Dec. 17, 1946. E. D. MCARTHUR 2,412,824 MAGNETRON ‘ Filed June 22, 1942 2 Sheets-Sheet .1 Fig. I. 3%! /4f | 70 ‘z 22X , 3:. J)’ > 7/“ I, , // / ' 40 ' 37’ 4: \ J2 49 #49’ Inventor‘: Elmer’ D. McArthun by iVa/wy 63W His Attorney. Dec. 17, 1946. E. D. MGARTHUR 2,412,824 ' MAGNETRON Filed June 22, 1942 2 Sheets-Sheet 2 \\\\\\\ \\\\\\ \\\\\\\\\\\\\\ ‘ E by M”?vrW/eADLa?.LmMi“IA/We .5he w U r. 0cn M:r Patented Dec. 17, 1946 . 2,412,824 " UNITED STATES PATENT OFFICE Elmer D. McArthur, Schenectady,- N. Y., assignor to General Electric Company. a corporation of New York ‘ Application June 22, 1942, Serial No. 447,903 9~ Claims. The present invention relates to improvements in high frequency electronic devices of the‘ mag netron type. a ‘ ‘ As is well-known, the functioning of a ( Cl. 250-275) tion of the cathode of the device of Fig. 1; Fig. 4 is a detail view of one of the structural ele ments of the device of Fig. 1; Fig. 5 is a longi tudinal section of a modi?cation of the inven magnetron as a generator of high frequency waves depends upon the combined action of ap 5 tion; Fig. 6 is a longitudinal section illustrating a further modi?cation, and Fig. 7 is a perspective propriately directed electric and magnetic ?elds of one element of the device of Fig. 6. ‘upon electrons which move in an interelectrode Referring particularly to Fig. 1 there is shown space. In general, the frequency of the waves which may be developed by such devices is a func 10 an elongated cylindrical container, the lateral wall structure of which is provided by a single tion of the strength of the magnetic ?eld em metal tube IU consisting of ferromagnetic ma-_ ployed, the required ?eld strength being higher terial such as cold rolled steel or the like. The for the higher frequencies. Because of this rela tlonship, magnetrons which are operable in the ‘ ends of the container are closed by?anged mem . ultra-high frequency band bers H and I2 which are welded or otherwise have heretofore been required to be associated with massive magnetic 15 hermetically joined to the inner surface of the structures, leading to a cumbersome construction for the apparatus as a whole. It is a primary object of the present invention part III. The outer surface of the envelope is provided with a series of circumferentially ex tending ?ns I4 which are adapted to serve as heat dissipating elements and a somewhat larger to provide an improved type of ultra-high fre quency magnetron in which the weight and size 20 circular element l5 provided near the upper end of the container acts as a‘ mounting '?ange for of the operative parts, including especially the magnetic elements, are reduced to a minimum. _ In general this object is realized by the use of a the device as a whole. (Any numbervof addi tional cooling ?ns may be used, as required.) Within the container and approximately at its construction in which the magnetic ?eld is pro duced by permanently magnetized pole pieces 25 central region there is provided an anode struc ture 20 shown in plan view in Fig. 2. This com located‘within a container which consists wholly prises a circular member which has a relatively or in part of ferromagnetic components arranged large central opening 22 and a series of smaller to provide a return path for magnetic flux openings 23 arranged symmetrically about the traversing the pole pieces. In this Way, with the electrodes of the device located Within the con 30 central opening. The central opening is joined to the openings 23 by means of radially extending tainer in appropriate proximity to the pole pieces, ‘ slots 25. it proves possible to obtain intense magnetic ?elds The structure 20, which preferably consists of in the interelectrode space without the use of a ‘ copper, is supported by being brazed to the in separately excited electromagnet or other external appurtenances. The resultant structure is light. terior Wall surface of the part l0. To facilitate the brazing operation, small channels 28 are cut in weight and has the further advantage that in the outer periphery of the structure and these its magnetic components may be adjusted in the _ are used to receive rings of brazing material ap factory for best operation with the assurance that plied before the anode structure is inserted with no further adjustment will be required in the 40 in the container. A relatively large circumferen ?eld. > A further important feature of the improved construction consists in an arrangement by. which the current supply wires for the cathode are introduced through the center of one of the magnetic pole pieces in a manner which avoids tially extending channel 29 serves to reduce the overall weight of the structure. Within the opening 22 of the anode structure there is provided an indirectly heated cathode comprising a‘sleeve 32 of nickel or other suitable material having ?anges 32' spun up at its ex coupling the cathode circuit to the high fre vquency ?elds generated by the operation of the tremities. This sleeve, which may be coated ex magnetron. ternally with a suitable activating material such as barium oxide, contains a ?lamentary heater The features of the invention desired to be protected herein are pointed out in the appended 50 34 by which it may be maintained at an emissive temperature. One end of the cathode sleeve is claims. The invention itself, together with its further objects and advantages may best be un- ' closed by a metal disk 36 while an apertured disk derstood by reference to the following descrip tion taken in connection with the drawings in which Fig. 1 is a vertical section of a magnetron device suitably embodying the invention; Fig. 2' is a transverse sectional view serving to illustrate the anode structure employed in the device of Fig. 1; Fig. 3 is an enlarged view in partial sec 31 partially closes its other extremity. In the operation of the device a space charge is assumed to be developed in the‘space between the structure by the application of a suitable poten tial impressed between one of the cathode lead-in wires 31’ and 31" and the container Ill to which the 31.10518 structure is directly conductively con 2,412,824 3 Fig. 1, each of these rings is interposed between charge are given a spiral or orbital motion by a one surface of the anode structure and the sur Vnected. The electrons which compose this space face of an apertured disk 56, 51, each disk in magnetic ?eld produced by means shortly to be tumrbeing in abutment with an appropriately described, and their resultant gyrations about the formed‘ shoulder provided on the adjacent pole cathode produce excitation of the anode structure Cl piece as indicated at 58 and 59. The spacing at its resonant frequency. The functioning of rings 54 and 55 may be welded in place before the anode structure in the latter connection may the pole pieces are inserted within the container. be explained from one point of view by consider With the pole pieces 40 and 4| arranged inside ing that it is made up of a plurality of mutually container In it becomes convenient to use the coupled resonant units in each of which_>in-. 10 the pole pieces as a supporting means for the cathode ductance is provided by the wall surface bounding structure 32. This may be done, for example, one of the circular openings 23 and capacitance by the use of a pair of insulating beads 62 and is provided by the opposing surface of one of the 63 which are respectively centered in axially ex slots 25. Taking this viewpoint, it will be seen tending. openings 65 and 66 cut in the pole pieces. that the operating frequency is in a large measure The lower bead 63 is provided with a central determined by the dimensions of the openings 23. For the purpose of providing a magnetic ?eld of suflicient intensity to permit the apparatus to » apertureadapted to receive a. centering stud 68 projecting downwardly ,from the cathode end plate 36. The upper head 62 has two separate function in its intended fashion, there are pro vided within the container I0 tapered magnetic 20 openings 10 and ‘H through which the current supply wires 31' and 31" extend. These wires, pole pieces 4|] and 4| which are directed axially which are held in spaced relation within the of the container and which extend in close prox channel 65 by means of additional insulators 16 imity to the upper and lower surfaces of the an and 11, are joined at their extremities to rela ode structure 20. For present purposes these tively heavy lead-in wires 19 and 80. These in pole pieces are assumed to be permanently mag turn are sealed into the container through a netized in such a sense that the north pole of glass-to-metal seal which comprises a body of one faces the'south pole of the other. glass 8| fused to the extremity of a metal eyelet In order to assure the existence of a magnetic 82. This arrangement of the cathode supply ?eld of the required intensity the pole pieces 40 leads has the particular advantage that it avoids and 4| should be constituted of a magnetizable any substantial coupling between the cathode substance having a high coercive force and a high energy factor. One of the materials which may be used in this connection is that known as supply circuit and the high frequency ?elds gen erated in the interelectrode space, thus being a consequence of the fact that :both the supply leads Alnico, meaning a particular class of alloys of aluminum, nickel and cobalt. Alloys of this type 35 extend axially with respect to the‘ electrode structures and are fully shielded by the body of are described, for example, in Tokuschichi Mishi the pole piece 40. . ma Patents 2,027,994 to 2,028,000 inclusive and In fabricating the construction of Fig. 1 the are further described in W. E. Ruder Patents anode structure 20 is ?rst positioned within the 1,947,274 and 1,968,569. Other magnetic mate rials which may be employed are alloys of iron, 40 container part l0 and secured in place. There after, the spacing rings 54 and 55 are inserted nickel and titanium as described, for example, in and ?nally the pole pieces and their associated Honda Patents 2,105,652 and 2,105,658. basing structures are put in place. The cathode 32 may be preliminarily assembled with the pole piece 40 before that part is lowered into the con tainer. After the closure members II and |2 If the pole pieces 40 and 4| are constituted of Alnico, which'is considered to be a preferred ma terial, they are normallyprepared in cast form and have their critical surfaces ?nished by grind have been welded in, the container may be evacu- , ing. The ground surfaces may include, for exam ated through an exhaust tabulation 85, which is ple, the end surfaces of both pole pieces and the then sealed off as indicated at 86. peripheral surfaces indicated by the numerals 44 and 45 respectively. These latter surfaces, to 50 To permit the evacuation of all parts of the container, it is necessary to provide suitable pas gether with the end surfaces which adjoin them sageways connecting the various sections of the may advantageously be copper plated to reduce enclosed space. To this end, the disk-like mem losses attributable to high frequency circulating bers 48 and” may be provided with radially ex currents induced by the proximity of these sur tending slots such as the slot 49' which is illus faces to the interelectrode spaces in which high trated in Fig. 4 in connection with the part 49. frequency waves are generated. In order to provide a low reluctance connec In this way the channel 66 is enabled to commu nicate with the space outside the pole piece 4| through the channel 49', and a similar connection tainer, the pole pieces may be respectively seated 60 with reference to the channel 65 is provided by the corresponding slot in the part 48. With the upon relatively thick disk-like members 48 and same object in view, openings’ 90 may be provided 49 consisting of ferro-magnetic material such as in the positioning disks 56 and 51. An opening steel. For the purpose of securing the pole pieces tion between the base extremities of the respec tive pole pieces and the lateral wall of the con 92 provided in one surface of the anode structure ?xedly to these basing members, use may be made of clamping rings 5| and 52 slipped over the pole 65 20 makes the channel 29 accessible to the .evacu atingsystem. pieces and welded to the basing members. Each , After the container is fully evacuated and sealed basing member is of such diameter as to ?t snugly off, the pole pieces 40 and 4| may be magnetized within the tubular container part III so as to in a known manner by being placed in a magnetic provide a low reluctance connection with that ?eld of suitable intensity. It is an advantage of part, and-is welded to one of the closure mem 70 the illustrated construction that for each partic-. bers||,|2. - _ . Accurate spacing of the pole pieces 40 and with reference to the anode structure 20 may obtained by the use of spacing rings 54 and used in the manner indicated. As is 8.130“!!! 4| be 55 in ular device the degree of magnetization of the pole pieces can be adjusted in the factory to a value which assures the most satisfactory opera ' tion of the device as a whole. Since all the parts 2,412,824. 5 . of the tube structure are ?xed and since no ex ternal magnetic appurtenances have to be added in the ?eld, installation and use of these tubes is greatly simpli?ed. ‘ When a device such ‘as that‘illustrated in Fig. 6 structure by means of a coupling loop, which, however, does not appear in the particular view of the structure which is afforded by Fig. 5. The cathode, which extends centrally through 1 is placed in operation, it is, of course, necessary ‘ 5 the anode structure I24, comprises an emissive tubular part I3i9-which terminates in flanges I40 to provide some means for abstracting a portion of the energy developed in the interelectrode and I40’. A heater (not shown) is arranged with in the part I39 and serves to maintain it at emis sive temperature. The cathode ?ange I 40 is seated rangement which includes a coupling loop I00 introduced through an opening I02 in the wall of 10 in an. appropriately formed recess provided in the space. This may be done in one way by an ar lower extremity of the pole piece I20 so that the the anode structure. The coupling loop in the cathode is electrically grounded to the magnetic arrangement shown has an extension in the form structure. A lead-in wire I 4| which extends ax of a wire I04 which constitutes the inner con ially through the pole pieces I20 and through an ductor of a coaxial transmission line having a tubular part I05 as its outer conductor. The tube 15' insulating bead I42 at the upper end of the oath ode make it possible to supply heating current to I05 passes through the wall of the container cyl the cathode ?lament, a return path for this cur- _ inder I 0 and may be exteriorly connected through rent being provided through the grounded struc a tapering enlargement I01 with a somewhat larger tubualr part I08. In similar fashion, the 20 ture of the cathode proper. It is not essential that a magnetron produced wire I04 is merged into a larger conductor I09 in accordance with the invention be symmetrical through a tapered transition region II 0 which with respect to a central transverse plane, and is of such con?guration as to avoid any substan the alternative embodiment of Fig. 6 represents a tial change in the characteristic impedance of construction in which this condition is not ful the line. (The ful?llment of this latter condi tion requires the maintenance of a constant ratio 25 ?lled. In this case a permanently magnetized between the diameters of‘ the outer and inner conductors.) The conductors I08 and I09 may pole piece I50 is enclosed within a ferromagnetic container I5I which forms part of the magnetic circuit. The pole piece I50 is based upon a ferro connect with an antenna or other agency for uti magnetic header I53 which closes the upper end lizing the high frequency energy developed by the apparatus, and their size is determined with this 30 of the container I5I andvis partially supported within the container by means of a non-mag end in'view. The vacuum tightness of the con netic ring I54. A cathode structure I51 depends tainer is preserved by means of a head of glass centrally from the lower extremity of the pole II2 which forms a seal between the conductor piece I50, being insulated from the pole structure I09 and the surrounding tubular member I08. In an arrangment such as that of Fig. 1 in 35 by means of an interposed insulating element indicated at I58. Potential and heating current which the cathode is not at ground potential it are supplied to the cathode through lead-in is necessary to provide an insulating transformer wires I59. in connection with the supply of ?lament heating Below the cathode I51 there is provided a current. In order to avoid this requirement it is preferable in some instances to employ a struc 40 multicavity anode I62 which is shown in perspec tive detail in Fig. 7. This anode is formed of ture in which the cathode is grounded to the magnetic material (e. g., iron or steel) so that structure of the enclosure and to adopt provisions it serves not only as an anode but also as a oom_ for insulating the anode from ground. This pos plementary pole piece for the magnetic pole I50. sibility is illustrated; in Fig. 5. In the ?gure last referred to the magnetic ~35 However, it is not necessarily permanently mag-' structure is of the same general character as that described in connection with Fig, 1 and com netized. The exposed surfaces of the anode are 'coated, by plating or otherwise, with copper or other highly conductive material adapted to per prises permanently magnetized pole pieces I 20 mit the free circulation of high frequency cur and HI which are enclosed within a metallic cone tainer I22 consisting of ferromagnetic material. 50 rents. The whole anode structure is based upon the bottom closure I63 of the container so that a The pole pieces have a low reluctance magnetic complete magnetic circuit is provided through connection with the structure of the enclosure so the container walls. ‘ that a return path is provided for the magnetic As appears most clearly in Fig. 7 the anode is ?ux. The anode structure, which is indicated at I24, 55 provided with a number of radially extending circular channels I65 which communicate ‘with is functionally similar to the anode 20 of Fig. 1, the space'above the anode through slots I 66. The being provided internally with a plurality of res channels and the slots connect at their inner onant cavities (not shown) which have a reso ends with an opening I61 formed centrally in the nant frequency corresponding to the desired fre quency of operation of the apparatus. The struc (so anode structure. By virtue of this arrangement the anode is enabled to function as a multi-cavity ‘ture is insulated from the metallic enclosure I22 resonator adapted to be excited by the rotating and from the other parts of the device by means space charge developed in proximity to its upper of glass insulators I26 and I21 which serve also surface by the electrons emitted from the cathode as seal-in means for anode terminals I 28 and I29. These terminals are associated with ‘cup-like 0.; I51. The high frequency energy thus developed in the resonant cavities may be utilized externally members I30 and I3I which are sealed into the by the use of a coupling loop (not shown) extend glass rings I26 and I21 respectively, the rings in ing into one of the cavities in the manner indi turn ‘being supported from metal eyelets I33 and cated in Fig. l. I34 secured to the outer surface of the enclosure. To The arrangement of Fig. 6 has the particular Heavy conductive rods I36 and I31 extending be advantage that no signi?cant magnetic gap ex tween the anode structure I24 and the cap mem ists between the anode I62, viewed as a magnetic bers I 30 and I 3I afford a rigid support for the pole piece, andv thesource of the electrons de anode structure. Power is assumed to be taken out of the anode 75 sired to be a?ected by the magnetic ?eld. Be cause of this circumstance the effective reluc 9,419,884.‘ 7' '' tance of-the total magnetic path is reduced. This effect can-“be still further enhanced by fore shorteninglthe cathode structure to bring the pole pieces ISO-and I62 into closer proximity to piece, and an anode and a cathode in proximity to said pole piece and within the in?uence of said magnetic ?eld, said cathode comprising an equi potential emitting part, a ?lamentary heater for, - discharge devices having transversely extending said part and a pair of current supply wires for said heater extending axially through one of said pole pieces and sealed through a wall of said con anode cavity constructions such as those illus-’ trated by ‘Figures 6 and '1 since the invention tainer. 5. An electronic discharge device including an parting from the invention. I therefore aim in erating electrodes within said container and in ‘ scope of the foregoing disclosure. -What I claim as new and desire to secure by providing the envelope of said device and includ one another. ' ' In.this patent I do not claim magnetron type illustrated thereby is covered broadly by certain 10 elongated cylindrical container forming the en velope of said device and having its‘ lateral walls claims in my pending application Ser. No. 674,194, constituted principally of ferromagnetic material, ?led June 4, 1946, and constituting a continua ferromagnetic members closing the ends of the tion in part of the application for this patent. container, a pair of magnetic pole pieces'respec While the invention has been described by ref tively supported from said members in mutually erence to particular embodiments thereof, it will spaced relation within said container and in be understood that numerous modi?cations may magnetic contact with said members, and coop be made by those skilled in the art without de the space between said ‘pole pieces. the appended claims to cover all such equivalent 6. A magnetron device comprising a container variations as come within the. true spirit and 20 ‘ Letters Patent of the United States is: 1. An electronic device comprising a container forming the envelope of said device and having a part of its wall structure constituted of ferromag netic material, means including a permanently ing a hollow cylinder of ferromagnetic material, a self-resonant anode structure supported within said cylinder intermediate its ends, a cathode structure concentric with said anode structure, and magnetic pole pieces within said container adjacent the ends thereof and on opposite sides of said anode structure, each of said pole pieces having a direct ferromagnetic connection with ‘producing a magnetic ?eld in a particular region of the enclosed space; and cooperating electrode 30 said cylinder whereby the combination of said magnetized pole piece ‘within said container for - elements located in the said magnetic ?eld, said pole piece having a direct magnetic connection cylinder and said connections provides a low re luctance return path for magnetic flux traversing the pole pieces. "with the ferromagneticpart of said wall struc '7. An electronic device comprising an elon ture and forming therewith a low reluctance path which is-closed except for region of said elec 35 gated container forming the envelope of said detrodes. ' vice and having a part of its wall structure con stituted of ferromagnetic material, a self-reso nant anode structure within said container and ated'container having its walls constituted main intermediate the ends thereof, a‘ cathode in coop ly of ferromagnetic material, means including a permanently magnetized pole piece within the 40 eratively spaced relation with respect to said anode structure, magnetic pole pieces within said container for producing a localized magnetic ?eld, 2. An electronic device comprising an evacu-v ' a ferromagnetic member supporting said pole piece and providing a direct magnetic connection between the pole piece and a ferromagnetic'por tion of the wall of the container, whereby a low reluctance return path‘is provided for magnetic ‘ container'on opposite sides of said anode struc ture and having a low reluctance connection with said container, and spacing means interposed be tween said anode structure and said pole pieces maintaining them in a predetermined structural relationship. flux traversing the pole piece, and mutually co 8. A magnetron comprising an evacuated c011 operating discharge electrodes in proximity to tainer constituted principally of ferromagnetic said pole piece and within the in?uence of the 50 metal, electrodes cooperatively spaced within said said magnetic ?eld. container, one of said electrodes being connected ‘ 3. A magnetron device comprising a container directly to the container, another of said elec forming an envelope of the device and having its trodes being supported in insulating relationship lateral walls constituted principally of ferromag to said container, and means including a perma netic material, ferromagnetic members extending transversely of said container and presenting sur 55 nently magnetized element within said container for producing a magnetic ?eld in the space be faces within the container, a pair of magnetic tween said electrodes, said container having a pole pieces in mutually spaced relation within said direct ferromagnetic connection with said ele container, said pole pieces being respectively sup ‘ported by said ferromagnetic members, whereby a low reluctance ?ux path between the remote ex tremities of said pole pieces is provided through said members and. through. the lateral walls of the container, and cooperating electrode ele ments positioned in the space between said pole pieces. 4. Electronic apparatus comprising a container having a substantial part of its wall structure constituted of ferromagnetic material, means in cluding a permanently magnetized pole piece within said container for producing a magnetic ?eld therein, said pole piece having a low reluc tance connection with the wall structure of said container whereby said wall structure provides a return path for magnetic ?ux traversing the pole ment to provide a low reluctance return path for 60 magnetic ?ux traversing said element. 9. A magnetron device comprising a container providing the envelope of said device and includ ing a hollow cylinder of ferromagnetic material, a self-resonant anode structure supported within 65 said cylinder intermediate its ends, a cathode structure concentric with said anode structure, and pole pieces of permanently magnetized mate rial within said containeron opposite sides of said anode structure, said pole pieces each having a direct and continuous ferromagnetic connection with said cylinder whereby the cylinder provides a low reluctance return path for magnetic ?ux traversing the pole pieces. ELMER D. MCARTHUR.