# US 5,078,823 A · Plasma reactor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,078,823 A - Document ID: US5078823A - Status: Granted - Kind: A - Application number: 07/525,406 - Filed: 1990-05-18 - Granted: 1992-01-07 - Earliest claimed: 1989-05-18 - Assignees: Defitech - Inventors: M. Patrick Chollet; M. Serge Saada - Web page: https://patentgrep.com/patent/US5078823A ## CPC - H01J 37/32229: {Waveguides} - H01J 37/32192: {Microwave generated discharge (H01J37/32357, H01J37/32366, H01J37/32394, H01J37/32403 take precedence)} - H01J 37/32266: {Means for controlling power transmitted to the plasma} - H01J 37/32779: {of batches of workpieces} - H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H) ## Abstract A plasma reactor, of the type comprising an enclosure capable of receiving a gas flow, a generator of high-frequency electromagnetic waves and means for the non-resonant coupling of the generator with the enclosure, the coupling means including at least one horn with widening having an essentially rectangular cross-section, with its two walls perpendicular to the direction of the electrical field moving away angularly from each other, the two walls parallel to the direction of the electrical field remaining substantially parallel. Preferably, the reactor includes a horn with widening and a horn with narrowing parallel to the direction of the electrical field, placed essentially in succession in coupling means. The invention thus makes it possible to obtain large-sized plasmas of any shapes with high homogeneity. ## Claims ### Claim 1 A plasma reactor comprising an enclosure for receiving a gas flow, a generator of high-frequency electromagnetic waves consisting of electric fields and magnetic fields, said fields having directions orthogonal to each other and orthogonal to a propagation direction of said electromagnetic waves, and non-resonant coupling means free of any externally imposed magnetic field for the non-resonant coupling of said generator with said enclosure, said non-resonant coupling means comprising at least one widening horn having four walls defining an essentially rectangular cross-section, with two of said walls being fixed parallel to the direction of said electric field and angularly inclined away from each other, and another two of said walls being fixed perpendicular to the direction of said electric field and substantially parallel to each other. ### Claim 2 (depends on 1) A plasma reactor according to claim 1, wherein said non-resonant coupling means further comprises at least one narrowing horn having four walls defining an essentially rectangular cross-section, with two of the narrowing horn walls being fixed perpendicular to the direction of said electric field and angularly inclined toward each other, and another two of said narrowing horn walls being fixed parallel to the direction of said electric field and substantially parallel to each other, and wherein said widening horn and said narrowing horn are placed essentially in succession in said non-resonant coupling means. ### Claim 3 (depends on 1, 2) A plasma reactor according to any one of the claims 1 to 2, wherein said non-resonant coupling means includes, on at least a part of an inner face of one of said horns, obstacles to the propagation of the electromagnetic wave for correcting any phase root-mean-square error in said electric field. ### Claim 4 (depends on 3) A plasma reactor according to claim 3, wherein said obstacles comprise internal contours of symmetrically defined patterns extending along at least part of the two angularly inclined walls of at least one of said horns. ### Claim 5 (depends on 4) A plasma reactor according to claim 4, wherein said patterns are defined by a cylindrical surface having a generatrix, the generatrix extending longitudinally on said angularly inclined walls. ### Claim 6 (depends on 4) A plasma reactor according to claim 4 wherein said patterns form substantially a quarter-wave short-circuit of said electromagnetic wave. ### Claim 7 (depends on 4) A plasma reactor according to claim 4 wherein said patterns comprise two U-shaped profiles, the U-shaped profiles having an aperture opening towards the coupling means interior. ### Claim 8 (depends on 7) A plasma reactor according to claim 7, wherein said U-shaped profiles are positioned on the angularly inclined walls of said widening horn, the widening horn having an aperture of about 120.degree., the U-shaped profiles having a depth of about a quarter wavelength of said electromagnetic waves, the U-shaped profiles having an aperture of a tenth wavelength. ### Claim 9 (depends on 4) A plasma reactor according to claim 4, wherein said patterns are defined by a cylindrical surface having a generatrix, the generatrix extending transversally on said angularly inclined walls. ### Claim 10 (depends on 9) A plasma reactor according to claim 9, wherein said patterns comprise a succession of ribs that have substantially constant thickness and are evenly spaced out longitudinally on said angularly inclined walls. ### Claim 11 (depends on 1, 2) A plasma reactor according to any one of the claims 1 to 2 wherein said coupling means includes, on at least a part of an inner face of one of said horns, obstacles to the propagation of the electromagnetic waves comprising means for locally modeling the homogeneity of said electromagnetic field. ### Claim 12 (depends on 1, 2) A plasma reactor according to any one of the claims 1 to 2 wherein said non-resonant coupling means comprises mode eliminating means for eliminating at least one pre-determined mode of said electromagnetic waves. ### Claim 13 (depends on 12) A plasma reactor according to claim 12 wherein said mode eliminating means comprise plates located along the direction of propagation, in a part of the widening horn between said substantially parallel walls of said widening horn, and distributed according to a spacing that depends on the mode or modes to be eliminated. ### Claim 14 (depends on 12) A plasma reactor according to claim 12 wherein said mode eliminating means comprises a dielectric plate at an outlet of the horn. ### Claim 15 (depends on 12) A plasma reactor according to claim 12 wherein said mode eliminating means comprises a dielectric material filling said horn. ### Claim 16 (depends on 1, 2) A plasma reactor according to any one of the claims 1 to 2 wherein said widening horn includes matching means located on at least one of said substantially parallel walls of said widening horn. ### Claim 17 (depends on 16) A plasma reactor according to claim 16 wherein said matching means comprises adjustable penetrative screws located on at least one of said substantially parallel walls of said widening horn. ### Claim 18 A plasma reactor comprising an enclosure having means for admitting a gas flow, a generator of high-frequency electromagnetic waves consisting of electric fields and magnetic fields, said fields having directions orthogonal to each other and orthogonal to a propagation direction of said electromagnetic waves, non-resonant coupling means free of any externally imposed magnetic field including an inlet fixed to the generator and an outlet, the non-resonant coupling means comprising at least one widening horn having four walls defining an essentially rectangular cross-section, two of said walls being fixed parallel to the direction of the electric field and angularly inclined away from each other, and another two of said walls being fixed perpendicular to the direction of the electric field and substantially parallel to each other, and a housing coupled to said outlet and surrounding the enclosure, wherein said enclosure comprises a generally cylindrical shape concentric about an axis of revolution and includes a first internal tubular unit placed under vacuum, concentric with said enclosure, a wall of said first tubular unit being formed by a material having low dielectric losses, and wherein the housing further comprises a second short-circuit element coupled to said first tubular unit and having two ring-shaped plates surrounding said tubular unit, said ring-shaped plates being spaced from each other by a distance that is predefined and adjustable in order to confine a plasma in an included portion of said tubular unit between said ring-shaped plates. ### Claim 19 (depends on 18) A plasma reactor according to claim 18 wherein the housing comprises at least one plunger-type short-circuit element, positioned opposite said coupling means with respect to the enclosure, said at least one plunger-type short-circuit element being adjustable to define a desired high-frequency field in the enclosure. ### Claim 20 (depends on 18) A plasma reactor according to claim 18, wherein said first tubular unit houses a second tubular unit internally and concentrically, the plasma confinement taking place in a plasma-confinement space between the two tubular units, and further comprising a first sample-holder provided inside the first tubular unit, in the vicinity of a first end of the first tubular unit. ### Claim 21 (depends on 20) A plasma reactor according to claim 20, wherein said means for admitting a gas flow comprises an inlet placed in the vicinity of a second end of said first tubular unit, opposite the first end, and pumping means located opposite said inlet of the gas flow. ### Claim 22 (depends on 20) A plasma reactor according to claim 20, further comprising a second sample-holder placed inside said first tubular unit, in the vicinity of a second end of said first tubular unit, opposite said first sample-holder; and wherein said means for admitting a gas flow opens substantially into the middle of the plasma confinement space; and wherein pumping means are located in the vicinity of the first and second ends of said first tubular unit. ### Claim 23 (depends on 22) A plasma reactor according to claim 22 wherein said first and second sample-holders are rotationally movable on an axis parallel to the axis of said first tubular unit. ### Claim 24 (depends on 20, 21, 22) A plasma reactor according to any one of the claims 20 to 22, wherein the sample-holder(s) is (or are) rotationally movable on an axis parallel to the axis of revolution of the first tubular unit. ### Claim 25 (depends on 20, 21, 22) A plasma reactor according to any one of the claims 20 to 22, wherein said second tubular unit further includes means for putting the second tubular unit under a vacuum. ### Claim 26 A plasma reactor comprising an enclosure having at least one internal unit, means for placing the internal unit under a vacuum, the internal unit possessing two walls that define a conduit receiving, at a first end, a chosen gas to flow in a selected direction through the conduit, the conduit opening, at a second end, into a sample conveyor for making a sample move across in translation in a direction substantially perpendicular to the direction of the gas flow, a generator of high-frequency electromagnetic waves consisting of electric fields and magnetic fields, said fields having directions orthogonal to each other and orthogonal to a propagation direction of said electromagnetic waves, and non-resonant coupling means free of any externally imposed magnetic field including an inlet fixed to the generator and an outlet coupled to said enclosure the non-resonant coupling means comprising at least one widening horn having four walls defining an essentially rectangular cross-section, two of said walls being fixed parallel to the direction of the electric field and angularly inclined away from each other, and another two of said walls being fixed perpendicular to the direction of the electric field and substantially parallel to each other. ### Claim 27 (depends on 26) A plasma reactor according to claim 26, comprising at least two of said internal units positioned in line with respect to each other, and cooperating with only one non-resonant coupling means for coupling to a common generator of electromagnetic microwaves, said sample conveyor being arranged so as to move a sample placed on said conveyor to said second ends of all of said internal units.