US2485084A

US2485084A - Electron discharge device

Info

Publication number: US2485084A
Application number: US587725A
Authority: US
Inventors: William C Brown
Original assignee: Raytheon Manufacturing Co
Current assignee: Raytheon Co
Priority date: 1945-04-11
Filing date: 1945-04-11
Publication date: 1949-10-18
Anticipated expiration: 1966-10-18

Description

Oct. 18, 1949. w. c. BRowN 2,485,084

ELECTRON DISCHARGE DEVICE Filed April 11, 1945 2 SheetS-Sheet l Oct. 1s, 1949.

w. c. BROWN ELECTRO DISCHARGE DEVICE 2 Sheets-Sheet 2 Filed April 11, 1945 Patented Oct. 18, 1949 UNITED STATES PATENT OFFICE ELECTRON DISCHARGE DEVICE Application April 11, 1945, Serial No. 587,725

(Cl. Z50-27.5)

4 Claims.

This invention relates to electron-discharge devices of the type intended to amplify or generate ultra-high frequency oscillations. The invention is particularly applicable to magnetrons, or other electron-discharge devices of the type having a plurality of cavity resonators all of which are intended to oscillate at the same frequency and jointly contribute to the output of the device.

It is among the objects of the present invention to provide an electron-discharge device of the type described which may be tuned through a wide range of frequencies.

Devices of the type to which the invention relates include an anode structure of highly conductive material, such as copper, comprising a cylindrical body having a plurality of interiorlyextending arms or vanes. Each pair of adjacent arms together with that portion of the cylindrical body lying therebetween constitute a resonant cavity. The resonant cavities being of the same geometry are intended to oscillate at the same frequency. Since other oscillatory circuits exist in the tube other than the circuit defined by the cavities, such other circuits may result in oscillations at other than the desired output frequency of the device. In order to limit such spurious oscillations, strapping means may be provided adjacent the interior ends of the anode arms interconnecting alternate of said arms. In my copending application, Serial No. 583,624, filed March 19, 1945, I have disclosed a means for tuning such devices by varying the capacitance provided by adjacent straps.

It is among the objects of the present invention to improve devices of the type described and provide a construction which permits less critical mechanical tolerances, to provide a still wider tuning range, and to provide a construction permitting the coupling of either inductance or capacitance into the circuits provided by the resonant cavities.

The above and other objects and features of the invention will be made fully apparent to those skilled in the art from a consideration of the following detailed description taken in conjunction with the accompanying drawing in which:

Fig. 1 is a longitudinal section through a magnetron constructed in accordance with the present invention; and

Fig. 2 shows a transverse section taken on the line 2 2 of Fig. 1.

Referring to the drawing, reference numeral 4 indicates an electron-discharge device, in this instance of the magnetron type, comprising a tubular body 5 of a highly conductive material, such as copper. The tubular body 5 is provided with a central annular projection 6 from the interior surface of which a plurality of anode arms or vanes 1 and 8 of copper or other conductive material project radially in regularly spaced relation to points adjacent a central cathode structure 9. The cathode structure 9 comprises a sleeve IIJ conventionally of nickel. The sleeve Il! is provided with projecting flanges II, one adjacent the upper interior end of the anode arms 'I and 8 and the other adjacent the lower end of said arms. The intervening portion coextensive with the arms 1 and 8 is coated in a known manner with an electron-emissive material. In order to support the cathode sleeve I0 in proper spaced relation with the anode arms 1 and 8, the sleeve I8 is provided with a reduced portion I2 at the lower end thereof adapted to be received in the upper end of an elongated tubular conductor I3. The conductor I3 extends through a central bore I4 through a pole piece I5, and is supported in spaced relation to and concentric with said bore by means of a cup-shaped member I6 having an opening in the bottom portion thereof through which the tubular member I3 extends and to which it is hermetically sealed. The other end of the cup-shaped member I6 is sealed to the lower end of a glass tube I1 the opposite end of which tube is sealed to a sleeve I8 of Kovar or other material readily fusible to glass. The other end of the sleeve I8 is hermetically sealed in an enlargement of the bore I4. A conductor I9 extending through the tubular sleeve I3 is supported in spaced relation thereto by means of a glass bead 20 within the tube I3 and a glass seal ZI hermetically closing the outer end of said tube. The upper end of the conductor I9 is welded to a conductor 22 leading to a heating filament 23 in the tube I0 and coextensive with the activated surface thereof. The upper end of the heating lament 23 is connected by Wire 24 to the upper end of the nickel sleeve I0. From the foregoing it will be seen that the conductor I9 constitutes one of the lead-in conductors for supplying heating current to the coil 23 and supplying a biasing potential to the cathode structure 9. The other connection for the heating current is effected through the tubular conductor I3, the outer end of which projects beyond the cupshaped member I6 and is connected to the other terminal of the source of heating and biasing potential. It will also be seen that the cathode structure is insulated from the anode, externally by the glass sleeve I1 and internally by the spacing between the cathode structure and adjacent metallic structure of the anode.

The pole piece l5 is provided with a shouldered portion at which it is sealed through an opening in an end cap 26 closing the lower end of the tubular body 5. The opposite end of the tubular body 5 is likewise closed by an end cap 27, hermetically sealed thereto and having a central opening 28 therein. A pole piece 29 is sealed in the opening 28 at a shouldered portion thereof.

Each of the anode vanes 'l is provided with a notch 30 adjacent the inner end thereof and each of the vanes 8, one of which intervenes between successive arms 1, is provided with a similar notch 3l of the same dimensions as the notch 30 but positioned closer to the inner ends of the arms. A pair of concentric sleeves 3-2 and 33 mounted in the pole piece 29 project downwardly into the notches 33 and 3l. One of the sleeves, in this instance 32, is positioned to contact each of the arms 'l along one edge of the notch 30 and is soldered thereto at this point. The sleeve 32 passesr freely through the notches 3| in the intervening vanes 8 without contacting said vanes. The other of the concentric sleeves 33 passes freely through the notches 30 in the vanes 'l without contacting said vanes and contacts each of the vanes 8 at the outer edge of the notches 3|. The two sleeves 32 and 33provide a section of a concentric line, the inner conductor 32 of which is connected to the vanes 'l and the outer conductor 33 of which is connected to the intervening vanes 8. Thus the two sleeves, in addition to the function of limiting spurious oscillations in the manner of known strapping means, also provide a concentric line circuit connected in parallel with the resonant circuits with each of the resonant cavities. In order to vary the parameters of the parallel circuit so formed I provide an annular piston 34 of conductive material adjustable in the annular space between the two

sleeves

32 and 33. In order to vary the position of the annular piston 34 the pole piece 29 is provided with a central bore 35 coaxial with the cathode structure 3. Within the' bore 35 a plunger 36 having a recess 31 in the lower end thereof lto permit the same to clear the upper end of the cathode structure `il has its upper end face soldered to the lower face of a Sylphon bellows 38. The bellows 33 is provided with an outwardly extending flange 39 at its upper end, which flange is soldered upon a shoulder provided by an enlarged portion of the bore 35 thereby hermetically sealing said bore. An adjusting rod 40 is connected to the upper interior face of the bellows 38 and extends upwardly through the bore 35. A micrometer screw 4l on the projecting end of the rod 40 permits longitudinal adjustment of the rod by means of a nut 42 connected to a knurled plate 42. The reciprocatory movements of the plunger 36 are transmitted to the annular piston 34 by means of a plurality of radially-extending arms 43 connecting said piston and plunger. The arms 43 project inwardly from the annular piston 34 through slots 44 in the material of the pole piece 23 adjacent the lower end of the bore 35 and through slots 45 in the inner ring 32 to connect with the plunger 36.

In order to limit radiation outwardly over the face of the pole piece 29'1 provide an annular slot 43 in the face of this pole piece. This slot has a depth corresponding to approximately onequarter of the length of the wave generated by the tube and functions as a wave trap.

The length of the

sleeves

32 and 33 is such that the annular piston 34 may be adjusted so that the distance between thev upper edge of the anode arms 'l and 8 and the lower face of the piston when in its outermost position will be substantially greater than one-quarter of the length of the wave generated by the tube. That portion of the

sleeves

32 and 33 below the upper edge of the arms 'I and 8 may be considered as introducing additional capacitance in parallel with the oscillatory circuit provided by the resonant cavities and functions as known strapping means interconnecting alternate arms to reduce or suppress spurious oscillations. That portion of the

sleeve

32 and 33 above the upper edges of plates 'l and 8 and below the lower face of piston 34 may be considered'a'sa variable length of coaxial line and introduces an impedance dependent upon the effective length of the line, which length may be varied by adjustment of the annular piston 34. If the piston be so adjusted that the distance between the lower face thereof and the upper edge of the arms 'l and 8, which distance is designated as :c inthe accompanying drawing, is equal to one-quarter of the length of the waves generated by the device, then the impedance becomes infinite. If the piston 34 is adjusted so that' the distance is less than one-quarter of the length of the waves generated by the system, then the effect of the line is to add inductance. If the piston is so adjusted that the distance :c is greater than one-quarter of the length of the waves generated by the system, then the line adds capacitance. By adding or subtracting capacitance or inductance, the resonant frequency may be varied over wide limits. The frequency of operation f when the effective length of the coaxial line is less than may be plotted from the following formula:

Cf=tube capacity,

Zo=characteristic impedance of the coaxial line,

C=velocity of light,

=length of coaxial line to lower face of piston 34.

The frequency of operation where the effective length coaxial line is greater than may be determined by the following formula:

There has been herein described a preferred embodiment of the invention. Other embodiments within the scope of the following claims will be apparent to those skilled in the art from a consideration of the form shown and the teachings thereof.

What is claimed is :l

1. A tunable electrondischarge device comprsing an anode structure provided with a plurality of anode members; each pair of adjacent anode members, together with that portion of said 'anode structure lying therebetween, constituting a cavity resonator; each anode member having a slot formed therein; a pair of 'conductors disposed in said slots and alternately contacting successive anode members; said conductors providing a transmission line having impedance; and means on said line for altering the effective length thereof from values greater than one-quarter of the length of the waves corresponding to the natural frequencies of said cavity resonators to values less than one-quarter of the length of said waves.

2. A tunable electron-discharge device comprising: a cathode; an anode structure provided with a plurality of anode members spaced from said cathode; each pair of adjacent anode members, together with that portion of said anode structure lying therebetween, constituting ya cavity resonator; each anode member having a slot therein; a pair `of conductive sleeves extending into said slots fand alternately contacting successive anode members; said sleeves providing a coaxial transmission line coupled to said cavity resonators; and means movable intermediate said sleeves for altering the eiective electrical length of said transmission line.

3. A tunable electron-discharge device comprising: la cathode; an anode structure provided with a plurality of anode members spaced :from said cathode; each pair of adjacent anode members, together with that portion of said anode structure lying therebetween, constituting a'cavity resonator; each anode member having a slot therein; a pair of spaced, concentrically disposed, conduotive sleeves extending into said slot-s and alternately contacting successive anode members; said sleeves providing ia coaxial transmission line coupled :to said cavity resonators; and an annular piston slidably contacting the facing surfaces of said sleeves for altering the effective electrical length of said transmission line.

4. A tunable electron discharge device comprising: an anode structure incorporating a cavity resonator; a pole piece carried by said anode structure and provided with -acentral bore, an `annular recess surrounding said bore, and 1a slotted wall intermediate said bore and recess; a pair of annular conductors alternately contacting successive anode members and extending into the annular recess of said pole piece; one of said conductors being provided with slots in register with the slots in said Wall of said pole piece; a :third con-ductor mounted for reciprocation intermediate said pair of conductors; a plunger mounted for reciprocation in the central bore of said `pole piece; and a plurality of arms connecting said 1plunger and s-aid third conductor through the registering slots in said Wall of said pole piece and said yone of said conductors.

WILLIAM C. BROWN.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,167,201 Dallenbach July 25, 1939 2,252,118 Dallenbach et al. Aug. 12, 1941 2,329,778 Nergaard Sept. 21, 1943 2,414,084 Bowen Jan. 14, 1947 2,414,085 Hartman Jan. 14, 1947