Патент USA US3052627код для вставки
Sept. 4, 1962 R. F. POST 3,052,61 7 I STELLARATOR INJECTOR’ Filed June 23, 1959 2 Sheets~Sheet 1 MFAGINETLDC INTESY MFAGINETLDC INTESY Hc DISTANCE MFAGINETLDC INTESY DISTANCE * INVENTOR RICHARD F POST , BY ATTORNEY: Sept. 4, 1962 R. F. POST 3,052,617 STELLARATOR INJECTOR Filed June 23, 1959 2 Sheets-Sheet 2 D. c. POWER )’ 1? SUPPLY 2/ 36 _ENERGETIC NEUTRAL ION SOURCE 27 26 CONTROLLED RECTIFIER 24 CONTROLLED RECTIFIER 24’ CONTROLLED RECTIFIER 26' CONTROLLED RECTIFIER 27" CONTROLLED RECTIFIER CONTROLLED RECTIFIER 3/ THREE PHASE SOURCE I PROGRAMMING MEANS 29 34 ; _ _ INVENTOR. RICHARD POST BY ATTORNEY. Patented Sept. 4, 1962 2 3,052,617 STELLARATOR INJECTOR Richard F. Post, Walnut Creek, Calif., assignor to the United States of America as represented by the United States Atomic Energy Commission Filed June 23, 1959, Ser. No. 822,404 6 Claims. (Cl. 204-4932) acted particles, impurities, and the like in the outer pe ripheral regions of the plasma column follow the diverted ?eld lines and leave the container to be neutralized at the outside wall of the diverter. From the diverter, the neu tral gas may be extracted by pumps and the reactant ma terial separated from the other constituents of the ex tracted gas for purposes of reinjection into the container with additional reactant material so as to continuously maintain reaction conditions. Since an outer shell of the The present invention relates to the injection of atomic constituents into a column of plasma contained by axial 10 plasma is the ?rst to be withdrawn by the diverter, it will be appreciated that it is extremely inefficient to introduce lines of magnetic force, and more particularly to method and means for replenishing reactant material to a stel new or recovered reactants near the Walls of the container. The probability that the newly introduced reactants near the walls are substantially immediately removed by the The term “stellarator” is widely accepted and employed herein as designating a device of the general character 15 diverter before performing bene?cial functions in the cen tral interior of the plasma column is untenably high. disclosed in “Proceedings of the Second United Nations Therefore the injection of reactants in the very desirable International Conference on the Peaceful Uses of Atomic larator. Energy,” volume 32, Controlled Fusion Devices, United Nations Publication, Geneva, 1958, pages l81—196. As described therein a “stellarator” is a device for the con ?nement and heating of an ionized gas or plasma in a mag forms of energetic-neutral atoms (i.e., ions preaccelerated to high energy and then neutralized) or molecular ions has been heretofore precluded in a stellarator because these forms of reactants break up near the container walls at the plasma densities employed for steady-state opera netic con?nement ?eld in which each single line of force, tion of a stellarator. followed inde?nitely, generates an entire toroidal surface. The present invention overcomes the foregoing dif? In other words, a stellarator magnetic ?eld is one which has a twisted toroidal con?guration and which therefore 25 culties encountered in the injection of energetic-neutral possesses a rotational transform. As noted in the publi atoms or molecular ion reactants in a stellarator by pro— of such a ?eld. A planar toroidal vacuum envelope may be provided which carries coils to generate an axial viding a method and apparatus by which the density of the plasma column in a localized injection zone is peri odically instantaneously diminished to facilitate the in axial ?eld to thus produce a resultant con?nement ?eld of ment ?eld. cation, several alternatives are possible in the generation magnetic con?ning ?eld through the envelope. A mag 30 jection at this time of the above-noted forms of reactants well into the central axial region of the plasma column netic transverse ?eld whose direction rotates with dis before breaking up and being trapped within the con?ne tance along the magnetic axis is superimposed upon the It is therefore a principal object of the present invention twisted toroidal con?guration within the envelope. Al ternatively, the con?nement ?eld may be produced in a 35 to inject replenishing reactant charges to the central axial region of a stellarator undergoing steady-state operation. vacuum envelope of twisted toroidal or ?gure-8 con Another object of this invention is the provision of a ?guration which carries coils to generate a magnetic ?eld method and apparatus for diminishing the density of a axially of the envelope. Since the envelope is twisted, so plasma column in a localized region thereof. is the con?nement ?eld. This latter alternative is his It is a further object of the present invention to provide torically the ?rst geometry proposed for the generation a method and apparatus for injecting energetic-neutral of a stellarator con?nement ?eld and is embodied in the atoms or molecular ions into a dense plasma column. complete stellarator device disclosed in the copending ap The invention, both as to its organization and method plication of Lyman Spitzer, Jr., Serial No. 239,419, which of operation, together with further objects and advantages matured into US. Patent No. 2,910,414 on October 27, 45 thereof, will be better understood by reference to the 1959. As disclosed in said patent, the stellarator embodi following speci?cation taken in conjunction with the ac ment thereof includes a twisted toroidal or ?gure-8 shaped container or envelope in which an axial magnetic con?ne ment ?eld is established, the con?nement ?eld being thus companying drawing, of which: FIGURE 1 is a diagrammatic illustration of an intense column of plasma as constrained radially by a uniform also of twisted toroidal con?guration. A reactant plasma 50 axially symmetric magnetic ?eld; is con?ned within the ?eld and heated to high kinetic FIGURE 2 is a graphical illustration of the axial in temperatures conducive to the establishment of various tensity pro?le of the uniform magnetic ?eld of FIG. 1; nuclear reactions between the plasma constituents. FIGURE 3 is a diagrammatic illustration of the plasma The con?ned plasma constitutent particles are heated column constrained by the magnetic ?eld of FIG. 1 as or accelerated in the container by the magnetic con 55 modi?ed by a magnetic ?eld in accordance with the pres ?ning ?eld and in some instances by an applied alter ent invention during the early stages of its application; nating magnetic ?eld to induce neutron producing reac ‘FIGURE 4 is a graphical illustration of the axial in tions in the reactant plasma. In addition, at least one tensity pro?le of the modi?ed ?eld of FIG. 3; point in the length of the container a gap is provided to FIGURE 5 is a diagrammatic illustration of the plasma gether with means to divert the magnetic ?eld lines in 60 column in the modi?ed magnetic ?eld at a time later than the peripheral portions of the container at the gap radially that depicted in FIG. 3; ' therethrough. Such means are commonly referred to as ' FIGURE 6 is a graphical illustration of the axial in a “diverter” and in the stellarator, the employment of at tensity pro?le of the modi?ed ?eld at the time of FIG. 5; least one diverter facilitates the maintenance of steady and state operating conditions by removing reactants and neu 65 FIGURE 7 is a schematic sectional View of preferred ' tral gas diffusing through the outer peripheral regions of apparatus in accordance with the present invention as the plasma column toward the material walls of the con embodied as an injector for a stellarator. tainer for recovery and injection as fresh or enriched re Considering now the invention in some detail, par actant material to the plasma. More particularly, in each ticularly as to the method thereof, and referring to FIG. diverter a thin shell of magnetic ?eld lines next to the 70 1 of the drawing, there is shown generally a plasma column 11 as constrained radially or collimated by an ax material walls of the container is bent radially outward ially symmetric magnetic ?eld 12 of uniform ?eld strength from the container axis and any unreacted reactants, re 3,052,617 3 H0 (see FIG. 2). The density of the charged particle constituents of the plasma column 11, i.e., ions and neu tralizing electrons, is relatively high and substantially uni formly distributed along the length of the column. Mag netically collimated ionized gaseous discharge columns of plasma of this type are commonplace in various charged 4 ions may then be directed radially into the central ?eld re gion of low density and by virtue of such low density have an increased probability of penetrating to the interior axial region of the column before suffering an ionizing collision and being trapped in the region 16. Subsequent to trap ping of the injected material, the re?ector ?eld regions 13, 14 may be diminished to the intensity H, of the mag particle sources and plasma heating apparatus such as a stellarator. Such a column of plasma as is well known netic ?eld 12 such that uniform ?eld conditions as de is a potent ionizing agent and is effective in ionizing or picted in FIGS. 1 and 2 are again established. The breaking up neutral molecules or molecular ions sub 10 plasma in the portions of the column which were pre stantially immediately upon their entry into the column. viously outwardly adjacent the re?ector ?eld regions 13, I-llence neutral molecules or molecular ions directed transversely into the plasma column are broken up or 14 is hence now unrestricted from the previously de?ned it is desired that neutrals or molecular ions penetrate to method in accordance with the present invention may be central ?eld region of the plasma column. The injected ionized in the peripheral regions of the column and material hence is admixed with the remainder of the plas constrained thereat by the magnetic ?eld before they 15 ma in the column by interdiffusion of the plasma constit can penetrate to the interior regions of the column near uents and the region 16 is hence enveloped within the the axis. Hence in instances such as in a stellarator where plasma column. Thereafter the foregoing steps of the the interior axial region of the plasma column prior to be periodically repeated. Alternatively, the re?ector ?eld ing ionized therein, a serious problem is posed. 20 regions may be relaxed to an intermediate intensity at To overcome the foregoing problem, in accordance which plasma particles can penetrate the same and be with the present invention the plasma constituent particles mixed with the injected material while gaining energy in are periodically swept magnetically from a localized re the region 16 by virtue of the greater ?eld intensity gion in the plasma column to establish a relatively low therein compared to that of the uniform con?nement density in such region. Neutrals or molecular ions may 25 ?eld. then be directed into the low density region and penetrate Considering now preferred structure for conducting substantially to the axis of the column before breaking the method of the present invention and referring to FIG. up by collision processes with the plasma particles in the 7 of the drawing, the invention is embodied therein as an low density region. The low density region is then en injector for a stellarator as shown generally at 17. More veloped by the remainder of the plasma column with the speci?cally, as regards the stellarator 17, same includes newly injected particles being admixed with the previous plasma constituents by relaxation of the ?elds, normal diffusion processes, or the like. More speci?cally, the any ‘known means for the generation of a twisted toroidal magnetic con?nement ?eld in an evacuated space. Pref erably such means is as disclosed in the previously ref magnetic sweeping of plasma particles from a localized erenced Spitzer patent and accordingly comprises a region of plasma column 11 is preferably periodically 35 vacuum envelope 18 in the form of a twisted toroid or accomplished as depicted in FIG. 3 by ?rst generating ?gure 8, although for purposes of simplicity and clarity a pair of closely axially spaced gradientially-intensi?ed re of illustration, the envelope 18 is shown in the ?gure as ?ector ?eld regions 13, 14 of intensity HR greater than a plane toroid. A uniform axially symmetric magnetic intensity H, (see FIG. 4) within magnetic ?eld 12. The ?eld is established longitudinally through envelope 18 by re?ector ?eld regions 13, 14 bound a central ?eld region means of a plurality of axially spaced solenoids 19 dis 16 of lesser initial intensity, He, disposed therebetween. posed concentric with reference to the envelope and con Magnetic ?elds of this con?guration HR—Hc—-HR are nected in series with a DC. power supply 21. The mag discussed in extensive detail relative to their effect on netic ?eld is accordingly of the general type depicted by plasmas in my copending application, Serial No. 443,447, FIGS. -1 and 2 of the drawing and hereinbefore discussed and accordingly are not detailed herein. For the purposes 45 relative to the method of the invention. of the present disclosure it su?ices to state that the re ?ector ?eld regions 13, 14 of intensity HR are effective in The outer shell of force lines of the magnetic ?eld near the walls of envelope 18‘ are diverted radially outward from the envelope in the two curved end sections there therefrom to regions of lesser intensity, i.e., central ?eld of by means of magnetic diverters Z2 communicably cou region 16 of intensity Hc and the bounding regions of 50 pled therewith. The diverters 22 are of the same general the ?eld 12 of intensity H0. Hence the plasma particles character as the ?eld diverter means disclosed in the previ within the region 16 of relatively short axial length at ously referenced Spitzer patent and such means are the time of establishment of the re?ector ?eld regions accordingly not discussed in detail herein. 13, 14 are con?ned therein. Moreover, the plasma par In the operation of a stellarator, a gaseous reactant, ticles in plasma column 11 disposed outwardly from the such as deuterium, is ionized within envelope 18 and con re?ector ?eld regions 13, 14 being re?ected therefrom ?ned in the axial region thereof as a relatively dense are prevented from entering the central ?eld region 16. column by the magnetic ?eld due to solenoids 19. The The re?ector ?eld regions 13, ‘14 are next moved out“ plasma is raised to high temperature and neutrons are wardly apart through the plasma column 11 to positions produced by nuclear reactions therein by means including of relatively wide axial spacing as depicted in FIGS. 5 60 the magnetic ?eld of solenoids 19' in the manner detailed and 6. By virtue of the charged particle re?ective prop in the previously referenced copending Spitzer application. re?ecting or repelling the plasma charged particles axially erties of the re?ector ?eld regions 13, 14, the plasma in the portions of column 11 outwardly adjacent the re?ector ?eld regions is urged in the direction of re?ector ?eld Partially burned reactant, relatively low temperature plasma, and the like in the outer peripheral portions of the plasma column are extracted through the diverters 22 and movement away from central ?eld region 16. The in 65 fresh reactants are introduced to the envelope 18 in order tensity of the central ?eld region simultaneously decreases to maintain steady-state operation. In order that the from the initial intensity Hc to substantially the intensity fresh reactants be introduced to the envelope in the H, of the con?nement ?eld 12. The dimensions of the desirable forms of energetic-neutral ‘atoms or molecular central ?eld region 16 are hence materially increased ‘ions, the stellarator 17 is modi?ed in accordance with without the entry of additional plasma particles thereinto. 70 the present invention to include means for periodically Consequently, the plasma particles originally trapped in establishing a low density injection zone in the plasma the central ?eld region occupy a much larger volume than column according to the method hereinbefore described. before and therefore the plasma density in the central ?eld More speci?cally, means are provided for establishing a region is materially lessened from that of the remainder of pair of gradientially-intensi?ed re?ector ?eld regions in the plasma column 11. Neutral molecules or molecular 75 the con?ning ?eld of solenoids 19 with the re?ector ?elds 3,052,617 6 5 column in the manner previously described to periodically periodically moving in opposition from‘ proximal sub stantially overlapping positions to distal positions of in creased axial spacing, thence disappearing. ‘It will be ap establish a relatively low plasma density in such injection zone. In order to introduce fresh reactants to the plasma preciated that many means exist in the art for establishing the moving re?ector ?eld regions, for example a pair of axially slideable direct current energized solenoids may be suitably mounted for mechanical translation in one of the straight sections of envelope 18. Such solenoids are column in envelope 18, an energetic-neutral atom source 36 is advantageously provided in communicable radial then mechanically reciprocated between proximal and attachment with the interior of envelope 18 at the mid point of injection zone 28‘, i.e., between the pair of sole noids 19 connected to recti?ers 2.4, 24'. Molecular ion ‘distal limits with the solenoids being correlatively ener gized at the proximal limit and de-energized or relaxed at the distal limit. Alternatively, the re?ector ?elds may fectively utilized. Energetic neutral ion sources generally comprise an ion accelerator which accelerates ‘appropriate be moved electrically by programming the energization of pairs of solenoids (either several of the existing sole reactant ions such as deuterons to high energy followed by means such as a transverse jet target of vapor inter solenoids) in ‘corresponding outward succession. ions thereof by charge-exchange processes. The neutrals thus formed upon being ionized produce fast atoms of sources and other sources may also be alternatively ef noids 19 of the stellarator or a separate set of injection 15 secting the accelerated ion beam to neutralize the energetic Both mechanical and electrical means for producing moving re ?ector ?elds are disclosed in more detail in my copending substantially the same energy as that of the ions prior to neutralization. For a more thorough understanding of energetic neutral ion sources reference may be had to application, Serial No. 443,447. ‘For purposes of illus tration, an electrical injection circuit 231 is depicted in University of California Radiation Laboratory report UCRL-4643, I anuary 24, 1956, by Eugene J. Lauer. FIG. 7 of the drawing which coacts with a group of the existing stellarator solenoids 19 in a straight section of envelope 18 to produce moving re?ector ?elds; how Energetic neutral atom source 36 is preferably pro grammed to inject the neutral atoms to the injection zone ever, the invention is in no way limited to such circuit in view of the alternative mechanical means mentioned previ 25 28 correlatively with the establishment of low plasma density conditions therein by the moving re?ector ?elds. ously as well as a variety of alternative circuits which To facilitate the foregoing, programming means 34 is will be apparent to those skilled in the electronics art. connected in delayed triggering relation to the energetic As regards the speci?c injection circuit 23, it is to be neutral ion source 36 to gate the source just after the noted that same preferably includes a plurality of con trolled recti?ers 24, 24', '26, 216', 27, 27’, for example 30 most central pair of solenoids 19 are energized by rec ti?ers 24, 24'. More particularly, a delayed gate genera conventional grid controlled recti?ers, which are respec tor of conventional design may be included in the pro tively connected in energizing relation to pairs of the gramming means and pulsed on after a slight delay by solenoids 19 of stellarator 17 in outward succession from the initiation of control voltage applied to recti?ers 24, a ?rst pair in juxtaposition. These solenoids connected to the recti?ers de?ne in envelope 18 a magnetically swept 35 24’ and pulsed off by the termination of control voltage injection zone 2'8 in accordance with the present invention applied to recti?ers 27, 27’. The gate pulse from the disposed substantially between transverse median planes gate generator may then be for example applied to the of the solenoids connected to recti?ers 27, 27’. The ion extraction structure of the ion accelerator portion controlled recti?ers are energized at their inputs by a of the energetic neutral source 36 to facilitate the direc multiphase power supply which in the case of the present 40 tion of energetic neutral atoms into the injection zone embodiment is a three-phase source 2.9. More particu correlaively during the movement of the re?ector ?elds larly, the recti?ers 24, 24’ coupled vto the central pair of therethrough. Various speci?c circuits which may be solenoids 19 relative to injection zone 28‘ are coupled employed in programming means 34 to accomplish the in parallel to the leading phase output 31 of three-phase foregoing are well known and will suggest themselves source 29. The recti?ers 2:6, 26' coupled to the next out wardly successive pair of solenoids are coupled in parallel 45 to those skilled in the art. In summary, the operation of the injection circuit 23 and associated injection apparatus of the present invention generally follows from the method thereof. With the stellarator 17 undergoing continuous pair of solenoids are coupled in parallel to the lagging operation and an intense plasma column established with phase output 33 of the source 29‘. in envelope 18, programming means 34 ?res recti?ers 24, 50 The control inputs of controlled recti?ers 24, 24’, 26, 24'; 26, 26’; and 27, 27' in respective succession to 26’, 27, 27' are responsively connected to suitable pro sequentially energize the corresponding pairs of solenoids to the intermediate phase output 32 of source 29‘. Simi larly, the recti?ers '27, 217' coupled to the most outward gramming means 34. Such programming means applies control voltage in the usual manner to the recti?ers to ?re recti?ers 24, 24'; "26, 26’; and 27, 27' in respective 19 in injection zone 28 in an axially outward direction relative to the midpoint of the zone. As the re?ector ?elds move outwardly, the plasma particles in the plasma sequence and to correlatively maintain conduction of same 55 column are swept axially outward thereby to materially during substantially the entire durations of the positive alternations of the cycles of phased voltage appearing at the outputs 311, 32, 33 of three-phase source 29. The corresponding pairs of solenoids 191 coupled to the con decrease the plasma density in the injection zone 28. Just after the re?ector ?elds begin to move axially out ward, programming means 34 ?res energetic neutral source trolled recti?ers are thus energized in outward succession therefrom to superirnpose upon the uniform con?nement into the injection zone between the moving re?ector ?elds. The energetic neutral atoms signi?cantly penetrate the low plasma density region so established between the re ?ector ?elds to substantially the axis of the plasma col umn before being ionized and trapped between the re ?ector ?elds. A-fter termination of conduction of recti ?ers 27, 27’ and de-enerization of the solenoids 19 con ?eld generated by the solenoid pairs of gradientially-in tensi?ed re?ector ?elds moving outwardly in axial op position from the center to the ends of the injection zone 28 as depicted in FIGS. 4-6 of the drawing and herein before described relative to the method of the present in vention. Subsequent to termination of conduction in the last pair of recti?ers 27, 27’, corresponding to the end of the positive alternation of the lagging phase voltage at output 33 of source 29,,the positive alternation of the leading phase volt-age is again initiated at output 31 of source 29 and recti?ers 24, 24-’ are again ?red to initiate another cycle of magnetic sweeping by the moving re— ?ector ?elds. The moving re?ector ?elds in injection zone 36 to direct a beam of energetic neutral reactant atoms nected thereto, the intensity of the magnetic ?eld within injection zone 28 becomes equal to that of the uniform con?nement ?eld established longitudinally of envelope 18 or is relaxed to an intermediate value. The fresh charge of energetic reactant ions previously trapped in the injection zone 28 between the re?ector ?elds conse quently is free to di?use into the remainder of the plasma 28 hence periodically sweep particles from the plasma 75 column to replenish the reactants continuously removed 3,052,617 7 8 by diverters 22. Programming means 34 thereafter ef fects repetition of the foregoing injection cycle. While the invention has been disclosed with respect to a single preferred embodiment, it will be apparent ?ector ?eld regions superimposed upon said magnetic ?eld to those skilled in the art that numerous variations and modi?cations may be made within the spirit and scope of the invention and thus it is not intended to limit the and moving distally through the localized region, a re actant source for generating reactant material selected from the group consisting of neutral atoms and molecular ions communicating radially with the interior of said envelope at a position between said ?rst pair of solenoids, and gate means coupled between said energizing means and said source for rendering the source operative during movement of said re?ector ?eld regions. invention except as de?ned in the following claims. What is claimed is: l. A method of injecting reactants into a stellarator 10 4. In a stellarator including at least a toroidal vacuum having a toroidal heated plasma column collimated by envelope, a plurality of axially spaced solenoids disposed a uniform axial magnetic ?eld and magnetic diverter concentric with reference to the envelope and energized means removing a peripheral layer of the column, com to (generate an axial magnetic ?eld therethrough for con prising the steps of periodically generating a pair of ?ning and heating a column of plasma extending axially gradientially-intensi?ed partially overlapping re?ector ?eld 15 through the envelope, and magnetic diverter means di regions of peak intensity HR greater than the intensity vetting a peripheral layer of the plasma column radially H, of the uniform magnetic ?eld, translating both said outward from the envelope, an injector for introducing re?ector ?eld regions axially apart to positions of in fresh reactants to the plasma column within the envelope creased axial spacing and thereat diminishing the peak comprising a plurality of controlled recti?ers correspond intensity of both said re?ector ?eld regions to the inten ingly connected to a plurality of said solenoids in a local sity H0, and directing reactant material selected from the ized injection zone of said envelope, said recti?ers each group consisting of neutral atoms and molecular ions having an energy input and a control input, a multiphase radially inward into said plasma column at a position in power source having a plurality of successive phase out termediate said re?ector ?eld regions during translation puts correspondingly connected in energizing relation to of same. 25 the energy inputs of pairs of said recti?ers in outward 2. In a stellarator including at least a toroidal vac succession with the leading phase output being connected uum envelope, a plurality of axially spaced solenoids disposed concentric with reference to the envelope and energized to generate an axial magnetic ?eld therethrough to the recti?ers connected to the most central pair of for con?ning and heating a column of plasma extending axially through the envelope, and magnetic diverter means diverting a peripheral layer of the plasma column radially outward from the envelope, improved injection respective outward sequence by pairs and to correlatively maintain conduction of the recti?ers during the positive alternations of the cycles of phased voltage correspond ingly applied thereto from said multiphase power source, apparatus for introducing reactants to said plasma col umn, comprising magnet means disposed concentrically about said envelope for periodically generating a pair of axially symmetric closely axially spaced re?ector ?elds therein having gradientially increased intensities relative solenoids in said injection zone, programming connected to the control inputs or said recti?ers to ?re same in a reactant source for generating reactant material selected from the group consisting of neutral atoms and molecular ions communicating radially with the interior of said envelope intermediate said central pair of solenoids in said injection zone, and means connecting said program to the intensity of said con?ning ?eld, means coupled ming means to said reactant source in delayed triggering to said magnet means for moving both said re?ector 40 relation thereto to gate the reactant source on subsequent ?elds in axial opposition to distal positions of increased to the initiation of a positive alternation of leading phase spacing, means coupled to said magnet means for de voltage of said multiphase source and gate the reactant creasing the intensity of both said re?ector ?elds to source off upon the termination of a positive alternation zero at said distal positions, and reactant source means of lagging phase voltage of said multiphase source. communicating with the interior of said envelope between 5. In a stellarator, an injector according to claim 4 said re?ector ?elds for directing reactant selected from further de?ned by said reactant source being a neutral the group consisting of neutral atoms and molecular ions atom source. thereto during movement of the re?ector ?elds. v6. In a stellarator, an injector ‘according to claim 4 3. In a stellarator including at least a toroidal vacuum further de?ned by said reactant source being a molecular envelope, a plurality of axially spaced solenoids disposed ion source. concentric with reference to the envelope and energized to generate an axial magnetic ?eld therethrough for con References Cited in the ?le of this patent ?ning and heating a column of plasma extending axially UNITED STATES PATENTS through the envelope, and magnetic diverter means di 55 2,892,114 Kilpatrick ___________ __ June 23, 1959 verting a peripheral layer of the plasma column radially 2,910,414 Spitzer ______ __‘ ______ __ Oct. 27, 1959 outward from the envelope, an injector for introducing 2,946,914 Colgate et al. ________ __ July 26, 1960 fresh reactants to the plasma column within the envelope comprising energizing means connected to a plurality of said solenoids in a localized region for periodically ap 60 plying energizing current to pairs of the solenoids in corresponding outward succession from a ?rst pair thereof in juxtaposition at the midpoint of the localized region to generate a pair of spaced gradientially-intensi?ed re 2,969,308 Bell et al. ___________ __ Ian. 24, 1961 OTHER REFERENCES Proceedings ‘of the Second United Nations International Conference on the Peaceful Uses of Atomic Energy, vol ume 32 (1958), pages 273-278.