Patent Grant
9299554
This application is for entry into the U.S. National Phase under §371 for International Application No. PCT/GB2013/051170 having an international filing date of May 3, 2013, and from which priority is claimed under all applicable sections of Title 35 of the United States Code including, but not limited to, Sections 120, 363, and 365(c), and which in turn claims priority under 35 USC 119 to United Kingdom Patent Application No. 1208368.9 filed on May 10, 2012.
1. Field of the Invention
The present invention relates to a Lucent Waveguide Electromagnetic Wave Plasma Light Source.
2. Description of the Related Art
In our European Patent No. EP2188829—Our '829 Patent, there is described and claimed (as granted):
A light source to be powered by microwave energy, the source having:
As used in Our '829 Patent:
“lucent” means that the material, of the item which is described as lucent, is transparent or translucent—this meaning is also used in the present specification in respect of its invention;
“plasma crucible” means a closed body enclosing a plasma, the latter being in the void when the void's fill is excited by microwave energy from the antenna.
We describe the technology protected by Our '829 Patent as our “LER” technology.
In our patent application No. PCT/GB2011/001744 (our '744 Application), we defined an LUWPL as follows:
A microwave plasma light source having:
For the purposes of this specification, we define “microwave” to mean the three order of magnitude range from around 300 MHz to around 300 GHz. We anticipate that the 300 MHz lower end of the microwave range is above that at which a LUWPL of the present invention could be designed to operate, i.e. operation below 300 MHz is envisaged. Nevertheless we anticipate based on our experience of reasonable dimensions that normal operation will be in the microwave range. We believe that it is unnecessary to specify a feasible operating range for the present invention.
In our existing LUWPLs, the fabrication can be of continuous solid-dielectric material between opposite sides of the Faraday cage (with the exception of the excitable-material, closed void) as in a lucent crucible of our LER technology. Alternatively it can be effectively continuous as in a bulb in a bulb cavity of the “lucent waveguide” of our Clam Shell. Alternatively again fabrications of as yet unpublished applications on improvements in our technology include insulating spaces distinct from the excitable-material, closed void.
Accordingly it should be noted that whereas terminology in this art prior to our LER technology includes reference to an electroplated ceramic block as a waveguide and indeed the lucent crucible of our LER technology has been referred to as a waveguide; in the this specification, we use “waveguide” to indicate jointly:
Insofar as the lucent material may be of quartz and/or may contain glass, which materials have certain properties typical of solids and certain properties typical of liquids and as such are referred to as super-cooled liquids, super-cooled liquids are regarded as solids for the purposes of this specification.
Also for the avoidance of doubt “solid” is used in the context of the physical properties of the material concerned and not to infer that the component concerned is continuous as opposed to having voids therein.
There is a further clarification of terminology required. Historically a “Faraday cage” was an electrically conductive screen to protect occupants, animate or otherwise, from external electrical fields. With scientific advance, the term has come to mean a screen for blocking electromagnetic fields of a wide range of frequencies. A Faraday cage will not necessarily block electromagnetic radiation in the form of visible and invisible light. Insofar as a Faraday cage can screen an interior from external electromagnetic radiation, it can also retain electromagnetic radiation within itself. Its properties enabling it to do the one enable it to do the other. Whilst it is recognised that the term “Faraday cage” originates in respect of screening interiors, we have used the term in our earlier LUWPL patents and applications to refer to an electrical screen, in particular a lucent one, enclosing electromagnetic waves within a waveguide delimited by the cage. We continue with this use in this present specification.
In that application—our '744 Application—we described and claimed in first aspect, a LUWPL for our now so-called LEX technology, as follows:
A Lucent Waveguide Electromagnetic Wave Plasma Light Source comprising:
In this specification, this is called a first aspect LEX LUWPL.
The object of the present invention is to provide an improved LEX LUWPL.
According to a first aspect of the present invention, there is provided a first aspect LEX LUWPL, in which the at least partially inductive coupling means for introducing plasma exciting electromagnetic waves into the waveguide extends out of the first region and into the second region.
In other words, according to the first aspect of the present invention, there is provided:
A Lucent Waveguide Electromagnetic Wave Plasma Light Source comprising:
Preferably:
Whilst the antenna could extend through an aperture in a back wall of the fabrication and into a cavity therein without any sheath and the antenna could be sealed in the back wall; preferably, the antenna extends into the fabrication within a sheathing tube, conveniently of the material of the fabrication.
In preferred embodiments the sheathing tube is the same tube which has the plasma void formed in it beyond a seal from the antenna.
Also in our '744 Application we claimed in a second aspect, a LUWPL for our now so-called LEX technology, as follows:
A Lucent Waveguide Electromagnetic Wave Plasma Light Source comprising:
In this specification, this is called a second aspect LEX LUWPL.
According to a second aspect of the present invention, there is provided a second aspect LEX LUWPL, in which the at least partially inductive coupling means for introducing plasma exciting electromagnetic waves into the waveguide extends out of the rear semi-volume and into the front semi-volume.
Also in our '744 Application we claimed in a third aspect,
A Lucent Waveguide Electromagnetic Wave Plasma Light Source comprising:
In this specification, this is called a third aspect LEX LUWPL.
According to a third aspect of the present invention, there is provided a third aspect LEX LUWPL, in which the at least partially inductive coupling means for introducing plasma exciting electromagnetic waves into the waveguide extends out of the alumina body and into the quartz fabrication.
Also in our '744 Application we claimed in a fourth aspect,
A Lucent Waveguide Electromagnetic Wave Plasma Light Source comprising:
In this specification, this is called a fourth aspect LEX LUWPL.
According to a fourth aspect of the present invention, there is provided a fourth aspect LEX LUWPL, in which the at least partially inductive coupling means for introducing plasma exciting electromagnetic waves into the waveguide extends into the fabrication having the closed void.
Also in our '744 Application we claimed in a fifth aspect,
A Lucent Waveguide Electromagnetic Wave Plasma Light Source comprising:
In this specification, this is called a fifth aspect LEX LUWPL.
According to a fifth aspect of the present invention, there is provided a fifth aspect LEX LUWPL, in which the at least partially inductive coupling means for introducing plasma exciting electromagnetic waves into the waveguide extends out of the said body and into the second fabrication.
Also in our '744 Application we claimed in a sixth aspect,
A light emitter for use with a source of electromagnetic waves, an antenna and a Faraday cage, the light emitter comprising:
In this specification, this is called a sixth aspect LEX LUWPL.
According to a sixth aspect of the present invention, there is provided a sixth aspect LEX LUWPL, in which the antenna extends out of the said body and into the enclosure.
For the avoidance of doubt, the above statement of invention is that set out in the priority application No GB1021811.3. It is recognised to be narrower than some of the other statements of invention set out above. The following paragraphs down to the description of the drawings are also taken verbatim from the priority application. Their subject matter is not limited to the narrow priority statement of invention, but is applicable to the invention as stated broadly above and indeed as claimed below.
It should also be noted that in these paragraphs, the term:
“enclosure” refers to the “fabrication” of the above paragraphs at least where the fabrication includes a cavity distinct from the void enclosure and
“bulb” refers to the “void enclosure” of the above paragraphs.
Our '744 Application had not yet published been published as of the priority date of this application. Insofar as the present invention is an improvement in the invention of our '744 Application, in its different aspects, as quoted above, LUWPLs including features described in our '744 Application can all be improved with the present invention. Accordingly the following wording in quotation marks below from our '744 Application is repeated for the purposes of disclosure of this invention.
“We determine whether the coupling means is or is not “at least partially inductive” in accordance with whether or not the impedance of the light source, assessed at an input to the coupling means has an inductive component.
“We can envisage certain arrangements in which the coupling means may not be totally surrounded by solid dielectric material. For instance, the coupling means may extend from solid dielectric material in the waveguide space and traverse an air gap therein. However we would not normally expect such air gap to exist.
“The excitable plasma material containing void can be arranged wholly within the second, relatively low average dielectric constant region. Alternatively, it can extend through the Faraday cage and be partially without the cage and the second region.
“In certain embodiments, the second region extends beyond the void in a direction from the inductive coupling means past the void. This is not the case in the first preferred embodiment described below.
“Normally, the fabrication will have at least one cavity distinct from the plasma material void. In such case, the cavity can extend between an enclosure of the void and at least one peripheral wall in the fabrication, the peripheral wall having a thickness less than the extent of the cavity from the enclosure to the peripheral wall.
“In a possible, but not preferred embodiment, the fabrication has at least one external dimension which is smaller than the respective dimension of the Faraday cage, the extent of the portion of the waveguide space between the fabrication and the Faraday cage being empty of solid dielectric material.
“In another possible, but not preferred embodiment, the fabrication is arranged in the Faraday cage spaced from an end of the waveguide space opposite from its end at which the inductive coupler is arranged.
“In another embodiment, the solid dielectric material surrounding the inductive coupling means is the same material as that of the fabrication.
“In the first, preferred embodiment described below, the solid dielectric material surrounding the inductive coupling means is a material of a higher dielectric constant than that of the fabrication's material, the higher dielectric constant material being in a body surrounding the inductive coupling means and arranged adjacent to the fabrication.
“Normally, the Faraday cage will be lucent for light radiation radially thereof. Also the Faraday cage is preferably lucent for light radiation forwardly thereof, that is away from the first, relatively high dielectric constant region of the waveguide space.
“Again, normally the inductive coupling means will be or include an elongate antenna, which can be a plain wire extending in a bore in the body of relatively high dielectric constant material. Normally the bore will be a through bore in the said body with the antenna abutting the fabrication. A counterbore can be provided in the front face of the separate body abutting the rear face of the fabrication and the antenna is T-shaped (in profile) with its T head occupying the counterbore and abutting the fabrication.
“In the case of the third aspect, The difference in front and rear semi-volume volume average of dielectric constant can be caused by the said fabrication having end-to-end asymmetry and/or being asymmetrically positioned in the Faraday cage.
“Preferably:
“Possibly:
“Further, preferably:
“Where a separate body is used of the same or different dielectric material to that of the fabrication, the inductive coupling means can extend beyond the rear semi-volume into the front semi-volume as far as the fabrication.
“Again, preferably:
“Whilst, the or each cavity can be evacuated and/or gettered, normally the or each cavity will be occupied by a gas, in particular nitrogen, at low pressure of the order of one half to one tenth of an atmosphere. Possibly the or each cavity can be open to the ambient atmosphere1. 1 Whilst this paragraph was our preference at the date of our '744 Application, we now prefer that the cavity be gas filled, to a pressure of 5 mbar to 1500 mbar and in particular that it is filled with nitrogen at a pressure of 100 mbar to 700 mbar.
“It is possible for the enclosure void to extend laterally of the cavity, crossing a central axis of the fabrication. However, normally the enclosure of the void will extend on the central longitudinal, i.e. front to rear, axis of the fabrication.
“The enclosure of the void can be connected to both a rear wall and a front wall of the fabrication. However, preferably the enclosure of the void is connected to the front wall only of the fabrication.
“Preferably, the enclosure of the void extends through the front wall and partially through the Faraday cage.
“Possibly the front wall can be domed. However, normally the front wall will be flat and parallel to a rear wall of the fabrication.
“Normally, the enclosure of the void and the rest of the fabrication will be of the same lucent material. Nevertheless, the enclosure of the void and at least outer walls of the fabrication can be of the differing lucent material. For instance, the outer walls can be of cheaper glass for instance borosilicate glass or aluminosilicate glass. Further, the outer wall(s) can be of ultraviolet opaque material.
“In the preferred embodiment, the part of the waveguide space occupied by the fabrication substantially equates to the front semi-volume.
“Where provided, the separate body could be spaced from the fabrication, but preferably it abuts against a rear face of the fabrication and is located laterally by the Faraday cage. The fabrication can have a skirt with the separate body both abutting a rear face of the fabrication and being located laterally within the skirt.
“Preferably the void enclosure is tubular.
“Preferably the fabrication and the separate body of solid dielectric material, where provided, are bodies of rotation about a central longitudinal axis.
“Alternatively, the fabrication and solid body can be of other shapes for instance of rectangular cross-section.
“Conveniently the LUWPL is provided in combination with
“Preferably the electromagnetic wave circuit is a tunable comb line filter; and.
“The electromagnetic wave circuit can comprise:
“A further tuning element can be provided in the iris between the PECs.
“Conveniently, particularly in the case of the third aspect, the fabrication and the alumina body together fill the waveguide space.
“Conveniently, particularly in the case of the fifth aspect:
“Alternatively:
“The separate bodies where provided can be abutted against a rear face of the fabrication and be located laterally by the Faraday cage. However, preferably, the fabrication has a skirt with the separate body both abutting the rear face of the fabrication and being located laterally within the skirt.
“Whilst the body could be of the same lucent material as the enclosure, with the primary difference from the LERs of our WO 2009/063205 application, being the provision of the cavity in which the bulb extends; preferably, the body of solid dielectric material will be of higher dielectric constant than the lucent material of the enclosure and normally will be opaque.
“It should be particularly noted that we expect certain embodiments of the present invention to fall within the scope of the LER patents, because these are broad patents.
“The cavity can be open, allowing air or other ambient gas into the enclosure to substantially surround the bulb. However the cavity will normally be closed and sealed, with either a vacuum in the enclosure or a specifically introduced gas.
“The enclosure and the cavity sealed within it can be of a variety of shapes. Preferably the enclosure is a body of rotation. It could be spherical, hemispherical with a plane back wall for abutting a plane front face of the solid dielectric body, or as in the preferred embodiment, circularly cylindrical, again with a plane back wall for abutting the solid dielectric body.
“Normally the enclosure will have constant thickness walls, whereby the enclosure and the cavity will have the same shape.
“Whilst it is envisaged that the bulb could be spherical, it is preferably elongate with a circular cross-section, typically being formed of tubular material closed at opposite ends,
“The bulb can extend into the cavity from a front wall of the enclosure towards its back wall. Alternatively, it can extend from a side wall of the enclosure parallel with the back wall.
“It can also be envisaged that the bulb could extend from the back wall of the enclosure.
“Whilst it can be envisaged that the bulb could be connected to walls of the enclosure at opposite sides/ends of the bulb, it is preferably connected to one wall only. In this way the material of the bulb is substantially thermally isolated from the material of the enclosure; albeit that they are preferably of the same lucent material.
“Normally the bulb, or part of it will be at the centre of the light emitter, experiencing the highest electric field during resonance.
“In a simple arrangement, the enclosure and the solid body can be of equal diameters and abutted together, back wall to front face, being held against each other by the Faraday cage. However it is preferred that the enclosure is extended backwards with a rim fitting a complementary rebate in the body or with a skirt within which the body is received.
“Preferably, the bore in the body for the antenna is central and passes to the front face of the body, whither the antenna extends, with the bulb being arranged to have a portion thereof spaced from the back wall of the enclosure by a small proportion of the enclosure's front to back dimension. In the preferred embodiment, the front face of the body has a recess occupied by a button head of the antenna.
“Alternatively, it can be envisaged that the antenna could be:
In all embodiments which we described in our '744 Application, the inductive coupling means is an antenna, preferably with a button head, stopping short of entering the second region or front semi-volume having the lower volume average dielectric constant.
To help understanding of the invention, specific embodiments thereof will now be described by way of example and with reference to the accompanying drawings, in which:
For the avoidance of doubt the description that follows is that to of our '744 Application, modified in accordance with the present invention. For the assistance of the reader, the wording describing the modification is in italics.
Referring to
The tube 71 from which the void is formed is continued backwards from the inner end of the void enclosure as an antenna sheath 72.
The end plate 5 is circular and has the enclosure 2 sealed in a central bore in it, the bore not being numbered as such. The plate is 2 mm thick. A similar plate 6 is positioned to leave a 10 mm separation between them with a small approximately 2 mm gap between the inner end of the enclosure and the inner plate 6. The antenna sheath is fused to the plate 6, with an aperture 73 in the plate allowing the antenna described below to pass into the sheath. The plates are 34 mm in diameter and sealed in a drawn quartz tube 7, the tube having a 38 mm outside diameter and 2 mm wall thickness. The arrangement places the two tubes concentric with the two plates extending at right angles to their central axis. The concentric axis A and is the central axis of the waveguide as defined below.
The outer end 10 of the outer tube 7 is flush with the outside surface of the outer plate 5 and the inner end of the tube extends 17.5 mm back from the back surface of the inner plate 6 as a skirt 9. This structure provides:
Accommodated in the skirted recess is a right-circular-cylindrical block 14 of alumina dimensioned to fit the recess with a sliding fit. Its outside diameter is 33.9 mm and it is 17.7 mm thick. It has a central bore 15 of 2 mm diameter. The rim of the outer face is chamfered against sealing splatter preventing the abuttal being close. An antenna 18 is housed in the bore 15. The antenna is of a length to extend into the antenna sheath 72. The latter has an internal length of 2 mm.
The quartz fabrication 1 is accommodated in hexagonal perforated Faraday cage 20. This extends across the fabrication at the end plate 5 and back along the outer tube for the extent of the cavity 10. The cage has a central aperture 21 for the outer end of the void enclosure and an imperforate skirt 22 extending 8 mm further back than the quartz skirt 9, which accommodates the alumina block 14. An aluminium chassis block 23 carries the fabrication and the alumina body, with the imperforate cage skirt partially overlapping the aluminium block. Thus, the Faraday cage holds these two components together and against the block 23. Not only does the block provide mechanical support, but also electro-magnetic closure of the Faraday cage.
The above dimensions provide for the Faraday cage to be resonant at 2.45 GHz. We believe that the extension of the antenna to within the thickness only of the seal at the inner end of the void enclosure contributes to better transfer of microwave energy from the antenna to the plasma in the void and hence enhancement of efficiency of the LUWPL in terms of lumens of light generated per watt of electricity consumed in powering the LUWPL.
The waveguide space being the volume within the Faraday cage is notionally divided into two regions divided by the plane P at which the alumina block 14 abuts the inner plate 6 of the fabrication. The first inner region 24 contains the antenna, but this has negligible effect on the volume average of the dielectric constant of the material in the region. Within the region are the alumina block and the quartz skirt. These contribute to the volume averages as follows:
The second region 25 comprises the fabrication less the skirt. Its part contribute to the volume averages as follows:
The contrasting average values for the two regions, 8.26 and 2.24, can be usefully contrasted with the average for the entire waveguide space of (20403.7×8.26)+(15869.5×2.24)/(20403.7+15869.5)=5.62. This figure is not altered significantly by the modification.
If the comparison of regions is not done on the basis of the first and second regions being divided by the abuttal plane between the fabrication and the alumina block, but between the two equal semi-volumes the comparison has an essentially similar result. The division plane V, parallel to the abutment plane, falls 1.85 mm into the alumina block. The latter is uniform in the direction of the axis A. Therefore the volume average of the first, rear semi-volume 26 remains 8.26. The second, other, front semi-volume 27 has a contribution from the slice of alumina and quartz skirt. This contribution can be calculated from its volume average dielectric constant:
Thus it can be said that the two ratios which are alternative comparisons of the inventive concept of our '744 Application are not affected by the present modification.
It will be noted that this LUWPL is appreciably smaller than an LER quartz crucible operating at 2.45 GHz, eg 49 mm in diameter by 19.7 mm long.
Turning now to
It should be noted that the arrangement described may not start spontaneously. In prototype operation, the plasma can be initiated by excitation with a Tesla coil device. Alternatively, the noble gas in the void can be radio-active such as Krypton 85 or at least a minor proportion thereof. Again, it is anticipated that the plasma discharge can be initiated by applying a discharge of the automotive ignition type to an electrode positioned close to the end 4 of the void enclosure.
The resonant frequency of the fabrication and alumina block system changes marginally between start up when the plasma is only just establishing and full power when the plasma is full established and acts as a conductor within the plasma void. It is to accommodate this that a bandpass filter, such as described, is used between the microwave generator and the LUWPL.
Turning now to
Turning to another modified LUWPL as shown in
In the modified LUWPL of
In another modification, as shown in
In yet another modification, shown in
Turning to
Normally the components that are sealed to form the fabrications will be of quartz which is transparent to a wide spectrum of light. However, where it is desired to restrict the emission of certain coloured light and/or certain invisible light such as ultra-violet light, doped quartz which is opaque to such light can be used for the outer components of the fabrication or indeed for the whole fabrication. Again, other parts of the fabrication, apart from the void enclosure can be made of less expensive glass material.
The invention is not intended to be restricted to the details of the above described embodiments. For instance, the Faraday cage has been described as being reticular where lucent and imperforate around the alumina block and aluminium chassis block. It is formed from 0.12 mm sheet metal. Alternatively, it could be formed of wire mesh. Again the cage can be formed of an indium tin oxide deposit on the fabrication, suitably with a sheet metal cylinder surrounding the alumina and aluminium cylinders. Again where the fabrication and the alumina block are mounted on an aluminium chassis block, no light can leave via the alumina block. Where the alumina block is replaced with quartz, light can pass through this but not through the aluminium block. The block electrically closes the Faraday cage. The imperforate part of the cage can extend back as far as the aluminium block. Indeed the cage can extend onto the back of the quartz with the aluminium block being of reduced diameter.
Another possibility is that there might be an air gap between the fabrication and the alumina block, with the antenna crossing the air gap to extend on into the fabrication. We anticipate that this will normally be via an antenna sheath, to allow the cavity around the void enclosure to be at least partially evacuated. However we envisage that whether there is an air gap or not the antenna may extend on its own into the cavity, with the cavity being in communication with the ambient atmosphere via the aperture passing the antenna. Another possibility is for the aperture to be sealed against the antenna.
Whereas above, the fabrication is said to be of quartz and the higher dielectric constant body is said to be of alumina; the fabrication could be of other lucent material such as polycrystalline alumina and the higher dielectric material body could also be of other high dielectric material such as barium titinate.
As regards frequency of operation, all the dimensional details above are for an operating frequency of 2.45 GHz. It is anticipated that since this LUWPL of the invention can be more compact at any specific operating frequency than an equivalent LER LUWPL, the LUWPLs of this invention will find application at lower frequencies such as 434 MHz (still within the generally accepted definition of the microwave range), due to the balance between greater size due to the longer wavelength of electromagnetic waves and reduced LUWPL size resulting from the invention. For 434 MHz frequency, a solid-state oscillator is expected to be feasible in place of a magnetron, such as is used in productions LUWPLs operating at 2.45 GHz. Such oscillators are expected to be more economic to produce and/or operate.
In all the above embodiments, the fabrication is asymmetric with respect to its central longitudinal axis, particularly due to its normally provided skirt. Nevertheless, it can be anticipated the fabrication could have such symmetry. For instance, the embodiment
Further, the above fabrications are positioned asymmetrically in the waveguide space. Not only is this because the fabrications are not arranged with the inter-region abutment plane P coincident with the semi-volume plane V, but also because the fabrication is towards one end of the waveguide space; whereas the separate solid dielectric material body is towards the other end. Nevertheless, it can be envisaged that the separate body could be united into the fabrication where it is of the same material. In this arrangement, the fabrication is not positioned asymmetrically in the waveguide space. Nevertheless it is asymmetric in itself, with a cavity at one end and being substantially voidless at the other to provided different end to end volume average of its dielectric constant.
Another possible variant is the provision of a forwards extending skirt on the aluminium carrier block. This can be provided with a skirt on the fabrication or not. With it, the Faraday cage can extend back outside the carrier block skirt and be secured to it. Alternatively, where the cage is a deposit on the fabrication, the carrier block skirted can be urged radially inwards onto the deposited cage material for contact with it.
The invention is not intended to be restricted to the details of the above described embodiments. For instance, the void enclosure runs a lot hotter than the outer tube enclosing the annular cavity. To avoid high thermal stresses in the quartz fabrication, the antenna sheath can be separate from the void enclosure in a manner similar to
In a variant of the embodiment of
In another variant, described with reference to
| Number | Date | Country | Kind |
|---|---|---|---|
| 1208368.9 | May 2012 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2013/051170 | 5/3/2013 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2013/167879 | 11/14/2013 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 20100194257 | Neate | Aug 2010 | A1 |
| 20110204781 | Espiau | Aug 2011 | A1 |
| Number | Date | Country |
|---|---|---|
| 2012004557 | Jan 2012 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20150097481 A1 | Apr 2015 | US |
