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WO1997021331A1 - Dispositif de generation de plasma - Google Patents

Dispositif de generation de plasma Download PDF

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Publication number
WO1997021331A1
WO1997021331A1 PCT/GB1996/003007 GB9603007W WO9721331A1 WO 1997021331 A1 WO1997021331 A1 WO 1997021331A1 GB 9603007 W GB9603007 W GB 9603007W WO 9721331 A1 WO9721331 A1 WO 9721331A1
Authority
WO
WIPO (PCT)
Prior art keywords
chamber
gas
housing
electrodes
frequency
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/GB1996/003007
Other languages
English (en)
Inventor
Victor John Law
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ham Let CFS Ltd
Original Assignee
Cambridge Fluid Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Cambridge Fluid Ltd filed Critical Cambridge Fluid Ltd
Priority to AU10383/97A priority Critical patent/AU1038397A/en
Publication of WO1997021331A1 publication Critical patent/WO1997021331A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/32—Gas-filled discharge tubes
    • H01J37/32009—Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B13/00—Oxygen; Ozone; Oxides or hydroxides in general
    • C01B13/10—Preparation of ozone
    • C01B13/11—Preparation of ozone by electric discharge
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/32—Gas-filled discharge tubes
    • H01J37/32009—Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources
    • H01J37/32082—Radio frequency generated discharge
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/32—Gas-filled discharge tubes
    • H01J37/32009—Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources
    • H01J37/32348—Dielectric barrier discharge
    • 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
    • H05H1/46—Generating plasma using applied electromagnetic fields, e.g. high frequency or microwave energy
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2201/00—Preparation of ozone by electrical discharge
    • C01B2201/10—Dischargers used for production of ozone
    • C01B2201/14—Concentric/tubular dischargers
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2201/00—Preparation of ozone by electrical discharge
    • C01B2201/60—Feed streams for electrical dischargers

Definitions

  • This invention relates to apparatus for generating plasma, a method of operating such apparatus, and a method of processing a gas by converting it into a plasma so as to enable a desired chemical reaction to occur.
  • the invention is of particular application to dielectric barrier discharge devices.
  • a co-axial dielectric barrier discharge device comprises a cell into which a central electrode extends, and which has a wall formed from a dielectric material which is surrounded by a conductive jacket which constitutes a second electrode.
  • the electrodes and dielectric material act as a capacitor, in conjunction with a slow wave transmission line which stores an electrical charge in response to electromagnetic energy which is supplied to the cell.
  • gas between the electrodes is ionised, allowing a series of micro discharges to occur across the inter-electrode volume.
  • Such apparatus is commonly referred to as a plasma cell.
  • the conversion of the gas into the plasma allows various chemical reactions to occur, for example the conversion of oxygen to ozone, formation of metastable nitrogen molecules and the decomposition of a CFC gas.
  • apparatus for generating a plasma comprising a housing having a chamber for containing a gas and two electrodes between which a first dielectric member and at least part of the chamber are interposed, coupling means for coupling the chamber to an electrical radio frequency (RF) input, such that the input produces in the chamber an electromagnetic wave which gives rise to a sufficient potential difference between the electrodes to ionise gas in the chamber, wherein the housing also includes matching means for tuning the housing so that the resonant frequency of electromagnetic wave set up therein is substantially the same as the frequency or fundamental frequency of the RF input.
  • RF radio frequency
  • the RF matching means proposed by the present invention enables the apparatus to be configured so as to accept a high frequency RF input from an RF generator without the need for separate impedance matching circuitry since, when operating at resonance, the apparatus will absorb substantially all the power fed to it. As a result, the apparatus can produce plasma which is maintained continuously.
  • the matching means is situated in, and tunes, the chamber.
  • the matching means preferably comprises an impedance transformer which reduces the resonant frequency for the electromagnetic wave in the housing and/or the physical length of the electromagnetic wave.
  • the apparatus comprises an open circuit quarter wave coaxial line, the coupling means and impedance transformer being situated in an end region thereof which is axially spaced from the portion of the chamber between the electrodes.
  • the coaxial line preferably has a central conductor which extends from the end region into the chamber and which constitutes one of the electrodes, and also has an outer conductive jacket which surrounds the chamber and constitutes the other of said electrodes.
  • the impedance transformer may to advantage comprise a secondary dielectric member.
  • the secondary dielectric member is conveniently annular, the central conductor extending therethrough.
  • the secondary dielectric member is formed from a plurality of axially spaced sections, at least one of which is interchangeable with another section having different dielectric properties, so that the electromagnetic resonant frequency for the device can be varied, and matched to a given RF input.
  • each section is coated with an electrically conductive (preferably metallic) material.
  • each annular section may to advantage extend over the outer curved surface of the section and the inner periphery of the section.
  • Said coating preferably extends over the end faces of at least one of the sections.
  • the housing contains an inert, low dielectric loss tangent oil extending between the secondary dielectric member and the housing so as to avoid air gaps between the secondary dielectric member and the portion of the housing in which it is contained.
  • the dielectric properties of the sections may differ by virtue of differences in the dimensions of the sections, or the relative permittivity of the material constituting the sections, or by virtue of a combination of those factors.
  • the coupling means comprises a magnetic loop which in turn comprises a conductor which extends through at least part of the secondary dielectric member.
  • An alternative form of impedance transformer comprises an inductor, such as an electrically conductive helical coil formed from material having a low electrical resistance.
  • the coil is terminated at an open-circuit probe within the chamber, said probe constituting one of the electrodes of the apparatus.
  • the coil may to advantage be hollow, thereby defining a helical passage for gas to be introduced into the chamber through an outlet at the probe, the gas being introduced at an inlet at the opposite end of the coil.
  • the inlet end of the coil is grounded.
  • the coil is surrounded by an electrostatic shield.
  • the coil has a 50 ohms impedance point, and the RF input is terminated at that point or at the best dynamic impedance point during operation, ihe best dynamic impedance point corresponding to an inductive match and compensating for the capacitive load of the plasma.
  • the coupling means comprises a dielectric concentric spacer which forms a gas-tight seal between the coil and the housing.
  • a device according to the invention can be so arranged as to accept RF power supplied at the ISM frequency of 27.12 MHz.
  • the device preferably also includes transmission means for transmitting electromagnetic radiation from an external source into the chamber. This enables the device to be used for reactions which require, for example, light, ultra violet or infrared radiation.
  • the transmission means comprises one or more apertures in the jacket.
  • a method of processing a gas comprising the steps of introducing a gas into a chamber of a housing through an impedance transformer, which chamber extends between two electrodes, supplying an electrical RF potential to coupling means associated with the housing, thereby inducing to a sufficiently high potential difference between the electrodes to ionise the gas and thereby at least initiate the conditions necessary for the ionised gas to undergo a chemical reaction, wherein the RF voltage produces a train of micro-discharges between the electrodes.
  • said discharges take the form of arc-like filaments.
  • the electrical half-life of each micro-discharge is of the order of 10 nanoseconds.
  • the peak RF potential gradient, between the electrodes is such as to maintain said conditions.
  • the intervals between successive discharges are such as to maintain a time average concentration of activated chemical species between each discharge.
  • the intervals between successive discharges are preferably between two and three times the half-life of the reaction.
  • the method may also comprise transmitting electromagnetic radiation from an external source into the chamber to enable, for example, reactions which require ultra violet radiation to occur.
  • the invention also lies in the method of operation of a dielectric barrier discharge device wherein the frequency of an electrical RF input fed to the device is substantially the same as the electromagnetic resonant frequency of the device.
  • the device may have a bandwidth at the 3dB point of 1-4 MHz.
  • Figure 1 is a partially cut away side view of the first embodiment
  • Figures 2 and 3 are respective end views of the first embodiment
  • Figure 4 is a side view of a portion of the first embodiment
  • Figures 5 and 6 are respective end views of that portion
  • Figures 7 and 8 are respective side and end views of a component of the portion shown in Figures 4 to 6;
  • Figures 9 to 11 are each end and side views, in third angle projection, of various components which are contained in the portion shown in Figures 4 to 6;
  • Figure 12 shows in third angle projection side and end views of an electrode which fits onto the component shown in Figures 7 and 8;
  • Figure 13 shows a component of a second portion of the first embodiment from the side and one end, in third angle projection;
  • Figure 14 consists of end and side views, arranged in third angle projection, of part of a further electrode structure for fitting onto the component shown in Figure 13;
  • Figure 15 is a side view of a part of that structure
  • Figure 16 comprises three sketch graphs which illustrate an RF signal fed to the first embodiment, the amplitude of micro-discharges set-up within the device as a result of that RF input, and the concentration of plasma generated by those micro-discharges.
  • Figure 17 is a partially sectional side view of a second embodiment of apparatus in accordance with the invention.
  • Figure 18 is an end view of a sub-assembly of a third embodiment of apparatus in accordance with the invention.
  • Figure 19 is a cut away view of the sub-assembly taken along the line X-X of Figure 18;
  • Figures 20 and 21 are side and end elevations of an end cap of the sub-assembly
  • Figures 22 and 23 are respective end and cut away side views of a housing forming part of the sub-assembly
  • Figures 24 and 25 are respective side and end views of a coil which is contained in the sub-assembly of the finished apparatus;
  • Figure 26 is a side view of a glass tube for attachment to the sub-assembly to define a reaction chamber
  • Figures 27 to 30 show, in third angle projection, components for mounting the tube on the sub-assembly, the side views of those components being sectional views.
  • Figure 31 shows those components mounted on the tube;
  • Figure 32 is a simplified cut away view oi the third embodiment when assembled, and
  • Figure 33 shows an alternative to the component shown in Figures 27 and 28
  • the apparatus shown in Figure 1 is a plasma cell which is in the form of an open circuit resonant coaxial line formed from two cylind ⁇ cal, axially spaced housing portions 1 and 2 and a central conductor 4 which extends through the portion 2 and into a chamber 6 defined by the portion 1 , in which chamber the conductor 4 is terminated by a central electrode 8
  • the device includes a further electrode 10 which is in the form ot a copper jacket surrounding the exterior of the cylindrical wall of the portion 1 That wall is formed from quartz glass or Pyrophic Boron Nit ⁇ ed (PBN), and accordingly acts as a dielect ⁇ c
  • the conductor 4 is hollow and its outboard end 12 constitutes an inlet for gas to be processed That gas is fed through the conductor 4 and into the chamber 6 through apertures in the electrode 8 Gas can then be expelled from the chamber 6 through an outlet 16 at the opposite end of the device from the inlet 12
  • the outlet 16 is provided with a perforated stainless steel plate 18 ( Figure 3) which acts as an RF shield
  • the energy necessary to convert the gas in the chamber 6 into plasma is obtained from an RF voltage which is applied to an input 14
  • the portion 2 comprises a cylinder 20 ot nickel plated steel which is attached at one end, by a process of fillet welding to a metal or alloy radial clamping flange 24, and which has a radial neck 22 situated approximately halfway along its length
  • the end of the cylinder 20 opposite the flange 24 is fillet welded to a circular plate 28 of a sub-assembly which is shown in more detail in Figures 7 and 8, and which also includes the central conductor 4.
  • the conductor 4 takes the form of a stainless steel tube which extends through a central aperture 30 in the plate 28 and is fillet welded to the plate 28 in that aperture.
  • the space between the conductor 4 and the cylinder 20 is occupied by a body 30 of a barium titanium loaded dielectric ceramic.
  • the body 30 is formed from five annular sections 32, 34, 36, 38 and 40. Three of those sections, 32, 34 and 36 are shown in Figures 9, 10 and 11.
  • Each section has a central passage, such as the passage 48 in the section 36. through which the conductor 4 extends.
  • the section 32 includes an axial passage 50
  • the section 34 has an axial passage 52 which intersects a radial groove 54 in one face of the section 34.
  • the passages 50 and 52 and the groove 54 define a path which extends from the input 14 to the plate 28, and which accommodates a magnetic loop coupling in the form of a length of copper wire (not shown) which is terminated at an aperture 55 in the plate 28.
  • Each of the sections has a high relative permittivity ( ⁇ r ) of, for example, 80 or 190.
  • ⁇ r relative permittivity
  • Each section can be exchanged with a similarly shaped section having a different relative permittivity so that the resonant frequency for electromagnetic radiation in the housing can be varied.
  • Each section is also coated with silver on its curved outer surface, central passage and end faces.
  • the body 30 extends into the portion 1, and the sections are held in position on the conductor 4 by the electrode 8.
  • the flange 24 includes a series of equi-angularly spaced, through bores (omitted from Figure 5), such as bore 26 ( Figure 6) through which the flange 24 can be attached to a corresponding metal or alloy radial flange 58 at one end of the portion 1 by bolts passing through the apertures in the flange 24 and through registering apertures (not shown) in the flange 58
  • the scai between each flange is made gas tight by means ot a copper gasket (not shown)
  • the flange 58 is formed with a metal cylindrical connector 59 attached to a quartz glass or Pyrophic Boron Nit ⁇ ed (PBN) cylinder 60 of the same diameter as the connector 59 via a graded fused joint
  • the cylinder 60 is fused at its opposite end to a similar cylinder 62, which is also attached to an end flange 64 via a graded fused connection with a cylind ⁇ cal connector 63
  • the dotted line 68 depicts the line along which the two cylinders 60 and 62 are fused together, whilst the shaded portion 70 indicates the portion ot the cylinders 60 and 62 around which ihe copper jacket extends
  • the construction of the copper jacket is shown in Figures 14 and 15
  • the jacket comprises two end rings, one of which is shown in Figure 14, which are formed by machining and are then split along the line X-X of Figure 14
  • Each ring has an axial flange 74, and has through bores 76 and 78 to enable it to be screwed back onto its other half
  • the top half of the ring 72 forms a sub-assembly with the corresponding top half of the opposite ring, reterenced 72 , and a semi-cylindrical piece ot copper mesh 80 formed by bending an initially rectangular piece ot mesh into a semi-cylindrical shape and soldering the mesh to the shoulders 74 (and 74 ) of the half-ring portions
  • the olher half-ring portions form a similar sub-assembly with a second piece of copper mesh so that the jacket is assembled on the portion 1 by bringing the two sub-assemblies together respectively trom the top and bottom of the portion 1 and then screwing the top halt of the ⁇ ng 72 to the bottom halt ot the same ring and similarly joining together the two halves of the ring 72 '
  • the electrode constituted by the jacket 10 is connected to earth
  • the jacket 10 has been shown in simplified form in Figure 1
  • the body 2 contains silicone oil which prevents air entrapmenl by the secondary dielectric 30.
  • the copper jacket is replaced by copper tape wound around the portion 1.
  • the other electrode 8 is formed from a cigar-shaped tube 82 ( Figure 12) which is provided at its inboard end with a screw-threaded portion 84 which cooperates with a corresponding portion on the end of the conductor 4 to enable the electrode to be screwed onto the portion 4.
  • the tip 82 includes a shoulder 83 which acts as a stop, retaining the section 40, and hence the body 30 in position.
  • the perforations through which gas passes from the interior of the conductor 4 into the chamber 6 are arranged in four lines, angularly spaced by 90°.
  • Reference Nos 86. 88, 90 and 92 in the end elevation of Figure 2 each denote a respective line, whilst the references 94, 96, 98 and 100 show the apertures in the line 90.
  • the flange 64 includes through bores which enable it to be bolted to a similar flange 102 by means of bolts, and the seal between those two flanges is made tight by a further copper gasket (not shown).
  • the flange 102 forms part of an end cap assembly which includes the outlet 16.
  • the input 14 is connected to a length of 50 ohm coaxial transmission line (not shown) which is fitted with an n-type connector, and the inlet 12 is connected to a gas supply via a T connector 104.
  • the coaxial line launches an RF signal into the device via the magnetic loop coupling.
  • the RF signal consists of a sinusoidal wave form, having a frequency of 27.12 MHz. This frequency is designated a free frequency and is not subject to full emission restrictions which would apply to devices which use a higher or lower frequency.
  • the body of dielectric material 30 compresses the wave by X ⁇ r , thus enabling the device to be of a relatively compact construction, in this example of a length of 0.5 metres.
  • the resonant frequency for electromagnetic waves in the housing is also 27.12 MHz, substantially all the energy supplied along the coaxial line is accepted by the apparatus.
  • initial coarse tuning of the electromagnetic wave can be achieved by substituting one of the sections of the body 30 for another of a different relative permittivity.
  • the substitution of a section having a relative permittivity of 190 with a section having a relative permittivity of 80 will move the antinode of the electromagnetic wave further into the chamber 6 (from the flange 58) by some 120mm.
  • Fine tuning can be achieved by placing a metallic slug, for example the slug 108 downstream of the electrode 8 but sufficiently close to the latter to act as a capacitor.
  • the standing wave generates a high voltage potential between the electrode 8 and the dielectric wall of the portion 1 which increases over successive cycles of the standing wave until the voltage is sufficient for multiple random micro-discharges of electricity to occur between the dielectric wall of the portion 1 and the electrode 8.
  • Those discharges convert gas in the chamber 6 into a plasma, thereby enabling a desired chemical reaction to take place .
  • the device may be used to generate ozone, in which case the relatively compact dimensions of the device enables it to be used in situ, where the ozone is to be used. This avoids the need to store large quantities of ozone, and thus also the expense and potential hazards associated with ozone.
  • the precursor gas for ozone (0 3 ) production is almost exclusively dioxygen (0 2 ) which is supplied through one branch of the connector, plus a source of electrons (from the RF source).
  • the rate of production and yield is enhanced by a factor of two by the addition of a small quantity of nitrogen (N 2 ), typically 1-5% by volume.
  • N 2 nitrogen
  • N 2 nitrogen
  • In addition to the direct electron dissociative attachment of dioxygen (e + 0 2 ⁇ O + O) metastable nitrogen molecules (*N 2 ;v 0.1) and ground state nitrogen atoms generate a substantial number of additional odd oxygen atoms via the following representative two step reaction.
  • the rate limiting step being the production of the odd oxygen atoms (reaction 8).
  • the line 110 in Figure 16 represents the RF input which is fed to the device. That input takes the form of a sinusoid having a frequency of 27.12 MHz. That input gives rise to a series of micro-discharges, two of which are shown at 112 and 114, to occur. Although the intervals and durations of the micro-discharges vary randomly, the average delay between successive discharges is approximately 37 nanoseconds, and the average half-life of each micro-discharge is approximately two nanoseconds.
  • Each micro-discharge generates plasma and thus increases the concentration of the plasma in a stepped fashion, as indicated by the steps 116 and 118 on the graph 120 of plasma concentration against time.
  • the concentration follows an inverse exponential decay as the plasma is used in the chemical reaction(s).
  • the second embodiment of device shown in Figure 17 differs from the first embodiment only in the nature of the plate at the inlet end of the device. Since all the other features are identical to those of the first embodiment, they have been denoted by the same reference numerals.
  • the second embodiment of device includes a plate 29 which is of substantially the same diameter as the cylinder 20 and is fillet-welded to the latter at the upstream end of the device.
  • the flange 102 and outlet 16 have been omitted from Figure 17.
  • the third embodiment of device uses an inductor as its impedance transformer instead of a secondary dielectric member.
  • the impedance transformer comprises a helical coil 150 which is housed within a cylindrical steel housing 152.
  • the housing 152 is closed at one end by a circular steel plate 1.54 welded to the housing 152.
  • the plate 154 includes an aperture 156 for a gas inlet.
  • the housing 152 also includes an aperture 158 positioned towards the plate 154. The aperture 158 enables the helical coil 150 to be connected an RF voltage input.
  • the turns of the coil 150 are hollow, so that the coil defines a helical passage extending from a gas inlet 160, defined by a VCR bulkhead connector, at the aperture 156 to the inlet end of a probe electrode 162 mounted on an end cap 164 at the opposite end of the housing 152.
  • the cap 164 comprises a metallic annular outer portion 166 welded to the housing 152, and a ceramic inner portion 168 attached at its outer periphery to the annular portion 166, and having a central cylindrical boss 170 (Figure 21) through which the electrode 162 is attached to the cap 164.
  • the annular member 166 also includes eight equi-angularly spaced screw-threaded blind bores, for example 172, on the exposed face of the member 166.
  • the electrode 162 incorporates a central passage 174 and a series of apertures such as 176 to enable gas supplied at the input 160 to be expelled.
  • Figure 24 which shows just the coil 150 and its end fittings, the end of the coil 150 remote from the inlet 160 is attached to an axial tube 178 which, in the assembled device, is welded to the passage 174 in the electrode 162.
  • the chamber for the third embodiment of device is defined by a generally cylindrical glass housing 180. which is attached to the cap 164 so that the electrode 162 extends into the glass housing 180.
  • the housing 180 has flared end portions 182 and 184.
  • the housing 180 is attached to the cap 164 by means of the components shown in Figures 27 to 30.
  • Figure 28 shows an annular PTFE member 186 which has a cylindrical outer periphery and a tapering inner surface 188. The taper on the surface 188 corresponds with the flared portion 184.
  • the inner radii of the member 186 corresponds to those of the flared portion 184.
  • the member 186 is split along the line A-A so that it can be placed around the flared portion 184 by bringing the two halves of the member 186 together from opposite sides of the portion 184.
  • the orientation of the portion 184 and the tapered surface 188 of the member 186 is such that the two surfaces complement each other, so that the outer surface of the member 186 remains substantially concentric with the other flared portion of the housing 180.
  • Figure 28 shows an annular collar 194 which includes a central reduced diameter opening 192 bounded by a radially inwardly directed annular flange 190.
  • a larger diameter opening 193, (defined by surface 198) is provided at the opposite side of the collar. The diameter of both openings are larger than the largest diameter of the flared portions 182 and 184.
  • the collar 194 includes a series of through bores, for example 196. However, the inner diameter of the opening 193 is slightly less than the combined diameter of the member 186 and the flared portion 184 on which it is fitted.
  • the collar 194 With the member 186 positioned on the portion 184, the collar 194 is slid over the tube 180 (from left to right as shown in 26) with the opening 193 in front of the opening 192 until the portion 184 and member 186 enter the opening 193. The collar 194 thus compresses the member 186 against the portion 184, thereby providing a compression fitting between the collar 194 and tube 180 through the member 186.
  • Figure 29 shows a PTFE seal which is fitted onto the end of the portion 184.
  • the seal includes an annular bead 200 which abuts the end face of the portion 164 and an axial flange 202 which extends over a short length of the portion 184.
  • the bead, in use, is sandwiched between the end of the portion 184 and an annular shoulder 206 of an interface flange 208.
  • the interface flange 208 also includes three screw-threaded blind bores 210, 212 and 214 each of which is (with the interface flange 208 in position on the end of the tube 180) in registry with a respective one of the through bores in the collar 194.
  • the flange 208 has eight through bores, such as 216, each of which is in registry with a respective blind bore in the member 166.
  • Figure 31 shows the relative positions of the tube 180, collar 194, member 186. flange 208 and seal 200, 202.
  • the shoulder 206 has been omitted from Figure 31 , and the collar 194 is shown in simplified form.
  • Screws extend into the blind bores 210, 212 and 214 through each of the corresponding through bores in the collar 194 to attach the collar 194 to the flange 208 and compress the collar 194 against the member 186 and flange 208 against the seal 200, 202. Further screws pass through the through bores in the flange 208 and into the corresponding blind bore in the cap 164, thereby attaching the flange 208 to the cap 164 as shown in Figure 32.
  • the device includes another collar (not shown) which is attached to the flared portion 182 through a PTFE member, such as a member 186, in a similar fashion to the collar 194, and to an end portion (not shown) similar to the flange 102 and outlet 16.
  • a PTFE member such as a member 186
  • the second electrode of the device comprises a copper tape (not shown) wound around the exterior of the housing 180.
  • Figure 33 shows a generally triangular collet which carries a PTFE lining 220 and replaces the collar 194 and member 186 in a modified version of the third embodiment.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Organic Chemistry (AREA)
  • Electromagnetism (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Inorganic Chemistry (AREA)
  • Physical Or Chemical Processes And Apparatus (AREA)

Abstract

Un dispositif permettant de générer du plasma comprend une enceinte (1, 2, 152, 180) comportant une chambre (6, 180) qui contient un gaz, et deux électrodes entre lesquelles sont interposés un premier élément diélectrique (1, 180) et au moins une partie de la chambre. Une entrée électrique d'audiofréquence (A.F.) est amenée dans la chambre de façon à y créer une onde électromagnétique qui donne naissance à une différence de potentiel entre les électrodes suffisante pour ioniser le gaz contenu dans la chambre. L'enceinte comprend également un système d'adaptation (30, 150) permettant d'harmoniser la chambre de façon que la fréquence de résonance de l'onde électromagnétique soit sensiblement la même que la fréquence ou la fréquence fondamentale de l'entrée audio. Le système d'appariement peut comprendre un autre diélectrique situé en amont de la chambre ou une bobine d'inductance. L'invention concerne également un procédé de traitement d'un gaz, consistant à introduire le gaz dans la chambre d'une enceinte et à y amener un potentiel électrique audio, par un système de couplage, de façon à donner naissance à une différence de potentiel entre les électrodes suffisamment grande pour ioniser le gaz et ainsi au moins amorcer les conditions nécessaires pour que le gaz puisse subir une réaction chimique. Cette ionisation produit un train de micro-décharges entre les électrodes.
PCT/GB1996/003007 1995-12-05 1996-12-05 Dispositif de generation de plasma Ceased WO1997021331A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU10383/97A AU1038397A (en) 1995-12-05 1996-12-05 Apparatus for generating plasma

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB9524888.6A GB9524888D0 (en) 1995-12-05 1995-12-05 Improvements in and relating to apparatus for generating plasma
GB9524888.6 1995-12-05

Publications (1)

Publication Number Publication Date
WO1997021331A1 true WO1997021331A1 (fr) 1997-06-12

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PCT/GB1996/003007 Ceased WO1997021331A1 (fr) 1995-12-05 1996-12-05 Dispositif de generation de plasma

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AU (1) AU1038397A (fr)
GB (1) GB9524888D0 (fr)
WO (1) WO1997021331A1 (fr)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3766051A (en) * 1971-09-22 1973-10-16 Pollution Control Ind Inc Liquid cooled ozone generator
US3824398A (en) * 1971-08-12 1974-07-16 Celanese Corp Method for plasma treatment of substrates
JPH04162388A (ja) * 1990-10-25 1992-06-05 Toto Ltd コロナ放電器
WO1993019573A1 (fr) * 1992-03-26 1993-09-30 General Atomics Appareil et methode d'obtention d'un plasma a haute densite mettant en ×uvre l'excitation en mode de sifflement
US5391855A (en) * 1991-08-01 1995-02-21 Komoto Tech, Inc. Apparatus for atmospheric plasma treatment of a sheet-like structure

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3824398A (en) * 1971-08-12 1974-07-16 Celanese Corp Method for plasma treatment of substrates
US3766051A (en) * 1971-09-22 1973-10-16 Pollution Control Ind Inc Liquid cooled ozone generator
JPH04162388A (ja) * 1990-10-25 1992-06-05 Toto Ltd コロナ放電器
US5391855A (en) * 1991-08-01 1995-02-21 Komoto Tech, Inc. Apparatus for atmospheric plasma treatment of a sheet-like structure
WO1993019573A1 (fr) * 1992-03-26 1993-09-30 General Atomics Appareil et methode d'obtention d'un plasma a haute densite mettant en ×uvre l'excitation en mode de sifflement

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 016, no. 459 (E - 1268) 24 September 1992 (1992-09-24) *

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AU1038397A (en) 1997-06-27

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