ZA200603357B - Thermionic electric converter - Google Patents

Description

WO» 2005/052983 PCT/US 22003/034501

THERMIONIC ELECTRIC CONVERTER

FIELD OF THE INVENTION

The present invention relates generally to the field of converting heat energy directly to electrical energy. More particularly, a thermionic electmric converter is provided.

BACKGROUND OF THE INVENTION

Heretofore, there have been known thermionic converters such as those shown in U.S. Pat. Nos. 3,519,854, 3,328,611, 4,303,845, 4,323,808, 5,459,367, 5,780,954 and 5,942,834 (all to the inventor of the pwesent invention and all hereby imcorporated by reference), which disclose various apparatus and methods for the direct conversion of thermal energy to electrical energy. In U.S. Fat. No. 3,519,854, there is described a converter using Hall effect techniquess as the output current collection means. The '854 patent teaches use of a stream of electrons boiled off of an emi ssive cathode surface as the source of electrons. The electrons are accelerated toward an anode positioned beyond the Hall effect transducer. The anode= of the '854 patent is a simple metallic plate, which has a heavily static charged member circling the plate and insulated from it. 20 .

U.S. Pat. No. 3,328,611 discloses a spherically configured thermionic converter, wherein a spherical emissive cathode is supplied with heat, thereby emitting electrons to a cawncentrically positioned, spherical anocle under the influence of a control memmber, the spherical anode having a high positive potentizal thereon and insulated from the control member. As =with the '854 patent, the anode of the '611 patent is simply a metallic surface.

U.S. Pat. No. 4,303,845 discloses a thermionic converter whe=rein the electron stream from the cathode passes through an air core inductiorm coil located within & transverse magnetic field, thereby generating an EMF in the induction coil by interaction of the electron stream with the transverse nmagnetic field.

The anode of the '845 patent also comprises a metallic plate which has a heavily~ static charged member circling the plate and insulate from it. :

U.S. Pat. No. 4,323,808 discloses a laser-excited thermionic converter that is very similar to the thermionic converter disclosed in the '845 patent. The main differerce is that the '808 patent discloses using a laser which is applied to a grid on: which electrons are collected at the same time the potential to the grid is removed, thereby creating electron boluses that are accele rated toward the anode through an air core induction coil located within a transsverse magnetic field. T he anode of the '808 patent is the same as that disclossed in the '845 patent. i.e., simply a metallic plate which has a heavily static charged member circling the plate and insulated from it. - U.S. P at. No. 5,459,367 advantageously uses an-improved collector element with ary anode having copper wool fibers and copper sulfate cyel instead of a metalli ¢ plate. Additionally, the collector element has a highly charged (i.e., static eslectricity) member surrounding the anode and insulate=d from it.

U.S. Patent Nos. 5,780,954 and 5,942,834 are directed to the provision of a cathode that is constructed as a wire grid, with the= cathode being of a non- planar shagoe to increase its emissive surface aream. These patents also disclose thee technique of using a laser to hit the st ream of electrons before they reach the anode, as a measure of providing cguantum interference such that the ele=ctronics may be more readily captured by the anode.

Another pr or design has an anode and cathode which are relatively close together sumch as two microns apart within a vacuu:m chamber. Such a prior design use-s no attractive force to attract electrons emitted from the cathode to the anode eather than induction of cesium into the chamber housing the anode and cathocEe. The cesium coats the anode with a peasitive charge to keep the electrons fleowing. With the cathode and anode so aclose together, it is difficult to maintain the temperatures of the cathode and amode at substantially different ternperatures. For example, one would ncermally have the cathode at 1800 degrezes Kelvin and the anode at 800 degree=s Kelvin. A heat source is provided to heat the cathode and a coolant circulattion system is provided at the anode i n order to maintain it at the desired tem perature. Even though the chamber is maintained at a vacuum (other than thes cesium source), heat from the cathode goes to the anode and it takes a signifSicant amount of energy to maintain thee high temperature differential between the closely spaced cathode and anode. This in turn lowers the efficiency of the system substantially.

OBJECTS AND SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is tc provide a thermionic converter having enhanced and/or improved feature=s over those previously designed or developed.

A further principal object of the present invention is provide a thermionic electric converter with improved conversion efficiency.

Another object of the present invention is to provide an improved cathode for a thermionic electric converter having an increased cathode output.

Yet another object of the present invention is to prov-ide a thermionic electric converter in which the cathode is bombarded by a la ser to increase the emissivity of the cathode.

A further object of the invention is to provide an anocde or target designed to capture electrons emitted from the cathode, while also accommodating a laser cathode enhancer.

The above and other objects of the present invention , which will be apparent as the description proceeds, are realized by a thermieonic electric converter having a casing member, a cathode within the casingg member operable when heated to serve as a souree of electrons, and an ano-de within the casing member operable to receive electrons emitted from the cathode. The cathode may be a wire grid having wires going in at least two directions that are transverse to each other. A charged first focusing ring is in the casing member, between the cathode and the anode, and is operable to direct electrons emitted by the cathode through the first focusing ring on their way to the anode. A charged second focusingg ring is in the casing member, betuaeen the first focusing ring and the anode, a nd is operable to direct electrons emitted by the cathode through the second focusing ring on their way to she anode. Additional focusing rings may oe necessary. The cathode is prefezrably separated from the anode at a distances between about 4 microns to about five centimeters. More preferably, the catrmode is separated from the anode boy a distance of one to three centimeters. Ax laser operable to hit electrons (j.e=., apply a laser beam to the electrons) is positioned between the cathode a nd anode. The laser hits the electrons just before they reach the anode. The= laser is operable to provide quantum irmterference with the electrons such that «electrons are more readily captured by the anode. ~The cathode may be either a solid material or formed of a wire grid. Whe=n the wire grid construction is used, the wire grid preferably includes at least fomur

Mayers of wires. Further, each of the wire layers has wires extending in a different direction from each of the othe=r of the wire layers, the wire grid o-f the cathode thus including wires extending in at least four different directions. “This is designed to greatly increase the- emissive surface of the cathode. . “The present invention may altemately b>e described as a thermionic electric converter having a casing member, a cathode within the casing member

Operable when heated to serve as a sowurce of electrons, an anode within ~the casing member operable to receive electrons emitted from the cathode: amd a laser operable to hit electrons between -the cathode and anode. The laser thus provides quantum interference with the electrons such that electrors are more readily captured by the anode. The laser is operable to hit electronss just before they reach the anode. The laser is operable to hit electrons ~within 2 microns of when they reach the anode. The cathode is a wire grid faving wires going in at least two directions thaat are transverse to each otlner. The cathode is separated from the anode att a distance of about 4 microns to about five centimeters.

The present invention may alternately toe described as a thermionic electric converter having a casing member, a c-athode within the casing meamber operable when heated to serve as a so urce of electrons, and an amode within the casing member operable to receive= electrons emitted from the «cathode and which proceed generally along a movement direction defining the direction from the cathode to the anodes. The cathode has a planar cross section area normal to the movement direction, the cathode has arm electron emission surface area for electron emission towards the anode, an«d the ‘ electron emission surface area is at leamst 30 percent greater than tlhe planar cross section area. The cathode is a wi re grid having wires going ir at least two directions that are transverse to ea ch other. Alternately, or ad-litionally, the cathode is curved in at least one diwection perpendicular to the :amovement - - direction. A laser is positioned so as to be operable to hit electrons between the cathode and anode just before they» reach the anode. Preferab ly, the electron emission surface area is at leamst double the planar cross ssection area. More preferably, the electron emLission surface area is at lea=st double the planar cross section area. The smaller the diameter of the wire, the larger the emissive area. This is an expotential relationship.

The present invention also involves the use of a laser positioned to impinge upon the cathode while being rastered or stepped along the cathode emissive surface, for the purpose of enhancing the output of electrons emitted from the cathode. The laser may be positioned behind the anode or target and aimed at the cathode, and the laser bean may be emitted through an opening in the target to impinge on the cathode. A target or anode specially designed to

LO have an opening therein, preferably through the center thereof, is provided to accommodate the operation of the laser.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in detail herein with reference to the following 1s figures in which like reference numerals denote like elements, and wherein:

FIG. 1 is a schematic diagram of a prior art thermionic electric converter;

FIG. 2 is a schematic diagram of a prior art laser-excited thermionic electric converter;

FIG. 3 is a side view with parts in cross section and schematic diagram of a 20m thermionic electric converter accord ing to the present invention;

FIG. 4 is a top view of a wire grid structure used for a cathode; -

FIG. § is a side view of a part of the wire grid structure;

FIG. 6 is a side view of a part of an alternate wire grid structure;

FIG. 7 is a side schematic diagram iJlustrating multiple layers in a wire grid structure; and

FIG. 8 is a simplified side view of an alternate cathode s-tructure.

FIG. 9 is a side view with parts in cross-section and scheematic diagram of a thermionic converter accordimg to another preferred emkoodiment of the present invention.

FIG. 10 is a substantially schwematic front elevation view of the target subassembly employed in thee FIG. 9 embodiment.

FIG. 11 is a substantially sch ematic side view of the targget subassembly of

FIG. 10. : 1.0

DETAILED DESCRIPTION OF THE PREFERRED EME3ODIMENT

FIGS. 1 and 2 show prior art thermionic electric convertears as shown and described in U.S. Pat. Nos. 4-,303,845 and 4,323,808, ree=spectively, both to

Edwin D. Davis, the inventor of the present invention, the= disclosures of which are incorporated by reference herein in their entirety. While the operation of both thermionic converters is described in detail in the inmcorporated patents, a general operational overview is presented herein with re—ference to FIGS. 1 and 2 This may provide bacl<ground useful in understanmding the present invention. 2.0

FIG. 1 shows a basic thermionic electric converter. FIG. 2 shows a laser- : excited thermionic converter. The operation of both converters is very similar.

With reference to the figures, a basic thermionic electric converter 10 is shown. Tie converter 10 has an elongated, cylindrica _lly shaped outer housing 12 fitted with a pair of end walls 14 and 16, thereby fosrming a closed chamber 18. The heousing 12 is made of any of a number of known strong, electrically non-condmuctive materials, such as, for example, high--temperature plastics or ceramics, while the end walls 14, 16 are metallic plate=s to which electrical connectio ns may be made. The elements are mecharically bonded together and hermeetically sealed such that the chamber 18 mauy support a vacuum, - and a moderately high electrical potential may be app lied and maintained across the end walls 14 and 16.

The first e=nd wall 14 contains a shaped cathode regio n 20 having an electron emissive coating disposed on its interior surface, while the second end wall 16 is formed as a circular, slightly convex surface which i. s first mounted in an insulating ring 21 to form an assembly, all of which is #hen mated to the housing 122. In use, the end walls 14 and 16 function reespectively as the cathode terminal and the collecting plate of the convemrter 10. Between these two walls, an electron stream 22 will flow substantially— along the axis of symmetry of the cylindrical chamber 18, originating at the cathode region 20 and termirating at the collecting plate 16. : An annulaar focusing element 24 is concentrically posit :ioned within the chamber ~18 at a location adjacent to the cathode 20. 2A baffle element 26 is concentrically positioned within the chamber 18 at a lao cation adjacent to the collecting plate 16.

Disposed between the=se two elements is an induction asse-mbly 28 comprised of a helical induction ceil 30 and an elongated annular magmnet 32. The coil 30 and the magnet 32 are= concentrically disposed within, and occupy the central region of, the chamber 18. Referring briefly to the schematiec view of FIG. 2, the relative radial posit ioning of the various elements and assemblies may be seen. For clarity of pressentation, the mechanical retaining means for these interiorly located elements have not been included in either figure. Focusing element 24 is electrically connected by means of a lead 34 sand a hermetically sealed feed through 36 to an external source of static poten tial (not shown).

The induction coil 30 iss similarly connected via a pair of leacds 38 and 40 and a pair of feed-throughs 422 and 44 to an external load element shown simply as : a resistor 46.

The potentials applied &o the various elements are not explicitly shown nor discussed in detail as thhey constitute well known and convemtional means for implementing related ellectron stream devices. Briefly, considering (conventionally) the cat-hode region 20 as a voltage referenc=e level, a high, positive static charge iss applied to the collecting plate 16 and the external circuit containing this voltage source is completed by connection of its negative side to the cathode 20. This applied high, positive sstatic charge causes the electron strezsam 22 which originated at the cathode region 20 to be accelerated towards thes collecting plate 16 with a magnitude directly dependent upon the magnitude of the high static charge applied. The electrons impinge upon the collecting plate 16 at a velocity s ufficient to cause a certain amount of ricowchet. The baffle element 26 is configured and positioned to prevent these ricochet electrons from reaching the main section of the converter, and electrical connexctions (not shown) are applied thereto as required. A negative voltage of low to moderate level is applied to the focussing element 24 for focusing the electron =stream 22 into a narrow beam. In operation, a heat source 48 (which could be derived from diverse sources such as combustion of fossil fuels, solar devices, atomic devices, atomic waste or heat exchangers from existimg atomic operations) is used to heat —the electron emissive coating on the cathmode 20, thereby boiling off quantities of electrons. The released electrons are= focused into a narrow beam by focussing element 24 and are accelerated towa. rds the collecting plate 16. While transiting the induction assembly 28, the electrons come under the influence of the magnetic field produced by the magnet 32 and execute an interactive motion which causes an EMF to be imduced in the turns of the induction coil 30. Actually, this induced EMF is the =sum of a large number of individual a5 electrons executing small circular curmrent loops thereby developing a correspondingly large number of minute EMFs in each winding of the coil 3€0.

Taken as a whole, the output voltage of the converter is proportional to the velocity of the electrons in transit, andl the output current is dependent on thme size and temperature of the electron ssource. The mechanism for the induce-d

EMF may be explained in terms of thes Lorentz force acting on an electron having an initial linear velocity as it ermters a substantially uniform magnetic field orthogonally disposed to the elecstron velocity. In a properly configured device, a spiral electron path (not sho»wn) results, which produces the desiread net rate of change of flux as required Boy Faraday's law to produce an induced

EMF.

This spiral electron path results from a conmbination of the linear translatisonal path (longitudinal) due to the acceleration action of collecting plate 16 arad a circumlar path (transverse) due to the interacstion of the initial electron veloecity

S and the transverse magnetic field of magnest 32. Depending on the relative mag nitude of the high voltage applied to thee collecting plate 16 and the stremgth and orientation of the magnetic fie 1d produced by the magnet 32, othe r mechanisms for producing a voltage «directly in the induction coil 30 may be p ossible. The mechanism outlined above is suggested as an illustrative one only, and is not considered as the only operating mode available. All mec hanisms, however, would result from vaarious combinations of the appl icable Lorentz and Faraday considerat ions.

The basic difference between the basic corverter shown in U.S. Pat. No_. 4,30 3,845 and the laser-excited converter sshown in U.S. Pat. No. 4,323,808, is that the laser-excited converter collects ealectrons boiled off the surface of the cathode on a grid 176 having a small neegative potential applied thereon by a negative potential source 178 through lead 180, which traps the eleectron flow and mass of electrons. The electrical potential imposed on the grid i=s removed, while the grid is simultaneously e=xposed to a laser pulse disch=arge from laser assembly 170, 173, 174, 20 cau=sing a bolus of electrons 22 to be released. The electron bolus 22 is then electrically focused and directed through the interior of the air core inductiorw coils located within a transve=rse mag. netic field, thereby generating an EMF in the induction coil which is appl ied to an external circuit to perform wowrk, as set forth above with respect to the basic thermionic converter.

As set forth the present inventor's porior U.S. Pat. No. 5,459,367, there= are numerous attendant disadvantagess usually associated with having a collecting element simply made up of a conductive metal plate. Therefore, the collecting element of that design in cludes a conductive layer of coppe=r sulfate gel impregnated with copper wool fibers. The present invention may muse such an anode. However, the present in vention aiso may use a conductive metal plate anode as other aspects of thes present invention will minimize omr avoid some of the disadvantages that su ch a plate anode might otherwise acause.

Basically then, the specifics of the anode are not central to the prefer—red design of the present invention.

With reference now to FIG. 3, a thearmionic electric converter 200 according to the present invention includes a casing member 202 in which a vacu um would be maintained by vacuum apparatwus (not shown) in known fashion. Whe casing member 202 is preferably cylindrical about a central axis 202A which serves as an axis of symmetry of tthe member 202 and the componemts therein except where otherwise nosted.

The collector 204 may include a flat anode circular plate 206 (made eof copper for example) surrounded by a statically charged ring 208 (charged tam 1000

Coulombs for example) having insulating rings 210 concentric therewith. The ring 208 and rings 210 may be comstructed and operable as discussed in the

U.S. Pat. No. 5,459,367. A coolingg member 212 is thermally coupled to the plate 206 such tlhat coolant from coolant source 2214 is recirculated therethrough by coolant circuit 216. The cooling rmnember 212 maintains the anode plate at a desired temperature. The cooling member 212 may alternately be thee same as the anode plate 206 (im other words coolant would circulate throughm plate 206). A feedback arrangenment (not shown) using one or more sensors (not shown) could be used to staabilize the temperature of anode 206.

The cathode asssembly 218 of the present inventicon includes a cathode 220 heated by a healt source such that it emits electro ns which generally move along movement direction 202A towards the anocde 206. (As in the U.S. Pat.

No. 5,459,367, thine charged ring 208 helps attract the electrons towards the anode.) Although the heat source is shown as a ssource 222 of heating fluid (liquid or gas) flomwing to heating member 224 (which is thermally coupled to the cathode 2207) via heating circuit 226, alternate= energy sources such as a laser applied to t=he cathode 224 might be used. The energy input into source 222 could be fos sil fuel, solar, laser, microwave, or radioactive materials.

Further, used nu clear fuel that would otherwise simmply be stored at great expense and witlihout benefit might be used to pro-vide the heat to source 222, -Electrons energizzed to the Fermi level in cathode 220 escape from the surface thereof amnd, attracted by static charge ring 208, travel along movement directzion 202A through first and seconcd focussing rings or cylinders 228 aned 230, which may be constructed and operable in similar fashion focussing element 24 of the prior art arrarmgement discussed above. In order to help the electrons move in the proper direction a shield 2232 may surround the cathode 224. The shield 2232 may be cylindrical or conical or, as shown, include a cylindrical portion clossest the cathode 224 and a conical portion further from the cathode 224. I any case, the shield tencHs to keep = electron movement in direction 202A. Whe electrons will tend to [oe repelled from the shield 232 since the shield wil | be at a relatively high termnperature (from its proximity to the relatively high temperature cathode 220°). Alternately, : or additionally, to being repelled by the high temperature of the s hield, the shield 232 could have a negative charcge applied to it. In the latte r case, insulation (not shown) could be used beetween the shield 232 and cathode 220.

The electrical energy produced corresponding to electron flow from cathode 220 to anode 206 is supplied via cathoade wire 234 and anode wime 236 to an external circuit 238.

Turning from the overall operation of th € converter 200 to specific advantageous aspects thereof, electrors such as electron 240 te nd to have a high energy level as they approach the anode 206. Therefore, the= normal 20m tendency would be for some to bounce off the surface and not be= captured therein. This normally results in electromn scatter and diminishes tHe conversion efficiency of a converter. In order to avoid or greatly reduce this tendency, the present invention uses a laser 242 which hits the e -lectrons : (e.g., hits them with a laser beam 244) _just before they hit the ancode 206. The quantum interference between the photons of the laser beam 244% and the electrorms 240 drops the energy state of the electrons such that they are more readily czaptured by the surface of anode 206.

As will bbe understood from the dual wave-p-article theory of physics, the electrors hit by the laser beam may be exh ibiting properties of waves and/or particless. Of course, the scope of the claimss of the present invention are not limited to any particular theory of operation unless and except where a claim expresssly references such a theory of operation, such as quantum interfereance. ‘

As usec! herein, when reference is made to the laser 242 hitting the electrons with be=am 244 "just before" the electrons reach the anode 206 means that the electrors which have been hit do not pass #through any other components (such a=s a focusing member) as they contirue to the anode 206. More specifically, the electrons are preferably hit within 2 microns of when they reach tie anode 206. Even more preferably, the electrons are hit by the laser with 1 rmnicron of reaching the anode 206. Indeed, the distance from the second focusing element 230 to the anode 206 may be 1 micron and the laser may hit electrons closer to the anode 206. Bn that fashion (i.e., hitting the electrors just before they reach the anode): , the energy of the electrons is reducec at a point where reduced energy iss most appropriate and useful. -

Although casing member 202 may be opacgue, such as a metal member, a laser wilindow 246 is made of transparent nmaterial such that the laser beam 244 car travel from laser 242 into the chamber within member 202.

Alternately, the laser 242 could bea disposed in the chambenr.

In addition to improving conversio n efficiency by using the laser 242 to reduce the energy level of electrons just before they reach the anoede 208, the cathode 220 of the present invent jon is specifically designe«d to improve efficiency by increasing the electrcon emission area of the cathode 220.

With reference to FIG. 4, the catheode 220 is shown as a circular grid of wires 248. Wires 250 of a top or first lay-er of parallel wires extencd in direction 252, whereas wires 254 of a second la-yer of parallel wires exten d in direction 256, transverse to direction 252 and pr-eferably perpendicular to direction 252. A third layer of parallel wires (only o_ne wire 258 shown for ea=se of illustration) extend in direction 260 (45 degrees from directions 252 and 256. A fourth layer of parallel wires (only one wi re 262 shown for ease of illustration) extend in direction 264 (90 degrees from direction 260).

It should also be noted that FIG. 4- shows the wires with relatively large separation distances between themm but this is also for ease- of illustration.

Preferably, the wires are finely ext-ruded wires and the sepamration distances between parallel wires in the same layer would be similar tos the diameter of the wires. Preferably, the wires ha.ve diameters of 2 mm or Ness to fine filament size. The wires may be tusngsten or other metals used in cathodes.

With reference to FIG. 5, the wiress 250 and 254 may be offset from each other with all wires 250 (only one sshown in FIG. 5) disposed in a common plane offset from a different common plane in which all wires 254 are disposed. An alternate arrangement shown in FIG. 6 has wires 25-0" {only one visible) and 254' which are interwoven in the manner of fabric,

With reference to FICS. 7, an alternate cathode 220" may have threee portions 266, 268, and 270. Each of portions 266, 268, and 270 may have two perpendicular layers of wires (not shown in FIG. 7) such as 250 an d 254 (or 250' and 254"). Portion 266 would have wires going into the plane of view of

FIG. 7 and wires parallel to the plane of FIG. 7. Portion 268 has two layers of wires, each having wires extending in a direction 30 degrees from One of the directions of the wires for portion 266. Portion 270 has two layers off wires, each layer having wires extending in a direction 60 degrees from ore of the directions of the wires_ for portion 266.

It will be appreciated tihat FIG. 7 is illustrative of the point that multip le layers of wires extending in different directions could be used.

The various wire grid sstructures for the cathode increase the effective= electron emission surface area by way of the shape of the wires and their multiple layers. An alternative wosay of increasing the surface area is illustrated® in FIG. . 8. FIG. 8 shows a side cross section view of a parabolic cathode 280 operable to emit electrons for movement generally along movement direction 2®20A".

The cathode 280 has a planar cross section area A normal to the mowement direction 202A. Significantly, the cathode 280 has an electron emissicon surface area EA (from tFre curvature of the cathode) for electron emission towards the anode which is at least 30 percent greater than the planar cross section area _A. Thus, a greater density of electrons are generated for & given size cathode Although the cathode 280 is =shown as a parabola, other curved surfaces may be used. The cathode 280 m ay be made of a solid member or may also incorporate multiple layer wire gri d structures like described or

FIGS. 4-7 execept that each layer would be curved and not planar.

Although the curved cathode arrangement of FIG. 8 provides an electraon emission surfface area EA that is at least 30 percent greater than the slide cross sectiorm area A, the various wire grid arrangements such as FIG. 4 provide an el ectron emission surface area hat is at least double the sicde cross section area (i.e., defined as shown f-or FIG. 8). Indeed, the electron emission surface area in the grid arrangem ents should be at least ten &imes the side crosss section area. 1s

Advantageoumsly, the present invention allowvs the cathode 220 and anode 206 to be offset from each other by from 4 microns to 5 cm. More specifically, that offset or separation distance will be from 1 -to 3 cm. Thus, the cathode =and anode are su fiiciently far apart that heat fro m the cathode is less likely to be conveyed to &he anode than in the arrangerments where the cathode ard anode must oe in close proximity. Therefore, the coolant source 214 canbe a relatively low coolant demand arrangement. since less cooling is requiread than in many prior designs.

Turning now to FIGS. 9-11, a further embodiment of the thermionic eleactric converter of the present invention is illustrated. This embodiment is designed to further increase the output of electrons from the cathode, thereby further increasing the conversion efficiency and electrical current generation of the converter.

The thermionic electric converter 300 according to the embodiment shown in

FIGS. 9-11 may preferably employ many of the same or similar components to the converter 200 illustrated and described with respect to FIGS. 3-8. In particular, the converter 300 preferably includes a casimng member 302, which may preferably be cylindrical along at least a portion of" its longitudinal extent. “The converter 300 further includes an electron target scabassembly or collector 2304, the constructional details of which will be discusse=d later. A cooling mmember 312 is provided to maintain the target subasse=mbly 304, or specific components thereof, at a desired temperature, generalEy lower than an operating temperature of cathode subassembly 318. THhe cathode subassembly 318 preferably includes a cathode 320 ha ving a cathode emitter 321, the cathode being heated by a heat source 322 thermally coupled to the cathode such that the heating of the cathode will cause electrons to become energized and escape from the surface of the cathode emitter 321.

TF he heat source 322, as illustrated, includes a heating rember 324 coupled to the cathode, and a heating circuit 326 which delivers :a heating fluid (liquid ow gas) to cathode 320. As with the embodiments disclosed in FIGS. 3-8, it will be recognized by persons of ordinary skill in the art that the source of thermal energy for heating the cathode from an external source may take the

W” 0 2005/052983 PCT/USS2003/034501 form of solar energy, fossil fuel, laser energy, microwave energwy, or thermal energy derived from radioactive materials, such as radioactive waste or spent radioactive materials. Used nuclear fuel that would otherwise b-e required to be stored at great expense coul d be used to provide thermal en: ergy for heat source 322. The construction o-f basic systems or subassemblie=s for providing the various types of trmermal energy will be readily apparent to persons of ordinary skill in the art.

Converter 300 may also preferably employ first and second focusing rings 328, 330, in a manner similar to that shown in FIG. 3. A shield 332 may also be provided to surround cathode 320, to perform essentially the= same function as does shield 232 in the FIG. 3 embodiment.

Electrical energy produced corresponding to an electron flow from cathode emitter 321 to anode 306 of target subassembly 304 is supplied via cathode wire 334 and anode wire 336 to an external circuit 338. Circuit : 338 thus receives energy in electrical fori, which energy is produced or sgenerated from thermal energy by convertear 300. Circuit 338 may preferably include a transistor 337 connected in the circuit return line (shown as catiode wire 334 in FIG. 9), so that the current in the circuit is restricted to flowing in only one direction, i.e., in the direction baack to cathode emitter 321, via a. feedthrough 339 in casing member 302.

The converter 300 further prefemrably includes an electron interfearence laser 342, which operates to lower thee energy state of the electrons ams they reach

=anode 306, as by quantum interference or other particle interaction fphenomena. Laser beam 344 passes throucgh laser window 346 and iintersects the path of, or “hits”, the incoming electrons fo reduce the energy =stored in the electrons. Reference may be haad to the discussion of this aaspect of the invention in connection with lasser 242 and laser beam 244, and

I-IG. 3 herein, insofar as the theory of operation is concerned. The reduction #n the energy level of the electrons immediateely prior to contacting anode 306 «decreases the tendency of electrons to hit armode 306 and to bounce off and scatter because of the collision. Anode 306 will thus capture a larger poercentage of the incoming electrons. “Target subassembly or collector 304 is prefe rably constructed so as to have a central opening 370 sized and adapted to alleow a cathode output enhanc ing device or auxiliary cathode enhancer 372, in the form or a laser 374, to emit a | aser beam 376 in the direction 376a of the e-mitting surface 321 of cathode 320. Alternatively, target subassembly may Ehave such an opening in an ooff-- center location, or, altematively, may be sizead and positioned within casirg rnember 302 such that laser 374 can direct laaser beam 376 from a positioen outside the periphery of the target subassemibly.

Referring to all of FIGS. 9-11, target subasse mbly 304 may preferably comprise an anode 306 having opening 370 therethrough, shown centrall=y in the drawing figures, for the sake of convenierce. An insulating (electrically imnsulating) ring 378 is positioned at an edge of opening 370, and is preferaably ssecured to anode 306 at that edge. An electron repulsion ring 380 is disposed sat an inner periphery of insulating ring 378. This repulsion ring 380 is provideed in order to substantially prevent electrons emanating from cathode 320 and twraveling along path 302a from passsing into and through the sopening defined bwy repulsion ring 380, or to minimize= the number of electrons passing therethroiLigh. Electron repulsion ring 380 is preferably provided with =a negative ccharge imposed by an external sowarce (not shown) coupled —to the repulsion ring at feedthrough 379, or may operate in a different manneer to repel electrons. Preferably, the ring 380 will. operate to deflect at leasst portion of the ele=ctrons into a path that will result in the electrons colliding with anode 306 of tar-get subassembly 304.

Anode 306 may be formed as a flat circular plate, as illustrated, or may alternatively be curved in either a direction t-oward or away from catheode 324, or otherwise shaped in 2a manner designed tto effectively capture elec=trons traveling along paths from the cathode 320 into contact with the anocle.

Anode 306 preferably has, at its outer perip hery, a highly statically ciarged, or

Faraday, ring 308 bounded by inner and outer insulating rings 310. Whis portion of the target subassembly will be es sentially the same as thal disclosed with respect to the FIG. 3 embodiment, and will operate in generally | the same= manner, to aid in attracting the ele=ctrons toward anode 306, where . the electrons can be collected in order to ge=nerate an electrical curreant. A feedthromagh connector, shown schematicallly in FIG. 11 at 382, is enployed to couple the Faraday ring 308 to a means for imparting the desired high static charge. Insulating rings 310 operate to electrically insulate anode 3(O6 and the maim electrical circuit 338 from the stati«c charge imposed on ring 308.

The plate anode 306 may be constructed of the same materials as is thes anode 206 in FIG. 3, or may be of any other type known in the art to be suitable for this use. Cathode 320 may also be constructed of the same = materials and in the same manner as is cath ode 220 discussed and illusstrated with respect to FIGS. 3-8, or any other cathosde structure disclosed in th e prior patents discussed in the Background sectior herein.

In the embodiment of FIGS. 9-11, the output of the cathode is greatly 1-0 increased over that obtained in the embodinment shown in FIGS. 3-8. A=s noted previously, an auxiliary cathode enhancer 372, in the form of lase=r 374, is provided to direct a laser beam 376 at the emissive surface 321 of thee cathode, which further excites the electrons on that surface, over and allbove the excitation obtained by the thermal energy supplied by heating source 322. -

In the illustrated preferred embodiment, the Maser 374 is positioned insicle of casing member 302 and on a side of anode 306 opposite the side at wimich cathode 320 is positioned. Laser 374 is aim ed to direct laser beam 3763 such that the photons travel along path 376a in essentially the opposite direc=tion of the path 302a of the electrons traveling frome cathode 320 to anode 306-.

Laser beam 376 preferably strikes the emisssive surface 321 of the cath ode either orthogonally to that surface, or at a smnall angle of incidence thereto, to maximize the energy transfer to the electrorms.

The la ser 374 will preferably be controlled by co-ntroller 400 to emit “shots” or pulsess having, for example, a duration on the order of one to several picoseaconds, at a frequency of about 10-100 MHz. Other operational regimes may a:lso be adopted, and it should be recognized that these parameters are provideed primarily for illustrative purposes.

The atuxiliary cathode enhancer 372 will also preeferably include a rastering device=, shown schematically at 382 in FIG. 11. The rastering device 382 will be cortrolled, preferably also by controller 400, #0 cause the laser beam 376 to swe=ep in both lateral (side-to-side) and vertical (up-to-down, or vice versa) directions, in a manner that will be readily appar-ent to persons skilled in the art upon reading this description. The rastering device 382 is used so as to prevert erosion of the emissive surface of the cathode. 320 at regions where the laser beam might otherwise constantly or frequently impinge, thus prolon ging the life of the cathode. The rasterings device will preferably : compleete a sweep from side-to-side and from to p to bottom of the cathode at a frequiency on the order of one to several nanosseconds. Again, this period may d iffer from the stated preferred range, and nmay be coordinated with the freque=ncy and duration of the laser pulses to provide different desired degrees of auxiliary excitation of the electrons at the cathode surface. it is exxpected that the use of an auxiliary.cathod«e enhancer of the type disclossed will increase the output of the cathode- by approximately 20-25 times the ou-tput of the cathode in FIGS. 3-8, for exam ple, when that converter is operatced without the auxiliary enhancer. Again, the operating parameters of the enhamcer may be varied as desired to either increase= or decrease the level of emhancement to the cathode output.

In FIG. 108, possible alternative positions for the laser 374- of the auxiliary cathode e nhancer 372 are shown at A, B and C. These clesignations are intended t-o show that the laser 374 may be mounted off-csenter, relative to target sub assembly 304, whereby the opening in the anode 306 would be off- center, or may be mounted outside the outer periphery of target subassembly 304. In thiis latter case, there would be no need to provides an opening in the anode, nom would an electron repulsion ring be necessary . As noted previously, it is desired to maintain a relatively small angle of incidence of the laser beam relative to the emissive surface 321 of the cathode, in order to maintain a n efficient transfer of energy. The off-center po=sitionings could possibly re=sult in a less-efficient enhancement of cathode output, however, other design consideration may be simplified using such peositions, which could compoensate for the slightly lower efficiency.

Further, to this point, the discussion of the positioning of tine laser has focused on position ing the laser at the back side of the target suba=ssembly 304, opposite thie side at which the cathode is positioned. While such positioning tends to maintain a smaller angle of incidence of the laser beam with respect to the cathoode surface, it would be possible to position the laser 374 forward of the anodlle 306 (i.e., longitudinally between the anode armd cathode), provided it Fs positioned radially outside the path of the elecztrons traveling from the ca thode to the anode.

A further feature of the invention illustrated in FIG. 11 is the provision of a plurality of electrets 398 around the inner periphery of casing smember 302, to aid in scavenging any stray electrons that may bounce off of &anode 306 or otherwise fail to be capptured by the anode. Such stray electrons can create a space charge within the vacuum chamber. The electrets 398 will be connected to ground, =so as to substantially prevent any space charge buildup.

While the invention haas been described in conjunction with specific embodiments thereof, itis evident that many alternatives, moadifications and variations will be apparent to those skilled in ‘the art. Accordin gly, the preferred embodimen-ts of the invention, as set forth herein, a _re intended to be illustrative, not limiting. Various changes may be made withott departing from the spirit and scope o¥ the invention as defined herein and in —the following claims.

Claims (1)

1. PCT/US2003/08 34501 CLAIMS:

   1. A thermionic electric converter comprising: a casing member; a cathode within said casing member having a cathode emitter operaable, when heated, to serve as a source of electrons; a target structure within the casing rmember comprising an anode op erable to receive electrons emitted from th-e cathode emitter; and a cathode output enhancing device operable to increase an excitation energy of electrons disposed at saicd cathode emitter, and said cathode output enhancing device comprisess a cathode enhancing laser posi&ioned to direct a laser beam to strike an e=missive surface of said cathode emitter.

   2. A thermionic electric converter conmprising: a casino member; a cathode within said casing member having a cathode emitter opewable, when heated, to serve as a source of electrons; a target structure within the casing member comprising an anode ogoerabie to receive electrons emitted from tthe cathode emitter; and a cathode output enhancing device: operable to increase an excitati-on energy of electrons disposed at sa id cathode emitter, and said cattmode enhancing device is positioned in tthe interior of said casing membe=r.

   3. A thermionic electric converter as -set forth in Claim 2, wherein saidli cathode enhancing device comprises: a cathode enhancing laser control led by a rastering device operabBe to cause the laser beam to sweep accross an emissive surface of said cathode.

   4. A thermionic electric converter as set forth in Claim 3, wherein said rastering device is operable to cause the laser beam to sweep across substantially the entire emissive ssurface of said cathode. 28 AMENDDED SHEET

   PCT/US2®003/034501 1 5 . A thermionic electric converter as set forth in Claim| wherein s=id 2 cathode is positioned at a first side of sai d anode, and said cathode= 3 eanhancing laser is positioned at a second side of said anode oppossite said 4 first side.

   1 5. A thermionic electric converter as set forth in Claim 5, wherein ssaid anode 2 has an opening therein to allow a laser toeam emanating from said cathode 3 enhancing laser to pass therethrough.

   1 7. Athermionic electric converter as set forth in Claim §, wherein said 2 opening in said anode is located substamtially in a center of said amode.

   1 8. A thermionic electric converter as se=t forth in Claim 6, wherein said target 2 structure further comprises an electron repulsion ring positioned ir the 3 opening in said anode, said electron repoulsion ring having an opemning 4 therethrough.

   1 9. A thermionic electric converter as sset forth in Claim 8, whereimn said 2 electron repulsion ring is joined to said anode by an electrically ins sulating ring 3 positioned at an edge of said opening Ln said anode. 1 10. A thermionic electric converter as =set forth in Claim 9, whers=ein said 2 electron repulsion ring is operatively coupled to a source operabBe to impose a 3 negative charge on said electron repulsion ring. 29 AMENDED SHEET

   PCT/US200=3/034501

   1 11. A thermionic electric converter as set forth in Claim 6 where:n said target 2 structure further compriseSs a highly staticaily charged ring disposed a an 3 outer periphery of said arode.

   1 12. A thermionic electric converter as set forth in Claim 11 wherein sa. id 2 anode and said highly statically charged ring are joined together via am inner 3 insulating ring, and whereein said highly statically charged ring has an =outer 4 insulating ring adapted tc mount said target structure inside said casirg member.

   1 13. A thermionic electric converter as set forth in Claim 1, wherein sald

   2 cathode emitter comprises a wire grid having wires going in at least tv=vo

   3 directions that are trans\werse to each other.

   1 14. A thermionic electrics converter as set forth in Claim 1, wherein sa id anode 2 is a substantially planar plate anode. :

   1 15. A thermionic electric converter as set forth in Claim 1, further conmprising 2 an electron interference laser operable to hit electrons between the czathode 3 and anode.

   1 16. A thermionic electrics converter as set forth in Claim 1, further conmnprising 2 an electron interferences laser operable to hit electrons between the c=athode 3 and anode.

   AMENDED SHEET

   . PCT/LJS2003/034501 1 17. A thermionic electric converter as set forth in Claim 1 furtheer comprising at 2 least one electret positioned within said casing member and being operable 10 3 scavenge stray electrons present within said casing membter.

   1 18. A thermionic elexctric converter comprising: 2 a casing memb er; 3 a cathode within said casing member having a cathode ermitter operable, 4 when heated, to se rve as a source of electrons, a target structure within the casing member comprising ar anode 6 operable to receive electrons emitted from the cathode emitte=r; 7 a cathode enhancing laser positioned to direct a laser bezam to strike an 8 emissive surface o f said cathode emitter; and 9 a controller op erable to raster said laser beam across said emissive surface of said cathode emitter. 1 19. A thermionic electric converter as set forth in Claim 18, wvherein said 2 cathode and said cathode enhancing laser are positioned ora opposite sides of 3 said target structure, and 4 wherein said anode has an opening therein to allow a la=ser beam 5 emanating from said cathode enhancing laser to pass theretzhrough; and 6 wherein said target structure further comprises an electr-on repulsion ring 7 positioned at said opening in said anode, and a highly static-ally charged ring 8 extending around an outer periphery of said anode, operabl eto aid in 9 attracting electrons in said casing member toward said anode. 31 AMENDED SHEET

   PCT/IUS2003/034501

   20. A thermionic electric converter as set forth in Claim 19, further comprising an electron interfer-ence laser operable to hit electrons between the cathode and anosde.

   21. A thermionic electric converte tT as set forth in Claim 2, wherein said cathode emitter comprises a wire grid having wires going in at least two directions that are= transverse to each other.

   22. A thermionic electric converte ras set forth in Claim 2, wherein said anode is a substantially planar plate anode.

   23. A thermionic electric converte=r as set forth in Claim 2, further comprising an electron interfe=rence laser operable to hit electrons between the cathode and anode. 24 A thermionic electric converter as set forth in Claim 2, further comprising at least one electr-et positioned within said casing member and being operable “to scavenge stray electrons present within said casing member.

   25. A thermionic electric converteer comprising: a casing member, a cathode within said cas ing member having a cathode emitter operable, when heated, {o serve= as a source of electrons; a target structure within tke casing member comprising an anode operable to receive electrons emitted from the cathode emitter; a cathode output enhanc ing device operable to increase an excitation energy of electrons di. sposed at said cathode emitter, and characterized in that said cathoede output enhancing device 32 AMENIDED SHEET

   PCTT/1S2003/034501 comprises a cath ode enhancing laser positioned to direct a laser beam to strike am emissive surface of said cathode e=mitter; and an electrom interference laser disposed at a sLubstantially perpendicular an gle to an axis between the cathode and anode and the electron interference laser operable to hit the emaitted electrons between the cathode and anode to provide quantum. interference to the emitted elect rons, such that the emitted electronss are more readily captured by the anode.

   26. A thermionic electric converter as set forth in claim 25 wherein said cathode enhancing device is positioned in the= interior of said casing member.

   27.A thermionic electric converter as set forth in Claims 25 and 26, wherein said cathode enhancing device compris. es: a cathodes enhancing laser controlled by a ra stering device operable to causse a laser beam to sweep across stabstantially the entire emissive surface of said cathode.

   28. A thermionic electric converter as set forth in Claims 25-27 wherein said cathode is positioned at a first sides of said anode, and said cat:hode enhancing laser is positioned at a second side of said anode opposite said first side.

   29. A thermionic electric converter as set forth in Cl aims 25-28, wherein saicd anode has an opening substantial ly in a center of 33 AMENDED SHEET

   PCT/US2003/034501 said anode to allow a laser beaam emanating from said cathode enhancing laser to pass therethrough.

   30. A thermionic electric converter as set forth in Claims 25-29, wherein said target structure further comprises an electron repulsion ring positioned in the= opening in said anode, said electron repulsion ring having an opening therethrough.

   31. A thermionic electric converter as set forth in Claim 30, wherein said electron repulsion ring is Joined to said anode by an electrically insulating ring positioned at an edge of said opening in said anode and said electron repulsion ring is operatively coupled to a source operable to impos e a negative charge on said electron repulsion ring.

   32. A thermionic electric converte r as set forth in Claims 25-31 further comprising at least one electr-et positioned within said casing member and being operable to scavenge stray electrons present within said casing member.

   33. A thermionic electric converter as set forth in Claims 30 and 32 wherein said target structure further comprises a highly statically charged ring disposed at an outer periphery of said anode.

   34. A thermionic electric convertear as set forth in Claim 33 wherein said anode and said highly sftatically charged ring being joined together via an inner insulatirmg ring, and wherein said highly 34 AMEN DED SHEET

   PCT /US2003/034501 statically charged ring has an outer insulating ring adapted to mount said target structure inside said casing mermber.

   35. A thermionic electric converter as set forth in Clairms 25-34 wherein the cathode enhancing laser is operable Zo emit a laser beam to strike a cathode emitter for one to five hu ndred picoseconds.

   36.A thermionic electr-ic converter as set forth in Clairm 35 wherein the cathode enharmcing laser is operable to emit the laser beam at a frequency in the range of from 10 to 100 MHz.

   37.A thermionic elect ric converter as claimed in any -one of Claims 1, to 36, substantiallmy as herein described with reference to and as illustrated in any ofthe drawings. AMENDED SHEET