US2784346A - Electron discharge device - Google Patents

Description

March 5, 1957 w. J. DODDS 2,784,346

ELECTRON DISCHARGE DEVICE Filed Jan. 28, 1950 INVENTOR Wellese JDodds ATTORNEY United States Patent ELECTRON DISCHARGE DEVICE Wellesley I. Dodds, Cranbury, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application January 28, 1950, Serial No. 141,006 32 Claims. (Cl. 31539.63)

In the prior art, there have been very few successful methods of achieving amplification at frequencies above 300 megacycles (mc.), and these have been subject to.

many limitations and shortcomings. For example, specially-built triodes have been used in a so-called groundedgrid circuit up to about 4000 mc.; but the gain of such stages has been low, particularly with wide bandwidths, and the performance becomes steadily poorer as the frequency is increased. It does not appear to be feasible to use grid-controlled tubes of this kind much above 4000 mc. On the other hand, the Klystron, particularly the cascade type, does operate successfully in the super-high frequency range. However, the bandwidths attainable are inherently small, because of the need of three or more cascaded circuits in each tube, because of the necessity of long electron beams wherein the current density is inherently limited by space charge to relatively small values,

and also because of the high resonator impedances required even when a load is connected.

It has been successfully demonstrated that a multicavity magnetron is one of the most etlicient and successful oscillators in the super-high frequency region (3000 to 30,000 megacycles). This tube is readily operable at high current densities and with low loaded resonator impedances, such as would be suitable for wide bandwidths. Although many attempts have been made to control the magnetron, so as to make it an amplifier, no successful results at the higher frequencies have been reported. Previous attempts to build a high-frequency magnetron amplifier have usually involved applying a signal voltage to a control grid interposed between the cathode and the anode, or varying the cathode-anode voltage.

A typical magnetron comprises essentially a hollow anode, a cathode for supplying electrons Within the anode, and some means for providing a constant magnetic field within the anode and extending transverse to the paths of electrons traveling toward the anode. In operation, the anode is maintained at a relatively high positive potential with respect to the cathode, and the crossed electric and magnetic fields cause the electrons from the cathode to traverse curved paths within the anode. The earliest magnetrons had a single, cylindrical anode and were used as low frequency amplifiers. The electric and magnetic fields were adjusted near cut-01f condition, in which the majority of the circling electrons just missed the anode. The signal was applied to vary the magnetic field, and the variable anode current yielded the amplified output signal by application to a load. Because it is necessary to vary the magnetic field to control the current, such a device is useful only at very low frequencies and, even there, substantial input power is required compared with grid control tubes.

In later magnetrons the anode was split into two or larger even number of segments arranged in a circle about the cathode. Such split-anode magnetrons could be used in either of two ways. In one method of operation, the magnetic field is so adjusted that the voltage-current characteristic of each of the anode segments has a negative-resistance region, i. e., an increase of potential on an anode segment causes a decrease of current to it. Such operation is readily adapted to production of oscillations in an associated circuit up to quite high frequencies. Under carefully controlled and very critical operating conditions, a negative-resistance magnetron can even be used as an amplifier at the higher frequencies. Unfortunately,

such an amplifier is of the two-terminal type, requiring the same circuit to be used as both input and output, so that it is very prone to oscillate and of little practical utility. In the second method of operating the splitanode magnetron, electron transit-time eifects are utilized and the device heretofore has been useful only as an oscillator, though it is operative up to extremely high frequencies. In such split-anode magnetrons, the electron cloud sweeping past the gaps between adjacent anode segments induce alternating charges on the anode segments, and when the two segments, or two sets of alternate segments, are connected to an external output circuit, the magnetron functions as an oscillator or a generator of alternating current. Because the operation requires alternating electric fields to be set up between anode segments which progressively move in phase around the anode segments, magnetrons designed for this second mode of operation are often called traveling-wave magnetrons.

In one modern counterpart of the traveling-wave splitanode magnetron, the output circuit is incorporated directly into the tube in the form of cavity resonators connected between each pair of adjacent anode elements. By utilizing a large number of anode elements and cavity resonators of small dimensions it has been possible to construct very efficient multi-cavity magnetrons capable of oscillation at extremely high frequencies, up to 60,000 megacycles or more.

In the multi-cavity type traveling-wave magnetron, oscillation results from the interaction of the cavity resonator fields with the electrons between the cathode and the anode segments in such manner as to synchronize the rotating electron-cloud motions with the high frequency field, assuming the magnetic field and anode voltage are properly chosen. Thus, as the high frequency field between a particular pair of adjacent anode segments reverses so as to aid the electron-cloud rotation to the next pair of anode segments or next resonator, some of the electron energy imparted by the direct current anode voltage induces a current in this next resonator. After passage of a half period of the generated frequency, the rotating elec tron-cloud passes on to the third resonator which then also is given energy by the electron motion. The entire operation is apparently the result of uniform emission of electrons around the periphery of the cathode, and this emitted current, as the electrons travel toward the anode under the influence of the direct current field, is gradually controlled by the alternating field fringing out from the anode elements and bunched into space-charge groups which rotate like spokes in a wheel and in turn excite the resonators. Thus the anode cavity resonator structure may be considered as constituting both an output circuit and a control circuit which provides the necessary feedback to the electron stream to produce self-oscillation. It is obvious that a simple alternating control of the magnitude of the electron current, by means of a control grid located between the cathode and anode, would cathode surface where the electrons are moving more 3 slowly and are highlysusceptible to a small change in electric field.

In the copending application for Magnetron Amplifier and Mixer, by Edward W. Herold, Serial No. 116909, filed September 21, 1949, now abandoned, and'in a copending continuation application Serial 'No. 405,346, filed by Herold, January 21, 1954-, prior to abandonment of said application Serial No. 116,909, and assigned to the same assiguee as the instant application, the highly efiicient and advantageous characteristics of the'travelingwave magnetron are made use of for an amplifier, rather than for an oscillator, by utilizing control action of a new type at, or in the region of the cathode, While taking the amplified output from the anode. In said copending Herold applications, the control action of :the output or anode circuit on the electron stream which exists in a conventional magnetron, is eliminated, or at least substantially reduced, and a control action by means of control electric fields at or near the cathode is substituted. In one form, a split cathode is used inside a split anode, with the input signal applied across the two halves of the split cathode and the output taken from the split anode. In another form, a cathode structure in the form of a multi-cavity, self-resonant structure is used inside a multi-cavity anode. The control action of the anode is reduced by a suitable design of the anode structure and/ or by useof an electron-pervious shieldinterposed between the anode and the cathode, and the desired control action is introduced by exciting the cavity resonator structure of the cathode in accordance with the signal to be amplified to provide electric fields between adjacent cathode elements or parts. The cathode structure thus serves not only as an emitter but also as a control means for the tube.

The present invention is concerned with improved magnetron structures employing the same basic principles but having greater stability and ease of control than those disclosed in said copending Herold applications. In accordance with one feature of the invention, an elongated cathodc-control electrode assembly is mounted inside a split or rnulti-cavity cylindrical anode. Either the cathode electrode or the control electrode is made up of a plurality of separate parts and the other electrode comprises conductive portions interposed between said separate parts and completely shielding them from each other in the interaction space, and also partially shield ing them from the surrounding anode. Signal voltages to be amplified by the device are applied either between said separate parts or between the cathode and the control, to establish control electric fields extending between adjacentcathodc and control electrode portions. Another feature of the invention is that the cathode and control electrode portions are positioned substantially equidistant from the surrounding anode, so that the control electric fields established between said portions have substantial tangential components, that is, components tangent to a cylinder adjacent to and concentric with the cathode-control assembly, similar to the tangential control fields utilized in said Herold applications. Such tangential control fields are highly efiective in controlling the space charge circulating in the cathode-anode space, due to the curved paths traversed by electrons from the cathode in their travel toward the anode through the axial magnetic field.

The principal object of this invention, therefore, is to provide a novel magnetron tube structure particularly adapted for use as an amplifier at high frequencies.

Another object is to provide improved means in a magnetron amplifier tube for introducing control electric fields at or near the surface of the cathode.

Still another object of the invention is to provide an improved electron discharge device or tube having a thermionic cathode which serves as a control memher as well as an emitter.

Another object is to provide an improved magnetron 4 amplifier tube having a multi-part cathode-control assembly associated with a multi-cavity anode. In the accompanying drawing:

Pig. 1 is a view in perspective of a split-anode magnetron incorporating the invention, the magnet and envelope being partly broken away to reveal the internal structure of the device;

Fig. 2 is a transverse section, taken on the line 22 of Fig. 1;

Fig. 3 is a partly schematic section view, similar to Fig. 2, showing a modification of the structure of Figs. 1 and 2.

Fig. 4 is a transverese section, similar to Fig. 2, of a modification utilizing a multi-cavity anode and a multipart cathode control electrode assembly;

Fig. 5 is a plan view, partly in section on the line 5-5 of Fig. 6, of a multi-cavity type magnetron incorporating the invention; and

Fig. 6 is a longitudinal section, taken on line 6-6 of Fig. 5.

Referring to the drawing, Figs. 1 and 2 illustrate the invention incorporated in a split-anode magnetron. The numeral 1 indicates a glass envelope which contains a hollow anode 3 consisting of two semi-anode segments or elements 5 and 7 spaced apart to provide a pair of anode gaps 9 and 9. The anode segments 5 and 7 are supported by rods 11 and 13 which extend through one end of the envelope 1 and also serve as anode circuit leads. The outer ends of the rods 11 and 13 are connected by an adjustable shorting rod or bar 15 to form a Lecher or shorted transmission line type of tuned output circuit. An axial magnetic field is provided by an electromagnet 16, for example, mounted on the outside of the envelope 1.

A thermionic cathode 17 is disposed axially within the anode 3. The cathode 17 is divided into two parts which are illustrated, for example, in Figs. 1 and 2, as being in the form of parallel elongated rods 19 and 21. The cathode rods may be indirectly heated by conventional internal heaters, whose leads and construction are not shown, and the portions of the rods lying within the hollow anode 3 may be coated with electron-emissive material. The rods 19 and 21 extend through the end of the envelope opposite the anode leads 11 and 13 and serve as cathode supports and leads. An adjustable shorting bar 23 connecting the outer ends of the rods 19 and 21 completes a Lecher-type tuned input circuit.

The structure described so far is substantially the same as that shown in Figs. 1 and 2 of'said Herold applications. In accordance with the present invention, a shield 25 isinterposed between the cathode part 19 and 21. One form of shield which may be used is shown in Figs. 1 and 2, and consists of anelongated member of H shaped cross section having end portions 27 and 29 connected by a web portion 31. The shield 25 is supported within the envelope by any suitable means, such as a rod 33 which extends through the envelope to serve as a potential lead to the shield. The shield 25 is oriented coaxially within the anode 3 and the two cathode parts 19 and 21 are positioned substantially tangent to an imaginary cylindrical surface circumscribed about the shield, so that the cathode and shield parts are equi-distant from the anode 3.

In operation, the anode 3 and cathode 17 are connected to the positive and negative terminals, respectively, of a high voltage direct current source, as shown schematically in 'Fig. 1, and the electromagnet 16 is energized, to produce the usual crossed direct current electric and magnetic fields. These'fields are adjusted as to produce an amplifying and nOn-self-oscil'lating condition of the magnetron, in which there is no alternating voltage generated in the output circuit 11, 13, 15 in the absence of an input signal across the cathode circuit 19, 21, 23. The shield 25 is connected through the support 33 to a direct-current potential source,

' the magnitude of which relative to the average potential of cathode potential. To operate the tube as an amplifier, thev input circuit to the cathode is excited in accordance with the signal to be amplified, as by means of a transmission line terminating in a loop 34 inductively coupled to the input circuit 19, 21, 23. The signal produces variable electric control fields extending between'the cathode parts 19 and 21 and the adjacent edges of the shield parts 27 and 29 and fringing outwardly toward the anode 3. Thus, the shield parts serve also as control elements. An important feature of the invention lies in the fact that a substantial portion of the control field is in a direction substantially tangent to a circle surrounding the cathode region to effectively control the electrons traversing curved paths as described above. Furthermore, the control electric field is applied near the cathode where the electrons are traveling slowly and are more susceptible to control. The control field alfects the electrons substantially at right angles to the radial direction towards the anode, so as to produce spoke-like space charge groups similar to those which are produced by the anode of the conventional oscillating multicavity magnetron. The tangential control fields produce velocity modulation of the space charge which causes changes in the trajectories of the electrons and also bunching therealong. By virtue of this bunching due to the radio frequency input signal, and the added energy which the electrons receive from the field established by the cathode-anode voltage, more radio frequency energy is given up to the anode circuit by interaction with fringe fields between anode segments than was put into the tube by the input signal, which results in amplification of the signal.

The dash lines E in Fig. 2 illustrate one possible instantaneous orientation of the control fields in the form of tube shown, neglecting the D.-C. field due to anode voltage. It is to be noted that the electrons emitted from the two cathode parts 19 and 21 in all directions are subjected to control fields which accelerate or decelerate and which deflect the electrons. With no input signal, the electron paths of the electrons from the two cathode parts are symmetrical with respect to the anode segments, so that there is no tendency to induce differential currents between anode segments. On the other hand, as soon as an input signal is applied, at such an instant as shown by the field lines E in Fig. 2, the electrons from one of the cathode parts are reduced in velocity while those from the other are increased. These velocity effects in turn cause the two groups of electrons to traverse paths of different curvature and a strong differential current is induced be tween anode segments.

The net eifect of the control fields adjacent to the cathode 17 is to produce a corresponding current of increased amplitude to the two anode segments 5 and 7 and the output circuit connected thereto. Amplified signal energy may be extracted from the output circuit 11, 13, 15 by any suitable means, such as a transmission line and coupling loop 35 inductively coupled to the output circuit.

In showing the approximate field pattern E in Fig. 2 the effects thereon of the electric field induced between the anode segments has been neglected. Since it is this field which might, either through control of the electron stream, or through coupling to the input circuit, cause oscillation, the anode load should, ordinarily, be tightly coupled to prevent high anode field. The fact that the two cathode parts 19 and 21 are mounted in registry with the anode gaps 9 and 9', respectively, also helps to minimize undesired coupling between the output and input circuits. The control action of the anode on the electron stream is further reduced by use of small anode gaps. The use of the shield 25 between the cathode parts minimizes the loading effect of electron currents which would otherwise flow from one cathode to the other, and gives greater stability and ease of control. The shield not only effectively shields the two cathode parts from each other, but also partly shields each cathode part from a large portion of the anode. The latter reduces feedback coupling between the anode and the cathode. Power gains as high as 25 decibels at 400 megacycles have been achieved with tubes made according to Figs. 1 and 2.

Fig. 3 illustrates partly schematically a modification of the embodiment of the invention shown in Fig. 1. As

modified, the device is particularly adapted for use as a frequency multiplier.

ode-shield assembly of Figs. 1 and 2. The two parts 27 and 29 of the H-shaped shield are mounted opposite the midpoints of anode segments 5a, 5b, and the two cathode parts 19 and 21 are mounted opposite the mid-points of segments 7a, 7b. The oppositely located anode segments are connected together in pairs by conductors 37 and 39, respectively. When an input signal of a given frequency is applied between the separate cathode parts, an

output current of twice that frequency is induced in the anode circuit 11, 13, 15. 7

Figs. 4, 5 and 6-illustrate the invention as incorporated in cavity resonator structures particularly adapted for use as amplifiers at very high frequencies. In Fig. 4, the anode is made up of a drum-shaped metal member 41, which serves also as the tube envelope, and eight anode vanes 43 which extend radially inwardly from the member 41. The member 41 cooperates with the vanes 43 to form an annular series of inwardly-facing cavity resonators 44. The inner ends 45 of the vanes 43 constitute anode elements which define a central interaction space in which a cathode-shield assembly is axially mounted. This assembly comprises a series of spaced parallel cathode parts 47 and a series of spaced parallel shield parts 49 alternately disposed between the cathode parts 47, in ai circle. The several parts 49 of the shield are mounted on the radially extending arms 51 of a cross, as shown.

Direct coupling between the output and input is minimized by mounting the cathode and shield parts opposite the mid-points of the gaps between adjacent anode vanes the cathode-shield assembly, as indicated by the field ar-.

rows in Fig. 4. The shield may be operated at the same direct current potential as the cathode, or at a different value. Since the input signal is applied between the cathode parts and the shield, the instantaneous potential of the shield parts 49 will vary with the signal. Otherwise,.the

operation of the device shown in Fig. 4 as an amplifier is substantially the same as that described above for Figs. 1 and 2. Amplified signal energy may be taken from the anode circuit by means of a coaxial transmission line 53 having an inner conductor 55 terminating in a coupling [loop 57 connected to one of the vanes 43 and linked with the electromagnetic field within one of the resonators 44.

Figs. 5 and 6 show a vane type magnetron comprising a hollow cylindrical metal member 61 closed'at the ends by metal plates 63 and 65 to form a vacuum envelope. Extending radially inward from the cylindrical member 61 are eighteen anode vanes 67 providing anode gaps 69 therebetween. The inner ends of the vanes 67 constitute anode elements 71. The member 61 and vanes 67 provide anode cavity resonators 72. Axially positioned within the cylindrical space defined by the anode elements 71 is a multi-rib cathode 73, which consists essentially of a plurality of ribs 75 extending radially from a central tubular member 77. The cathode ribs 75 provide spaces therebetween in which the control elements 79 of a control electrode are mounted. Since the useful emitting portions of the cathode are chiefly the rib tips,

it is not necessary to coat other portions of the cathode.

Two pairs 5a, 5b and 7a, 7b of anode segments or elements are employed with the cath-- A heater-81 for raising the cathode to electron-emitting temperature is mounted within the tubular member 77 ofjthe cathode. The control elements 79 are in the form of elongated thin metal strips integrally or otherwise mounted on a tapered tubular member 83. The latter is mounted JOB a tubefiS extending through plate 65 and insulatedtherefrom by a dielectric seal 87. *The cathode is supported by tubes 89 and 91 coaxially mounted within members83 and 85 by a dielectric seal 93. The heater 81 is connected at its upper end to thecathode member 77 and at its lower end to a lead 95 extending through a seal 97 in tube 91. The threemembers 85, 91 and 95 also serve as terminal leads for the control electrode, cathode and heater, respectively. An electrostatic shield or end hat 99may be provided at the upper end of the cathode member 77, if desired.

' Alternate anode vanes 67 may be strapped together in conventional manner, as by strapping rings 101 and 103, to favor 1r-mode operation wherein adjacent vanes operate 180 out of phase at all times.

An axial magnetic field may be provided by any suitable means, such as an external permanent magnet (not shown) with pole pieces mounted adjacent to the plates 63 and 65. In operation, the anode and cathode are connected to a high voltage direct current source which isadjusted to produce an amplifying condition. The signal to be amplified is applied between the cathode and the control elements. An output line 105 and loop 107 coupled into one of the anode resonators 72 may be provided for extracting amplified signal energy from the device. It is, of course, understood. that the normal amplifier will have anode resonators tuned close to, or at, the normal operating frequency and, if required, tuning means of the types commonly used with oscillating magnetrons may be provided. A plate 109 of magnetic niaterialmay be provided between the end plate 65 and the anode structure, to shorten the magnetic gap.

In Fig. 5, the alternating control field pattern between adjacent cathode and control elements at one instant, neglecting the radial field due to the direct current anode voltage supply, will be similar to that shown in Fig. 4. It should be noted that the alternating electric field components most effective in controlling the electrons are largely tangential to circles coaxial with and spaced slightly from the cathode. Thus, the electrons emitted by the cathode rib tips are subjected primarily to controlling accelerating and decelerating forces acting at right angles to the directions the electrons would travel in the absence of the magnetic field. In fact, the control fields set up in accordance with the invention are closely analogous to the anode control fields in a conventional Inulti-cavity-anode oscillating magnetron, and hence, are effective toinstitute and control the spoke-like rotating bunches of electrons desired for optimum excitation of the output circuit. These spoke-like bunches occur only when an input signal is applied to the cathode-shield circuit and are respousive'to the input signal, in both magnitude and frequency.

The undesired control action of the anode, ordinarily present in oscillating magnetrons, is greatly reduced by use of small anode gaps, and by locating the cathode ribs halfway between the anode vanes, as shown in Fig. 5. Moreover, reducing the anode alternating electric field by coupling the output load tightly, so as to lower the resonator impedance efiective across vane tips, will reduce the possibility of anode control and, at the same time, broaden the bandwidth advantageously.

The present state of the art does not permit an exact and rigorous understanding of all magnetron phenomena. For this reason, although theexplanation of the behavior of the invention is believed to be substantially as described, it is conceded that the explanation as described may not be complete, or even entirely correct.

It will be apparent that the present invention provides magnetron tube structures, capable of operation as high frequency amplifiers or frequency multipliers, including a novel cathode-shield assembly to which the signal is applied.

Whatis claimed is:

l. A magnetron including an anode, a series of alternately arranged, spaced, emissive and nonemissive electrode parts arranged in a row spaced from and substantially equi-distant from said anode, means for providing a magnetic field in the space between said parts and said anode and extending transverse to the paths of electrons therebetween to cause said electrons to follow curved paths, high frequency input means coupled to said parts for applying a signal voltage between two of said parts, at least one of which is an emissive part, for establishing control electric fields having substantial components extending between adjacent parts for controlling said electrons during operation of said magnetron, and high frequency output means coupled to said anode for extracting high frequency electrical energy from said magnetron.

2. A magnetron according to claim 1, wherein said input means includes a resonant circuit coupled between said parts.

3. A magnetron according to claim 1, wherein said input means includes a section of coaxial transmission line having two conductors connected respectively to said emissive parts and to said non-emissive parts.

4. A magnetron according to claim 1, wherein said two parts are both emissive.

5. A magnetron according to claim 1, wherein the other of said two parts is non-emissive.

6. A magnetron including a 'hollow anode, a plural ity of alternately arranged, spaced, emissive and non-emissive electrode parts disposed entirely within and substantially equi-distant from said anode, means for providing a magnetic field in the space between said emissive parts andsaid anode and extending transverse to the paths of electrons therebetween to cause said electrons to follow curved paths, high frequency input means coupled to said parts for applying a signal voltage between two of said parts, at least one of which is an emissive part, for establishing control electric fields having substantial components extending between said parts for controlling said electrons during operation of said magnetron, and high frequency output means coupled to said anode for extracting high frequency electrical energy from said magnetron.

7. A magnetron including a hollow cylindrical anode comprising a plurality of anode segments forming anode gaps therebetween, a'thermionic cathode having a plurality of parts and a non-emissive electrode having a plurality of parts disposed entirely within and spaced from said anode, said cathode and electrode parts being alternately disposed on a cylinder concentric with said anode, the number of parts being equal to the number of anode segments, means for providing a magnetic field in the space between said cathode and said anode and extending transverse to the paths of electrons therebetween to cause said electrons to follow curved paths, high frequency input means coupled to said parts for applying a signal voltage between two of said parts, at least one of which is a cathode part, for establishing control electric fields having substantial components extending between adjacent parts for controlling said electrons during operation of said magnetron, and high frequency output means coupled to said anode for extracting high frequency electrical energy from said magnetron.

8. A magnetron having a hollow anode and an electrode assembly including an electron-emissive electrode and a non-emissive electrode disposed entirely within and spaced from said anode, one of said electrodes having a plurality of parts, the other electrode having solid portions interposed between and shielding said parts from each other, means for providing a magnetic fieldin the space between said electron-emissive electrode and said anode and extending transverse to the paths of electrons therebetween to cause said electrons to follow curved paths, high frequency input means coupled to said parts for establishing control electric fields extending between said parts and said other electrode for controlling said electrons, and high frequency output means coupled to said anode for extracting high frequency electrical energy from said magnetron.

9. An electron discharge device including an anode comprising a plurality of spaced segments disposed in a row and forming anode gaps therebetween, a plurality of spaced emissive and non-emissive elements alternately disposed in a row'adjacent to said anode row with all portions of said elements spaced from said anode row, the spatial relation between each element and the nearest anode gap being the same for all elements.

10. A device according to claim 9, wherein each of said elements is positioned opposite the midpoint of an anode gap.

11. A device according to claim 9, further including high frequency input means coupled to said elements for establishing control electric fields between adjacent elements during operation of said device and high frequency output means coupled to said anode for extracting high frequency energy from said device.

12. A device according to claim 11, wherein said input means comprises a coaxial transmission line having one conductor connected to said emissive elements and the other conductor connected to said non-emissive elements.

13. A device according to claim 9, further including means for providing a magnetic field in the space between said elements and said anode segments and extending transverse to the paths of electrons therebetween.

14. An electron discharge device including an anode comprising an annular array of spaced anode segments forming anode gaps therebetween, a plurality of spaced emissive and non-emissive elements alternately disposed in a second annular array located concentrically within said anode array with the outerpost portions of said elements spaced inwardly from said anode array to form a continuous annular electron-interaction space therebetween, the spacial relation between each element and the nearest anode gap being the same for all elements.

15. An electron discharge device including an anode comprising a number of spaced parallel elongated anode segments disposed in a row and forming elongated anode gaps therebetween, and the same number of spaced parallel elongated emissive and non-emissive elements alternately disposed in a row spaced from and substantially equidistant from said anode row, the spatial relation between each element and a corresponding anode gap being the same for all elements.

16. A device according to claim 15, wherein adjacent anode segments are connected by cavity resonators.

17. A device according to claim 15, wherein said anode segments and said elements are respectively disposed on two concentric cylinders.

18. A device according to claim 15, wherein said emissive elements are connected by solid material interposed between and completely shielding said non-emissive ele ments from each other.

19. A device according to claim 15, wherein said nonemissive elements are connected by solid material interposed between and completely shielding said emissive elements from each other.

20. A device according to claim 15, further including high frequency input means coupled to said elements for establishing control electric fields between adjacent elements during operation of said device, and high frequency output means coupled to said anode for extracting high frequency electrical energy from said device.

21. A device according to claim 15, further including means for providing a magnetic field in said space and extending transverse to the paths of electrons therein.

22. An electron discharge device including a hollow anode comprising a plurality of spaced anode segments forming anode gaps therebetween, and an electrode assembly comprising an electron-emissive electrode and a non-emissive electrode disposed entirely within said anode with the outerpost portions of 'said electrodes spaced from said anode, each of said electrodes having a plurality of spaced parts, each part being positioned opposite the midpoint of an anode gap, one of said electrodes having solid portions interposed between and completely shielding said parts of the other electrode from each other.

23. A magnetron including a hollow anode, an electrode assembly comprising an electron-emissive electrode and a non-emissive electrode disposed entirely within said anode with the outermost portions of said electrodes spaced from said anode, said non-emissive electrode having a plurality of spaced parts, said electron-emissive electrode having solid portions interposed between and completely shielding said parts from each other, and means for providing a magnetic field in the space between said electrodes and said anode and extending transverse to the paths of electrons in said space.

24. An electron discharge device including a hollow anode comprising a plurality of spaced segments forming anode gaps therebetween, a plurality of spaced nonemissive elements disposed within said anode and a cathode having solid portions disposed between and shielding said elements from each other and having electron-emissive portions disposed between said elements, each of said electron-emissive portions being positioned opposite the mid-point of an anode gap.

25. An electron discharge device according to claim 24, including means for providing a magnetic field in the space between said cathode portions and said anode and extending transverse to the paths of electrons therebetween.

26. An electron discharge device according to claim 24, wherein said anode has a cylindrical shape, said nonemissive elements lie on a cylinder concentric with said anode and said cathode comprises a cylindrical portion having radially-extending ribs terminating substantially on said cylinder.

27. An electron discharge device according to claim 26, including a cathode heater mounted within said cylindrical portion.

28. An electron discharge device including a hollow anode comprising a plurality of spaced segments forming anode gaps therebetween, a plurality of spaced nonemissive elements disposed within said anode and a cathode having solid portions disposed between and shielding said elements from each other and having electronernissive portions disposed between said elements, each of said elements being positioned opposite the mid-point of an anode gap.

29. A magnetron comprising a drum-shaped metal envelope, a plurality of anode vanes extending inwardly from said envelope and defining a central cylindrical interaction space, said vanes and the parts of said envelope therebetween forming anode cavity resonators, a cathodecontrol electrode assembly mounted within said interaction space and comprising a series of elongated emissive and non-emissive elements alternately positioned on a cylinder coaxial with said space, means within said envelope connecting said emissive elements together, means within said envelope connecting said non-emissive elements together, and a pair of conductors extending through said envelope and connected respectively to said connecting means, to permit the application of a signal voltage to said elements, and means coupled to one of said cavity resonators for extracting electrical energy from said magnetron.

30. A magnetron according to claim 29, wherein each 11 of said elements is positioned opposite the mid point of the gap between two adjacent anode vanes.

31. A magnetron according to claim 29, wherein said emissive elements are in the form of parallel longitudinal ribs extending radially from a cylindrical cathode support, whereby said non-emissive elements are shielded from each other.

32. A magnetron according to claim 29, wherein said means connecting said non-emissive elements together comprises a tubular conductor on which said non-emissive elements are mounted outside said interaction space.

UNITED STATES PATENTS Thomas Mar. 5, 1929 Mouromtsefi I an. 23, 1934 Mendenhall Jan. 18, 1938 Bennett Nov. 2, 1943 Hansell Oct. 8, 1946 Fisk Feb. 25, 1947 Blewett June 29, 1948 Ludi May 16, 1950 Sproull Apr. 8, 1952

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