Patent Application
20120160168
The present invention relates to a device for generating a plurality of electron cyclotron resonance plasmas having a common magnetic structure.
To create an electron cyclotron resonance (ECR) plasma, it is necessary to generate magnetic fields which confine the plasma and which make it possible to satisfy the condition of resonance of the plasma electrons. These magnetic fields may be created by an electric current circulating in coils or by permanent magnets.
Permanent magnets have the advantage of having zero electrical consumption, but pose the drawback of not being able to generate short-range magnetic fields. For example, if a person skilled in the art decides to create a long and/or tall plasma (for example measuring a few metres) confined by permanent magnets, the ECR plasma will only be able to be a few centimetres thick. If a person skilled in the art also wants to produce a thick plasma (for example measuring a few tens of centimetres) he will have to use solenoids, which are high consumers of energy.
Such electron cyclotron resonance plasma generation devices are used for example for hydrogen production.
In fact, hydrogen (H2) now appears to be a very interesting energy vector which is increasingly gaining in importance and could eventually advantageously substitute petrol and fossil fuels, of which the reserves will decrease rapidly in the coming decades. In view of this, it is necessary to develop effective hydrogen production methods.
A method for producing hydrogen by injecting water vapour into a plasma is described in particular in document US2004/0265137. This patent describes a method for obtaining hydrogen from the vapour dissociated in a plasma. In particular, the document mentions the use of electron cyclotron resonance (ECR) to produce said plasma. Compared to other known hydrogen production methods, the use of an ECR plasma machine provides a number of advantages:
However, in spite of the above-mentioned advantages, such a plasma machine which breaks, by electronic impact, the bonds of the water molecule, has two major drawbacks: the range of the plasma, which does not reach far enough, makes it impossible to produce a large amount of hydrogen, and there is difficulty in separating the products formed by the dissociation of the water molecule.
On this basis, the object of the present invention is to provide an electron cyclotron resonance plasma generation device which enables effective dissociation of injected molecules, simple separation of formed products not necessarily requiring implementation of considerable magnetic fields, and which enables for example substantial production by volume of hydrogen by dissociation of water, whilst minimising the consumption of electrical energy.
To this end, the invention proposes an electron cyclotron resonance plasma generation device characterised in that it comprises:
“Sealed chamber under vacuum” is understood to mean a chamber in which a working pressure less than or equal to 5·10−3 mbar prevails, said working pressure corresponding substantially to the partial pressure of the molecules injected into the chamber.
“Longitudinal axis of the chamber” is understood to mean the axis along which the plasma has its greatest dimension.
“Magnetic field substantially equal to the magnetic field corresponding to the electron cyclotron resonance” is understood to mean a magnetic field equal, give or take, to ±10% of the magnetic field corresponding to the electron cyclotron resonance.
“Substantially constant magnetic field” is understood to mean a magnetic field value which does not deviate by more than 10% of the value of the resonance magnetic field.
According to the invention, the magnetic structure is a structure of permanent magnets, of zero electrical consumption, generating in each chamber a volume of (ECR) plasma whilst minimising the number of permanent magnets used.
The magnetic structure generates a magnetic field of which the minimum value of the module of the magnetic field is extended, at least in part, over a large portion of the inner volume of the chambers.
The device according to the invention comprises a plurality of sealed chambers under vacuum, each for containing a volume of plasma, such that two successive chambers communicate at one of their ends and two adjacent chambers share at least the same common magnetic element on their common wall.
The two adjacent chambers preferably share a plurality of magnetic elements on their common wall.
In this way, it is possible to stack a plurality of plasma chambers of which the common magnetic structure makes it possible to generate a plurality of plasma volumes.
When the device according to the invention is used for hydrogen production, this production of hydrogen from water vapour is thus very effective, producing a large amount of hydrogen which consumes little energy whilst having a compact hydrogen production device.
The hydrogen production is based on the dissociation of water by the use of electron cyclotron resonance plasma. However, the efficacy of the device according to the invention can be increased by placing in parallel a plurality of chambers and by using common magnetic means which generate two adjacent plasmas, it being possible for the plasmas to be generated either in the same chamber or in separate chambers.
Thanks to the principle of the electron cyclotron resonance plasma, when passing from the proximity of the resonance zone, the electrons acquire energy. They will therefore be able to dissociate the injected molecules, for example water molecules, then ionise the dissociation products. Thanks to the electroneutrality of the plasma, these ions will follow the electrons along the magnetic field lines.
According to the invention, the mirror configuration of the magnetic field forms a magnetic field profile having a non-point minimum called a “flat field” minimum along the longitudinal axis of the chamber, of which the value of the module of the magnetic field is equal to the value of the resonance magnetic field, give or take ±10%. This value of the module of the minimum magnetic field, which is equal to or very close to the electron cyclotron resonance is extended at least in part along the longitudinal axis of the sealed chamber of the device, typically over a length greater than ten centimetres and possibly reaching a few metres, between the two maxima of the magnetic field.
According to the invention, the shape, positioning and dimensions of the magnetic structure make it possible to extend this minimum value of the module of the magnetic field, which is equal to or very close to the electron cyclotron resonance, at least in part along the second axis perpendicular to the longitudinal axis, and parallel to the surface of the permanent magnets, typically over a length which is greater than five centimetres so as to have in each sealed chamber an extended volume of hot plasma.
The magnetic structure must satisfy the condition of electron cyclotron resonance over volume. If we consider a microwave frequency of 2.45 GHz, the condition of resonance requires a magnetic field of Bres=0.0875T. A person skilled in the art will use a magnetic structure calculation code so as to meet this condition of resonance uniformly for each plasma of each sealed chamber. The magnetic structure will be determined as a function of the hysteresis magnetic field and of the coercive magnetic field of each magnetic material, such as an alloy of samarium cobalt or an alloy of neodymium iron boron.
In this way, the electrons will be able to acquire a large amount of energy so as to effectively dissociate the water molecules and ionise the dissociation products. Moreover, during the production of hydrogen, the oxygen produced by the dissociation of the injected molecules could, for example, be trapped by selective cryogenic condensers along the length of the sealed chamber over a large length as well as over a large width.
It is noted that, although it uses an electromagnetic field, the device according to the invention does not use a method of thermal stirring of the water molecules, but in contrast breaks the atomic bonds by collisions with the plasma electrons.
The device according to the invention may also have one or more of the features below, considered individually or in any technically feasible combination:
The invention also relates to a hydrogen production device having an electron cyclotron resonance plasma comprising:
The hydrogen production device preferably comprises a recovering device for recovering undissociated water, said recovering device being formed by a condenser and/or being arranged substantially along the axis of injection of the water vapour.
The hydrogen production device preferably comprises at least one system for re-injecting the undissociated water in vapour phase provided by said recovering device for recovering undissociated water.
The hydrogen production device is such that said recovering device for recovering hydrogen produced by the dissociation comprise a pump for pumping the hydrogen in gaseous phase and/or at least one cryogenic condenser for freezing the hydrogen.
The hydrogen production device is such that said water vapour injector injects said water vapour in the form of a supersonic jet, said water vapour injector comprising a flat nozzle and a divertor, said divertor being used to shape said vapour jet so that it is directed along the longitudinal axis of said at least two chambers.
The hydrogen production device is such that said hydrogen and oxygen separator is formed by at least one selective cryogenic condenser for freezing the oxygen produced by the dissociation without freezing the hydrogen produced by the dissociation, said at least one selective cryogenic condenser freezing the oxygen along said volume of plasma generated in said at least two chambers.
The hydrogen production device is such that said at least one selective cryogenic condenser for freezing the oxygen forms the inner wall of said chamber and/or is situated at said magnetic field non-point minimum.
The hydrogen production device preferably comprises a second cryogenic condenser for freezing the oxygen produced by the dissociation, said condenser being located at the end of said at least two chambers between said magnetic mirror configuration and said hydrogen recovering device.
The hydrogen production device is such that said hydrogen and oxygen separator is formed by a hydrogen-permeable membrane, said permeable membrane separating the hydrogen produced by the dissociation along said volume of plasma generated in said at least two chambers.
The invention also relates to a device for producing thin layers, comprising:
The device for producing thin layers preferably comprises a system for displacing said substrate by positioning said substrate successively in front of each plasma.
The device for producing thin layers is such that said component injected into each of said at least two chambers is different in nature so as to form a stack of thin layers of different natures on said substrate.
The invention also relates to an implantation device comprising:
Further features and advantages of the invention will become clearer from the non-limiting description given below by way of indication and with reference to the accompanying figures, in which:
In all the figures, like elements are denoted by the same reference numerals.
The device 600 comprises:
The chambers 601 and 602 of the device 600 are placed under vacuum, the vacuum being produced by ad hoc pumping means. So as to have minimal impurities in the chambers 601 and 602, a residual vacuum of at least 10−4 mbar is required. During operation of the device 600, the working pressure in the chambers 601 and 602 is typically less than or equal to 5·10−3 mbar, this pressure being linked to the partial pressure of the molecules injected into the chambers 601 and 602.
The eight permanent bar magnets 610, 611, 612, 613, 614, 615, 616, 617 of the magnetic structure have the same direction of magnetisation and surround the first chamber 601.
The shape and orientation of the permanent magnets 610, 611, 612, 613, 614, 615, 616, 617 are such that, inside the chamber 601, the magnets produce an axial magnetic field of which the configuration of the module corresponds to a configuration of the magnetic mirror type, of which the profile 630a has at least two maxima (Bmax) at the abscissae located respectively in the zones of injection and extraction and a non-point minimum (Bmin) extended at least in part and preferably over a large portion along the chamber 601, along the longitudinal axis AA′, and is located between the two maxima (Bmax).
The magnetic structure is also formed by the four permanent bar magnets 618, 619, 620, 621 having the same direction of magnetisation which, combined with the bar magnets 614, 615, 616, 617, surround the second chamber 602 so as to produce inside the chamber 602 a second axial magnetic field, of which the configuration of the module corresponds to a configuration of the magnetic mirror type of which the profile 630b has at least two maxima (Bmax) at the abscissae located respectively in the zones of injection and extraction and a non-point minimum (Bmin) extended at least in part along the chamber 1, along the longitudinal axis AA', and is located between the two maxima (Bmax).
The bar magnets 614, 615, 616, 617 of the magnetic structure are common to the two chambers 601 and 602 and are dimensioned to produce an equivalent magnetic field both inside the chamber 601 and inside the chamber 602. The magnetic fields thus have the same profile 630a and 630b inside the chambers 601 and 602.
The bar magnets 614, 615, 616, 617 are placed under vacuum in welded casings which are made of a non-magnetic metal material and are vacuum sealed, thus making it possible to overcome problems linked to the degassing of magnets.
The maxima (Bmax) of the profiles 630 have a value greater than the value of the resonance magnetic field (Bres) for which the electron cyclotron resonance is obtained. The minimum (Bmin) is a minimum called a flat field, of which the value is equal to or slightly less than the value for which the electron cyclotron resonance is obtained, and is extended over a large length of the device 600.
The magnetic structure as shown in
The magnetic structure described above thus makes it possible to obtain, inside the chambers 601 and 602, an extended volume of the hot plasma.
The mirror configuration of the magnetic field is a configuration called minimum-B: the plasma electrons are confined in a magnetic well. The greater and more extended the length of the minimum-B, which is less than or equal to the value of the resonance magnetic field, the more the plasma volume will contain rapid electrons leading to improved dissociation of the injected molecules.
Thanks to the principle of electron cyclotron resonance, when passing from the resonance zone the electrons will acquire energy. They will therefore be able to dissociate the injected molecules, then ionise the dissociation products in part. The electrons follow the magnetic field lines thanks to Laplace's law; and, thanks to the electroneutrality of the plasma, these ions will follow the electrons along the magnetic field lines.
The microwaves injected into the plasma tend to propagate through the plasma as far as the resonance zone. In fact, the transfer of energy of the injected microwave power to the electrons of the plasma is produced in a magnetic field location (Bres) so that the condition of electron cyclotron resonance is established, that is to say there is equality between the pulse of the high-frequency wave ωHF and the cyclotron pulse of the electron:
ωHF=ωce=qeBres/me
in which qe is the charge of the electron (Cb);
Bres is the magnetic field corresponding to the resonance (T);
me is the mass of the electron.
A microwave generator (not shown) is placed outside the chambers 601 and 602 of the device 600; this generator injects high-frequency waves into the chambers 601 and 602 via the transmission medium 15. The frequency range of the microwaves may range from one GHz to about 100 GHz, the most common generator being the 2.45 GHz magnetron used commonly for domestic microwave ovens. For a frequency of 2.45 GHz, there is a resonance magnetic field Bres=0.0875 T. However, for miniature devices (for on-board systems for example), it is also possible to use power transistors. In fact, there are now field-effect transistors which are capable of supplying approximately 60 W at 14.5 GHz.
Advantageously, the aperture for inlet of high-frequency waves is placed in a strong magnetic field zone, for example at the first maximum (Bmax) of the profiles 630 of the module of the magnetic field, in such a way that the plasma volume diffuses towards the chambers 601 and 602 and not towards the inlet aperture so as to avoid any bombardment of this aperture by the plasma, thus ensuring a significant service life. It is also possible to use plasmas called “overdense” plasmas, where the plasma frequency is greater than the microwave frequency. The use of overdense plasmas advantageously makes it possible to increase the electronic density and thus increase the efficacy of the system.
Thanks to the magnetic structure and the flat minimum-B magnetic configuration along the longitudinal axis AA′, the chambers 601 and 602 have a plasma volume extending over a large portion inside each chamber with a significant density at the outlet of the jet of molecules to be dissociated and with a pressure gradient along each chamber.
Similarly to the description above, the chamber 602 is surrounded by a magnetic structure comprising permanent bar magnets 614, 615, 616, 617, 618, 619, 620, 621 all having the same direction of magnetisation.
The specific positioning and dimension of the bar magnets 614, 615, 616, 617, 618, 619, 620, 621 of the magnetic structure make it possible to produce, inside the chamber 602, a magnetic field of which the module has a mirror configuration about the axis AA′ and of which the value of the module is extended over a large portion of the width of the chamber 602, along the axis y.
The magnetic field within the chamber 602 thus has a minimum value (Bmin) equal to or very slightly less than the value of the resonance magnetic field (Bres), which is very extended in the central portion of the chamber 602.
In particular,
Thus, for any axis parallel to the axis AA′ and whatever the position along the y axis, the module of the magnetic field inside the chamber 602 has a profile with a mirror configuration comprising a flat non-point minimum-B extended along the chamber 602 and located between two maxima (Bmax).
In accordance with the specific embodiment of the device according to the invention described above, the bar magnets 610, 611, 612, 613, 614, 615, 616, 617, 618, 619, 620, 621 surrounding the chambers 602, 601 are formed by two types of rectangular magnet frames 60 and 70. The bar magnets 610, 613, 614, 617, 618, 621 shown in
Thus, for a frequency of 2.45 GHz, the magnet frame 60 typically has, along the xy plane, a rectangular section measuring 15.8 cm wide along the y axis and 26 cm long along the x axis and is hollowed at its centre by a rectangular section 6 cm wide and 16 cm long (this is one embodiment but of course there may be other combinations at a given frequency).
For the frequency of 2.45 GHz, the magnet frame 70 typically has, along the xy plane, a rectangular section measuring 15.8 cm wide along the y axis and 26 cm long along the x axis and is hollowed at its centre by a rectangular section 9 cm wide and 19 cm long (this is one embodiment but of course there may be other combinations at a given frequency).
The height along the z axis is defined by a person skilled in that art as a function of the space available and his needs. In fact, it may range from a few centimetres to several metres.
However, the dimensions of these magnets 60, 70 are not limiting; it is also possible to use bar magnets having dimensions ranging from a few tens of centimetres to several metres if it is desired to obtain a greater production of dissociation products, for example a greater production of hydrogen.
The hydrogen production device 100 comprises, unless otherwise indicated, all the features of a plasma generation device 600 described above.
To this end, the device 100 comprises:
In accordance with a first embodiment of such a hydrogen production device, the hydrogen-oxygen separation system 20 is a system for cryogenic separation of the dissociation products, formed by:
The chambers 1 and 2 of the device 100 are placed under vacuum, the vacuum being produced by ad hoc pumping means. So as to have minimal impurities in the chambers 1 and 2, a residual vacuum of at least 10−4 mbar is required. During operation of the device 100, the working pressure in the chambers 1 and 2 is typically less than or equal to 5·10−3 mbar, said pressure being linked to the partial pressure of water vapour injected into the chambers 1 and 2.
The magnetic structure is formed in particular by the eight permanent bar magnets 7, 8, 9, 10, 11, 12, 13, 14 having the same direction of magnetisation, the eight bar magnets 7, 8, 9, 10, 11, 12, 13, 14 surrounding the first chamber 1.
The orientation of the permanent magnets 7, 8, 9, 10, 11, 12, 13, 14 is such that, inside the chamber 1, the magnets produce an axial magnetic field of which the configuration of the module corresponds to a configuration of the magnetic mirror type, of which the profile 30a has at least two maxima (Bmax) at the abscissae located respectively in the zones of injection and extraction, and a non-point minimum (Bmin) extended at least in part and preferably over a large portion along the chamber 1, along the longitudinal axis AA′, and is located between the two maxima (Bmax).
The magnetic structure is also formed by four permanent bar magnets 3, 4, 5, 6 having the same direction of magnetisation which, combined with the bar magnets 7, 8, 9, 10, surround the second chamber 2 so as to produce inside the chamber 2 a second axial magnetic field, of which the configuration of the module corresponds to a configuration of the magnetic mirror type of which the profile 30b has at least two maxima (Bmax) at the abscissae located respectively in the zones of injection and extraction, and a non-point minimum (Bmin) extended at least in part along the chamber 1, along the longitudinal axis AA′, and is located between the two maxima (Bmax).
The bar magnets 7, 8, 9, 10 of the magnetic structure are common to the two chambers 1 and 2 and are dimensioned to produce a magnetic field equivalent both to the inside of the chamber 1 and to the inside of the chamber 2. The magnetic fields thus have the same profile 30 inside the chambers 1 and 2; the magnetic profile denoted by 30 being equivalent to the profiles 30a and 30b illustrated in
The bar magnets 7, 8, 9, 10 are placed under vacuum in welded casings which are made of a non-magnetic metal material and are vacuum sealed, thus making it possible to overcome problems linked to the degassing of magnets.
The maxima (Bmax) of the profiles 30 have a value greater than the value of the resonance magnetic field (Bres) for which the electron cyclotron resonance is obtained. The minimum (Bmin) is a minimum called a flat field minimum, of which the value is equal to or slightly less than the value for which the electron cyclotron resonance is obtained, and is extended over a large length of the device 100.
The maximum values (Bmax) of the magnetic field are preferably quite high, approximately from 0.15T to 0.3T, so as to limit axial leaks of the plasma.
The minimum value (Bmin) is a value equal to or less than the value of the resonance magnetic field (Bres) by approximately 90% of (Bres), that is to say approximately 0.08T for a frequency of 2.45 GHz. This value of the magnetic field equal to or slightly less than the electron cyclotron resonance is extended over a large portion of the length of the device along the longitudinal axis AA′, approximately 25 cm. The electrons can thus acquire a large amount of energy so as to effectively dissociate the water molecules over the entire length of the device 100.
The magnetic structure as shown in
The magnetic structure described above makes it possible to obtain, within the chambers 1 and 2, an extended volume of hot plasma.
The mirror configuration of the magnetic field is a configuration called minimum-B: the plasma electrons are confined in a magnetic well. The greater and more extended the length of the minimum-B, which is less than or equal to the value of the resonance magnetic field, the more the plasma volume will contain rapid electrons leading to improved dissociation of the water vapour into oxygen and hydrogen.
In the hydrogen production device 100, the water vapour injector 18 and the chambers 1 and 2 are preferably placed close to the microwave transmission medium 15 (however, another location may also be selected for reasons of convenience). The water is introduced into the chambers 1, 2 in the form of a supersonic jet of vapour with the objective of obtaining a high level of directivity of water vapour so as to direct the water vapour directly into the volume of hot plasma towards the resonance zone of the chambers 1 and 2. This jet is ejected from a nozzle acting as an orifice in an enclosure in which the water vapour is located. Divertors are placed at the outlet of the nozzle so as to define the angular opening of the jet. These divertors are formed by pipes in which a liquid circulates, of which the temperature approaches 5° C. (a lower temperature would lead to solidification of the water over the divertors). The water vapour which comes into contact with the divertors is immediately condensed and runs along the divertors.
So as to further improve this directivity by reducing the size of the vapour jet, the cryogenic condensers 16 formed for example by cryogenic rings are placed at the first maxima (Bmax) of the magnetic fields, of which the profiles 30, 30a, 30b represent the modules of the magnetic fields along the chambers. The cryogenic condensers 16, of which the temperature approaches 200 K, are used as diaphragms with the aim of trapping, by cryocondensation, the water vapour located in the external portion of the vapour jet. The condensers 16 also prevent saturation with undissociated water of the main cryogenic condensers 21 and 22, which are required for dissociation of ionised elements. If the cryogenic condensers 16 are saturated with water, a device (not shown) makes it possible to isolate the condensers 16 with the aim of regenerating them. For this, the device re-heats the cold walls of the condensers 16 so as to recover the water from the cold walls in liquid or gaseous form to be re-injected into the device 100 by the recycling pumps 17.
The cryogenic condensers 16 may also be replaced by liquid condensers comprising a vertical tubing in which a pressure gradient (from 10−3 mbar to 102 mbar or 1 bar) is established. The water, which passes from the vapour form into the liquid form, thus runs along the vertical tubing by gravity and is advantageously recycled via the recycling pump 17. However, if the recycling tubing is short, the pressure gradient in the tubing may remain low, and the water may be re-injected into the device 100 directly in vapour phase.
Thanks to the magnetic structure and the flat minimum-B magnetic configuration along the longitudinal axis AA′, the chambers 1 and 2 have a plasma volume extending over a large portion inside each chamber, with a significant density at the outlet of the vapour jet and a pressure gradient along each chamber.
The device 100 does not radially confine the plasma owing to the radial inhomogeneity of the magnetic field. In this case, the ionised particles forming the plasma tend to experience a radial drift, which is a known phenomenon in plasma physics.
The cryogenic condensers 21, 22, 23 are cold wall condensers, called cryo-panel or cryogenic panel condensers. The condenser 21 is advantageously placed over the inner walls of the outer surface of the chambers 1 and 2, and the condenser 22 is advantageously placed over the inner walls of the inner surface of the two chambers so as to condense the desired ionised particles. The cold walls of the condensers 21 and 22 have a temperature approaching, for example, 20 to 30 K so as to condense all the elements present in the plasma chambers except for hydrogen, which remains in gaseous form at this temperature at the working pressure of 0.1 Pa.
In fact, according to the phase diagrams illustrated in
Thus, by using one or more cryogenic condensers 21, 22 forming the walls of the plasma chambers, cooled to a temperature such that the two elements, hydrogen and oxygen, constituting the plasma are in different phases (gaseous hydrogen and solid oxygen), the oxygen may be trapped in solid form without trapping the hydrogen, this being recovered by other means. The temperature of the condenser depends on the partial hydrogen pressures from the initial density of the plasma, which is itself a function of the microwave frequency injected. The oxygen being trapped, recovering device for recovering the hydrogen are then used, such as a conventional pump (a turbomolecular pump, for example) to pump the hydrogen. It is also possible to advantageously use the fact that the ionised particles follow, by plasma electroneutrality, the electrons which are guided by the magnetic field lines.
In fact, if the cryogenic oxygen condensers 21, 22, 23 are placed in the magnetic field lines, the cryogenic hydrogen condensers may then advantageously be placed outside the magnetic field lines.
It will be noted that the different components produced by the dissociation of water are basically H2, O2, OH, H, O, O+, H+, H2+, O2+, OH−. All the ionised elements neutralise before touching a wall (either a cold wall of a cryo-panel condenser or another wall), whilst the neutral elements recombine to form stable elements: H2, O2, H2O.
The cryogenic condensers 23 are advantageously placed in the axis of vapour jets outside plasma volumes before the hydrogen pumping system 24, so as to condense the ionised particles of oxygen as well as the undissociated water vapour. Since the oxygen produced by the dissociation of water is trapped over the entire length of the device 100, it is thus suffice to pump the hydrogen axially at the other end of the device 100 and the send it into a compressor (not shown).
A high-frequency (HF) screen 25 is placed in front of the cryo-panels 21, 22 so as to protect the cryo-panels and to avoid heating thereof by the microwaves, the mesh of the HF screen 25 being determined as a function of the wavelength of the microwaves.
It will be noted that, in accordance with the grid shown in
The best rate of dissociation of water being obtained for pressures below 5·10−3 mbar, this value is considered to be a maximum pressure in the chambers 1 and 2, all the more so since the electrons would no longer be guided magnetically if this pressure were increased above 5·10−3 mbar.
It is also possible to use a source for injection of multi-frequency microwaves of which the bandwidth of each frequency forms a wide frequency band leading to the formation of a large resonance zone; the width of the resonance zone corresponding substantially to the bandwidth of the microwave source.
In this variant of the device, the magnetic structure is formed in particular by twenty permanent bar magnets numbered from 121 to 140 and having the same direction of magnetisation.
The bar magnets 121 to 140 are arranged in such a way that each chamber 110, 111, 112, 113, 114 is surrounded by eight permanent bar magnets, of which twelve bar magnets 125 to 136 are used commonly by two chambers so as to produce a magnetic field in each of the chambers which they surround. The bar magnets 125 to 136 are placed under vacuum in welded casings which are made of a non-magnetic metal material and are vacuum sealed, thus making it possible to overcome problems linked to the degassing of magnets.
The orientation of the permanent magnets 121 to 140 is such that, inside the chambers 110, 111, 112, 113, 114, the magnets produce an axial magnetic field of which the configuration of the module corresponds to a configuration of the magnetic mirror type, of which the profiles 30 have at least two maxima (Bmax) at the abscissae located respectively in the zones of injection and extraction, and a non-point minimum (Bmin) extended at least in part and preferably over a large portion along the chambers 110, 111, 112, 113, 114 along the Z axis corresponding to the longitudinal axis of the device; the minimum (Bmin) being located between the two maxima (Bmax).
In accordance with a specific embodiment of the invention, the bar magnets 121, 124, 125, 128, 129, 132, 133, 136, 137 and 140 have the same dimensions, this detail also being applicable to the bar magnets 122, 123, 126, 127, 130, 131, 134, 135, 138 and 139.
It will be noted that the device 200 comprises, in each chamber 110, 111, 112, 113, 114, a water vapour injector 18 and a high-frequency waves of the microwave type transmission medium 15.
In this second embodiment, the hydrogen/oxygen separation system is formed by:
By contrast, the device 200 according to the invention only comprises one pump 24 which is common to all the chambers 110, 111, 112, 113, 114 for the recovery of hydrogen in gaseous form.
In this embodiment the magnetic structure 400 is formed of three permanent magnet blocks 310, 320, 330 aligned with the z axis corresponding to the longitudinal axis of the plasma chambers 301, 302, 303, 304, 305.
The two magnet blocks 310 and 320, located at the ends of the device 300, are magnet blocks said to be “closed” magnet blocks, whereas the central magnet block 330 is said to be “open” since it has openings in the upper part and in the lower part so as to facilitate the insertion of the cryo-panels for trapping oxygen as defined with reference to
The magnet blocks 310 and 320 typically represent a portion of the magnetic structure 400 of the device 300 making it possible to surround each chamber 301, 302, 303, 304, 305, the magnet blocks 310 and 320 representing the bar magnets of each chamber located at the maxima Bmax of the profiles of the module of the magnetic field present in each chamber 301, 302, 303, 304, 305.
The central magnet block 330 typically has a length of 600 cm (along x), a width of 644 cm (along y) and a depth of 240 cm (along z). The magnet block 330 also has five recesses each corresponding to one of the chambers 301, 302, 303, 304, 305. These recesses typically have a width of 104 cm or 98 cm (along y) and a length of 600 cm (along x), which makes it possible to have a magnet block 330 with openings in the upper part and in the lower part to facilitate the extraction of oxygen trapped by the cryo-panels.
The dimensions, along the y axis, of the chambers 301, 302, 303, 304, 305 are advantageously different and are alternated so as to produce magnetic fields leading to the production of a significant electron cyclotron resonance volume.
The central magnet block 330 typically represents part of the magnetic structure of the device 300 making it possible to surround each chamber 301, 302, 303, 304, 305 by bar magnets, the bar magnets being located at the minimum (Bmin) of the profiles of the module of the magnetic field present in each chamber.
Moreover, the central magnet block 330 makes it possible to reduce the number of bar magnets surrounding each plasma chamber by proposing a single magnetic structure by replacing the plurality of separate bar magnets, as shown with reference to
In accordance with this fourth embodiment, the device 400 differs from the device 100 of
The permeable separation membranes 421, 422 may also be formed by a metal membrane (such as a palladium membrane), a chemical membrane which absorbs oxygen, or else a magnetic membrane which traps oxygen by paramagnetism.
The surface-treatment device 500 comprises, unless otherwise indicated, all the features of a plasma generation device 600 described above.
The device 500 comprises a plurality of chambers, of which two chambers are denoted by reference numerals 501 and 502.
The two chambers 501, 502 communicate, at their end opposite the injector 18, by means of a chamber 521 in which a substrate able to receive the different dissociation products of the chambers is displaced, the nature of the dissociation products being a function of the nature of the plasmas generated in each chamber.
By way of example, the device 500 may be used for an application of hardening of an aluminium substrate by implantation of nitrogen ion at the surface. For this, the device 500 for example has seven chambers each comprising a plasma making is possible to provide different nitrogen ions. The aluminium substrate moving in front of each chamber will first receive N+ ions when passing from the first plasma, then N2+ ions when passing from the second plasma, up to N7+ ions when passing from the seventh plasma. The assembly being brought to a fixed high voltage, the energy of the ions is thus proportional to the charge of the ion, and different penetration depths of the nitrogen atoms in the aluminium will be obtained.
The device 500 is thus a compact device which may comprise adjacent plasmas of the same nature or of different nature for the surface treatment of a sample.
The sample to be treated passes successively in front of the different plasmas, for example passing from the stripping of the argon then to the deposition of the catalyst so as to finish with the implantation of the desired element (for example carbon).
For example, in an application intended for the growth of carbon nanotubes, the substrate passes successively in front of four plasmas so to as to undergo the different phases of production of carbon nanotubes: stripping, deposition of silicon, deposition of the catalyst, growth of nanotubes.
The invention thus proposes a compact device for generating electron cyclotron resonance plasma and having a plurality of plasmas, the plasmas possibly being identical, for example for high-volume production of hydrogen, or different, for example for surface treatment.
The invention has primarily been described for an application enabling extraction of the hydrogen, in gaseous form, located at the end of the chambers and pumping the hydrogen axially; however, it is also possible to equip the device, in the case of an application of hydrogen production, with a hydrogen extraction means which pump the hydrogen from the chamber radially at the end of each chamber. In fact, in the case of use of a single magnetic mirror configuration, as shown in
The invention has primarily been described, in the embodiments illustrated with reference to
The invention has primarily been described with a plurality of microwave generators injecting high-frequency waves via a plurality of propagation means in each plasma chamber; however, it is also possible according to the invention to only use a single microwave generator for the entire device comprising a plurality of plasma chambers by using a multi-guide high-frequency injection device possibly with high-frequency cones.
The invention has primarily been described with a plurality of means for injecting water vapours; however, it is also possible in accordance with the invention to provide a single means for injecting water vapours having a main entry into the device and a system for distributing vapour towards each chamber and each plasma volume.
The invention has primarily been described with a magnetic configuration comprising a minimum-B substantially equal to or less than the value corresponding to the resonance magnetic field, of which the value of the minimum-B is a value which is constant over a specific length of the chamber of the device corresponding to the distance between the two maxima (Bmax); however, in another representation of the invention, the minimum-B of the magnetic configuration may fluctuate around a minimum value, whilst remaining very close to said minimum value over a large distance of the chamber of the device corresponding to the distance between the two maxima (Bmax).
Lastly, the invention has primarily been described with an axial magnetic field; however, it is also possible to add a radial component to the axial magnetic field, for the dissociation for example of other elements requiring the use of a radial magnetic field and/or to avoid radial leaks of the plasmas caused by the drift of the particles and to thus ensure an improved confinement of the plasmas.
Of course, the invention is not limited to the embodiments which have just been described.
Thus, if it is desired to treat a greater number of molecules to be dissociated, it is possible to increase the dimensions of the assembly whilst ensuring that there are resonance zones in each plasma chamber. Thus, it is possible in accordance with requirements to increase the length or volume of the minimum-B, which is equal to or slightly less than the resonance, up to several metres or several m3. It will be noted that the longer the volume of the minimum-B, the more effective the device according to the invention.
Although the invention has been more specifically described for low-frequency microwave frequencies of approximately 2.45 GHz, it is of course also possible to use higher microwave frequencies, as well as two injections of microwaves with similar frequencies so as to obtain a minimum-B value between the two resonance values, as well as a plurality of injections of microwaves of which the bandwidth of each (several MHz) leads to a very wide frequency bandwidth and thus to a larger resonance zone.
In particular, the other advantages of the invention are as follows:
| Number | Date | Country | Kind |
|---|---|---|---|
| 0953740 | Jun 2009 | FR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2010/057838 | 6/4/2010 | WO | 00 | 3/12/2012 |
