US3250947A - Discharge device having electron grids with heights rising substantially above the grid support rims - Google Patents

Description

May 10, 1966 A. J. FIEDOR ET AL 3,250,947

DISCHARGE DEVICE HAVING ELECTRON GRIDS WITH HEIGHTS RISING SUBSTANTIALLY ABOVE THE GRID SUPPORT RIMS Original Filed Aug. 11, 1960 I I 7 axe/0 616/0 SUP/D027- Q/M United States Patent 3 259 947 DISCHARGE DEVHZE IIAVING ELECTRON GRIDS WITH HEIGHTS RESING SUBSTAN- TIALLY ABOVE TIE GRID SUPPORT RIMS Adolph J. Fiedor, Palo Alto, and Robert G. Rockwell, Menlo Park, Calif., assignors to Varian Associates, Palo Alto, Calif., a corporation of California Original application Aug. 11, 1960, Ser. No. 48,889, now Patent No. 3,104,341, dated Sept. 17, 1963. Divided and this application June 10, 1963, Ser. No. 286,823

Claims. (Cl. 315-537) The present application is a division of application of U.S. Serial No. 48,889, now Patent No. 3,104,341 titled Electron Discharge Device, inventors Adolph J. Fiedor et, al., filed August 11, 1960, and assigned to the same assignee as the present invention.

This invention relates in general to high frequency emissive devices and more particularly to a novel improved electron tube.

The present invention is embodied for the purposes of disclosure in a Ku-band klystron amplifier which, because it is electrostatically focused, and thereby requires no magnet, weighs only about eight ounces and is well suited for aerial navigation systems in which weight is a prime factor. One such tube has been built with four tunable resonator cavities spaced along the electron beam having a C.W. power output from 1-25 watts with a gain of approximately 30 decibels.

In order to produce a tube of such small size with sufiicient gain and output power it was necessary to improve the resonator grid structure to obtain enhanced cavity resonator characteristics.

It is, therefore, the main object of the present invention to provide a small, rugged, high power and gain klystron incorporating novel cavity resonator grid structure.

One feature of the present invention is a novel grid design which reduces grid capacitance for the same gap length and thus permits an increase in the cavity diameter to obtain more inductance and thereby increase R /Q and Q.

Other features and advantages of the present invention will be more apparent upon a perusal of the following specification taken in connection with the accompanying drawing wherein:

FIG. 1 is an isometric view of a klystron tube made in accordance with the present invention,

FIG. 2 is an enlarged cross-section taken along line 22 in FIG. 1,

FIG. 3 is an enlarged view of a novel raised grid taken along line 33 in FIG. 2 in the direction of the arrows,

FIG. 4 is an enlarged cross-section of the novel raised grid taken along line 4-4 of FIG. 3 in the direction of the arrows, and

FIG. 5 is an enlarged partial cross-section view showing another embodiment of the novel raised grid.

Referring now to FIGS. 1 and 2, the klystron made in accordance with the present invention includes a central -body portion 11 which is made from a unitary block of metal having a longitudinal bore extending therethrough. Hollow cylindrical drift tubes 12, having circular resonator grids 13 on the ends thereof, are posi tioned within the longitudinal bore of central body portion 11 by outwardly extending annular headers 15. The walls of drift tubes 12 are parallel to the axis of the electron beam passing therethrough. Fixedly secured as by brazing in one end of the longitudinal bore of the central body portion 11, is a narrow, annular anode structure 17, having a resonator grid 18 positioned in the aperture therethrough. Within the other end of central body portion 11 is an annular header 19 with a 3,258,947 Patented May 10, 1966 resonator grid 21 positioned in the aperture therethrough. By positioning the resonator grid 18 within the anode structure 17 the resonator grid 18 serves as an anode portion thereby minimizing the distance a focused electron beam must traverse through the klystron tube.

Within the central body portion 11, annular anode structure 17 and first annular header 15 on the first drift tube 12 define a single re-entrant first cavity resonator 22. Three doubly re-entrant cavity resonators 23 are defined by the annular headers 15 and annular header 19.

Fixedly secured, as by brazing, to the central body portion 11 and sealing off the end thereof adjacent to the anode structure 17 is a beam generating assembly 26 including hollow cylindrical focus electrode 27.

The beam collector assembly 41 includes a hollow cylindrical end portion 42 closed at its outward end and fixedly secured to the end of central body portion 11 adjacent the annular header 19 by a braze therebetween. Beam collector assembly 41 also includes a fin assembly comprising annular fin members 45 brazed to the cylindrical end portion 42 whereby the tube is air cooled. It is noted that central body portion 11 is provided with a fin assembly to further aid in air cooling the entire device thereby removing the necessity of an internal liquid cooling system. An evacuation pinch-01f tube 46 is provided in the closed end portion 42 with four entrants 46' into the collector cavity for pumping the tube. It is further noted that a conical member 47 is provided at the closed end of beam collector assembly 41 to diffuse the electron beam striking the end of beam collector assembly 41 thereby reducing the possibility of secondary electrons released by impinging primary electrons from entering into the drift tube and cavity section of central body portion 11.

Identical input and output waveguides 48 and 49 respectively are secured to the central body portion 11 and respectively communicate with the first cavity resonator 22 and the third double re-entrant cavity resonator 23 through milled openings, not'shown, within central body portion 11. The outwardly projecting end of each Waveguide is provided with a waveguide flange member 51 which carries a ceramic window 52 sealed therein by a window frame 53.

Referring now to FIGS. 3 and 4 there is shown a novel grid support structure 70 for mounting the resonator grids 13, 18 and 21 wherein the grid elements or vanes on opposing drift tube ends are held a certain distance apart while the rim members 71 in which the grid vanes 13' are mounted are set back thus efiecting a greater spatial distance between opposed rim members 71. The rim members 71 for supporting the grid members 13 consist of steel or nickel be'nt as to have a U-shaped cross-section with an inner wall, an outer wall and a lower connecting wall formed in a ring. In the present invention a circular ring 73 made of, for example, nickel plated copper wire is positioned in the bottom of the U-shaped channel of rim 71 and brazed therein. In this manner the grid vanes 13 are mounted within the U-shaped channel of rim member 71 and extend through a plurality of equally spaced openings or slits 72 on the inner side of end cap rim member 71. The gridded vanes 13 are now raised or projected upward from the top surface of rim ,71 due to circular ring 73. In this manner the rim 71 when mounted on the end of drift tube 12 will be spaced farther apart from the opposite rim on the opposing drift tube while the spatial relationship between opposing vanes 13' will be less.

It is noted that the type of member supporting the grid members would be a matter of choice. For example, in FIG. 5 a solid ring end cap member 71' supports the grid member 13 as by welding, the important feature being the grids raised above the rim.

An arrangement such as this has a considerable advantage. In the prior series of tubes the gap spacing between both the rim and the grid vanes has been 0.015 inch. In the present invention the gap spacing between grid vanes is the same, 0.015 inch, while the spacing between the rims has been increased to 0.035 inch. The result of this arrangement is that the capacitance between opposing rims is reduced greater than /2. Now, as the capacitance has been reduced, in order to maintain a constant frequency and at a fixed gap spacing it is necessary to increase the inductance within the cavity. This is accomplished by increasing the dimensions of the cavity which will increase the R Q and Q of each of the cavities resulting in a better overall Q for the entire tube output.

It is herein noted that there are several different con-' figurations of grid vanes 13 available which may be sub stituted for those shown. Reference is made to U.S. Patent 2,738,438 issued to G. S. Shepherd on March 13, 1956, for several other types of grid configurations available depending upon the beam interception desired.

What has been shown is a new klystron amplifier having no increase in weight or size over the previous light weight C.W. medium power level tubes yet an increase in gain has been accomplished due to increasing beam bunching by increasing the number of cavities within the tube structure. Further better power and gain have been accomplished through the use of a new grid structure.

It is here noted that the novel raised grid structure may be equally well adapted and used in other types of klystrons.

Since many changes could be made in the above construction, and many apparently widely different embodiments of this invention could be made Without departing from the scope thereof it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

What is claimed is: I

1. A high frequency electron tube apparatus including, means for forming and projecting a beam of electrons over an elongated beam path, means arranged along the beam path in energy exchanging relations-hip therewith,

said energy exchanging means including an electron pe-rmeable metallic grid structure, said grid structure including a plurality of metallic vanes projecting into said beam path, said vanes being of sheet-like geometry, a supporting rim structure surrounding the beam path for directly supporting said vanes directly connected thereto and with said vanes projecting into the beam from said support rim structure, and said vanes having a height where afiixed to said support rim structure substantially rising above said support rim structure in an axial direction to decrease the stray capacity of said support rim structure.

2. A high frequencyelectron tube apparatus including, means for forming and projecting a beam of electrons over an elongated beam path, means arranged along the beam path in energy exchanging relationship therewith, said energy exchanging means including an electron permeable metallic grid structure, said .g'rid structure including a plurality of metallic vanes projecting into said beam path, said vanes being of sheet-like geometry, a plurality of said vanes having an elongated main body portion projecting into the beam and a shorter base support portion vanes projecting radially inwardly of said beam path, said vanes terminating internally of the beam path, and said base portions of said vanes having a preponderance of their height rising above said support ring in an axial direction to reduce the stray capacity of said vane support ring.

3. High frequency electron tube apparatus including, means for forming and projecting a beam of electrons over an elongated beam path, a cavity resonator arranged along the beam path in energy exchanging relationship with the beam, said cavity resonator having a pair of mutually opposed electron permeable wall portions for passage of the electron beam through said cavity resonator, said electron permeable wall portions of said cavity resonator including a pair of mutually opposed grid structures, said grid structures including a plurality of metallic vanes projecting into said beam path, said vanes being of sheet-like geometry with a maximum :height taken in the direction of the beam path of at least five times their thickness and disposed with the plane of said sheet vanes being substantially parallel to the direction of the beam path, a support ring surrounding said beam path and said vanes for supporting said vanes directly and carrying said vanes such as to project radially inwardly of said beam path and said supporting ring, said vanes terminating internally of the beam path and said vane s having an axial preponderance of their maximum height rising above said support ring taken in a direction toward the opposing grid structure to reduce the stray capacity of said support ring.

4. The apparatus according to claim 3 wherein a plurality of said vanes have an elongated main body portion projecting into the beam and a shorter base support portion turned at a substantial angle to the main body portion for supporting said vane in position from said support ring.

5. A high frequency tube apparatus including, means for forming and projecting a beam of electrons over an elongated beam path, a cavity resonator positioned along the beam path for interaction with the beam passable therethrough, said cavity resonator having a pair of electron permeable wall portions axially spaced apart in the direction of the beam path for passage of the beam through said resonator, said pair of electron permeable wall portions being defined by a pair of metallic grid structures, each of said grid structures including a plurality of sheetlike vanes having central body portions projecting inwardly of the beam path from a support ring structure which surrounds root end portions of said vanes and directly supports said vanes, and said inwardly projecting central body portions of said vanes being mounted in a raised fashion in the axial direction from said surrounding support ring structure such that the axial spacing in the direction of the beam path between opposed central body portions of said grid structures is substantially less than the axial spacing between opposed surrounding support ring structures in order to reduce stray capacity of said sup port ring structures.

References Cited by the Examiner UNITED STATES PATENTS 2,463,519 3/1949 Cooke et al. 3l55.37 2,475,652 7/1949 Varian et a1 3155.37 X 2,750,531 6/1956 Sterling 3155.52 X

HERMAN KARL SAALBACH, Primary Examiner. GEORGE N. WESTBY, Examiner.

S. CHATMON, JR., Assistant Examiner.

Claims (1)

1. A HIGH FREQUENCY ELECTRON TUBE APPARATUS INCLUDING, MEANS FOR FORMING AND PROJECTING A BEAM OF ELECTRONS OVER AN ELONGATED BEAM PATH, MEANS ARRANGED ALONG THE BEAM PATH IN ENERGY EXCHANGING RELATIONSHIP THEREWITH, SAID ENERGY EXCHANGING MEANS INCLUDING AN ELECTRON PERMEABLE METALLIC GRID STRUCTURE, SAID GRID STRUCTURE INCLUDING A PLURALITY OF METALLIC VANES PROJECTING INTO SAID BEAM PATH, SAID VANES BEING OF SHEET-LIKE GEOMETRY, A SUPPORTING RIM STRUCTURE SURROUNDING THE BEAM PATH FOR DIRECTLY SUPPORTING SAID VANES DIRECTLY CONNECTED THERETO AND WITH SAID VANES PROJECTING INTO THE BEAM FROM SAID SUPPORT RIM STRUCTURE, AND SAID VANES HAVING A HEIGHT WHERE AFFIXED TO SAID SUPPORT RIM STRCUTURE SUBSTANTIALLY RISING ABOVE SAID SUPPORT RIM STRUCTURE IN AN AXIAL DIRECTION TO DECREASE THE STRAY CAPACITY OF SAID SUPPORT RIM STRUCTURE.

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