).

In step l .b), the pressure is exerted on the insulating material through the at least one of the electrode 2, 3 to be isolated, i.e the at least one electrode is pushed towards the insulating material to be put into its hydrostatic state. Thus, the area 13 or 14 between the at least one electrode to be isolated and the insulating material is a high pressure area, while the area 9 between the at least one electrode to be isolated and the conduit 7 is a low pressure area. In other words, the pressure in the area 9 is lower than in the area 13 or 14. Once the insulating material is put into its hydrostatic state, it is attracted towards the low pressure area 9 due to the hydrostatic nature of pressure distribution. This way, the hydrostatic insulating material infiltrates into the intermediate space 9 between the conduit 7 and the at least one electrode 2, 3 through which the pressure is exerted . That means that there is, after the step l .b) of placing an electrically insulating material in a hydrostatic state around the conduit, and for each one of the electrodes 2 and/or 3 to be isolated, an infiltration of only a part the insulating material 5, 6, 51, 61, 52, and/or 62 in its hydrostatic state into an intermediate space 9 that is not between the electrodes but that is between the conduit 7 and this electrode to be isolated . Once it is into the intermediate space 9, the insulating material starts solidifying inside the space 9 because in this space 9 the pressure of the insulating material is lower than the pressure necessary to put it into its hydrostatic state. The solidification step 2) comprises, for each one of the electrodes to be isolated, a solidification of at least a part 24 the insulating material 22 infiltrated into the intermediate space 9 while the pressure exerted on the part of insulating material staying between the electrodes in its hydrostatic state is maintained . Thus, in the intermediate space 9 of each electrode 2 and/or 3 to be isolated, a solid plug is formed avoiding the hydrostatic insulating material to be completely ejected from the plasma source.

In the illustrated plasma sources 1, 10, 103, for each of the electrodes 2 and/or 3 to be isolated, the insulating material 5, 6, 51, 52, 61, and/or 62 extends up to the intermediate space 9 between the conduit 7 and this electrode 2, 3 in a solid state once the plasma source is manufactured .

Furthermore, after the solidification step 2), i.e. once the plasma source 1, 10 or 103 is manufactured, there is no open empty space or channel linking the electrodes 2, 3 between the electrodes; in particular there is no open empty space or channel linking the electrodes 2, 3 between each electrode and the conduit or between each electrode and the insulating material. Indeed :

- there is no open empty space, in particular no open air space, between the insulating material and the housing 18, because the hydrostatic insulating material has wet the housing,

- there is no open empty space 12, in particular no open air space, between the insulating material and the conduit 7, because the hydrostatic insulating material has wet the conduit between the electrodes and because the hydrostatic insulating material has wet the conduit before the solidification step inside intermediate space 9,

- for each one of the electrodes to be isolated, there is no open empty space 13, 14, in particular no open air space, between the insulating material and this electrode, because the hydrostatic insulating material has wet this electrode to be isolated between the electrodes and because the hydrostatic insulating material has wet this electrode to be isolated before the solidification step inside intermediate space 9,

- for each one of the electrodes to be isolated, the intermediate space 9 between the conduit 7 and this electrode is filled with insulating material in its solid state.

There is no open empty space linking the electrodes between the electrodes. Thus, the electrodes 2, 3 are perfectly electrically insulated .

The insulating material remains in its hydrostatic state between the electrodes preferably during all the lifetime of the plasma source, whereas some of the insulating material remains in its solid state in each intermediate space 9 where insulating material is infiltrated, preferably during all the lifetime of the plasma source.

Description of the first illustrated embodiment of plasma source

According to a first embodiment of a plasma source 1 according to the invention illustrated in figure 3, the insulating material 5, 6 surrounds all the part of the conduit 7 comprised between the electrodes.

The insulating material 5, 6 comprises at least one ring of insulating material slipped onto the conduit 7 (figure 3 illustrates two rings respectively 5 and 6).

The process for manufacturing the plasma source 1 comprises:

1') the step of placing the electrically insulating material 5, 6 in a hydrostatic state around the conduit 7 and between the two electrodes 2, 3, said hydrostatic insulating material 5, 6 being in contact with the inner side of each of the electrodes 2, 3, the housing 18 and the conduit 7, and surrounding all the part of the conduit 7 comprised between the electrodes, this step of placing a hydrostatic electrically insulating material comprising :

l'.a) as illustrated in figure 4, a step of placing the electrically insulating material 5, 6 in a solid state around the conduit 7 and between the two electrodes 2, 3, said insulating material 5, 6 being in contact with the inner side of each of the electrodes 2, 3 and surrounding all the part of the conduit 7 comprised between the electrodes; then

l'.b) as illustrated in figures 4 and 5, a step of changing the insulating material 5, 6 from its solid state to its hydrostatic state by exerting a pressure on the solid insulating material 5, 6 up to reaching the hydrostatic state of the insulating material 5, 6; The step of exerting a pressure can be preceded by increasing the temperature of the insulating material in order to facilitate the step of changing the insulating material from its solid state to its hydrostatic state.

2') after step 1'), a step of solidifying only a part of the hydrostatic insulating material 5, 6.

3') a step of connecting the electrodes 2, 3 to the means 9 for generating an electric field between the two electrodes 2, 3.

In this first embodiment, both electrodes 2, 3 are isolated .

To implement step l'.a), the conduit 7 is inserted through the electrode 3. The conduit 7 and the electrode 3 are inserted into the housing 18. Then at least one ring 5, 6 of solid insulating material is slipped onto the conduit 7, for example two rings of rubber. Thus in step l'.a), the insulating material is placed in a solid state around the conduit such that said insulating material surrounds at least a part of the conduit designed for being located between the two electrodes 2, 3. Then, the conduit 7 is inserted through the other electrode 2, in such a way that the rings 5, 6 are between the two electrodes 2, 3 and are in contact with the inner side of each of the electrode 2, 3 and surround all the part of the conduit 7 comprised between the electrodes.

For the reasons already disclosed previously, in step l'.a), (i.e. before solidification step 2') ) there is:

- an air space 9 between each one of the electrodes and the conduit 7, and

- an air space 12 between the insulating material 5, 6 and the conduit 7, and

- an air space 13, 14 between the insulating material 5, 6 and each one of the electrodes 2, 3. In step l'.b), the pressure is exerted on the insulating material through the electrode 2, 3, i.e each electrode is pushed towards the insulating material to be put into its hydrostatic state. In other words, the pressure is exerted by pressing the insulating material 5, 6 between the two electrodes 2, 3, said insulating material 5, 6 being in contact with the inner side of each one of the electrodes 2, 3. Thus, the areas 13, 14 between each electrode and the insulating material are high pressure areas, while the areas 9 between each electrode and the conduit 7 are low pressure areas. In other words, the pressure in the areas 9 is lower than in the area 13 or 14. Once the insulating material is put into its hydrostatic state, it is attracted towards the low pressure areas 9. This way, the hydrostatic insulating material infiltrates into the intermediate spaces 9 between the conduit 7 and each electrode 2, 3. That means that there is, after the step l'.b) of placing an electrically insulating material in a hydrostatic state around the conduit, and for each one of the electrodes 2 and 3, an infiltration of only a part the insulating material 5, 6 in its hydrostatic state into an intermediate space 9 that is not between the electrodes but that is between the conduit 7 and this electrode. Once it is into the intermediate spaces 9, the insulating material starts solidifying inside the spaces 9 because the pressure is lower than the pressure necessary to put it into its hydrostatic state in these spaces 9. The solidification step 2') comprises, for each one of the electrodes 2, 3, a solidification of at least a part the insulating material infiltrated into the intermediate space 9 while the pressure exerted on the part of insulating material staying between the electrodes in its hydrostatic state is maintained. Thus, a solid plug is formed in each one of these spaces 9, avoiding the hydrostatic insulating material to be completely ejected from the plasma source.

In this first embodiment, the hydrostatic insulating material simultaneously infiltrates into each intermediate spaces 9 between the conduit 7 and each electrode 2, 3 and solidifies simultaneously into the intermediate space 9 between the conduit 7 and the first electrode 2 and into the intermediate space 9 between the conduit 7 and the second electrode 3. Description of the second ill ustrated embod iment of plasma source

According to a second embod iment of a plasma source 10 according to the invention il lustrated in fig ure 6, the cond uit 7 is immovably attached to a plate 8 extend ing partially between the two electrodes 2, 3. The plate 8 is paral lel to the electrodes 2, 3.

The electrodes 2, 3, the conduit 7, the plate 8 and the insulating material 51 , 52, 61 , and 62 have a revol ution symmetry around the arrow

4.

A first part of the insulating material 51 , 61 is in contact with the inner side 16 of the first electrode 2 and with a first face 19 of the plate 8. The first part of the insulating material 51 , 61 su rrounds all the part of the conduit 7 comprised between the first electrode 2 and the first face of the plate 8. The first part of the insu lating material 51 , 61 comprises at least one ring of insulating material sl ipped onto the condu it 7 (fig ure 6 ill ustrates two rings respectively 51 and 61 ) .

A second part of the insulating material 52, 62 is in contact with the inner side 17 of the second electrode 3 and with a second face 20 of the plate 8. The second part of the insulating material 52, 62 surrounds al l the part of the cond uit 7 comprised between the second electrode 3 and the second face of the plate 8. The second part of the insulating material 52, 62 comprises at least one ring of insulating material sl ipped onto the cond u it 7 (fig ure 6 ill ustrates two rings respectively 52 and 62) .

A process for manufacturing the plasma source 10 comprises :

1") the step of placing the electrical ly insu lating material 51 , 61 , 52, 62 in a hydrostatic state around the cond uit 7 and between the two electrodes 2, 3, the first part 51 , 61 of the insulating material being in contact with the inner side of the first electrode 2 and surround ing all the part of the cond uit 7 comprised between the first electrode 2 and the first face of the plate 8, the second part of the insulating material 52, 62 being in contact with the inner side of the second electrode and surround ing all the part of the cond uit 7 comprised between the second electrode 3 and the second face of the plate 8, this step of placing a hyd rostatic electrical ly insulating material comprising : l".a) for each one of the electrodes 2, 3 to be isolated, as illustrated in figure 7, a step of placing the electrically insulating material 51, 61, or 52, 62 in a solid state around a portion of the conduit 7 intended to be between the two electrodes 2, 3, said insulating material 51, 61, 52, 62 being in contact with the inner side of an electrode to be isolated; to implement step l".a) , at least one ring 51, 61 of solid insulating material is slipped onto the conduit 7. Then conduit 7 is inserted through the first electrode 2, in such a way that the rings 51, 61 are between the first electrodes 2 and the plate 8, are in contact with the inner side 16 of the first electrode 2 and with a first 19 face of the plate 8 and surrounds all the part of the conduit 7 comprised between the first electrode 2 and the first face of the plate 8. Thus in step l".a), the first part of the insulating material 51, 61 is placed in a solid state around the conduit such that said insulating material surrounds at least a part of the conduit designed for being located between the two electrodes 2, 3. Then, the electrode 2, conduit 7, and rings 51, 61 are inserted into the housing 18. Then, at least one ring 52, 62 of solid insulating material is slipped onto the conduit 7. Then conduit 7 is inserted through the second electrode 3, in such a way that the rings 52, 62 are between the second electrode 3 and the plate 8, are in contact with the inner side 17 of the second electrode 3 and with a second face 20 of the plate 8 and surrounds all the part of the conduit 7 comprised between the second electrode 3 and the second face of the plate 8. Thus in step l".a), the second part of the insulating material 52, 62 is placed in a solid state around the conduit such that said insulating material surrounds at least a part of the conduit designed for being located between the two electrodes 2, 3. ;

l".b) as illustrated in figures 7 and 8, a step of changing the insulating material 51, 61, 52, 62 from its solid state to its hydrostatic state by exerting a pressure on the solid insulating material 51, 61, 52, 62 up to reaching the hydrostatic state of the insulating material 51, 61, 52, 62, the pressure being exerted by pressing the insulating material between the two electrodes; The step of exerting a pressure can be preceded by increasing the temperature of the insulating material in order to facilitate the step of changing the insulating material from its solid state to its hydrostatic state.

2") after step 1"), a step of solidifying only a part of the hydrostatic insulating material 51, 61, 52, 62.

3") a step of connecting the electrodes 2, 3 to the means 9 for generating an electric field between the two electrodes 2, 3.

In this second embodiment, both electrodes 2, 3 are isolated .

In step l".b), the pressure is exerted on the insulating material through the electrode 2, 3, i.e each electrode is pushed towards the insulating material to be put into its hydrostatic state. The pressure is exerted :

- simultaneously on the first and second parts of the insulating material, by pressing the insulating material 51, 61, 52, 62 between the two electrodes 2, 3.

- or:

o firstly on the first part 51, 61 of the insulating material, before that the at least one ring 52, 62 of solid insulating material is slipped onto the conduit 7, by pressing the first part of the insulating material 51, 61, between the first electrode 2 and plate 8; but there is an important risk of breaking plate 8 by implementing this other manufacturing process, and o after that, by pressing the second part of the insulating material 52, 62, between the second electrode 3 and plate 8, 3;

In both case, for the reasons previously disclosed, there is one infiltration of the first part of the hydrostatic insulating material 51, 61 into the intermediate space 9 between the conduit 7 and the first electrode 2 followed by a solidification of at least a part of this infiltrated material, and there is also one infiltration of the second part of the hydrostatic insulating material 52, 62 into the intermediate space 9 between the cond uit 7 and the second electrode 3 fol lowed by a sol id ification of at least a part of this infiltrated material .

In the first case, the hydrostatic insulating material simultaneously infiltrates into each intermed iate space 9 between the condu it 7 and each electrode 2, 3 and sol id ifies simultaneously into the intermediate space 9 between the condu it 7 and the first electrode 2 and into the intermed iate space 9 between the cond uit 7 and the second electrode 3.

In second case, there is one infiltration and one solidification of hydrostatic insulating material into the intermed iate space 9 between the cond uit 7 and the first electrode 2. There is also one infiltration and one sol id ification of hyd rostatic insulating material into the intermediate space 9 between the cond uit 7 and the second electrode 3. The two infiltrations happen one after the other. The two solidifications happen one after the other.

Description of the third il l ustrated embod iment of plasma source

Accord ing to a third embod iment of a plasma source 103 accord ing to the invention ill ustrated in fig ure 10, the cond uit 7 is immovably attached to a plate 8 extend ing partial ly between the two electrodes 2, 3. The plate 8 is paral lel to the electrodes 2, 3.

The electrodes 2, 3, the conduit 7, the plate 8 and the insulating material 52, have a revol ution symmetry around the arrow 4.

A first face 19 of the plate 8 is in contact with the inner side 16 of the first electrode 2

The insulating material 52 is in contact with the inner side 17 of the second electrode 3 and with a second face 20 of the plate 8. The insulating material 52 surrounds all the part of the conduit 7 comprised between the second electrode 3 and the second face of the plate 8. The second part of the insulating material 52 comprises one ring of insulating material sl ipped onto the conduit 7.

A process for manufacturing the plasma source 10 comprises :

1"') the step of placing the electrically insulating material 52 in a hyd rostatic state around the cond uit 7 and between the two electrodes 2, 3, the insulating material 52 being in contact with the inner side of only one electrode 3 and surrounding all the part of the conduit 7 comprised between this electrode 3 and the second face 20 of the plate 8, this step of placing a hydrostatic electrically insulating material comprising :

l"'.a) a step of placing the electrically insulating material 52 in a solid state around a portion of the conduit 7 designed for being between the two electrodes 2, 3, said insulating material 52 being in contact with the inner side of the only one electrode 3 to be isolated; to implement step l"'.a), conduit 7 is inserted through the first electrode 2, in such a way that first face 19 of the plate 8 is in contact with the inner side 16 of the first electrode 2. Then, the electrode 2, and conduit 7 are inserted into the housing 18. Then, the ring 52 of solid insulating material is slipped onto the conduit 7. Then conduit 7 is inserted through the second electrode 3, in such a way that the ring 52 is between the second electrode 3 and the plate 8, are in contact with the inner side 17 of the second electrode 3 and with a second face 20 of the plate 8 and surrounds all the part of the conduit 7 comprised between the second electrode 3 and the second face 20 of the plate 8. Thus in step l"'.a), the insulating material 52 is placed in a solid state around the conduit such that said insulating material surrounds at least a part of the conduit designed for being located between the two electrodes 2, 3;

l"'.b) a step of changing the insulating material 52 from its solid state to its hydrostatic state by exerting a pressure on the solid insulating material 52 up to reaching the hydrostatic state of the insulating material 52, the pressure being exerted by pressing the insulating material between the two electrodes; The step of exerting a pressure can be preceded by increasing the temperature of the insulating material in order to facilitate the step of changing the insulating material from its solid state to its hydrostatic state.

2"') after step 1"'), a step of solidifying only a part of the hydrostatic insulating material 52. 3"') a step of connecting the electrodes 2, 3 to the means 9 for generating an electric field between the two electrodes 2, 3.

In this third embodiment, only one electrode 3 is isolated. Only the cathode 3 is isolated . This allows to avoid the presence of insulating material near the hot region of the anode 2.

In step l"'.b), the pressure is exerted on the insulating material through the electrode 2, 3, i.e each electrode is pushed towards the insulating material to be put into its hydrostatic state. The pressure is exerted by pressing the insulating material 52 between the two electrodes 2, 3.

For the reasons previously disclosed, there is one infiltration of the hydrostatic insulating material 52 into the intermediate spaces9 between the conduit 7 and the second electrode 3 followed by a solidification of at least a part 24 of this infiltrated material 22.

In the case of the third embodiment of plasma source 103 the conduit 7 goes through and extends beyond one electrode 2 (the anode) in order to improve the lifetime of the plasma source, and goes only partially through the other electrode 3 (the cathode).

Indeed, as illustrated in figure 11, it is not necessary that the conduit 7 goes through and extend beyond the isolated electrode, as long as the length of the conduit inside this isolated electrode is longer than the length of the infiltration of insulating material in space 9 between this isolated electrode and conduit 7.

Choice of the insulating material

Of course, for each embodiment previously described, the insulating material must be a material able to pass from a solid state to a hydrostatic state by increasing pressure, and be thus a "rubber like material". This is not the case of all materials.

The insulating material is in its solid state at standard pressure and temperature conditions (lbar, 25°C).

The insulating material can be for example an "inverse melting material" or an "inverse melting polymer". The insulating material can be for example a latex, a silicone rubber or a compressible fluorocarbon.

The insulating material is preferably rubber and/or elastomer.

An other example of usable insulating polymer is polymer poly-4- methyl pentene-1 (P4MP1).

The manufacturing process according to the invention can further comprise heating the insulating material or maintaining the insulating material at a desired temperature while exerting the pressure for passing the insulating material from its solid state to its hydrostatic state. Thus, the step of exerting a pressure can be preceded by increasing the temperature of the insulating material in order to facilitate the step of changing the insulating material from its solid state to its hydrostatic state.

Figure 9 is a simplified phase diagram of P4MP1.

As illustrated in Figure 9, a manufacturing process according to the invention can comprise:

- increasing the temperature of the insulating material (see arrow 73),

- maintaining the insulating material at a desired temperature (typically the increased temperature, having in this particular illustrated case a value around 250°C (more generally between 200°C and 300°C)) while increasing the pressure (for example from 5 kilobars to 6 kilobars) for passing the insulating material from its solid state to its hydrostatic state, as illustrated by arrow 15,

- once the necessary surfaces are wetted by the insulating material, cooling the insulating material while maintaining the exerted pressure (see arrow 74).

Other Variants

Of course, the invention is not limited to the examples which have just been described and numerous amendments can be made to these examples without exceeding the scope of the invention. In particular, in an other embodiment of the invention, the process according to the invention comprises heating the insulating material for melting it in order to change the insulating material form its solid state to its hydrostatic state, instead of exerting a pressure, while keeping the complete device under vacuum to remove the air trapped in space 9.

In an other embodiment of the invention, the step of placing an electrically insulating material in a hydrostatic state comprises a step a directly placing a hydrostatic material, like a mixture of two liquid that becomes solid due to a chemical reaction between the two liquids (like a mixture of a liquid comprising polymers or monomers, and a liquid comprising cross-linking agent arranged for cross-linking the polymers or monomers), instead of placing the electrically insulating material in a solid state and changing the insulating material from its solid state to its hydrostatic state. In this case, all the insulating material (i.e. the surrounding part and the infiltrated part) is solidified after being infiltrated in the intermediate space(s) 9.

In the first and second embodiments of plasma source 10, 100 the conduit 7 goes through and extend beyond each electrode.

In a variant of these first and second embodiments of plasma source 10, 100 :

- the conduit 7 goes through and extend beyond the anode 2, and

- the conduit 7 goes only partially through the cathode 3,

as illustrated in the case of the third embodiment of plasma source 103.

In other variants of these first, second and third embodiments of plasma source 10, 100, 103, the conduit 7 goes only partially through both electrodes 2, 3.

In an other variant of the third embodiment of plasma source 103 :

-the conduit 7 does not at all go through electrodes 2, and/or

-the conduit 7 goes through and preferably extends beyond electrode

3.

Claims

1. A process for manufacturing a plasma source (1; 10; 103), said plasma source (1; 10; 103) comprising a first electrode (2), a second electrode (3), a conduit (7) linking the two electrodes (2, 3) and going at least partially through at least one of the electrodes (2, 3), said conduit (7) being arranged for guiding a gas (4) inside the conduit (7), the process being characterized in that it comprises:

- a step of placing an electrically insulating material (5, 6; 51, 61, 52, 62) in a hydrostatic state around the conduit such that said insulating material (5, 6; 51, 61, 52, 62) surrounds at least a part of the conduit (7), and

- a step of solidifying at least a part of the hydrostatic insulating material (5, 6; 51, 61, 52, 62).

2. Process according to claim 1, characterized in that the step of placing an electrically insulating material (5, 6; 51, 61, 52, 62) in a hydrostatic state comprises:

- a step of placing the electrically insulating material (5, 6; 51, 61, 52, 62) in a solid state around the conduit such that said insulating material (5, 6; 51, 61, 52, 62) surrounds at least a part of the conduit (7), and

- a step of changing the insulating material (5, 6; 51, 52, 61, 62) from its solid state to its hydrostatic state.

3. Process according to claim 2, characterized in that the step of changing the insulating material (5, 6; 51, 52, 61, 62) from its solid state to its hydrostatic state comprises a step of exerting a pressure on the insulating material (5, 6; 51, 61, 52, 62) in its solid state up to reaching the hydrostatic state of the insulating material (5, 6; 51, 61, 52, 62).

4. Process according to claim 3, characterized in that:

it comprises, after the step of placing an electrically insulating material (5, 6; 51, 61, 52, 62) in a hydrostatic state around the conduit, and for each one of the electrodes (2; 3) to be isolated, an infiltration of only a part the insulating material (5, 6; 51, 61, 52, 62) in its hydrostatic state into an intermediate space (9) between the conduit (7) and this electrode (2; 3) to be isolated, and

- the solidification comprises, for each one of the electrodes (2;

3) to be isolated, a solidification of at least a part the insulating material infiltrated into the intermediate space (9) while the pressure exerted on the part of insulating material staying between the electrodes in its hydrostatic state is maintained .

5. Process according to claim 3 or 4, characterized in that the pressure is exerted by pressing the insulating material (5, 6; 51, 61, 52, 62) between the two electrodes (2, 3).

6. Process according to claim 5, characterized in that the insulating material (5, 6) surrounds all the part of the conduit (7) comprised between the electrodes.

7. Process according to claim 3 or 4, characterized in that the conduit (7) is immovably attached to a plate (8) extending between the two electrodes (2, 3), the step of changing the insulating material (51, 52, 61, 62; 52) from its solid state to its hydrostatic state comprising :

pressing at least a part of the insulating material (51, 61; 52) between one of the electrodes (2; 3) and the plate (8) up to reaching the hydrostatic state of this at least a part of the insulating material (51, 61; 52), said at least a part of the insulating material (51, 61; 52) being in contact with a face of the plate (8).

8. Process according to claim 7, characterized in that the step of changing the insulating material (51, 52, 61, 62; 52) from its solid state to its hydrostatic state further comprises: pressing an other part of the insulating material (52, 62) between the other electrode (3) and the plate (8) up to reaching the hydrostatic state of the other part of the insulating material (52, 62), said other part of the insulating material (52, 62) being in contact with an other face of the plate (8).

9. Process according to any of the previous claims, characterized in that there is no empty space (12), in particular no air space, between the insulating material (5, 6; 51, 61, 52, 62) and the conduit (7) after the solidification.

10. Process according to any of the previous claims, characterized in that, for each one of the electrodes to be isolated, there is no empty space (13, 14), in particular no air space, between the insulating material (5, 6; 51, 61, 52, 62) and this electrode (2, 3) after the solidification.

11. Process according to any of the previous claims, characterized in that the insulating material (5, 6; 51, 61, 52, 62) comprises a material able to pass from a solid state to a hydrostatic state by increasing pressure, like rubber.

12. Process according to any of the previous claims, characterized in that the insulating material (5, 6; 51, 61, 52, 62) comprises at least one ring of insulating material slipped onto the conduit (7) before being put into its hydrostatic state.

13. A plasma source comprising :

- a first electrode (2),

- a second electrode (3),

- a conduit (7) linking the two electrodes (2, 3) and going at least partially through at least one of the electrodes (2, 3), said conduit (7) being arranged for guiding a gas (4) inside the conduit (7), and - an electrically insulating material (5, 6; 51, 61, 52, 62), said insulating material surrounding a least a part of the conduit,

14. The plasma source according to claim 13, characterized in that said insulating material comprises:

- a surrounding part located around the conduit such that said surrounding part of the insulating material (5, 6; 51, 61, 52, 62) surrounds a least a part of the conduit (7), and

- for each one of the electrodes (2; 3) to be isolated, an infiltrated part of the insulating material, infiltrated from the surrounding part of the insulating material (5, 6; 51, 61, 52, 62) into an intermediate space (9) between the conduit (7) and this electrode (2; 3) to be isolated .

15. The plasma source according to claim 14, characterized in that:

- the surrounding part of the insulating material is in its hydrostatic state, and

- for each one of the electrodes (2; 3) to be isolated, at least a part of the infiltrated part of the insulating material is in its solid state.