US3020445A - Cross-field electric discharge devices - Google Patents

Description

Feb. 6, 1962 M. WEINSTEIN 3,020,445

CROSS-FIELD ELECTRIC DISCHARGE DEVICES Filed Nov. 24, 1958 2 Sheets-Sheet 1 1 i L INVENTORI MYRON WEINSTEIN HIS ATTORNEY.

Fgb. 6, 1962 M. WEINSTEIN 3,020,445

CROSS-FIELD ELECTRIC DISCHARGE DEVICES Filed Nov. 24, 1958 2 Sheets-Sheet 2 WATTS FREQUENCY "c INVENTOR MYRON WEINSTEIN,

awful HIS ATTORNEY.

Sates Unite My invention relates to improved cross-field electric discharge devices and more particularly to such devices including improved means for increasing the operating efficiency and power output thereof and for better adapting the devices for increased stability of performance.

In U.S. Patent No. 2,930,933 issued on March 29, 1960, on co-pending U.S. application Serial No. 723,926, Voltage Tunable Magnetron, filed by G. J. Griffin, Jr. et al. on March 25, 1958, and assigned to the same assignee as the present invention, is described and claimed a cross-field device of the voltage tunable magnetron type and comprising an anode circuit including a plurality of segments supported in a cylindrical array in mutually spaced sideby-side relation and having coaxially extending therein a non-emissive electrode or cold cathode. The anode circuit and cold cathode define an annular interaction region and displaced longitudinally therefrom in electrically and physically spaced relation to the cold cathode is an emitter. A control electrode surrounds the emitter and is shaped to provide an axial component of electric field to assist in directing electrons from the region surrounding the emitter into the interaction region. The control electrode, by determining the amount of electrons entering the interaction region, is effective for determining the power level at which the voltage tunable operation takes place. In the just-described structure the cold cathode is substantially coextensive with the anode, or, in other words, extends for substantially the full axial length of the anode, and is provided at the end opposite the emitter with a cylindrical boss-like end cap serving to block electrons tending to migrate from the corresponding end of the interaction region. This type of device is adapted for operating in a magnetic field extending coaxially through the device and transverse electric fields established between electrodes and, hence, the designation cross-field device in reference thereto. Additionally, this type of device is generally highly desirable in that it is capable of operation over a wide frequency range, can be effectively easily cut-off, can be operated over a substantial range of control electrode voltages and can be manufactured consistently from tube to tube to assure substantially uniform operation of tubes manufactured in production quantities.

Accordingly, an important object of my invention is to provide a new and improved cross-field electric discharge device capable of substantially increased operating efiiciency, power output and stability of performance while affording also all of the above-described desirable capabilities of prior devices.

Another object of my invention is to provide a new and improved cross-field device including a new and improved electrode arrangement for determining the manner in which electrons from the emitter are effectively introduced into the interaction region.

Another object of my invention is to provide a new and improved cross-field device including a new and improved electrode arrangement adapted for efiecting a more rapid introduction of electrons from a longitudinally displaced emitter into the interaction region thereof.

Another object of my invention is to provide a new and improved cross-field device including a new and improved electrode arrangement for affording a smooth transition in the average velocity of electrons introduced from the emitter into the interaction region.

Another object of my invention is to provide a new and "ice improved cross-field device including a new and improved electrode arrangement effective for increasing the energy potential of the electrons introduced into the interaction region of the device, thereby to increase operating efliciency.

Another object of my invention is to provide a new and improved cross-field device including new and improved means for virtually increasing the effective length of the interaction region without physically increasing the lengths of the elements defining that region.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty whichcharacterize my invention will be pointed out with particularity in the claims annexed to and forming part of this specification.

In carrying out the objects of my invention I provide a cross-field electrode arrangement including an anode circuit comprising a plurality of elongated conductive segments arrayed in mutually spaced, side-by-side relation. An emitter and control electrode therefor are disposed in spaced relation to the ends of the anode segments. A nonemissive electrode extends in laterally spaced relation to the anode and includes an active surface which extends only partially the length of the segments for defining therewith an interaction region which is substantially spaced from the emitter. Additionally, I provide the non-emissive electrode with a surface portion inclined toward the plane of the anode on the side of the anode opposite the emitter.

For a better understanding of my invention reference may be had to the accompanying drawing wherein:

FIGURE 1 is an enlarged elevational view of a section of a magnetron device incorporating my invention;

FIGURE 1A illustrates a modified form of the structure shown in FIGURE 1;

FIGURE 2 is a schematic illustration of the configuratino of the electric fields afforded by my improved electrode arrangement;

FIGURE 3 is a family of curves illustrating the power capabilities of a device incorporating the shortened inter-.

action region of my invention compared with the power capabilities of a prior art device incorporating a longer interaction region; and

FIGURE 4 is a somewhat schematic illustration ofpa modified form of my invention.

Referring now to the drawing, there is shown in FIG-- URE 1 a magnetron device embodying a form of my invention. The device of FIGURE 1 includes an envelope generally designated 1 and constituted of a stacked assembly of alternately arranged and suitably sealed metal and ceramic members wherein some of the metal members serve as electrical terminals of thedevice and the ceramic members serve as insulative spacers between the metal members. The metal members which serve as electrical terminals include a pair of annular anode terminals 2 and 3, separated by a ceramic cylinder-.4. The metal members further include a frusto-conical control electrode 5 which includes a flanged or annular portion 6 separated 13 comprises the cold or non-emissive cathode of the device and the dimensions and disposition of the cylindrical active surface portion thereof relative to other electrode elements in the device, aswell as the shape and disposition of the surface '12, play important parts in my invention and will be described in greater detail hereinafter. The outer surface of the member comprises an electrical terminal for the cold cathode.

The magnetron device illustrated is of the interdigital type and the cold cathode 13 extends partially in an anode assembly or circuit which includes two sets of axially extending elongated anode segments alternately arranged in a cylindrical array supported concentrically within the envelope 1 by the anode terminals 2 and 3. Alternate segments 14 and 15 are connected to different ones of the annular anodes 2 and 3, respectively, thus to provide two groups of anode segments alternately arranged in the array with each group connected to one of the terminals 2 or 3. The segments 14 and 15 are slightly separated to provide axially extending interaction gaps. As is well understood in the art, it is the interaction between the high frequency field across these gaps and a rotating and bunched space charge that effects the desired energy transfer from the space charge to the oscillatory circuit of the anode. As is also Well understood in the art, the electron rotation results from the provision of an axial magnetic field through the device. Such a field is usually provided by disposing the magnetron between the opposed poles P of a magnet in the manner illustrated in FIGURE 1.

The electrons constituting the rotating beam are emitted from a hot cathode or emitter 16 disposed in a region of the envelope longitudinally displaced from the array of anode segments, and the entrance of the electrons into the region of the interaction gaps is under control of the control electrode 5. In the embodiment illustrated, the emitter 16 is supported by a ceramic or disk 17 which serves also to close the other end of the envelope 1. The emitter 16 can be of the directly-heated filamentary type illustrated and formed, for example, of thoriated tungsten Wire. Additionally, it can be bifilar and contrawound or, in other words, can comprise a double helix structure wherein the helices are mutually oppositely wound. Both ends or leads 18 of the filament are disposed at one end thereof and, as shown, the hot cathode can be mounted and solely supported in the envelope by means of the leads 18. The leads 18 include portions which extend radially substantially from the axis of the cathode and are suitably sealed in apertures 20 parallelly extending in spaced relation through the ceramic disk 17. Connected to the outer extremities of the leads 18 is a pair of contact buttons 21 which can be suitably brazed to the outer surface of the ceramic disk 17. The buttons 21 are effective for completing an electrical circuit through the countrawound filamentary emitter, thereby to render same emissive and provide a cloud of electrons about the filament in the lower region of the device.

Also brazed to the outer surface of the ceramic disk 17 is a control electrode contact'button 22. The button 22 can be brazed to the disk 17 in the same manner as the buttons 20. Additionally, the button 22 is suitably electrically connected to a tantalum or tungsten lead 23 which extends through and is sealed ina suitable aperture 24 extending through the disk 17. The upper end of the aperture 24 opens directly beneath the flange 6 of the control electrode 5 and the upper or inner end of the lead 23 is suitably electrically connected to the flange 6, whereby the button 22 is adapted for serving as the contact for making an electrical connection to the control electrode 5.

The control electrode 5 includes, in addition to the flange 6, a tubular portion 25 extending from the flange 6 thereof toward the interaction space of the device. The tubular portion 25 is frusto-conical in shape and includes an inner surface which is spaced progressively closer to the filamentary cathode 16 in an axial direction toward the anode assembly. In operation, the control electrode 5 is maintained at a positive potential with respect to the emitter 16 so that an axial component of velocity toward the interaction space is imparted to the electrons emanating from the emitter. As illustrated, the frusto-conical portion of the control electrode terminates in closely spaced relation to the anode. This spacing is preferably about 10 mils. Additionally, and as also illustrated, the control electrode is provided with an internal cylindrical surface 26 adjacent the anode. The cylindrical surface 26 is preferably about 20 mils in length and has a diameter at least equal to and optionally slightly smaller than that of the cylindrical surface defined by the inner surfaces of the anode segments. Additionally, the inner edge 27 of the surface 26 corresponds generally in axial position to the upper end of the emitter. This arrangement minimizes back-heating of the cathode and undesirable electron impingement and collection on the lower ends of the anode array, or, in other words, relatively disposes the control electrode, emitter and lower ends of the anode segments such that the control electrode shields the lower ends of the anode segments and directs substantially all electrons into the cylindrical space defined by the anode segments.

The control electrode 5 and the particular spacing thereof from the anode contribute to the effectiveness of the control electrode in injecting a substantial number of electrons into the annular interaction region between the cold cathode 13 and the anode segments 14 and 15. This injection is particularly desirable in voltage-tunable magnetron devices since, under the conditions as existing during operation, the high frequency fields between adjacent anode segments are relatively weak in comparison with those existing in tank-tuned operation. In the specific embodiment of the device illustrated in FIG- URE 1 the injection is believed to be facilitated by the frusto-conical configuration of the control electrode. In this embodiment the wall of the control electrode extends at an angle of approximately 30 with respect to the axis of the conical portion and the cylindrical surface 26 of the control electrode, as pointed out above, has an axial length of approximately 20 mils.

The above-mentioned interaction region is defined by the cylindrical active surface of the cold cathode 13 and the anode segments 14 and 15 and in the illustrated embodiment of my invention the cold cathode is cylindrical throughout its full length and extends in the anode array only approximately two-thirds of the axial length of the latter. This disposes the specific interaction region, or the region in which the cylindrical active surface of the cold cathode 13 directly opposes the vertical surfaces of the anode segments 14 and 15, somewhat remote from the emitter and control electrode and leaves a substantial hollow space generally designated 30 between the inner end of the cold cathode and the inner ends of the control electrode and emitter. I have found this arrangement highly effective and advantageous from the standpoints of increased operating efficiency, increased power output and increased stability of performance. The manner in which these increased operating characteristics are obtained by the disclosed electrode arrangement will be better understood by reference to the schematic illustration of my improved electrode arrangement found in FIGURE 2.

In normal operation of my device, electric fields are established between the control electrode and emitter, between the anode and emitter, and between the anode and cold cathode of the device. In established electric fields between the several electrodes, and as seen in FIG- URE 2, there are substantially curved field lines shown in dash lines designated 31 and extending between the edge of the control electrode 5 and the emitter 16 and between the anode segments 14 and 15 and the emitter 16. These result in curved equi-potential surfaces generally of the hour-glass like configurations illustrated by solid lines 32 in FIGURE 2 and substantial axial and radially inwardly extending field components tending to act on electrons emanating from the emitter for directing them J axially toward the cold cathode and inwardly toward the center of the hollow space 31 It will also be seen from FIGURE 2, that substantially curved field lines exist between the anode segments 14 and 15 and the transverse end surface 13a of the cold cathode 13. These result in substantial axial and radially outwardly extending components tending to direct the electrons axially and somewhat radially outwardly into the interaction region between and defined by the lateral surface of the cold cathode 13 and the anode segments 14 and 15.

It will be understood that the static axial magnetic field provided between the poles P additionally affects the movement of the electrons and tends to rotaate them about the axis of the device as they emanate from the emitter, while in the space 30 and subsequently in the interaction region for effecting transfer of energy to the radio frequency field. Additionally, when electrons start rotating at a small radius they are thereby adapted for surrendering greater energy to a radio frequency field. In my disclosed improved electrode arrangement the hollow space 3% enables the electrons emanating from the cathode to approach the axis of the device before being rotated outwardly toward the interaction region and the axial and radially inwardly extending field components in the lower portion of the space 3% are effective for quickly directing electrons from the emitter toward the central region of the space 30 wherein they are adapted for being rotated at a small radius relative to the radius of the interaction region. Thus, my electrode arrangement is effective for adapting the electrons to surrender greater energy to the radio frequency field when the axial and radially outwardly extending field components in the upper portion of the space 30 subsequently direct the electrons into the interaction region between the cylindrical surface of the cold cathode 13 and the anode segments 14 and 15.

Additionally, the manner in which my improved electrode arrangement directs the electrons into the interaction region also has the desirable effect of minimizing the collection of electrons on the transverse end surface 13a of the cold cathode and, thus, increasing the total amount of electrons entering the interaction region wherein they can be effective for transferring energy to the radio frequency field, thereby to increase the power output.

My improved electrode arrangement and the electric field configuration established thereby are also effective for rotating the electrons transferred from the emitter into the interaction region in circumferential direction at an average velocity in a manner which aids in the interaction. The average circumferential velocity which is determined by the combined effect of the radial electric field components and the axial magnetic components is gradually increased in the injection area or in the space 36 so that there results a smooth transition from the angular velocity of the electrons emanating from the control elect-rode to the velocity in the interaction region. In prior art devices the interaction region defined by the active surface of the cold cathode and the anode extends to the immediate vicinity of the emitter and control electrode and the cold cathode is sometimes cylindrical throughout its length and is physically connected to the emitter with the result that the change in velocity of electrons rotating in the injection area to the velocity in the interaction region between the cold cathode and anode is substantially sudden. In my improved electrode arrangement the space Sit and the field distribution therein affords a smooth transition in velocity of electrons rotating in the injection area to the velocity of electrons rotating in the interaction region for thus affording an increased stability of performance not obtainable with prior art structures. i

It will be understood that while I have found the extension of the cylindrical active surface of the cold cathode 13 into the anode assembly only approximately twothirds of the axial length of the latter produces an optimum arrangement of electrodes for increasing'efiiciency, power output and stability of performance, slight deviations can be made from this relationship'without deviating from my invention. However, any substantial deviation, such as an extension of the active surface of the cold cathode into the anode to a point immediately adjacent the innermost or bottom edges of the anode segments, will result in operation which is different in kind in that it will not afford the unexpected increases in.

operating efficiency, power output and stability of performance obtainable when the active surface of the cold cathode extends into the anode only approximately twothirds the length of the anode segments in accordance with my present teaching. 1

Increased power output is obtainable with my device efiect on the electrons in the upper portion of the inter-' action region which tends to reduce the amount of energy transferred from electrons rotating in the upper portion of the interaction region to the radio frequency field. I have also found that this end effect can be relieved and the effective length of the interaction region can be virtually increased by providing the tapered surface 12 in place of the previously employed cylindrical boss. It is believed that, unlike the cylindrical end bosses found in prior art devices, the tapered surface 12 results in a field distribution between the upper ends of the cold cathode 13 and the anode segments 14 and 15 which enables a more uniform reaction between electrons and the radio frequency field throughout the length of the reactive region. capabilities for the device over a substantially wide frequency range. It is also believed that the tapered surface 12 reduces capacity between the anode and cold cathode which is considered desirable because in operation these elements are generally connected to a modulating source and the reduced capacity reduces the required modulating power, especially at higher operating frequencies.

The increased power capabilities of magnetrons embodying my invention will perhaps be better appreciated by a consideration of the family of curves illustrated in FIGURE 3 and showing the different high'frequency power outputs obtained with voltage tunable magnetrons incorporating my invention wherein the interaction region extends only approximately two-thirds the length of the anode and a frusto-conical surface is provided on the upper .end of the cold cathode and a prior art device wherein the cold cathode extends for substantially the full length of the anode and a cylindrical boss is employed in the upper end of the cold cathode.

In FIGURE 3 the solid line curve represents the power output of a device incmporatingmy improved electrode arrangement and the dash line curve represents that of the .prior device. Both devices were operated in an axial magnetic field between the poles P and adjusted to a value of 2400 gauss.

The filament current was adjusted to approximately 3.0 amperes DC. at about 3.4 volts, the control electrode potential at approximately plus 450400 volts, and the from about 2150 megacycles to about 390 0 megacyclesj In this range of frequency and as illustrated in FIGURE 3, my improved device provided an averagepower output of approximately 4.5 watts, where the modulation voltage to sweep over the band of frequencies was a sinusoidal source, whereas the prior art device attained an'average power output of approximately only 1.7 watts. Thisty'pe of performance has been repeatable with different tubes I have found that This, it is believed, results in greater power.

with my improved structure always affording increased power outputs of at least more than 2 to 1 compared with the prior art device. Additionally, with some tubes incorporating my improved structure I have obtained up to 10 watts average power output. Also, I have attained these substantially higher average power outputs with increased operating efliciency and increased stability of performance.

It will be understood from the foregoing and reference to FIGURE 4 that my invention is not limited to structure wherein the anode segments are arrayed cylindrically. Alternatively, the anode can comprise a plurality of sets of interdigital anode segments supported in mutually spaced side-by-side relation in an elongated array in the manner shown in FIGURE 4. The structure of FEGURE 4 includes a first set of elongated anode segments 35 suitably conductively mounted on a conductive support bar 36. A second set of such segments designated 37 is mounted similarly on another conductive support bar 38. As shown, these sets of segments are interdigitally arranged and mutually spaced and insulated.

Cooperating with the anode is a non-emissive electrode or cold cathode 39. The cold cathode 39 is elongated and extends in spaced relation to the anode array. The underside of the cold cathode 39, as viewed in FIGURE 4, constitutes the active surface thereof for cooperating with the anode segments to define an interaction region. The width of the cold cathode 39 is such that the active surface thereof extends only approximately two-thirds the length of the segments 35 and 37. Additionally, the

cold cathode 39 includes a tapered surface 49 outwardly of the interaction gap and inclined toward the plane of the anode segments. This surface serves the same purpose as the frusto-conical surface 12 in the device illustrated in FIGURE 1.

Disposed in spaced relation to the side of the anode opposite the surface 40 on the cold cathode is an emitter 41. The emitter 41 is spaced from the corresponding ends of the anode segments and is elongated to extend the length of the array of segments. Cooperating with the emitter 41 is an elongated control electrode 42. The control electrode 42 can include tapered surfaces for facilitating and controlling direction or injection of electrons from the region surrounding the emitter toward the interaction region between the cold cathode and anode.

As seen in FIGURE 4, the just-described structure provides an arrangement of electrodes in which the interaction region is somewhat remote from the emitter while a portion of the anode extends to the immediate vicinity of the emitter. Additionally, the device is adapted for operating in a magnetic field extending parallel to the anode segments. This field can be supplied, for example, by magnet poles designated P and shown'in dash lines. Thus, the device of FIGURE 4 will be understood from the foregoing to be similar in structure and operation to the device shown in FIGURES 1 and 2. For ease of understanding the structure of FIGURE 4 will be understood from the foregoing to be similar in structure and operation to the device shown in FIGURES 1 and 2. For ease of understanding, the structure of FIGURE 4 might be reasonably viewed as a plan development of the cylindrical structure of FIGURE 1.

However, it will be noted that the structure of FIG- URE 4 enables the employment of an elongated emitter which increases substantially the amount of electrons which can be introduced into the interaction region. Thus, the structure of FIGURE 4 has substantially greater power capabilities due to the increased emission. This, together with the increased power output resulting from my disclosed arrangement of electrodes, results in still greater power capabilities.

In both of the illustrated embodiments I have shown cold cathodes having active surfaces extending the full lengths thereof and which cathodes determine the dispositions and lengths of the interaction regions by the dimensions of the cathodes relative to the lengths of the anode segments. However, it is to be understood that portions of the cathodes can, if desired, extend toward the emitter beyond the interaction region without departing from or losing the benefits of my invention. Thus, for example, the inner end of the cathode post 13, in FIGURE 1 can be tapered or conical in the manner shown at 13b in FIGURE 1A. The cylindrical active surface of the cold cathode in this form, and thus the interaction region, remains substantially the same length as the cold cathode in FIGURE 1 and the tapered end 13b extends about the length of the anode segments into the space designated 30. This type of arrangement is still effective for causing rapid introduction of electrons into the interaction region and for allowing the electrons to commence rotating at a small radius for increasing the energy transfer and to experience a smooth transition in the average velocity of electrons introduced into the interaction region. With this tapered form of cold cathode post I have been able to obtain consistently average power outputs up to 9 watts. It will be further understood from the foregoing that the end of the cold cathode 39 in FIGURE 4 can also, if desired, be tapered or otherwise shaped and in a manner such as not to interfere with the operation of the device to afford substantially increased power output and other improved operating characteristics.

While I have shown and described specific embodiments of my invention 1 do not desire my invention to be limited to the particular forms shown and described, and I intend by the appended claims to cover all modifications within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A cross-field electric discharge device comprising an interdigital anode circuit including a plurality of elongated segments supported in mutually spaced, side-by-side relation, an emissive cathode wholly disposed in longitudinally spaced relation at the ends of said segments at one side of said anode, a non-emissive cathode including an active surface extending only partially the lengths of said segments and cooperating with said segments to define an interaction region therebetween, said interaction region being shorter than said anode segments and being spaced a substantially greater amount from said emissive cathode than said ends of said segments, and means for directing electrons from said emissive cathode toward said interaction region.

2. A cross-field device comprising an interdigital anode circuit including a plurality of segments supported in mutually spaced relation and defining a cylindrical opening, an electron emissive cathode wholly disposed axially outwardly of one end of said opening, a non-emissive cathode axially spaced and electrically separated from said emissive cathode extending in said opening from the other end thereof and including a lateral active surface extending only partially the lengths of said segments, said active surface of said non-emissive cathode and said segments thus defining an annular interaction region therebetween in which the active surface of said non-emissive cathode is spaced a substantially greater amount from said emissive cathode than said anode, and means for directing electrons from said emissive cathode axially into said one end of said opening in said anode circuit toward said interaction region.

3. A magnetron comprising an anode circuit including a plurality of segments supported in mutually spaced relation and defining a cylindrical opening, an electron emissive electrode disposed axially outwardly of one end of said opening, a non-emissive electrode extending only partially in said opening from the other end thereof, whereby said non-emissive electrode and said segments define an annular interaction region therebetween and the partial extension of said non-emissive electrode in said opening affords a hollow space in said opening axially interposed between said interaction region and said emissive electrode, and means for directing electrons from said emissive electrode axially into said one end of said opening in said anode circuit toward said interaction region and inwardly toward the center of said hollow space, thereby to adapt said electrons for rotating in said hollow space at a smaller radius relative to the radius of said interaction region and before entering said interaction region.

4. A magnetron comprising an anode circuit including a plurality of segments supported in mutually spaced relation and defining a cylindrical opening, an electron emissive electrode disposed axially outwardly of one end of said opening, a non-emissive electrode extending in said opening from the other end thereof and including an active surface extending parallel to and only partially the lengths of said segments, said active surface of said non-emissive electrode and said segments defining an annular interaction region therebetween in which the active surface of said non-emissive electrode is longitudinally spaced from said emissive electrode a substantially greater amount than said anode, and a coaxial electrode about said emissive electrode, said electrodes cooperating to establish an electric field eifective for directing electrons first axially and radially inwardly toward the longitudinal axis of said opening and then axially and radially outwardly into said interaction region.

5. A magnetron comprising an anode circuit including a plurality of segments supported in mutually spaced relation and defining a cylindrical opening, an electron emissive electrode disposed axially outwardly of one end of said opening, a non-emissive electrode extending into said opening approximately two-thirds the axial length of said segments, whereby said non-emissive electrode and said segments define an annular interaction region therebetween and the partial extension of said non-emissive electrode in said opening aifords a hollow space in said opening axially interposed between said interaction region and said emissive electrode, and means directing electrons from said emissive electrode axially toward said interaction region and inwardly toward the center of said hollow space, thereby to adapt said electrons for rotation in said hollow space at a smaller radius relative to the radius of said interaction region and before entering said interaction region.

6. A magnetron comprising an anode circuit including a plurality of segments supported in mutually spaced relation and defining a cylindrical opening, an electron emissive electrode disposed axially outwardly of one end of said opening, a non-emissive electrode extending into said opening approximately two-thirds the axial length of said segments, whereby said non-emissive electrode and said segments define an annular interaction region therebetween and the partial extension of said non-emissive electrode in said opening affords a hollow space in said opening axially interposed between said interaction region and said emissive electrode, and a coaxial control electrode about the end of said emissive electrode adjacent said opening and having an edge axially interposed between said anode and said end of said emissive electrode, said control electrode and said emissive electrode cooperating to provide axial and radially inwardly directed field components for directing electrons from said emitter axially toward said interaction region and inwardly toward the center of said hollow space, thereby to adapt said electrons for rotation at a smaller radius than the radius of said interaction region before entering said interaction region, and said anode, emissive electrode and non-emissive elec trode cooperating to provide axially and radially outwardly directed field components for facilitating movement of rotating electrons into said interaction region from said hollow space.

7. A magnetron comprising an anode circuit including a plurality of segments supported in mutually spaced relation and defining a cylindrical opening, a coaxial emissive electrode disposed axially outwardly of one end of said opening, a non-emissive electrode extending only partially in said opening from the other end thereof, said non-emissive electrode having an annular tapered surface outside said other end of said anode opening and increasing in diameter away from said opening, said non-emissive electrode and said segments defining an annular interaction region therebetween and the partial extension of said nonemissive electrode in said opening affording a hollow space in said opening axially interposed between said interaction region and said emissive electrode, and means for directing electrons from said emissive electrode axials ly into said one end of said opening in said anode circuit toward said interaction region and inwardly toward the center of said hollow space, thereby to adapt said electrons for rotating in said hollow space at a smaller radius relative to the radius of said interaction region before entering said interaction region, and said tapered surface on said non-emissive electrode being effective for cooperating with said segments for virtually increasing the effective length of said interaction region.

.8. A magnetron comprising an anode circuit including a plurality of segments supported in mutually spaced relation and defining a cylindrical opening, a coaxial emissive electrode disposed axially outwardly of one end of said opening, a non-emissive electrode extending in said open ing approximately two-thirds the axial length of said segments, said non-emissive electrode having a frusto-conical surface outside said other end of said anode opening and increasing in diameter away from said opening, said nonemissive electrode and said segments defining an annular interaction region therebetween and the two-thirds extension of said non-emissive electrode in said opening affording a hollow space in said opening axially interposed between said interaction region and said emissive electrode, and a coaxial frustoconical control electrode surrounding said emissive electrode and having the smaller edge thereof axially interposed between said anode and said emissive electrode, said control electrode and said emissive electrode cooperating to provide axial and radially inwardly directed field components for directing electrons from said emissive electrode axially toward said interaction region and inwardly toward the center of said hollow space, thereby to adapt said electrons for rotating at a smaller radius-than the. radius of said interaction region before entering said interaction region, said anode, emissive electrode and non-emissive electrode cooperating to provide axially and radially outwardly directed field components for facilitating movement of rotating electrons into said interaction region from said hollow space, and

said frusto-conical surface on said non-emissive electrode cooperating with said segments for virtually increasing the effective length of said interaction region.

9. A cross-field electric discharge device comprising an interdigital anode circuit including a plurality of segments supported in mutually spaced side-by-side relation in an elongated planar array, an elongated emissive cathode disposed along one edge of said planar array in spaced relation to the ends of said segments, an elongated nonemissive cathode electrically separated from said emissive cathode extending in spaced co-extensive relation to said array and having an active surface for cooperating with said segments to define a planar interaction region therebetween, said interaction region being shorter in width than the length of said segments and being spaced a substantially greater amount from said emissive cathode than said anode, and means for directing electrons from said emissive cathode toward said interaction region.

10. A cross-field electric discharge device comprising an anode including a plurality of segments supported in mutually spaced side-by-side relation in an elongated array, an elongated emitter disposed along one edge of said array in spaced relation at the ends of said segments, an

elongated non-emissive electrode extending in spaced coextensive relation to said array and cooperating therewith to provide an interaction region, said non-emissive electrode extending toward said emitter only approximately two-thirds the length of said segments, whereby the interaction region defined by said non-emissive electrode and cathode is remote from said emitter relative to said one edge of said array, and means for directing electrons from said emitter toward said interaction region.

11. A cross-fieid device according to claim 9, wherein a control electrode cooperates with said emissive cathode and other electrodes for establishing an electric field effective for directing electrons toward said interaction region.

12. A cross-field device according to claim 9, wherein said non-emissive cathode has a surface thereon inclined toward said array of segments on the side of said anode opposite said emissive cathode for cooperating with said segments to increase virtually the effective length of said interaction region.

13. A cross-field electric discharge device comprising an anode including a plurality of elongated segments supported in mutually spaced, side-by-side relation, an emitter disposed in longitudinally spaced relation at the ends of said segments at one side of said anode, a nonemissive electrode extending in laterally spaced relation to said anode and having an active surface extending parallel to and cooperating with said segments to define an interaction region therebetween, said interaction region being spaced a substantially greater amount from said emitter than said ends of said segments, and said nonemissive electrode including a tapered end portion extending toward said emitter.

14. A magnetron comprising an anode circuit including a plurality of segments supported in mutually spaced relation and defining a cylindrical opening, an electron emissive electrode disposed axially outwardly of one end of said opening, a non-emissive electrode including a cylindrical active surface extending only partially in said opening from the other end thereof and defining with said segments an annular interaction region extending only partially the length of said segments, and said non-emissive electrode further including a tapered end extending toward said emissive electrode and longitudinally spaced and electrically separated therefrom by a void.

15. A cross-field electric discharge device comprising an envelope, said envelope supporting an anode including a plurality of elongated segments mounted in mutually spaced, side-by-side relation in said envelope, an insulative member closing one end of said envelope, a filamentary emitter in said envelope having both ends thereof sealed through said insulative member and solely supported thereby, said emitter being located in longitudinally spaced relation to the ends of said segments at one side of said anode, a non-emissive electrode extending in said envelope in laterally spaced relation to said anode and cooperating with said segments to define an interaction region therebetween extending only partially the length of said anode segments and being spaced a substantially greater amount from said emitter than said ends of said segments, and means for directing electrons from said emitter toward said interaction region.

16. A cross-field electric discharge device comprising an envelope, said envelope supporting an anode including a plurality of elongated segments mounted in mutually spaced, side-by-side relation in said envelope, an insulative member closing one end of said envelope, a filamentary emitter in said envelope having both ends thereof sealed through said insulative member and solely supported thereby, said emitter being located in longitudinally spaced relation to the ends of said segments at one side of said anode, a non-emissive electrode extending in said envelope in laterally spaced relation to said anode and cooperating with said segments to define an interaction region therebetween extending only partially the length of said anode segments and being spaced a substantially greater amount from said emitter than said ends of said segments, and said non-emissive electrode having a frustoconical surface thereof disposed outwardly of said interaction region at the other side of said anode and inclined toward said anode segments.

17. A magnetron comprising an anode circuit including a plurality of segments supported in mutually spaced relation and defining a cylindrical opening, an electron emissive electrode disposed axially outwardly of one end of said opening, a non-emissive electrode extending only partially in said opening from the other end thereof, whereby said non-emissive electrode and said segments define an annular interaction region therebetween and the partial extension of said non-emissive electrode in said opening affords a void in said opening axially interposed between said interaction region and said emissive electrode, and means for drecting electrons from said emissive electrode axially into said one end of said opening in said anode circuit toward said interaction region.

References Cited in the tile of this patent UNITED STATES PATENTS 2 409,038 Hansell Oct. 8, 1946 2,493,423 Spooner Jan. 3, 1950 2,509,419 Brown May 30, 1950 2,585,741 Clogston Feb. 12, 1952 2,810,096 Peters Oct. 15, 1957 en T

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