US2462698A - Electrical discharge device - Google Patents

Description

Feb. 22, 1949.

D. A. WILBYUR 2,462,698

ELECTRICAL DISCHARGE DEVICE Filed June 23, 1945 inventor: Donald /-\.Wilbur-,

His Attorney.

i atented F e1 22, 1949 ELECTRICAL DISCHARGE DEVICE Donald A. Wilbur, Troy, N. Y., assignor to Genera-l Electric Company, a corporation of New York Application June 23, 1945, Serial No. 601,126

14 Claims. 1

My invention relates to electric discharge devices and more particularly to improved high frequency electric discharge devices of the magnetron type.

In one type of magnetron construction that has been widely used a pair of mutually spaced anode members are provided with opposed curved faces which define a generally cylindrical boundary confining the space charge of the device. The conductors of a parallel wire transmission line are connected respectively with the anode members and extend through the envelope of the device. The operating frequency is readily controlled by adjusting the position of a short circuiting conductor connecting the conductors of the transmission line. Magnetrons having the above construction have been referred to as the split anode type. These devices have been satisfactory ior many applications, and the simplicity of the tuning arrangement required has been an outstanding advantage of the split anode magnetron over magnetrons of the type including an anode block shaped to define a plurality of space resonant circuits including gaps communicating with a region within which the space charge of the device is confined. However, magnetrons of the latter type, which may be referred to as the resonant anode type, have had certain advantages including higher operating frequencies, higher efficiencies and less back heating of the cathode. In accordance with the teachings of my invention I provide an improved magnetron construction which retains the simplicity of the split anode type, particularly with respect to tuning, and which at the same time provides to a substantial degree the advantages of the resonant anode type.

It is an object of my invention to provide a new and improved high frequency electric discharge device.

It is another object of my invention to provide a new and improved electric discharge deveice of the magnetron type.

It is still another object of my invention to provide a new and improved magnetron construction of the split anode type characterized by higher operating frequencies, higher efiiciencies and longer tube life.

In the illustrated embodiments of my invention, a magnetron of the split anode type and including a pair of conductors forming a parallel wire transmission line is provided with at least one anode segment in addition to the usual segments which are connected to the parallel wires. The additional anode is connected to a point which is neutral with respect to the high frequency voltage of the transmission line system. Th neutral, may to advantage be established by an internal loop conductor connected to the anode members and forming, in a sense, an extension of the parallel wire transmission line. A magnetrondevice of the split anode type including an internal loop conductor is described and-claimed in the copending Blewett application SerialNo. 555,497, filed September 23, 1944, Pat. No. 2,428,193, issued September 30, 1947, and assigned to the assignee of the present invention. The Blewett application is prior art with respect to myinvention. In the various illustrated embodiments, different arrangements ofthe anode Segmentsare provided in which the working gaps between adjacent segments are spaced by different angles, and in which the additional electrodes or anode sections connected to the high frequency neutral have different angular extents than the remaining anode sections. These discharge devices, which are readily tuned by a movable conductor short circuiting the parallel wires of the transmission line, function electronically in a manner which approaches that of the resonant anode type. A magnetron of the resonant anode type having anode face portions of unequal angular extent confining the space charge of the device is described and broadly claimed in the Bondley application, Serial No. 601,121, filed concurrently herewith and assigned to the assignee of the present invention.

My invention will be better understood by reference to the accompanying drawing and its scope will be pointed out in the appended claims. In the drawing, Fig. 1 is an elevational view of an electric discharge device embodying my invention; Fig. 2 is a side elevational View of the device shown in Fig. 1; Figs. 3 and 4 are, respectively, front and side elevational views of a l0dlfi6d anode construction; Figs. 5 and 6 are,

respectively, front and side elevational views of a second modification of an anode structure which may be employed in the device of Fig. Fig. 7 is a front elevational view of a third modification of an anode construction which may be employed in the discharge device of Figs. 1 and 2; and Fig. 8 is a sectional view taken along the line-B-8 of Fig. 7.

Referring now to Figs. 1 and 2 of the. drawing, I have shown my invention embodied in a magnetron device including an envelope I, preferably formed of glass, within which ismounted a generally. U-shaped conductor 2 which may-to advantage be formed of copper tubing. The arms of the U-shaped tubing extend through the end wall of the envelope and are sealed thereto by suitable seal constructions including sleeves 3 and 4 which are joined, respectively, to the envelope and the arms of the U-shaped conductor and which may be made of any of a class of compositions well-known in the art suitable for metal to glass sealing comprising the elements of iron, nickel, and cobalt. The conductor'2 including portions 5 and 6 which extend to the exterior of the envelope provide a parallel wire transmission line which is terminated by a short circuiting conductor 6 which is illustrated diagrammatically. This conductor is adjustable along the length of conductors 5 and 3 to determine the electrical length of the transmission line. Within the tube envelope a pair or" anode members 9 and II] are supported in opposed relation from the opposite arms of the U-shaped conductor 2. The anode members are spaced at the inner ends thereof and provided with arcuate surfaces H and I2, respectively, which cooperate with the arcuate surface l3 of a third anode member It to confine the space charge of the device supplied by an elongated cathode 18. The electrode 14 is supported from a neutral point with respect to the high frequency voltage of the magnetron which, in the illustrated embodiment, is provided by the base portion of the U-shaped conductor 2. The anode member l4 extends parallel to and midway between the arms of the U-shaped conductor and terminates short of the segments 9 and ii) to provide gaps l5 and I6. A third gap ll of the device is provided by the spaced ends of the anode segments 9 and ID. The cathode l8, which may be a tungsten wire, is supported on the axis of the generally cylindrical space defined by the curved face portions I I, I2 and I3 of the anode segments by resilient supporting conductors l9 and [9. These supporting conductors are secured to relatively rigid lead-in conductors 20 and 2|, respectively, which are, in turn, sealed through the end wall of the envelope in any suitable manner. Circular shielding members 22 and 23 are supported, respectively, from the flexible conductors I9 and I9 on opposite sides of the anode structure to prevent electrons escaping from the interelectrode space from impinging on the glass Walls of the envelope. Also, a shield member 24 may be connected to the anode member 9 and extend over the gap i? to collect electrons escaping therefrom. A suitable getter 25 is supported near the inner wall of the envelope by a conductor 25 secured to the end of the loop conductor 2.

In the modification shown in Figs. 1 and 2, the anode faces H and [2 of anode members 9 and I subtend an angle of 90 degrees at the center of the interelectrode space, neglecting the width of the gaps I5, l6 and H. The curved face portion l3 of the third anode segment or neutrode, as it may be called, subtends an angle of substantially 180 degrees, neglecting the width of the gaps l and I6. With this arrangement, the device operates electronically in a manner similar to a fourgap resonant anode magnetron and for a given magnetic field motion of the electrons past the gaps is at substantially the same velocity as would occur in such a magnetron. From the standpoint of tuning, however, the magnetron is controlled in the same manner as the conventional split anode type.

As will be well understood, the magnetrondevice shown in Figs. 1 and 2 may be operated as a high frequency oscillator by impressing a source of cathode heating voltage on the terminals 20 4 and 2| and impressing a high direct current voltage between one of the cathode terminals 20 or 2| and a direct current anode'terminal, which to advantage may be connected symmetrically with respect to the transmission line. As illustrated, this terminal is provided by a conductor 21 connected to the midpoint of the shorting conductor 3. This latter voltage, in conjunction with a magnetic'field produced in the interelectrode space parallel to the cathode by suitable permanent or electromagnetic means (not shown) produces curvilinear motion of the electrons to excite the resonant structure including the anode segments and the transmission line including conductors 2, 5 and 6. The frequency of operation is determined by the geometry of the anode system, the dimensions of the loop 2 and the position of the shorting conductor 8. The conductor 8 is positioned at a distance of a half wavelength, or multiples thereof, from the anode members 9 and ID with its effectiveness being a little greater at a half wavelength than at a greater distance. However, in some constructions the half wavelength of the line is not accessible from the exterior of the envelope for all operating frequencies.

In the modification shown in Figs. 3 and 4 the anode structure is modified so that it operates electronically like a six-gap magnetron having a symmetrical arrangement of gaps. As illustrated in Fig. 3, the anode segments 28 and 29, connected respectively to the parallel conductors 5 and 6 are provided with end portions 30 and 3| which extend substantially radially toward the center of a space charge confining region defined by the ends of the portions 30 and 3| and a cooperating arcuate surface 32 formed on theneutrode 33. In the particular arrangement illustrated in Figs. 3 and 4, the faces of each of the anode segments 28 and 29 subtend an angle of substantially 51.4 degrees or th of a circle. However, the distribution of the space charge follows substantially the pattern for 60 spacing of adjacent sections, and the device operates in a manner similar to a six-gap resonant anode magnetron. A suitable shield 34 connected with one of the anode members 28 may be provided to minimize the escape of electrons from the interelectrode space. It will be understood that the structure shown in Figs. 3 and 4 forms a part of a complete magnetron system of the same type as that illustrated in Figs. 1 and 2.

In Figs. 5 and 6 I have shown a still further modification of my invention in which the anode sections 35 and 35, connected respectively to the parallel conductors 5 and 6 of the transmission line, are substantially L-shaped with the long arms of the Us extending in spaced parallel relation intermediate the conductors 5 and 6. The inner ends of the anode members cooperate with an arcuate surface 31 forming a third anode member 38 which is connected symmetrically to the loop conductor 2. In this arrangement, the angle subtended by the arcuate surface of each of the anode members 35 and 36 is substantially 50, and the device operates electronically as a six-gap magnetron of the resonant anode type. However, the device is tuned as in the arrangement of Figs. 1 and 2 by means of the sliding short or the external conductors of the transmission line.

In Figs. '7 and 8 is shown a still further modification of my invention in which the two anode segments connected with the conductors of the transmission line are arranged alternately with a pairof conductors, both of which are connected to a neutral point established by the loop conductor of the transmission line 2. Referring to the drawing, anode members 39 and 48 are connected respectively to the conductors 5 and t and terminate in opposed spaced relation. An electrode connected With the loop conductor 2 and extending parallel to the arm portions 5 and 6 of the transmission line terminates in a curved surface 42 lying between anode members 39 and 40 and forming a part of the space charge confining structure. A similarly shaped surface 43 is provided on a member 44 which is mechanically and electrically connected with the electrode ll by a. pair of cylindrical members 45 and it which are received respectively in recesses formed in the opposite faces of members ii and 44-. In the modification shown in Figs. '7 and 8, the cathode designated by the numeral 47 is located unsymmetrically with respect to the arcuate surfaces on anode members 39, 40, 4| and G2. The interelectrode space, however, is made symmetrical by a generally cylindrical member 8 which is located concentrically with the space charge confining surfaces of the anode members and provided with an axial recess 49 for the reception of the cathode 41. An integral extension 59 on the member 48 provides a means for supporting the member 48 from one of the cathode supporting conductors such as H! of Figs. 1 and 2. In the particular arrangement shown in Figs. '7 and 8, the angle subtended by the anode section 39 and one of the adjacent gaps is substantially 36 and the device functions electronicalli, in a manner very similar to a ten-gap resonant anode magnetron.

The precise manner of operation of high frequency magnetron type discharge devices has been the subject of various theories advanced to explain the complex electronic actions involved. By way of further elucidation of the principle of the present invention, one view of the manner of operation may be stated as follows: It may he assumed that when a radially directed electric field of sufficient magnitude is imposed between a cathode and any configuration of a plurality of anodes having faces defining a preferably cylindrical chamber about the cathode illustrated by the embodiments of the present inven tion or by the conventional split anode type of magnetron, a generally cylindrical rotating space charge is established in the chamber provided, of course, that a magnetic field of sufficient magnitude is directed axially of the chamber. This behavior results from the well known interaction of electrons with the radially directed electric field and the magnetic field. It may also be as sumed that the high frequency oscillations known to be developed in the attendant resonant circuit (such as the resonant transmission lines shown) are sustained by the passage of portions of the rotating space charge past the gaps defined by the juxtaposed faces of the anodes. For example, in the case of the split anode type of magnetron illustrated by the aforementioned Blewett application Serial No. 555.497, oscillations are assumed to be developed by the passage of nor tions of the space charge past the two diametrically opposite gaps. Such passage is. in steady state operation, in synchronism with the high frequency oscillations of the resonant circuit.

As to the precise behavior at the gaps. it is believed that distortions of the radially directed electric field in the vicinity of these gaps caused by the instantaneous high frequency potentials causes the rotating. spacecharge to assume a dis torted'or cam-shaped form 'andthat it -is' the passage of the projecting'z portions thereof past the gaps: which delivers to the elect'rodes power impulses at the frequency of oscillation. It 'i-s thought that a projecting portion tendsto form wherever the instantaneous electric field atth'e gap is in the direction of rotation, a depressed portion tending toform where the instantaneous electric field is in theopposite direction. Thus, in the split-anode type onlyone projectin'gfportion is formed, whilerin the four-anode type two diametrically opposite projecting portions are formed.

On this theory, ituis apparent that fora-given angular velocity of the space charge (i. e. for given values. of the uni-directional radial electric and the magnetic field) the frequencyof the four anode type of tube is twice that of the'split an'ode type because, during rotation of thecspace char'ge, power impulses are delivered -tosuccessive g apsat double the frequencybyvirtue of their relatively closer spacing around the periphery of thechamher. The frequencyof tubes with greater-numbers of anodes is correspondingly higher. Bythe same reasoning, the frequency of the illustrated embodiments of the presentinvention should-be greater than that of the split-anode type because of the relatively closer. gap spacing. For examin the embodiment of Figures 1 and 2, the frequency behavior should be the same as fora four anode tube because anodes 9 and I8 have angular positions corresponding to their counterparts in a four anode tube. Unlike the four anodet'ype of tube in which all electrodes have high-frequency potential variations, the neutral element (third anode member M for example) hasno high frequencyv potential variations imposed upon it because it is connected to an electricallyneutral point on the transmission line constituting the resonant circuit. Theneutral element, there'- fore, serves only to maintain, throughout the entire 360 surrounding the cathode, the unidirectional radial electric field necessary'to maintain the rotating space chargein-the chamber. Thus, while retaining the same electric characteristics of the multi-electrodetypeheretofore known, the present invention addsrthe advantage of structural simplicity.

From the foregoing description, it is apparent that magnetrons embodying my invention" are readily tuned in the same manner as conventional magnetrons of the'split anodetype. I have found that these lnagnetrons also' possess to a high degree the advantages of the resonant anode type with respect'to operating frequency for a given magnetic field, the absence of back" heating of the cathode, and efficiency" of operation. All of the illustrated embodiments of my inventionare characterized by the use'of more than two anode members with at least one of the anode m'embers connected to a high frequencylneutral point on the transmission line. Intheforegoing-specification and in the appended claims, reference has been made to the U-shaped conductor of-the transmission line and the various anode members. It will be appreciated that these com ponents could be formed from a single block of conducting material if desired but-I prefer the fabricated structures of the illustrated embod-l-- ments. For example, the member 38 of Fig. 5 could be made larger and connected to the ends of the parallel conductors 5 and B .of the transmission line.

While I have'shown and described particular embodiments" of my invention, it will be obvious to those skilled in the art that changes and modifications may be made without departing from my invention in its broader aspects, and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

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

1. A magnetron device comprising, an em velope, a transmission line including a pair of parallel conductors extending through a Wall oi said envelope, mean electrically connecting said conductors within said envelope to provide an electrically neutral point, a plurality of anode members having portions cooperating to define a substantially cylindrical space within which the electrons constituting the space charge of the device are adapted to move, two of said members being connected respectively with said parallel conductors and a third of said members being connected with said neutral point.

2. A magnetron device comprising, a transmission line including a pair of parallel conductors, means interconnecting said conductors to provide an electrically neutral point, a plurality of anode members having portions cooperating to define a space within which the electrons constituting the space charge of the device are adapted to move, two of said members being connected respectively with said parallel conductors and a third of said members being connected with said neutral point, and an hermetically sealed envelope enclosing said anode members.

3. A magnetron device comprising, an envelope, at least three anode members in said envelope having curved surfaces cooperating to define a space within which the electron-s constituting the space charge of the device are adapted to move, a transmission line system including a substantially U-shaped conductor having a base portion positioned in said envelope and the arm portions extending through a wall of said envelope, two of said anode members being connected respectively with said arm portions and a third anode member being connected with the base portion of said U-shaped conductor.

4. A magnetron device comprising, an envelope, at least three anode members having surfaces cooperating to define a space within which the electrons constituting the space charge of the device are adapted to move, a transmission line system including a pair of parallel conductors each having a portion of the length thereof lying within said envelope, two of said anode members being connected respectively with said conductors and positioned within said envelope, and means connecting said conductors together to establish an electrically neutral point, the third of said anode members being connected with said neutral point and positioned symmetrically between said pair of conductors.

5. A magnetron device comprising, an envelope of vitreous material, a transmission line system including a substantially U-shaped structure mounted within said envelope with the arms of said U extending through said envelope, a pair of anode members connected respectively to the arms of said U-shaped conductor and a third anode member connected with the base portion of said U-shaped conductor and extending intermediate and parallel to the arm portions of said U-shaped structure, said anode members terminating in curved surfaces which cooperate to define. aspace Within which the electrons constituting the space charge of the device are adapted to move.

6. A magnetron device comprising a transmission line including a pair of parallel conductors and having a point electrically neutral with respect to high frequency voltage therein, a pair of anode sections connected respectively to said conductors, each of said sections having a curved surface of substantially less than and an additional anode section connected to said neutral point symmetrically with respect to both of said conductors and having a curved surface 00- operating with the curved surfaces of said first mentioned anode sections to define a substantially closed space within which the electronsconstituting the space charge of the device are adapted to move.

7. A magnetron device comprising a transmission line including a pair of parallel conductors, means connecting said conductors together to establish a high frequency neutral point, a plurality of anode sections having face portions separated from each other by gaps and cooperating to define a region within which the electrons constituting the space charge of the device are adapted to move, two of said anode sections arranged oppositely with respect to said region being connected with said neutral point, and other of said anode sections interposed between said first mentioned anode sections and connected respectively with said parallel conductors.

8. A magnetron device comprising a transmission line including a pair of parallel conductors and having a point electrically neutral with respect to high frequency voltage therein, a, pair of anode members connected respectively-witlr said conductors and having portions extending in mutually spaced relation to define a gap, an additional anode member connected to said neutral point symmetrically with respect to said conductors and having portions thereof extending in spaced relation to said first mentioned anode members to provide additional gaps, the surfaces of said anode members extending between said gaps cooperating to define a substantially closed region within which the electrons constituting the space charge of the device are adapted to move.

9. Electrical apparatus of the magnetron type comprising an oscillatory circuit having a point electrically neutral with respect to high frequency voltages established therein during normal operation of said apparatus, an electic discharge device of "the magnetron type for energizing said circuit comprising a'plurality of electrodes having juxtaposed faces defining a space charge chamber adapted to accommodate a rotating space charge of the magnetron type, one of said electrodes being conductively connected to'said neutral point, the voltage of said electrode thereby being substantially neutral with respect to high frequency voltages in said circuit during norma1 operation of said apparatus, at least one other of said electrodes being conductively connected to a clifferent'point in said circuit other than said neutral point, said other electrode being thereby subjected to the high frequency voltage of said difierent point during normal operation of said apparatus and an hermetically sealed envelope enclosing said plurality of electrodes and said space charge chamber.

10. Electrical apparatus of the magnetron type comprising a resonant circuit having a point electrically neutral with respect to high frequency voltages established therein during normal op-' ation of said apparatus, an electric discharge device of the magnetron type for energizing said circuit comprising a cathode and a plurality of anode electrodes having juxtaposed faces defining about said cathode a generally cylindrical a e harge chamber adapted to accommodate a rotating space charge of the magnetron type, one of said electrodes being conductively connected to said neutral point, the voltage of said electrode thereby being substantially neutral with respect to high frequenc voltages in said circuit during normal operation of said apparatus, at least one other of said electrodes being conductively connected to a different point in said circuit other than said neutral point, said other electrode being thereby subjected to the high frequency voltage of said different point during normal operation of said apparatus, and an hermetically sealed envelope enclosing said plurality of electrodes and said space charge chamber.

11. Electrical apparatus of the magnetron type comprising an oscillatory circuit having a point electtr'cally neutral with respect to high frequency voltages established therein during normal operation of said apparatus, an electron discharge device of the magnetron type for energizing said circuit comprising a plurality of electrodes having juxtaposed faces defining a generally cylindrical space charge chamber adapted to accommodate a rotating space charge of the magnetron type, one of said electrodes having a face subtending at least about 180 of the periphery of said chamber and being conductively connected to said neutral point, the voltage of electrode thereby being substantially neutral with respect to high frequency voltages in said circuit during normal operation of said apparatus, least two other of said electrodes having symmetrically subtending substantially equal angular portions of the remainder of said periphery bein conductively connected each to different pants in said circuit other than said neutral point, said other electrodes being thereby subjected to the high frequency voltages of said different points during normal operation of said apparatus, and an hermetically sealed envelope enclosing said plurality of electrodes and said space charge chamber.

12. Electrical apparatus of the magnetron type comprisin an oscillatory circuit having a point electrically neutral with respect to high frequency voltages established therein during normal operation of said apparatus, means for sustaining high frequency oscillations in said circuit including an electron discharge device of the magnetr-on type comprising a plurality of electrodes having juxtaposed faces defining a space charge chamber adapted to accommodate a rotating space charge of the magnetron type, one of said electrodes being conductively connected to said neutral point, the voltage of said electrode thereby being substantially neutral with respect to high frequency voltages in said circuit during normal operation of said apparatus, at least one other of said electrodes being conductively connected to a different point in said circuit other than said neutral point whereby oscillations in said circuit may be sustained by interaction between said space charge and said other electrode, and an hermetically sealed envelope enclosing 7 said plurality of electrodes and said space charge chamber.

13. Electrical apparatus of the magnetron type comprising a resonant transmission line having a point electrically neutral with respect to high frequency voltages established therein during normal operation of said apparatus, means for sustaining high frequency oscillations in said. circuit including an electron discharge device of the magnetron type comprising a cathode and a plurality of anode electrodes having juxtaposed faces defining about said cathode a generally cylindrical space charge chamber adapted to ac commodate a rotating space charge of the magnetron type, one of said electrodes being conductively connected to said neutral point, the voltage of said electrode thereby being substantially neutral with respect to high frequency voltages on said line during normal operation of said apparatus, at least one other of said electrodes being conductively connected to a different point on said line other than said neutral point whereby 2o oscillations in said line may be sustained by interaction between said space charge and said other electrode, and an hermetically sealed envelope enclosing said plurality of electrodes and said space charge chamber.

14. Electrical apparatus of the magnetron type comprising a resonant circuit having a point electrically neutral with respect to high frequency voltages established therein during normal operation of said apparatus, means for sustaining high frequency oscillations in said circuit including an electron discharge device of the magnetron type comprising a plurality of electrodes having juxtaposed faces defining a generally cylindrical space charge chamber adapted to accommodate a rotating space charge of the magnetron type, one of said electrodes having a face subtending at least about 180 of the periphery of said chamber and being conductively connected to said neutral point, the voltage of said electrode thereby being substantially neutral with respect to high frequency voltages in said circuit during normal operation of said apparatus, at least two other of said electrodes having faces symmetrically subtending equal angular portions of said periphery and being conductively connected each to diiferent points in said circuit other than said neutral point whereby 0scillations in said circuit may be sustained by interaction between said space charge and said other electrodes, and an hermetically sealed envelope enclosing said plurality of electrodes and said space charge chamber.

DONALD A. WILBUR.

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

UNITED STATES PATENTS Number Name Date 2,046,688 Kilgore July 7, 1936 2,063,342 Samuel Dec. 8, 1936 2,110,448 Linder Mar. 8, 1938 2,168,295 De Vries et a1 Aug. 1, 1939 2,173,252 Fritz Sept. 19, 1939 2,402,397 I-Iansell June 18, 1946 2,409,913 Tonks Oct. 22, 1946 FOREIGN PATENTS Number Country Date 215,600 Switzerland Oct. 16, 1941 486,244 Great Britain Jan. 13, 1938

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