Classifications

• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
  • H05H1/00—Generating plasma; Handling plasma
  • H05H1/24—Generating plasma
  • H05H1/47—Generating plasma using corona discharges
  • H05H1/471—Pointed electrodes
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
  • H05H2245/00—Applications of plasma devices
  • H05H2245/30—Medical applications
  • H05H2245/32—Surgery, e.g. scalpels, blades or bistoury; Treatments inside the body

Definitions

• the invention relates to a device for emitting a plasma jet from atmospheric air at a pressure and at ambient temperature, this device being adapted to form a self-projected plasma jet, that is to say not requiring, for this projection, the addition of a specific means for generating a gas flow.
• Such a device for emitting a plasma jet can find applications in particular in the field of nanotechnologies where plasma surface treatment is required, in the biomedical field for plasma localized treatments, in particular for blood coagulation or for the establishment and / or maintenance of asepsis at the site of a surgical procedure, and / or in the field of surface treatment with a view to their depollution, biological decontamination or sterilization.
• DBD dielectric barrier discharge
• Such a device comprises two electrodes which are subjected to a potential difference and which are traversed by an argon flow having a displacement speed estimated at about 500.degree.
• Such a solution involves providing means for storing argon under pressure and introducing a flow of argon flowing between the two electrodes.
• a solution poses practical problems related to the use of a gas under pressure, and does not produce a plasma of atmospheric air self-projected at ambient pressure and temperature.
• a second type of known solution similar to the previous one, consists of forming a plasma of the "crown plasma” type between two coaxial electrodes separated by a volume of insulating gas.
• Pointu et al. (2005) (Sharp AM, Ricard A., Dodet B., Odic E., Langle J. and Petchu MG, (2005), J. Phys D Appl Phys 38, 1905-1909; in N 2 -O 2 flowing post-discharges and atmospheric pressure for sterilization ”) describes a process for sterilization by a cold plasma produced during a treatment of a preformed gas stream of nitrogen and oxygen by a pulsed crown discharge at 10 kHz generated between two electrodes. Such a sterilization process requires external means for forming a gas flow. It does not allow the formation of a self-projected plasma from atmospheric air at atmospheric pressure.
• US 7,229,589 discloses a method of decontaminating a surface in which a flow of pre-pressurized molecular nitrogen is subjected to a pulsed discharge so as to treat the gas flow by discontinuous discharges.
• a decontamination process requires means for preparing high purity molecular nitrogen and pressurization prior to the decontamination treatment, and does not generate a self-projected plasma jet from atmospheric air at pressure. atmospheric.
• the invention aims to overcome the disadvantages mentioned above by proposing a device adapted to emit a cold plasma jet, in particular by corona discharge, which does not require additional specific member for establishing a flow of gas between electrodes.
• the invention aims to provide such a device adapted to be used in atmospheric air and requiring no means for evacuation or pressurization of the inter-electrode space.
• the invention also aims at providing a device adapted to emit a cold plasma jet at a distance from the discharge (that is to say, in the near after discharge), and which is therefore substantially free of ionic excited species, and rich in radiative and / or metastable neutral excited species, in particular radicals.
• the invention aims in particular to provide such a device capable of forming a cold plasma jet from atmospheric air at atmospheric temperature and pressure.
• the invention also aims to achieve all these objectives at lower cost, by proposing a cold plasma jet emission device, which is low cost and made from means - especially electronic and electrical components - usual and cheap.
• the invention also relates to the use of a device according to the invention in the field of surface treatment.
• the invention also aims at providing such a device which is particularly suitable for surface treatment, and a method of treating a surface to be treated in which a device according to the invention is used, this method being simple in its implementation. at least comparable to that of known methods.
• the invention is more particularly to provide such a device and such use whose implementation is safe for the user.
• the invention also aims at providing such a device and such a use for the treatment of a surface to be treated that are more efficient and are environmentally friendly.
• the invention further aims to achieve these objectives by preserving the work habits of staff. It aims in particular to provide such a device that is easy to use, and imply for its implementation that little manipulation.
• the invention relates to a device for transmitting a plasma jet at ambient pressure and temperature, comprising an electric field generator capable of generating discharges between an anode assembly and a cathode assembly, in which: the cathode assembly is shaped so as to define a dielectric space, called inter-cathodic space:
• said cathodic opening is defined by at least one edge, called the active edge, of the cathode surface, the said active edge (s) extending in a plane, called the cathodic opening plane; ,
• the anode assembly comprises at least one portion, said pointed portion, having a minimum radius of curvature, oriented towards the outside of the inter-cathodic space and disposed laterally and in depth with respect to the cathode opening of the cathodic assembly;
• said device being characterized in that the pointed portion of the anode assembly is arranged to extend to the cathodic aperture plane, and so as to cause an emission of a plasma jet spontaneously projected according to a predetermined orientation to the outside of the inter-cathode space.
• the electric field generator is connected to the anode assembly and to the cathode assembly so as to produce an electric field capable of generating the plasma jet. To do this, this electric field must have a higher potential value at the anode assembly and a lower potential value at the cathode assembly. When these potential conditions are satisfied, the plasma jet is emitted.
• the electric field generator is adapted to apply potentials of constant predetermined values (continuous or pulsed) to the anode and cathode assemblies.
• the electric field has invariable polarity, in particular non-alternating polarity.
• anode or “anode assembly” denote an electrode or, respectively, a set of electrodes placed at the highest potential of the electric field generated by the electric field generator (continuous or pulsed).
• cathode or “cathode assembly” denote an electrode or, respectively, a set of electrodes placed at the lowest potential of an electric field generated by the electric field generator, in particular corresponding to the potential of the mass. (normally that of the earth).
• the voltage generator is selected from the group consisting of DC voltage generators and pulsed voltage generators, in particular forming a pulsed field of frequency between 1 kHz and 100 kHz.
• the voltage generator is adapted to deliver between the anode assembly and the cathode assembly a voltage of between 0.5 kV and 20 kV.
• the inter-cathode space is a cavity that extends between cathodic surface portions (walls) of an electrically conductive material of the cathode assembly.
• the inter-cathode space is inscribed within the cathode assembly, said cathode assembly opening outwards from the inter-cathode space through the cathode opening.
• the inter-cathode space is filled with material, for example by atmospheric air at atmospheric pressure and at ambient temperature. However, it is also possible that the inter-cathode space is occupied by any other gas or dielectric gas composition, or by a solid dielectric.
• a device according to the invention further comprises means for introducing a gas composition into the inter-cathode space of the cathode assembly.
• Such means are however not necessary for the formation and emission of the self-projected cold plasma jet. They may, however, make it possible to produce a self-projected plasma jet containing excited species obtained from gaseous species other than those of atmospheric air. Nevertheless, in this variant, the plasma jet produced is not assured solely by the introduction of said gas composition.
• the pointed portion of the anode assembly is oriented toward the outside of the inter-cathode space so as to form a self-projected cold plasma jet in the space extending beyond the cathode aperture, to the outside of the inter-cathodic space, opposite the anodic set.
• the minimum radius of curvature of the pointed portion of the anode assembly is not oriented towards a cathode surface of the cathode assembly, but in a non-intersecting direction to a cathode surface, in particular in a direction substantially perpendicular to a plane defined by the cathodic opening of the cathodic assembly.
• the pointed portion of the anode assembly may be a simple tip of symmetrical shape of revolution, that is to say in the form of actual tip.
• the pointed portion of the anode assembly may also be non-symmetrical of revolution with a minimum radius of curvature in section in a single plane, and a different curvature in any other plane.
• the expression "pointed portion” also encompasses embodiments in which the pointed portion of the anode assembly is a simple ridge, more or less long, rectilinear or curved, extending longitudinally at the surface of the anode assembly and having in transverse cross-section, a minimum radius of curvature oriented towards the outside of the inter-cathode space.
• the inventors have surprisingly found that the application of a positive high voltage to the anode assembly comprising a pointed portion having a minimum radius of curvature arranged as indicated above with respect to the cathode opening, not only makes it possible to form a generation discharge of activated species from atmospheric air, at ambient pressure and temperature, but also allows, without the use of any specific external means of gas flow production in the inter-cathodic space of form a self-projected cold plasma jet directed towards the outside of the intercathodic space.
• the formation of a self-projected cold plasma jet directed towards the outside of the inter-cathode space occurs well in the presence of an anode assembly and a cathode assembly. adapted to form a discharge-in particular a discharge corona- and opposite the pointed portion of the anode assembly (where the excited species-and therefore substantially nonionic-are produced), out of the intercathodic space and in a direction substantially perpendicular to the cathodic aperture plane.
• the formation of a self-projected cold plasma jet does not occur (as in the devices of the state of the art) by forming an electric arc - between an anode assembly and a cathodic assembly and in which the ionic species formed are attracted by the cathode assembly.
• the self-projected cold plasma jet is produced from the pointed portion of the anode assembly and in a direction substantially parallel to the minimum radius of curvature of said pointed portion.
• the inventors have observed the formation of a luminous halo extending from the pointed portion of the anode assembly towards the outside of the inter-cathode space over a distance of the same order of magnitude as the distance separating the anode assembly from the cathode assembly of the device.
• This luminous halo reveals the formation of molecular species in excited radiative states, the de-excitation transition of which is accompanied by the emission of photons, said excited molecular species being projected towards the outside of the interstellar space. -cathodique.
• This jet of plasma gas self-projected result from the formation of a wind of ionic particles, consisting of a mixture of charged particles, set in motion and accelerated by the electric field formed between the anode assembly and the cathode assembly , a part of which would transmit its momentum to neutral particles during elastic shocks, leading to the emission of a self-projected plasma jet from atmospheric air, at ambient pressure and temperature.
• the spontaneous production of this stream of plasma material extending over a distance of several centimeters, beyond the luminous halo was observed and measured by means of an anemometer.
• Such a device makes it possible to form, from and in the immediate vicinity of the pointed portion of the anode assembly, an electric field leading to the formation of a self-projected plasma jet towards the outside of the internal space. cathode of the device, out of the inter-cathodic space.
• the formation of a self-projected cold plasma jet directed towards the outside of the inter-cathode space does not require the addition of a specific external device for the production of a flow of a gaseous composition in the inter-cathodic space.
• the pointed portion of the anode assembly is arranged to extend to the cathodic aperture plane without exceeding it (tangent to the cathodic aperture plane).
• the cathodic opening plane extends tangentially to the pointed portion of the anode assembly.
• the cathodic opening plane extends tangentially to the pointed portion of the anode assembly and perpendicular to the radius of curvature of said pointed portion.
• the plasma jet is sprayed spontaneously-that is to say without the use of a gaseous stream formed or flowing inside the inter-cathode space outside the inter-cathodic space and not towards a surface of the cathodic assembly.
• the voltage generator is able to generate crown discharges between the anode assembly and the cathode assembly.
• the voltage generator is suitable for generating crown discharges in the inter-cathode space extending within the cathode assembly and including the pointed portion of the anode assembly.
• the voltage generator is able to generate crown discharges in the inter-cathode space extending inside the cathode assembly and from the pointed portion of the anode assembly.
• Such a device is configured to allow the formation of positive polarity ring discharges between the anode assembly and the cathode assembly by generating activated species - especially activated nonionic species - from the air. atmospheric, at ambient pressure and temperature leading to the formation of a self-projected plasma jet in the direction perpendicular to the cathodic aperture plane, out of the inter-cathode space opposite said pointed portion of axial end, without using any external means for producing gas flow.
• such a device is adapted to avoid the formation of an electric arc producing ionized and dissociated species at high temperature.
• the cathode opening is defined by at least one edge, called the active edge, of the cathode surface, said active edge (s) extending in the plane cathodic opening.
• the cathodic aperture plane is a secant virtual plane with the cathode set.
• the anode assembly and the cathode assembly are then adapted to leave free a half-space defined by the cathodic opening plane beyond the inter-cathode space.
• the anode assembly (and the pointed portion) it is possible for the anode assembly (and the pointed portion) to extend for a certain distance on the outside of the inter-cathode space beyond the cathodic opening plane, or contrary, inside the inter-cathodic space.
• the cold plasma jet is self-projected from the pointed portion of the anode assembly in the space extending opposite said pointed portion of the anode assembly.
• the self-projected cold plasma jet is produced from the pointed portion of the anode assembly and in a direction substantially parallel to the minimum radius of curvature of said pointed portion.
• the self-projected cold plasma jet is produced from the pointed portion of the anode assembly in a direction substantially orthogonal to the active edges of the cathode assembly
• the anode assembly comprises at least one cylindrical anode of revolution about an axial direction (in the form of a needle) and the pointed portion is a pointed portion of axial end of said cylindrical anode, said axial end portion having a cross-section, in at least one axial plane containing said axial direction, having a minimum radius of curvature the value of which is adapted to allow the formation of discharges from this axial end pointed portion under the effect of an electric field formed by the generator (s).
• the active edge is an edge of a cathode of the cathode assembly, said edge surrounding the axial end portion of the cylindrical anode of the anode assembly to which this cathode is associated.
• the active edge (s) of the cathode (s) has (s) at least one plane of symmetry perpendicular to the cathode opening plane of said (said) cathode (s), said cathodic aperture plane comprising the axial end portion of each cylindrical anode with which this (these) cathode (s) is (are) associated (s), and adapted (s) to orient spontaneously the cold plasma jet perpendicular to the cathodic aperture plane.
• the cathode (or the cathodes) have active edges arranged so as to occupy the vertices of an isosceles triangle -particularly of an equilateral triangle-, and the pointed portion of axial end of the cylindrical anode is arranged to occupy the center of gravity of said triangle.
• the (the) edge (s) active (s) of the cathode assembly has (s) in section in at least one plane perpendicular to the cathodic aperture plane, said perpendicular plane comprising the portion pointed axial end of the cylindrical anode, a form symmetrical with respect to said axial end pointed portion to which this cathode assembly is associated.
• the cathode assembly comprises at least two active edge portions extending in the cathodic aperture plane symmetrically with respect to the axial end pointed portion of the cylindrical anode and is adapted to spontaneously orient the jet of cold plasma perpendicularly to the cathodic aperture plane.
• the cathode assembly has an active edge having in section in each plane perpendicular to said cathodic opening plane, a shape having a symmetry with respect to said axial end pointed portion of each cylindrical anode to which the cathode assembly is associated.
• the active edge of the cathode assembly is a continuous active edge extending in the cathodic aperture plane and of central symmetry with respect to the axial end pointed portion of the cylindrical anode of the anode assembly.
• the active edge of the cathode assembly has a circular shape or a polygonal shape with a center of symmetry-notably hexagonal, octagonal, parallelogram, preferentially square.
• Such a device makes it possible to form a corona discharge in positive polarity between the anode assembly and the cathode assembly by generating activated species from atmospheric air, at ambient pressure and temperature, leading to the formation of a self-projected plasma jet in the direction perpendicular to the cathodic opening plane, out of the intercathodic space opposite said axial end pointed portion, without the use of any external means for producing a gas flow.
• the cathode assembly comprises two cathode plates each having a rectilinear active edge, said rectilinear active edges of the two cathode plates being coplanar, parallel to each other and symmetrical to each other relative to a median plane including the pointed portion of the anode assembly.
• the anode assembly may be formed of a plurality of anodes cylindrical, the axial end pointed portion of minimum radius of curvature of each cylindrical anode extending in said median plane and in the cathodic aperture plane.
• the minimum radius of curvature of the pointed portion of the anode assembly is less than 500 ⁇ m, in particular between 1 ⁇ m and 500 ⁇ m, in particular between 10 ⁇ m and
• the minimum radius of curvature of the pointed portion of the anode assembly is of the order of 20 microns.
• the pointed portion of the anode assembly is formed of a conductive material selected from the group consisting of tungsten, tungsten carbides, aluminum and their alloys.
• the cathodic opening plane of the cathode assembly is substantially perpendicular to the axial direction of the cylindrical anode.
• the plasma jet is self-projected from the axial end pointed portion of the cylindrical anode in a direction perpendicular to the cathodic opening plane, and parallel to the axial direction of the cylindrical anode.
• the cathodic aperture plane of the cathode assembly is inclined relative to the axial direction of the cylindrical anode.
• the plasma jet is self-projected from the axial end portion of the cylindrical anode in a direction perpendicular to the cathodic opening plane, said direction being not parallel to the axial direction of the cylindrical anode.
• the (the) edge (s) active (s) of the cathode assembly is (are) formed (s) of at least one conductive material selected from the group consisting of brass, copper and their alloys.
• each cylindrical anode has in cross section perpendicular to its axial direction, a substantially discoidal shape, whose diameter is between 0.5 mm and
• a device comprises therefore at least one cylindrical anode, each cylindrical anode having a pointed shape whose tip is oriented substantially along the longitudinal axis of said cylindrical anode.
• each cylindrical anode having a minimum radius of curvature extends substantially in the cathodic aperture plane of the cathode assembly.
• each cylindrical anode of the anode assembly and each cathode of the cathode assembly are adapted to cooperate and generate crown discharges between the axial end portion of minimum radius of curvature of each cylindrical anode and the cathode assembly to which these cylindrical anodes are associated.
• a device according to the invention is adapted to produce a plasma jet at ambient pressure and temperature at a speed (gaseous flow rate of the plasma jet measured by means of an anemometer) of the order of 1 m / s at 10 m / s.
• a device according to the invention has a size adapted to be held, worn and handled by a single user.
• a device comprises a cathode assembly and an anode assembly formed of a single cathode and anode, said cathode and said anode being in one or more pieces, the active edge (s) of the cathode surrounding the axial end portion of the single anode.
• the invention also relates to the use of such a device for a surface treatment - particularly for the microbiological decontamination of said surface - in which said surface is disposed in the self-projected plasma jet.
• the inventors have found that exposure of adherent Escherichia coli bacteria on a solid surface to a cold plasma jet generated by a device according to the invention placed a few millimeters from said solid surface leads to a reduction in bacterial flora. , including a division by a factor of 1000 of the initial bacterial population after 10 minutes of treatment without it being necessary to use specific means known per se for forming a gaseous flow directed out of the inter-cathode space.
• a device for the emission of a self-projected cold plasma according to the invention for the decontamination of surfaces, in particular for the biostatic treatment and / or the biocidal treatment of these surfaces.
• a device according to the invention is used for the treatment of a surface in which the surface to be treated is not interposed between the electrodes of the plasma generator, but is exposed, outside the device, to the jet of self-projected cold plasma emitted by the device according to the invention.
• a device for emitting a self-projected plasma jet according to the invention is used for blood coagulation and asepsis.
• a device for emitting a self-projected plasma jet according to the invention for carrying out a blood coagulation operation, or for establishing and / or maintaining the asepsis.
• the invention also relates to a device, the use of such a device and a method characterized in combination by all or some of the characteristics mentioned above or below.
• FIG. 1 is a perspective view with ruptured proportions out of a device according to the invention
• FIG. 2 is a diagrammatic representation in section of a device according to the invention
• FIG. 3 is an illustration with broken away and out of proportions of a first variant of a device according to the invention
• FIG. 4 is a broken-away perspective view of a second variant of a device according to the invention.
• FIG. 5a is a plot of the kinetic evolution of the electrical intensity of a corona discharge obtained in a device according to the invention under a voltage of 5.6 kV,
• FIG. 5b is a plot of the kinetic evolution of the electrical intensity of a corona discharge obtained in a device according to the invention at a voltage of 9.1 kV,
• FIG. 6a is a spectral imprint of a corona discharge obtained in a device according to the invention.
• FIG. 6b is a spectral fingerprint of the self-projected plasma jet obtained in a device according to the invention.
• FIG. 7 schematically represents a third variant of a device according to the invention.
• FIG. 8 schematically represents a fourth variant of a device according to the invention.
• FIG. 9 schematically represents a fifth variant of a device according to the invention.
• FIG. 10 schematically represents a sixth variant of a device according to the invention.
• FIG. 11 schematically represents a seventh variant of a device according to the invention.
• FIG. 12 diagrammatically represents an eighth variant of a device according to the invention.
• FIG. 13 represents a variant of a device according to the invention as represented in FIG. 2.
• a device 1 for transmitting a self-projected plasma jet at ambient pressure and temperature comprises a conducting cathode 14 formed of a section of section tube. cylindrical of revolution, supported by a piece 18 of an electrically insulating material.
• the cathode 14 is formed of a conductive material, especially a conductive metal selected from the group consisting of copper, brass or a conductive alloy comprising these metals.
• the cathode 14 comprises a continuous active edge 7 formed of the inner radial edge of the tube section, extending in the cathode opening plane 8 of the cathode 14 and opposite a pointed end-end portion 13 of the cathode 14. a cylindrical anode 11.
• the pointed end-axial portion 13 of the cylindrical anode 11 forms a center of symmetry of the continuous active edge 7 of said cathode 14 facing the pointed axial end portion 13 of the cylindrical anode 11 and extends in the cathode aperture plane 8 of the cathode 14.
• the tube section forming the cathode 14 has an inside diameter of between 5 mm and 20 mm.
• the pipe section may have an internal diameter of 5 mm, 10 mm, 13 mm, 14 mm or 20 mm.
• the distance separating the sharp axial end portion 13 from the cylindrical anode 11 and the active edge 7 of the cathode 14 is respectively 2.5 mm, 5 mm, 6.5 mm, 7 mm or 10 mm.
• the outer diameter of the tube section forming the cathode 14 is 30 mm. This value has no influence on the implementation of the device 1 according to the invention.
• the cathode 14 has, in cross-section, a center of symmetry, said center of symmetry belonging to the axis of elongation of the anode 11 cylindrical in its axial direction 12.
• the cathode 14 may have any shape, if the active edge 7 of said cathode 14, formed of the inner edge of the tube section forming the cathode 14, has a center of symmetry formed of the pointed end portion 13 axial of the cylindrical anode 11.
• the cathode 14 may have a transverse cross section of circular shape.
• the active edge 7 of the cathode 14 which is facing the pointed portion 13 of axial end of the cylindrical anode 11 is then in transverse cross section in the cathodic aperture plane 8 of circular shape.
• the active edge 7 of the cathode 14 has, in transverse cross section in the cathodic opening plane 8, a polygonal shape having a center of symmetry, in particular a square shape, a rectangular shape, a hexagonal shape, an octagonal shape and a decagonal shape.
• the continuous active edge 7 of the cathode 14 present in transverse cross section in the cathodic aperture plane 8, a polygonal shape having an odd number of sides and admitting at least one plane of symmetry perpendicular to the plane 8 cathode opening, said plane of symmetry comprising the pointed portion 13 of axial end of the cylindrical anode 11 to which this cathode 14 is associated.
• the cylindrical anode 11 may be formed of a solid cylinder formed of an electrically conductive material. It is also possible that only an outer surface layer of the cylindrical anode 11 is made of a conductive material connected to a high voltage generator, and in which the pointed end portion 13 of said cylindrical anode 11 has a minimum radius of curvature oriented substantially in the direction perpendicular to the cathodic opening plane 8 defined by the (e) edge (s) 7 active (s) of the cathode 14 to which this cylindrical anode 11 is associated. Thus, it is possible that the pointed portion 13 of axial end of said cylindrical anode 11 has a minimum radius of curvature oriented substantially in the axial direction 12 of the cylindrical anode 11.
• a portion of an insulating solid material to cover the portion of the cathode 14 facing outwards of the inter-cathode space 9 and extending around the active edge 7 of said cathode 14, but without however covering the pointed portion 13 of axial end the cylindrical anode 11.
• the conductive cathode 14 is connected to ground via a current measurement resistor 19.
• the value of the measurement resistor 19, designed to measure the current is 50 ⁇ .
• the device 1 for transmitting a plasma jet 10 further comprises a cylindrical anode 11 formed of a conductive cylinder, extending along the axis of the hollow cylinder forming the cathode 14, electrically connected to a generator 2 of high voltage through a load resistor of 25 M ⁇ to limit the current in the case of the formation of an arc.
• the high voltage generator 2 may be a generator 2 adapted to distribute a continuous supply or a pulsed supply.
• the high voltage generator 2 is adapted to deliver in the cylindrical anode 11 a high voltage of up to 15 kV.
• the distance separating the axial end pointed portion 13 from the cylindrical anode 11 and the active edge 7 of the cathode 14 by the view of said pointed end axial portion 13 may vary according to the structure of the device 1.
• obtaining a positive polarity corona discharge generating a plasma jet 10 self-projected with more distant electrodes requires the application of a high voltage of higher value to the cylindrical anode 11 or a high potential difference between the cylindrical anode 11 and the cathode 14.
• a device 1 for transmitting a self-projected plasma jet 10 it is possible to connect electrically between the cylindrical anode 11 and the cathode 14, a voltage measuring member 20. and / or the intensity of the electric current across the cathode 14 and the cylindrical anode 11, in particular an oscilloscope 20.
• the cylindrical anode 11 and the cathode 14 are held in a stable position by means of a piece 18 of an electrically insulating material selected from the group consisting of glass, quartz, alumina, a polymer and ceramic with which they are held together.
• Sharp portion 13 axial end of the cylindrical anode 11 preferably extends in the cathodic opening plane 8 defined by the cathode opening of the cathode 14.
• the pointed end portion of the axial end of radius of minimum curvature of the cylindrical anode 11 extends axially out of the cathodic opening plane 8 of the cathode 14, in particular at a distance of a few millimeters, in particular 1 to 2 millimeters beyond or below the plane 8 of Cathode opening of the cathode 14.
• the piece 18 of electrically insulating material provides a free space between the axial end portion 13 of minimum radius of curvature of the cylindrical anode 11 and the active edge 7 of the cathode 14.
• the conductive cathode 14 has, in section in each axial plane of said cathode 14, a section of square shape.
• the cathode 14 of the cathode assembly does not form a rim of the intercathodic space 9.
• the crown discharges then occur directly between the active edge 7 of the cathode 14 and the axial end portion 13 of the cylindrical anode 11 and lead to the formation of a plasma jet from said portion 13 of FIG. axial end in a direction perpendicular to the cathodic aperture plane 8 and parallel to the axial direction of the cylindrical anode 11.
• a device 1 for transmitting a plasma jet 10 comprises a cathode assembly 4 formed of two lamellar cathodic plates 22 supported by a part 18 formed of an electrically insulating material.
• the two lamellar cathodic plates 22 each have an active edge 7 of said cathode assembly 4, the two active edges 7 of the cathode plates 22 being parallel to each other and defining the cathodic aperture plane 8.
• Such a device further comprises a plurality of cylindrical anodes 11 each having a pointed portion 13 of axial end of minimum radius of curvature, extending opposite the two active edges 7 of the cathode assembly 4 and forming the whole 3 anodic.
• the axial end portions 13 of the cylindrical anodes 11 extend in the plane median defined by the two parallel active edges 7 of the two cathode plates 22 and in the cathodic aperture plane 8 of the cathode assembly 4.
• the inventors have observed the formation of a plasma jet in the form of a curtain extending from the portions 13 of axial ends of the cylindrical anodes 11 in the median plane of the two parallel active edges 7 of the two cathode plates 22 of the cathode assembly.
• the voltage applied to each of the cylindrical anodes 11 of the plurality of cylindrical anodes 11 is substantially the same.
• the two cathodic plates 22 are coplanar, and the axial end portions 13 of the cylindrical anodes 11 of the anode assembly 3 extend in the median plane defined by the two active edges 7 of the cathode plates 22 forming the cathode 14.
• the two planar cathode plates 22, supported on a piece 18 of an electrically insulating material and forming the cathode 14, are of substantially rectangular shape, and the active edges 7 of each rectangular cathode plate 22 of the cathode 14. view of the portion (s) 13 of axial end of the cylindrical anodes 11 are substantially parallel to each other.
• a device 1 for transmitting a plasma jet 10 comprises a cathode assembly 4 formed of a tubular outer cathode 23 and a concentric cylindrical inner cathode 24.
• the tubular outer cathode 23 has an inner active edge 25 formed of the inner edge of the tube forming the tubular outer cathode 23 and extending in the cathodic opening plane 8 of the cathode assembly 4 of the device 1.
• the cathode 24 cylindrical interior also has an outer active edge 26 formed by the edge defined by the longitudinal plane end of the cylinder of the cylindrical inner cathode 24 and extending in the cathodic aperture plane 8.
• a device 1 for transmitting a plasma jet 10 represented in FIG. 4 further comprises an anodic assembly 3 formed of a plurality of cylindrical anodes 11 each having, in their axial direction, a pointed end-axial portion 13 whose section in at least one axial plane has a minimum radius of curvature adapted to allow the formation of a corona discharge in positive polarity.
• the pointed portion 13 of axial end of each cylindrical anode 11 extends in the cathodic aperture plane 8 of the cathode assembly 4.
• Each cylindrical anode 11 of the anode assembly 3 is positioned so that the axial end portion 13 of each cylindrical anode 11, the inner active edge 25 of the outer cathode 23 and the outer active edge 26 of the cathode 24 are substantially aligned in the cathode opening plane 8 of the device 1, and in such a way that the axial end pointed portion 13 of each cylindrical anode 11 is equidistant from the internal active edge 25 of the external cathode 23 and the outer active edge 26 of the inner cathode 24.
• a device 1 in a third variant shown schematically in FIG. 7, comprises a cathode assembly 4 formed of two cathode plates 22 each having a segment-shaped continuous rectilinear active edge 7, said active segments 7 of the two cathode plates 22 forming the cathode assembly 4 being coplanar and non-parallel.
• the active segments 7 of the two cathodic plates 22 form between them an acute angle and are symmetrical with respect to the median plane defined by the two active segments 7 of the two cathodic plates 22, said median plane comprising the portion (s) 13) end (s) axial (s) of said (one) anode (s) 11 cylindrical (s) to which the cathode plates 22 of the set 4 cathode are associated.
• the shortest distance separating the active segments 7 facing the two cathode plates 22 is variable and the distance separating each axial end portion 13 from each cylindrical anode 11 to which these plates 22 cathodic are associated through the inter-cathodic space 9 is also variable. Consequently, the voltage applied to each cylindrical anode 11 will be different: this voltage applied is lower for the cylindrical anode 11 closest to the active segments 7, and higher for the cylindrical anode furthest away from the active segments 7.
• the active edge 7 of the cathode 14 is a continuous active edge 7 formed of a plurality of active edge segments 7 facing each other.
• the segments of active edges 7 form a regular hexagon, extend in the cathode opening plane 8 of the cathode 14 and are distributed in this opening plane 8 cathodic so that the segments of active edges 7 in pairs centrally symmetry with respect to the pointed portion 13 axial end of the cylindrical anode 11 to which the cathode 14 is associated.
• the active edge 7 of the cathode 14 forms the sides and / or the vertices of a regular polyhedron extending into the cathodic aperture plane 8, wherein the axial end pointed portion 13 of the anode assembly 3 also extends substantially in the cathodic aperture plane 8, and forms the center of the circle circumscribing the regular polyhedron.
• the regular polyhedron may be an equilateral triangle, a square, a regular pentagon, a regular hexagon, a regular heptagon, a regular octagon, and any other regular polyhedron with many sides and higher vertices.
• the active edge 7 of the cathode 14 is formed of a plurality of discontinuous active segments extending in the cathodic opening plane 8 of the cathodic assembly 4.
• the active segments 7 are distributed in the cathodic aperture plane 8 of the cathode 14 so that the active segments 7 admit, in pairs, a central symmetry with respect to the pointed axial end portion 13 of the anode. 11 cylindrical to which this cathode 14 is associated. It is also possible for the distribution of the active segments 7 to have a center of symmetry formed of the pointed axial end portion 13 of the cylindrical anode 11 to which the cathode 14 is associated.
• the cathode assembly 4 is formed of a plurality of cathodes 14 connected to ground.
• Each cathode 14 has an active edge 7 extending in the cathode opening plane of the cathode assembly 4, said cathode opening plane comprising the axial end pointed portion 13 of a cylindrical anode 11.
• a device 1 in a seventh variant, shown diagrammatically in FIG. 11, comprises a cathode assembly 4 formed of two coplanar conductor wires 28, the two coplanar conductor wires 28 each forming an active edge 7 of the cathode assembly 4, extending facing the axial end pointed portion 13 of at least one cylindrical anode 11, the axial end portion (s) 13 of each cylindrical anode 11 extending in the plane 8 of cathodic opening formed by the active edges of the coplanar conductor wires 28, and extending in the median plane 17 of said active edges 7 to which this anode assembly 3 is associated.
• a device 1 in an eighth variant, shown schematically in FIG. 12, comprises a cathode assembly 4 formed of two cathode plates 22 each having an active edge 7, the two active edges being coplanar and parallel to each other. another, and an anode assembly 3 extending longitudinally between the two cathode plates 22 and having a pointed portion 6 extending longitudinally in the median plane of the active edges 7 of the two cathode plates 22 and in the cathodic opening plane 8 of the cathode assembly 4 towards the outside of the inter-cathodic dielectric space.
• the cathode 14 may have a shape of thin disc, in particular a few millimeters thick, hollowed at its center and supported by a piece 18 of a material electrically insulating, said hollow center of the cathode 14 leaving a space occupied in part for the pointed portion 13 of axial end of the cylindrical anode 11.
• the active edge 7 of the cathode 14 has in section in each radial plane, a shape symmetrical with respect to said pointed axial end portion 13 of this cylindrical anode 11 and the active edge 7 of the cathode 14, formed by the thickness of said hollow disc at its center, is opposite the pointed portion 13 of axial end of the cylindrical anode 11.
• a device comprises an anode assembly 3 formed of a plurality of anodes whose axial end portions 13 are coplanar and a cathode assembly 4 formed of a plurality of cathodes 14 comprising coplanar active edges 7, the cathodic opening plane 8 of the cathode assembly 4 comprising the axial end portions 13 of the anodes, said active edges 7 of the cathodes 14 being evenly distributed around the axial end portions 13 of the anodes and forming a planar network, in particular a hexagonal type network, of square type or of triangular type.
• EXAMPLE 1 Device for emitting a self-blown plasma jet
• a plasma device is produced in which the conductive anode is formed of a tungsten cylinder whose cross sectional diameter is of the order of 1 mm.
• the minimum radius of curvature of the axial portion of the end of said anode is 20 ⁇ m.
• the cathode is formed of a hollow copper cylinder having a transverse cross section whose inner diameter is 13 mm and the outer diameter is 30 mm.
• the cylindrical cathode is supported by an insulating ceramic hollow cylinder (alumina) 8 mm thick which is itself adapted to maintain the conductive anode in axial position.
• alumina insulating ceramic hollow cylinder
• the anode and the cathode are in contact with the atmospheric air at the pressure and at ambient temperature, that is to say at a temperature close to 22 ° C.
• Anode is applied to the anode. increasing and maximum voltage of 15 kV.
• the inventors have observed, up to a voltage threshold value of 2.6 kV, the formation of a non-repetitive corona discharge occupying a small volume in the immediate vicinity of the axial end of the anode.
• the flow maximum snapshot generated by this corona discharge and measured on the oscilloscope is 0.9 mA. This non-repetitive crown discharge was observed up to a voltage value of 5.3 kV.
• a repetitive corona discharge with a repetition frequency of the order of several kHz, is revealed by the appearance of a crown halo formed by a bluish-colored plasma. extending in the atmosphere along the longitudinal axis of the anode and a distance of about 10 mm beyond the axial end of said anode and a diameter of about 3 mm.
• This plasma jet is stable for a voltage between 5.3 kV and 9.1 kV and increases in light intensity proportionally with the increase in voltage. Beyond a voltage of 9.1 kV, sparks appear in the inter-electrode space between the anode and the cathode corresponding to the formation of an electric arc-type electric discharge, which is not desired in this mode of operation. operation.
• the inventors have noticed, by passing the hand in the free space facing the axial end of the anode and at a distance greater than 10 cm from said axial end of the anode, the emission of a gas flow in the axial direction of the anode and oriented outwards from the inter-electrode space and the speed of which has been evaluated by means of a millimeter-to-helical anemometer, from 1 m / s to 10 m / s .
• the temperature of the plasma jet was evaluated at the distal end of the crown halo, that is to say approximately 10 mm from the axial end portion of the anode of minimum radius of curvature at about 27 ° C. a temperature slightly above room temperature.
• the variation of the intensity of the electric current produced by the corona discharge is measured by means of an oscilloscope.
• the kinetic profiles of intensity of the instantaneous electric current are given in FIG. 5a and 5b respectively for applied voltages of 5.6 kV (FIG. 5a) and 9.1 kV (FIG. 5b).
• the maximum intensity of the instantaneous electric current generated by the Crown discharge is 2.4 mA for a supply voltage of 5.6 kV and 16 mA for a supply voltage of 9.1 kV.
• the natural frequency of repetition of such a corona discharge under these conditions is about 20 kHz.
• FIGS. 6a and 6b Analytical spectra, represented in FIGS. 6a and 6b, were made in the visible wavelength range and aimed axially at the discharge zone surrounding the anodic tip and at the other end of the jet plasma jet. about 10 mm above the plasma jet. These spectra respectively characterize the excited species present in the corona discharge (FIG. 6a) and in the plasma jet at a greater distance from the anode (FIG. 6b). The spectral plot in FIG.
• 6a shows the presence of characteristic bands of radiative excited species, in particular nitrogen, in particular the transition spectral bands of the second positive system (denoted SSP; N 2 (C 3 ⁇ u , ⁇ ) ⁇ N 2 (B 3 ⁇ * g g, ' ⁇ ') + hv) and the first negative system (noted PSN; N + 2 (B 2 ⁇ + U , ⁇ )
• a plasma device is produced in which the cathode is formed of a conductive cylinder with an outside diameter of 30 mm and an inside diameter of 10 mm, and in which the conductive anode is formed of a tungsten cylinder of which the diameter of the cross section is of the order of 1 mm.
• a DC voltage is applied to the anode adapted to generate a corona discharge in the ambient air and at atmospheric pressure and the value of which varies only slightly for the different minimum radii of curvature studied.
• the maximum instantaneous current intensities generated by the corona discharge are given in Table 1 below.
• the length (mm) of the part of the plasma jet generated and projected by crown discharge into the ambient air that is visible to the eye in the absence of external stray light, especially in the dark.
• the measured length of the plasma jet does not vary substantially with the value of the minimum radius of curvature of the apical end of the anode.
• the inventors have also observed that the width of the visible part of the plasma jet generated and projected by corona discharge in the ambient air increases with the increase in the value of the radius of curvature.
• the corona discharge at the origin of the plasma jet is generated at the top of the tip with a natural repetition rate of about 20 kHz.
• a plasma device is produced in which the cathode is formed of a conductive cylinder with an outside diameter of 30, and in which the conductive anode is formed of a tungsten cylinder whose diameter of the transverse cross-section is of the order of 1 mm and the minimum radius of curvature of the apical end is 10 microns.
• a DC voltage is applied to the anode adapted to generate a corona discharge in the ambient air and at atmospheric pressure.
• the values of the voltage required to generate the corona discharge and the maximum instantaneous current currents generated by said corona discharge are given in Table 2 below.
• the length (mm) of the portion of the plasma jet generated and projected by corona discharge is measured in the ambient air which is visible to the eye in the absence of external stray light, especially in the dark.
• the instantaneous current intensity does not vary with the value of the inside diameter ( ⁇ int ) of the cathode, that the voltage to be applied to the anode to obtain the corona discharge increases with the distance separating the cathode and the part apical portion of the anode, and that the length (mm) of the portion of the plasma jet generated and projected by corona discharge into the ambient air which is visible to the eye in the absence of external stray light, in particular to the darkness increases with said distance.
• EXAMPLE 6 Bactericidal and / or bacteriostatic treatment A bacterial culture of Esche richia coli is carried out on the surface of a solid support and this bacterial culture is subjected to a self-projected plasma jet according to the invention.
• the plasma jet device is placed a few millimeters from the surface supporting the E. coli bacteria. After about 10 minutes of exposure of the contaminated surface to the self-projected plasma jet according to the invention, there is a decrease in the viable bacterial population of the order of 3 log (the initial bacterial population is divided by 1000). This result is similar to that already obtained by other types of plasma reactor using, in particular, a post-discharge flow generated by microwaves at reduced pressure.

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