US2475960A - Electron discharge device - Google Patents

Description

H. R. HEGBAR ELECTRON DISCHARGE DEVICE July 12, 1949.

Filed Aug. 25, 1943 INVENTOR R. HEGBHR WW ATTORNEY HOUJHRD Patented July 12, 1949 ELECTRON DISCHARGE DEVICE Howard B. Hegbar, Princeton, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application August 25, 1943, Serial No. 499,925

13 Claims.

My invention relates to electron discharge devices, particularly to improved types of magnetrons useful at ultra high frequencies.

In one type of magnetron referred to as a multicavity resonator type, the anode block comprises a heavy ring provided in the interior thereof with a plurality of anode segments, the inner edges of which lie on the surface of a cylinder, the anode segments defining a gap in an inductive loop connected between the segments so that in effect a cavity resonator having inductance and capacity is connected between adjacent segments. In one form of the device the anode segments lie along the inner edges of radially positioned fins or slats supported by the anode block within the interior space of the ring. A cathode, preferably indirectly heated, is mounted axially of the anode segments and within the space between the anode segments. The usual magnetic field parallel to the axis of the cathode is provided.

In devices of this kind suitable insulation is required between the cathode structure and the anode structure to withstand applied anode voltages. A coupling device is required to take radio frequency energy from the cavity resonators to the output lead. This usually involves difiicult vacuum sealing problems. It has been shown by mathematical analysis of this type of magnetron that a tube of given geometry can operate in one or more of several modes, each having a diflerent output frequency. To insure operation in a chosen mode, magnetrons are strapped. This strapping usually consists of connecting alternate anode elements or anode segments with wires or rings soldered or brazed to the anode segments. This strapping of magnetrons for wavelengths below that of about five centimeters is mechanically diflicult to produce because of the reduced dimensions. Accurate reproduction of such strapping is consequently very difficult. In electron discharge devices of this kind, assembly becomes more difiicult as the parts grow smaller, which is required when the devices are to be operated at ultra high frequencies. Assembly problems make mass manufacture of such devices almost impossible. In certain types of applications lightweight, low-power, ruggedly built devices are required. With the conventional construction such devices are difficult to provide. Because of the peculiar operation to which devices of this kind are subjected, that is a pulsed input voltage of considerable magnitude, corona losses become a problem, particularly in high altitude applications with unpressurized equipment.

It is, therefore, an object of my invention to 2 provide an electron discharge device of the magnetron type, which is particularly suitable for use at ultra high frequencies.

Another object of my invention is to provide such a device which is simple in construction and which is easily assembled and facilitates mass manufacture.

A further object of my invention is to provide a low power magnetron which is light in weight, but which nevertheless is sturdy in construction.

A further object of my invention is to provide such a device in which conventional coupling elements are eliminated and in which coupling between adjacent cavity resonators is facilitated.

A further object of my invention is to provide such a device in which the seals for the coupling devices connected to the output or load are easily made and are insured against leaks, and which will facilitate coupling to other resonators or wave-guides.

A further object of my invention is to provide a mount assembly for a magnetron which may be completely assembled before incorporation in a metal envelope.

A still further object of my invention is to provide an electron discharge device of the type described in which corona is eliminated or substantially reduced.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims, but the invention itself will best be understood by reference to the following description taken in connection with the accompanying drawin in which Figure 1 is a longitudinal section of an electron discharge device made according to my invention; Figure 2 is a longitudinal section taken at to Figure 1; Figure 3 is an enlarged transverse section of a mount assembly taken along the line 33 of Figure 4; Figure 4 is a longitudinal section of the mount assembly shown in Figure 3 taken along the line 4-4; and Figure 5 is a side view showing details of construction.

In accordance with my invention I provide an anode assembly comprising an anode block, in this case a short thick ring-like member I0, provided with a plurality of radially positioned anode vane or slot elements ll mounted in radial slots l0, and the inner edges of which provide the anode segments and lie in the surface of an imaginary cylinder. The anode block is completed by means of the ring l0" mounted at the end of the slots in completing the anode block so that the longitudinal edges of the anode vanes are equally spaced from the top and bottom of the anode block. Mounted block and vanes or slots II is an indirectly heated cathode l2, provided with the end shields i3 and M and heater l5, see Figure 4. The cathode and heater are provided with a pair of leads l6 and I! which supply the heating current. Lead l6 alsdactsas the. cathoderlead. Thecathode leads l8 and I! are: fused within an insulating support l8, preferably of glass, which in turn is supported by an L-shaped member l9 extending; within a slot in a supporting tubular member 20 mounted on the outside of the anode block. This L-shaped member is fixed, withinthe slot by a pair of pins 2| which extend through tubular member 20 and apertures in the L-shaped member H]. The cathode leads l6 and I1 may be provided with flexible leads Hi" and H";

The envelope of an electron discharge device made according to my. invention comprises a flattened tubular. member 25 which. may be of. rectangular transverse. section closed at. its ends by means of closure members 26. and 21 which may be. brazed or welded to. the ends. of thev member 25. The envelope. may be. exhausted through tubular member 2.8.whichcan thenbe sealed-cit. Supported from the member 26 is the tubular member 29 sealed-on. by means of the. cap member 32.. The flexible members [6. and H are. connected to the. loads 30 and. 3]. sealed. throughthe cap member 32..

In order to couple the. output of. the tube toa radiator or resonator or some other load, I. provide a. coaxial line. coupling device comprising loop 35formedatthe. inner. end of the inner member 35. of. the. coaxial line, the outer sleeve 3.6 of which extends into. the. anode block. 10.. This sleeve fitsinto a second sleeve 3'Lhaving a collar 38 sealed thereto and closed. by means, of the cap member 39, the inner conductor 35! contact.- ing. the inner surface. of thecap-shaped member. This type of line. termination is. described. and claimed in co-pending. application of Howard B. Hegbar and John S. Donal, Jr., Serial. No. 496,570 filed July 29, 1943; now Patent 2,442,118, dated May 25,, 1948, and. assigned. to. the same assignee as the present. application. Radiating fins M. serve to cool the anode and coaxial line. assembly.

As. pointed out above, the conventional method of insuring the :proper mode of. oscillationot a device of the kind described, is. accomplished by means, of strapping. alternate vanes by means. of ring-like straps. According to my invention, however, I eliminate the. use of these. rings by providing in each vane an aperture H adjacent the inner wall of the anode block II]. Inasmuch as the circulating radio frequency currents in the vanes circulate. in planes passing longitudinally through tothe. axis of the anode block, a magnetic field is generated parallel to the. axis and is therefore capable of coupling. one cavity resonator with the next through, said apertures. In the present application the. term cavity resonator maybe applied. to the circuits provided by thev vanes and the anode block, this U-shaped formation providing the. necessary inductance and capacity for a resonant circuit operable at ultra high frequencies. The coupling loop 35 of course couples the magnetic-field of one ofv the cavity resonators with the coaxialline described above.

For the purpose. of assembly, the envelope and its end caps may beofisomesuitable non-magnetic material, which may be brazed or welded. As shown the outer member of the coaxial trans.- mission load line is brazed to the end cap 21. The

axially of the anode 4 anode-cathode assembly is mechanically connected to the removable end cap 26 by the leads [3 and H which connect the cathode and heater to the leads 30 and 3| sealed through the cap 32. The anode-cathode assembly is inserted in the envelope and the final closure is made by welding the endcap 26 tothe envelope and brazing the coupling unit in at 42.

It is apparent that this type of enclosure and assembly may be used with an anode of different geometry and strapping than that shown in the figures. The anode assembly which includes the cavity resonators is constructed by inserting the copper slats I I into slots machined in the copper cylinder ill. The assembly may then be silver soldered in a hydrogen furnace to reduce resistance toradio frequency currents flowing in the anode assembly. The cathode may be an ordinary oxide coated nickel cylinder fitted with a heater. This cathode may be spot welded 17.0.. a nickel or tantalum disc shield l3- which in turn may be welded to the leads, which may be, of molybdenum. These molybdenum leads may be glass beaded while the cathode and the leads are held in position in a jig. The whole assembly may thus be prepared to the correct dimensions and then mounted on an anode block by two pins which pass through jig drilled holes in the L-shaped element I!) as shown and jig drilled holes in the slotted nickel cylinder 20 previously soldered to the anode block in proper alignment.

Although the coupling apertures in the vanes H are shown as round, it is obvious that these apertures may be of various shapes other than circular, the geometry and position of the perforation determining the coupling obtained. A magnet 43, which maybe of the permanent type for producing a magnetic field parallel to the cathode and between the cathode and anodeseg-ments is positioned close to the envelope. The magnetron envelope and assembly is particularly adapted to the construction of lowpower, light-weight magnetrons. Because of the welded final closure, metals of greater strength than copper may housed and thus a thinner envelope may be obtained. Because the cathode is mounted directly from the anode block, the cathode lead seals in the envelope may be of a practical size and yet require no increase in the overall axial length of the magnetron. Thus for a given axial resonator length, this envelope structure permits a minimum external dimension in the direction of the magnetic field and consequently requires a lighter and smaller magnet for a given fiux density.

The method of mounting the cathode assembly, preassembled in a jig, permits rapid, convenient and sufiiciently accurate mounting without subjecting the anode block or other copper parts to the fires used in beading. This makes it possible to keep the parts clear and thus decrease the evacuation difficulty.

The cathode leadv seal with the two. wires brought out through the same. seal permits. the use of a single coaxial cable. for heater power and anode input power. The negative pulse input voltage is applied to the. outer conductor of, the coaxial cable and thus the cathode leads may be easily shielded from corona by thecable. terminat.. ing cup, which is important. in high altitude appli cations in unpressurized equipment.

The cavity wall perforation. method of pro. viding intercavity electromagnetic cow-pling as a means of strapping, permits precise mechanical construction and is advantageous in mass production where accurate duplication is required.

While I have indicated the preferred embodiments of my invention of which I am now aware and have also indicated only one specific application for which my invention may be employed, it will be apparent that my invention is by no means limited to the exact forms illustrated or the use indicated, but that many variations may be made in the particular structure used and the purpose for which it is employed without depart ing from the scope of my invention as set forth in the appended claims.

What I claim as new is:

1. An electron discharge device including an anode assembly having a plurality of radially extending slat-like elements of solid material providing cavity resonators between elements and a central space between the inner ends of said elements, a cathode adjacent said anode assembly for supplying electrons within said tral space, means adjacent said device for provid ing a magnetic field within said central for subjecting said electrons to crossed electrostatic and magnetic fields during operation of said electron discharge device, each of said radially extending elements being provided with an aperture extending therethrough electrically coupling the cavity resonators together.

2. An electron discharge device including an anode assembly having a central opening, radially extending slat-like anode elements of solid material supported within said central opening and providing cavities between elements, a cathode adjacent said anode assembly for supplying electrons within said opening, means adjacent said device for providing a magnetic field within said opening for subjecting said electrons to crossed electrostatic and magnetic fields during operation of said electron discharge device, each of said radially extending anode elements being provided with an aperture extending therethrough adjacent the end remote from said central opening electrically coupling the cavities together.

3. An electron discharge device having a mount assembly including a hollow anode block, a plurality of slat-like anode elements supported within said block and extending radially toward the axis of said block and providing a central space between the inner edges of said slat-like anode elements, each of said slat-like anode elements having an aperture extending through the element adjacent the end remote from said central space, and a cathode adjacent said hollow anode block for supplying electrons within said central space and means adjacent said device for providing a magnetic field within said block subjecting said electrons to crossed electric and magnetic fields during operation of said electron discharge device.

4. An electron discharge device having a mount assembly and including an anode block of hollow cylindrical shape, a plurality of slat-like anode elements of solid material supported within said cylindrical block and extending radially toward the axis of said block and providing a central space between the inner edges of said slat-like anode elements, each of said slat-like anode elements being provided with an aperture adjacent the inner wall of the anode block and extending through the element, and a cathode positioned axially of said anode elements and means adjacent said device for providing a magnetic field parallel to said cathode and between said cathode and said anode elements.

5. An electron discharge device having a mount assembly including an anode block of hollow cylindrical shape, a plurality of slat-like anode elements supported within said cylindrical block and extending radially toward the axis of said cylinder and providing a central space between the inner edges of said slat-like anode elements, said slat-like anode elements being provided with apertures adjacent only the inner wall of the cylinder and extending through the elements, and a cathode positioned axially of said anode elements within said central space, and means adjacent said device for providing a magnetic field parallel to said cathode and between said cathode and said anode elements.

6. An electron discharge device having a tubular metal envelope of flattened cross section, header members sealed to the ends of said envelope, a mount assembly within said envelope and comprising an anode block having a central opening and radially extending anode elements supported by said anode block within said central opening, a cathode positioned axially within said opening, leads for said cathode, said cathode and leads being supported in insulated relationship by said anode block, a tubular member extending from one of said header members and through which the cathode leads extend, and an insulating cup-shaped member sealing the end of said tubular member and through which the cathode leads are sealed, and a coaxial line coupling member supported by and extending through the other of said header members, the inner end of said coaxial line being coupled to the anode block and means adjacent said electron discharge device for providing a magnetic field parallel to said cathode and between said cathode and anode elements.

7. An electron discharge device having a tubular metal envelope of flattened cross section transverse to the longitudinal axis of said envelope, header members sealed to the ends of said envelope, a mount assembly within said envelope and comprising a flattened anode block having a central opening and radially extending anode elements supported by said anode block within said central opening, the flat sides of the anode block and of said envelope lying parallel to each other, a cathode positioned axially Within said opening, leads for said cathode, said cathode and leads being supported in insulating relationship by said anode block, a tubular member supported by and extending from one of said header members and through which the cathode leads extend, and an insulating cup-shaped member sealing the end of said tubular member and through which the cathode leads are sealed, and means adjacent said electron discharge device for providing a magnetic field parallel to said cathode and between said cathode and anode elements.

8. An electron discharge device having an envelope containing a mount assembly, said mount assembly including a hollow cylindrical member supporting a plurality of radially directed anode elements, each of said elements being provided with an aperture extending through said element adjacent the inner wall of the hollow cylindrical member, a cathode positioned axially of the anode elements and having a pair of leads, a tubular member extending from one side of said block and provided with a slot, an L-shaped member having a leg positioned within said slot and fixed to said last tubular ember, and an insulatingsupport extending from said L,-shaped member and rigidly supporting the cathode and cathode leads with respect to said hollow cylindrical member, and a shield connected to said cathode for shielding the cathode, said envelope comprising a hollow conducting body of rectangular transverse section and cup-shaped elements closing the ends of said body and sealed thereto, one of said closure members supporting a tubular member through which the cathode leads extend and the other of said closure members supporting a coaxial line coupling member having a loop within the hollow cylindrical member and radiating fins mounted on said coaxial line adjacent the envelope of the tube.

9. An electron discharge device having an elongated tubular metal envelope of flattened cross section transverse to the longitudinal axis of said envelope, a mount assembly within said envelope and comprising an anode block having a central opening and radially extending anode elements supported by said anode block within said opening, a cathode positioned axially within said opening supported on said block, the axis of said anode block and said cathode paralleling the shorter transverse axis of the flattened envelope, leads for said cathode, and a tubular member extending from one end of said envelope and through which the cathode leads extend, and means sealing the end of said tubular member, said cathode leads extending through said sealing means, and means external of and independent of said envelope for providing a magnetic field parallel to said cathode and within said central opening.

10. An electron discharge device having an elongated nonmagnetic metal envelope having a rectangularly shaped transverse section transverse to the longitudinal axis of said envelope, a mount assembly within said envelope comprising a hollow cylindrical anode block, a plurality of slat-like anode elements positioned within said hollow cylindrical anode block and extending radially providing a central space between the ends of said slat-like anode elements, a cathode positioned within said central space and leads for said cathode, said cathode and leads being insulatingly supported by said anode block, said leads being insulatingly sealed through said envelope, the longitudinal axis of said anode block and of said cathode extending parallel to the short axis of the envelope.

11. An electron discharge device having a nonmagnetic metal envelope having a rectangularly shaped transverse section, a mount assembly within said envelope comprising a hollow cylindrical anode block, a plurality of slat-like anode elements positioned within said hollow cylindrical anode block and extending radially providing a central space between the ends of said slat-like anode elements, a cathode positioned Within said central space and leads for said cathode, said cathode and leads being insulatingly supported by said anode block, the axis of said anode block and of said cathode extending parallel to the closing the ends of said envelope, one of said,

header members having a tubular member through which leads from said cathode member extend and are sealed, and a coaxial line transmission line extending through and supported by the other of said headermembers and coupled to said mount assembly.

12. An electron discharge device having a mount assembly comprising a hollow cylindrical anode block, said block having a plurality of radially directed slots extending therethrough and to one end thereof, and slat-like anode elements positioned within said slots and extending radially inward of said hollow cylindrical block, each of said slat-like members being provided with an aperture adjacent the inner wall of said anode block and a ring-like member forming part of said anode block and contacting said end of the anode block and retaining said slat-like members in said slots and spacing said slat-like members equally from both ends of said anode block, and a cathode positioned within said anode block and between the inner ends of said slatlike members.

13. An electron discharge device having a mount assembly comprising a hollow cylindrical anode block, said block having a plurality of radially directed slots extending therethrough and to one end thereof, and slat-like anode elements positioned within said slots and extending radially inward of said hollow cylindrical block, each of said slat-like members being provided with an aperture adjacent the inner wall of said anode block and ring-like member forming part of said anode block and contacting said end of the anode block and retaining said slatlike members in said slots and spacing said slatlike members equally from both ends of said anode block, and a] cathode within said anode block and having leads, a member extending radially from the external surface of said anode block and having an insulating member mounted thereon supporting said cathode and the cathode leads on said block.

HOWARD R., I-IEGBAR.

REFERENCES CITED The following referenices'are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,129,713 Southworth Sept. 13, 1938 2,167,201 Dallenbach July 25, 1939 2,247,077 Blewett June 24, 1941 2,284,405 McArthur May 26, 1942 2,314,794 Linder Mar. 23, 1943 2,410,396 Spencer Oct. 29, 1946 2,437,280 Spencer Mar. 9, 1948 FOREIGN PATENTS Number Country Date 445,084 Great Britain Apr. 2, 1936 509,102 Great Britain July 11, 1939

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