US2842713A - Electron discharge device - Google Patents

Description

ly 1953 P. P. DERBY 2,342,713

ELECTRON DISCHARGE DEVICE Filed July 3, 1953 2 Sheets-Sheet 1 7 2 a W I 4 3, is g: 27

T 24 L 6 9/ 22 I i L F3 l8 r 16 10 34 32 3/ F 8 {/23 i I 73; L??? 7 3a [in-- 20 36 24 I. I I 2 35 1 ,2 E 7/ n u a 26 INVENTOR QQLMEQ P. DERBY A 7TORNEY y 1958 P. P. DERBY ELECTRON DISCHARGE DEVICE 2 Sheets-Sheet 2 Filed July 3, 1953 INVENTOR QALMER P DERBY 8? 02% ATTo NEY FIG. 3

United States Patent ELECTRON DISCHARGE DEVICE Palmer P. Derby, Wellesley, Mass, assignor to Raytheon Manufacturing Company, Newton, Mass, a corpora tion of Delaware Application July 3, 1953, Serial No. 365,816

4 Claims. (Cl. 315-39) This invention relates to an electron discharge'device and more particularly to the structure and packaging an rangement for a microwave oscillator of the magnetron type.

In the commercial manufacture of magnetrons it is desirable to design and assemble a package in which the weight and size of the magnetron are minimized, yet which is mechanically rugged, cfiicient and easy to mount. When the design involves the use of a waveguide output system and an external cavity tuning arrangement, these features are more difiicuit to attain due to the increased complexity of parts required in such a magnetron assembly,

This invention involves the use of a novel magnetron assembly in which the desirable features described above are combined. In the particular embodiment illustrated herein the anode structure consists of a pair of fiat rectangular conductors capable of being produced in solid or laminar form. Each of the conductors has a semicircular opening centrally located thereon so that when these conductors are slightly separated and paired, the semi-circular portions thereof form a cylindrical wall on which the magnetron vane structure may be mounted. The balance of these rectangular conductors are mounted and spaced from each other within a pair of sleeves to form opposed H-shapcd waveguide transmission lines. These waveguide transmission lines couple the anode vanes to both an output assembly and a tunable cavity, and they also act as supporting members between the anode structure and the output and tuning assemblies. However, in a package of this type, it is practically impossible to couple efficiently the fields between the Waveguide transmission line to those in the cylindrical tuning cavity without the use of a coupling iris. A slotted disk positioned between the transmission line and the cavity has been used in this novel assembly to overcome this difliculty.

To minimize the weight of the magnets used in the magnetron package, the cavity tuning assembly is housed in a case made of ferromagnetic material. Thus, the magnets used in the tube may be mounted on the top and bottom surfaces of this case so the case will act as a return path for the magnetic circuit. As a result, the size of the magnets is reduced and the weight of the tube is decreased.

Another advantage to this packaging arrangement lies in using a face of the housing as a mounting plate through which the tuning shaft extends. Therefore, when the tube is panel mounted, the tuning shaft will protrude through the panel to permit the use of a simple control knob to actuate the tuning assembly. A further feature is that in an assembly of this type the center of gravity of the magnetron lies close to the mounting support which permits the tube to withstand considerable vibration and shock without sufiering detrimental effects.

This invention and the features therof will be understood more clearly and fully from the following detailed 2,842,713 Patented July 8, 1958 description of two embodiments of the invention with reference to the accompanying drawings wherein:

Fig. I is a top view of a magnetron oscillator made in accordance with this invention with a broken-away sec tion showing the anode and output assemblies;

Fig. 2 is a front view of Fig. l with a broken-away section showing the anode and mechanical tuning assemblies;

Fig. 3 is a cross-sectional view of Fig. 2 taken along line 3-3;

Fig. dis a view of the complete magnetron package; and r Fig. 5 is a view of a fixed frequency magnetron packaged in accordance with this invention.

Referring now to Figs. 1 and 2, an anode assembly made in accordance with this invention is shown. In this embodiment of the invention, the anode assembly 1 consists of a pair of flat substantially rectangular-shaped conductors 2 and 3, each of which includes a circular sector-shaped or semi-circular opening 4 and 5 centrally iocated thereon. These conductors may be made of oxygen-free copper, for example, and are capable of being produced in a laminar form as well as in the solid onepiece construction shown. It should be noted, however, that the shape and size of the conductors 2 and 3 and the openings 4 and 5 may be varied and are only limited in that when the conductors are paired they should form a cylindrical anode wall and oppositely disposed transmission lincs. T hcrefore, when the anode conductors 2 and 3 are paired, as shown in Fig. l, the semi-circular openings 4 and 5 form a cylindrical wall on which a series of strapped magnetron vanes 6 may be mounted. The sides of the conductors 2 and 3 are curved slightly so the balance of the rectangular conductors 2 and 3 may be easily mounted along the end sections thereof within a pair of cylindrical metal sleeves 7 and 8 to form a pair of oppositely disposed waveguide transmission lines 9 and 10. These lines are used to couple the vanes 6 to an output system 11 and a tuning cavity 12, as shown in Fig. 2. The complete waveguide output assembly may be seen in Fig. 4 and includes the output system 11 referred to above.

The tuning cavity 12 is a simple cylindrical resonator operating in the TM-010 mode, for example. To insure stable operation of the magnetron, it is necessary to adjust in frequency the relationships between the resonances in the tuning cavity 12 and the anode assembly 1. The proper adjustment may be obtained by introducing a shunt impedance in the transmission line 19 at the junction between this line and the anode assembly 1. This impedance is realized geometrically in the form of a capacitance efi'ected by the protuberances 13 and 14, shown in Fig. l, on the anode conductors 2 and 3, Likewise, the conductors 2 and 3 are tapered at the ends adjoining the output system 11 to improve the loading and coupling characteristics of the tube.

Fig. 2 also shows a ferromagnetic pole piece 15 which is supported on the upper surface 16 of a cylindrical chamber 17. The pole piece 15 extends into the chamber and is positioned adjacent to the upper edges of the anode vanes 6. The pole piece is also provided with a tube 18 whereby the magnetron may be evacuated. The tube 18 may be copper, for example, and can be pinched oi, as shown in Figs. 2 and 3, to hermetically seal the tube after it has been packaged. A second pole piece 19 is supported in the lower section of the chamber 17 and should be positioned adiacent to the lower edges of the vanes. The sleeves 7 and 8 are joined to the chamber 17 through two opposed openings located in the longitudinal wall of the chamber.

It should be noted that inner ends of the vanes 6 define a space centrally located in the anode assembly 1 wherein a cathode 20 may be mounted. The cathode is supported within a hole in the pole piece 19, and is provided with a pair of end shields 21 and 22 positioned between the pole pieces and 19 and the vanes 6. The end shields prevent the axial escape of electrons from the interaction space between the cathode and the vanes. The tuning assembly 23 shown in Fig. 2 consists of a shaft 24 having a differential threading arrangement whereby a coaxial member 25 threaded within the shaft and connected to a diaphragm 25 may be moved to vary the position of the diaphragm. Therefore, the shaft 24 is provided with an outer set of threads 27 which have a substantially greater pitch than those located in an inner threaded aperture 28. Thus. when the shaft is rotated toward the cavity 12 a certain distance, the tiifilml il' 22 and the diaphragm 26 will move away from the cavity a distance which is substantially less than that traversed by the shaft. A flanged section 29 located on the internal end of the shaft. and a ring 30. threaded onto an external section of the shaft. act as stops which prevent excessive inward or outward movement of the diaphragm 26.

The tuning assembly 23 is housed in a case 31. as shown in Figs. 1 and 2. made of ferromagnetic material. This case is provided with a pair of threaded openings 32 and 33 whereby the magnets. as described below, may be connected. Thus. the case acts as a return path for the magnetic circuit thereby decreasing the size of the magnets used in the magnetron. The tuning assembly 23 is completed by joining the case 31 to the outer edge of the cavity panel 34. This panel contains a series of circular recesses which form the tuning cavity 12 and provide surfaces for mounting the diaphragm 26. the sleeve 8 and a coupling iris 35. The panel 34 should be assembled so that the axis of the circular cavity 12 intersects and is perpendicular to the axis of the anode assembly I.

The unique packaging arrangement described above is provided with the coupling iris 35, shown in Figs. 2 and 3, without which it would be practically impossible to effciently couple the fields in the waveguide transmission line 10 to those in the cavity 12. It may be seen in Fig. 3 that the conductors 2 and 3 enter the area adjacent to the cavity 12 so that the lengths of these conductors, which form a part of the waveguide transmission line, are parallel to the axis of the cavity 12. With an arrangement of this type, the high frequency fields in the transmission line are perpendicular to those in the cavity 12. This condition does not permit coupling between the line and the cavity. However. coupling can be facilitated by using the iris 35 to rotate the fields in the transmission line to make a better match to the fields in the cavity. The iris 35 may be a thin disk of metal having a diametrical slot 36 therein. For example, highly-conductive oxygen-free copper has been used successfully to form the iris. By appropriately positioning the angle of the slot with relation to the fields in the transmission line and the cavity. the fields in the line may be twisted or rotated to more nearly match those in the cavity. It should be noted then an iris would not be necessary if the transmission line entered the cavity so that the parallel section of the conductors 2 and 3 of the H-guide were perpendicular, rather than parallel, to a diameter of the cavity. However, such an arrangement would not permit the compact packaging arrangement described herein. since the axis of the cavity would not intersect the axis of the anode assembly.

Referring now to Fig. 4, a complete magnetron assembly made in accordance with this invention is shown. Two magnets 37 and 38 of opposite polarity are con nected with a pair of threaded bolts 39 and 40 to the upper and lower surfaces of the case 31 and the panel 34. and are positioned adjacent to the pole pieces 15 and 19 shown in Fig. 2. The lower magnet 38 enters a cylindrical can 41 through an opening provided in the longitudinal wall thereof. The can 41 provides a housing for the leads and internal connections made to the cathode and the anode assemblies, and is joined to the chamber 17 at one end and to the tube pin assembly 42 at the other end. It should be noted that additional structural support is provided for the magnetron by the sleeves 7 and 3. The output system it is enclosed with a metal cover 43 having a Window 44 connected thereto whereby electrical energy may be extracted from the output system 11. A circular output flange 45 may be joined to the output system to complete the magnetron package.

Referring now to Fig. 5, a fixed frequency magnetron oscillator is shown as a second embodiment of the packaging technique prcviously illustrated. Since a tuning assembly is not needed. the magnets shown in Fig. 4 may be reversed as shown in Fig. 5. Thus. the magnets 46 and 47 are joined to an output flange 48 made of ferromagnetic matcrial so that the flange. instead of the tuning case, serves as a tube support. a mounting surface and as a return path for the magnetic circuit.

It should be understood that this invention is not limited to the particular details described above. as many equivalents will suggest themselves to those skilled in the art. For example, when a fixed frequency magnetron is packaged, the conductors 2 and 3, shown in Fig. 1, can be revised to include only an output transmission line which adjoins the output assembly as shown in Fig. 5. Likewise, the transmission lines need not be diametrically opposed. as shown in Figs. l and 2, and the shape of these conductors need not be limited to the substantially rectangular form illustrated therein. Also the case for the timing assembly can be fabricated frcm either ferromagnetic or magnetic material which is capable of producing additional magnetomotive force. Therefore, it is desired that the appended claims be given a broad interpretation commensurate with the scope of the invention within the art.

What is claimed is:

I. An electron discharge device comprising a pair of elongated anode conductors each having a semi-circular notch located along an edge and intermediate the ends thereof, said conductors being spaced from each other with their axes parallel and their notches aligned to define a substantially cylindrical aperture intermediate the ends of said conductors and a pair of oppositely disposed cylindrical metallic sleeves positioned respectively on each of the end sections of the conductors with the anode conductors centraily disposed therein so as to form an H-guidc. a plurality of anode vanes spaced on the wall of said aperture and extending radially inward therefrom and an electron source positioned in the space defined by the inner ends of said vanes.

2. An electron discharge device comprising a pair of elongated anode conductors each having a semi-circular notch locatde along an edge and intermediate the ends thereof, said conductors being enclosed on the end scetions thereof with a pair of sleeves and spaced from each other with their axes parallel and their notches aligned to define a cylindrical aperture intermediate the ends of a pair of oppositely disposed waveguide transmission lines, a plurality of anode vanes spaced on the wall of said aperture and extending radially inwardly therefrom and an electron source positioned in the space defined by the inner ends of said vanes. said aperture being connected by one of said transmission lines to an output system, said aperture being connected by the other of said transmission lines to a cylindrical cavity resonator and coupled thereto by an iris, a mechanical timing assembly adjoining said resonator for controlling the frequency of said oscillations. a ferromagnetic case housing said tuning assembly and forming with a pair of magnets connected to it a magnetic circuit.

3. An electron discharge device comprising a pair of elongated anode conductors each having a semi-circular notch located along an edge and intermediate the ends thereof, said conductors being spaced from each other with their axes parallel and their notches aligned to define a substantially cylindrical aperture intermediate the ends of said conductors and a pair of oppositely disposed cylindrical metallic sleeves positioned respectively on each of the end sections of the conductors with the anode conductors centrally disposed therein to form an H-guide, a plurality of anode vanes spaced on the wall of said aperture and extending radially inward therefrom, an electron source positioned in the space defined by the inner ends of said vanes, a tunable cavity resonator, and means including an iris coupling element for operativeiy connecting said cavity resonator with said H-guide.

4. An electron discharge device comprising a pair of elongated anode conductors each having a semi-circular notch located along an edge and intermediate the ends thereof, said conductors being spaced from each other with their axes parallel and their notches aligned to define a substantially cylindrical aperture intermediate the ends of said conductors and a pair of oppositely disposed cylindrical metallic sleeves positioned respectively on each of the end sections of the conductors with the anode conductors centrally disposed therein to form an H-guide, a plurality of anode vanes spaced on the wall of said aperture and extending radially inward therefrom, an electron source positioned in the space defined by the inner ends of said vanes, a tunable cavity resonator, and means including a disc-shaped iris coupling element for operatively connecting said cavity resonator with said H- guide, said iris having a diametrical slot therein aligned with regard to said H-guide to couple the high frequency fields in said H-guide, to the fields in said resonator.

References Cited in the tile of this patent UNITED STATES PATENTS 2,411,953 Brown Dec. 3, 1946 2,459,030 Jonas et al. Jan 11, 1949 2,523,841 Nordsieck Sept. 26, 1950 2,533,741 Okress Dec. 12, 1950 2,549,846 Nelson Apr. 24, 1951 2,555,349 Litton June 5, 1951

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