US3207942A - Cavity resonator structure for klystrons - Google Patents

Description

Sept. 21, 1965 F. L. SALISBURY CAVITY RESONATOR STRUCTURE FOR KLYSTRONS Original Filed May 2. 1960 'P/E. Z

IN VEN TOR. E'eMeWZ'CX L SZxZz'sZz/r) lay United States Patent 3,207,942 CAVITY RESONATOR STRUCTURE FGR KLYSTRQNS Frederick L. Salisbury, Los Altos, Calif, assignor to Varian Associates, Palo Alto, Calif., a corpnration of California Original application May 2, 1960, Ser. No. 26,249, new Patent No. 3,097,324, dated July 9, 1963. Divided and this application Apr. 24, 1963, Ser. No. 275,419 1 Claim. (Cl. 313-337) This application is a divisional of co-pending U.S. application Serial No. 26,249, by Frederick L. Salisbury, filed May 2, 1960, now titled, Cavity Resonator Structure for Klystrons, which has matured into US. Patent No. 3,097,324.

This invention relates in general to high frequency electron emissive devices and method of making same.

In electron discharge devices such as klystron tubes which have had a central body portion with an axial bore therein subdivided longitudinally by a plurality of cavity resonator partitions in the form of headers supporting drift tubes, the headers have been brazed at precise locations within the bore to provide specific gap spacings between the drift tubes supported by the headers. In the past, these headers were tightly held on shoulders within the bore of the tube prior to brazing, or in some instances spacers were provided in the gaps between adjacent drift tubes. In the latter case these spacers, of course, had to be removed from the tube after the brazing operation had taken place. These prior art assembly methods depended upon maintaining close tolerances in forming the bore and the headers so that the headers could be slideably positioned within the bore and held in axial alignment until the brazing operation could be completed.

Furthermore, in tubes of this nature it is necessary to provide an accurately aligned longitudinally positioned cathode assembly for producing the electron beam that is to pass through the tube. odes be easily assembled and accurately adjusted for the desired cathode-anode spacing regardless of discrepancies in the size of other parts of the tube. In many previous tubes the entire cathode assembly was assembled in one operation whereby allowances for variations in the dimensions of the tube could not readily be made.

The object of the present invention is to provide a novel electron discharge device and method for making the same whereby a rugged tube can be more easily and economically produced while keeping within close tolerances.

One feature of the present invention is the provision of a novel electron discharge device constructed from a bare minimum of separate components assembled in a rugged unitary device capable of meeting rigid requirements for reproducing specific electrical requirements in spite of mechanical variations in certain portions of the tube.

Another feature of the present invention is the provision of a novel cathode assembly including a stem-heater assembly and a cathode-electrode assembly which can be slideably adjusted and then fixed together to provide the desired cathode-anode spacing thereby compensating for any changes in the sizes or positions of other members of the tube.

Still another feature of the present invention is the provision of a novel method for forming the cathode assembly of an electron discharge device including the steps of forming a stem assembly with the heater filament thereon, forming a cathode and focus electrode assembly, slideably positioning the cathode-electrode assembly on the stem assembly for the desired cathode-anode spacing for the device, fixedly securing the cathode-electrode assembly to the stem assembly and mounting the stem assembly on the end of the device.

It is desirable that these cath-' 3,207,942 Patented Sept. 21, 1965 Other features and advantages of the present invention will become more apparent on a perusal of the following specification taken in connection with accompanying drawings wherein:

FIG. 1 is a longitudinal cross-section view, partially in elevation, of a klystron tube utilizing the features of the present invention,

FIG. 2 is an enlarged side cross-section view of the stem-heater assembly and the cathode-electrode assembly of the klystron tube shown in FIG. 1 and showing in phantom the manner in which these assemblies are put together,

FIG. 3 is a side cross-section view of the main body portion of a klystron tube showing the novel manner in which the annular headers are positioned within the bore of the main body portion,

FIG. 4 is a side cross-section view of a portion of the body of an electron discharge device utilizing the features of the present invention, and

FIG. 5 is a side cross-section view of a portion of the body of another electron discharge device utilizing features of the present invention.

Referring now to FIGS. 1 through 3 of the drawing, a klystron tube utilizing features of the present invention includes a central body portion 11 which is made from a unitary metallic block having a multidiarneter longitudinal bore 12 extending therethrough. A metallic hollow cylindrical drift tube 13 of a material with a relatively low coefficient of expansion such as steel and having circular resonator grids 14 and 15 on the ends thereof is positioned within the longitudinal bore 12 by an outwardly extending annular header 16. The Walls of the drift tube 13 are parallel to the axis of the electron beam passing through the central body portion 11 of the tube. Fixedly secured, as by brazing, within one end of the longitudinal bore 12 of the central body portion 11 having an enlarged diameter is an annular anode structure 17 as of, for example, copper having a resonator grid 18 positioned in the aperture therethrough, and within the other end of the central body portion 11 is an annular header 19 as of, for example, copper and with a resonator grid 20 positioned in the aperture therethrough. Within the central body portion 11, the annular anode structure 17 and the annular header 16 on the drift tube 13 serve as resonator partitions and define a re-entrant first cavity resonator 21; the header 16 on the drift tube 13 and the header 19 serve as resonator partitions and define a reentrant second cavity resonator 22. The header 16 on the drift tube 13 is provided with an aperture 23 therethrough for coupling the first and second cavity resonators 21 and 22 together. A milled opening 24 in the side wall of the central body portion 11 provides access to the second cavity resonator 22 for coupling oscillatory energy out of the tube.

The drift tube 13 which is made of a metal with a relatively low coeflicient of expansion prevents the gaps between the grids 14 and 18 and grids 15 and 20 from changing an appreciable amount when the klystron tube heats up.

The anode structure 17 and the headers 16 and 19 are positioned within the bore 12 of central body portion 11 by first providing raised portions such as knurls 25a, 25b and 250 respectively (see FIG. 3), encircling the wall of the bore 12 of central body portion 11 at the positions at which these members are to be fixed. The surface sur rounding the bore 12 of the central body portion 11 is then copper plated. The annular header 16 which is of smaller diameter then that portion of the bore 12 at which the anode structure 17 is positioned is pressed into place on its knurl 25b through the anode end of the central body portion 11 clearing the knurl 25a. Then the anode structure 17 is pressed into place on its knurl 25a a and the header 19 is pressed into position on its knurl 250 at the other end of the tube. In this manner the headers which constitute the cavity resonator partitions can be accurately positioned within the longitudinal bore and held therein until they can be more tightly secured to the tube body, as by brazing, if that is desired. The assembled central body portion may then be placed in a brazing oven to fixedly secure the members in place within the longitudinal bore 12, as by, for example, the use of rings of brazing material positioned around the edges of the partitions at the time of insertion of the partitions into the body.

The raised portions may be provided by knurling or embossing the surface surrounding the bore 12 so long as the surface is raised up into the bore such as a ridge or a series of ridges, a straight knurl or a diamond knurl, etc. Hereafter, in the specification and claims the word knurl will be used to indicate any such raised portion.

Although this method of assembly is illustrated as applied to a tube with only two cavity resonators it can be seen that this feature of the present invention can be used to assemble a tube with any number of cavity resonators (see FIG. 4). In a tube with, for example, five successive cavity resonators A, B, C, D and E formed by successive resonator partitions a, b, c, d, e and f, the longitudinal bore is provided with a stepped diameter, the narrowest portion of the surface surrounding the bore being substantially midway thereof and forming the circumferential wall for cavity resonators B, C and D. The diameter of the surface surrounding the bore is stepped outwardly in two places toward each end thereof to form the circumferential wall for cavity resonator A at one end of the bore and cavity resonator E at the opposite end of the bore. Knurls are provided at the desired locations for the resonator partitions a, b, c, d, e and f, and then partitions a, b and c are slideably inserted into their proper positions from one end of the bore and partitions d, e and f are slidably inserted into their proper position from the other end of the bore. Because of the stepped diameter of the bore each partition is of such a diameter as to clear all the knurls for larger diameter partitions. To facilitate construction of the tube equal steps in the diameter of the bore are used toward each end thereof, and these steps are provided at the desired location for the inner edge of a partition so that certain partitions are accurately positioned within the bore by being pressed against the steps in the diameter of the bore.

Referring to FIG. 5 as an alternative embodiment of this present invention a tube with any number of cavity resonators can be assembled by positioning cavity resonator partitions on knurls within a bore of uniform diameter. Successive cavity resonators A, B, C and D are formed along the length of the bore by successive partitions a, b, c, d and e. A knurl is provided on the surface of the bore adjacent the midportion thereof and the resonator partition c is slideably inserted into one end of the bore and positioned on this knurl. The knurls for walls b and d are then formed and associated walls b' and d then inserted thereon after which two additional knurls are formed and associated walls a and e secured thereon. In this embodiment of the present invention the knurls could be properly spaced along the length of the bore by placing a guide extension on the end of the knurling tool so that each successive knurl will be made at a desired distance from an existing partition within the bore. Obviously the two central-most partitions could be inserted into the bore and onto knurls at the same time from opposite ends of the bore. It should be noted that the knurls on the wall of the bore need not extend in a complete closed circle around the bore to perform their functions but may, for example, include two or more segments of a circle.

Fixedly secured, as by brazing, within an annular flange 26 on the end of the central body portion 11 adjacent the anode structure 17 is hollow cylinder 27 which supports a beam generating assembly 28. In order to assure proper alignment and spacing of the beam generating assembly 28, it is constructed from two sub-assemblies, a stemheater assembly 29 and a cathode-electrode assembly 31.

In the stem-heater assembly 29 an insulator disc 32 such as ceramic forms the end of the tube and is provided with an annular projection 33 projecting axially into the tube and covered with a disc-shaped sputter shield 34 which is dished to project into the space surrounded by the annular projection 33. Mounted on the sputter shield 34 is an open-ended, cup-shaped heat shield 35. Heater and cathode leads 36 project through and are sealed within apertures in the insulator disc 32 by means of brazing washers 37, and the leads 36 pass through apertures in the sputter shield 34. One end of an openended, cup'shaped stem assembly support member 38 is fixedly secured to the side of the disc 32 facing into the tube outside the annular projection 33, and the other end is adapted to support the stem-heater assembly 29 from the end of the hollow cylinder 27. All the parts of this stem-heater assembly 29 are held together in a jig and simultaneously brazed together in the brazing furnace.

Connecting tabs 39 are added connecting two of the leads 36 to the heat shield 35 thereby providing electrical connection to the cathode-electrode assembly 31 to be mounted on the stem-heater assembly 29. A spiral heater filament 40 projecting axially into the tube within the heat shield 35 is then connected to the remaining lead 36.

The cathode-electrode assembly 31 includes cathode button 41 connected, as by spot welding, to an annular flange on one end of a hollow heater housing support cylinder 42. The other end of the support cylinder 42 is axially supported within a hollow cylindrical support sleeve 43 by means of an annular sleeve adapter 44. The support cylinder 42, the support sleeve 43 and the sleeve adapter 44 are held in a jig and brazed together in a brazing furnace. An open-ended, cup-shaped focus electrode 45 with a stepped diameter fits within and is supported at the step in its diameter on the forward end of the support sleeve 43.

The critical adjustments in the beam generating assembly 28 are axially positioning the cathode button 41 with respect to the central body portion 11 to form a beam that will pass through the entire tube and achieving the proper distance from the cathode button 41 to the anode structure 17 to properly form the beam and to pass as much of the beam as possible through the anode structure 17.

The cathode-electrode assembly 31 is connected to the stem-heater assembly 29 by sliding the heater housing support cylinder 42 over the heater filament 40 and sliding the support sleeve 43 within the heat shield 35. In this manner, the heater filament 40 is positioned behind the cathode button 41 for initiating thermionic emission, and the cathode-electrode assembly is positioned axially of the stem-heater assembly 29. With the stern assembly support member 38 positioned within an annular flange 47 on the end of the hollow cylinder 27 the entire beam generating assembly 28 will be positioned axially with respect to the central body portion 11.

To position the cathode button 41 the proper distance from the anode structure 17 before mounting the cathodeelectrode assembly 31 on the stem-heater assembly 29, the distance between the tip of the anode structure 17 and the annular flange 47 on which the stem heater assembly will be supported is first measured. While mounting the cathode-electrode assembly 31 on the stemheater assembly 29 these assemblies are moved axially with respect to one another so that the difference between the distance from the forwardmost portion of the stem-heater assembly support member 38 to the cathode button 41 and the first distance measured will provide the proper space between the cathode button 41 and the anode structure 17. Then, the heat shield 35 and the support sleeve 43 are fixedly secured together, as by spot-welding, thereby connecting the stem-heater assembly and the cathode-electrode assembly 31. This connection can be more rigidly fixed, as by silver brazing, to make the tube more rugged.

As an additional feature in the beam generating assembly 28, as shown in phantom in FIG. 1 the support sleeve 43 can be divided into two portions insulated from one another by in insulator ring 48 such as alumina ceramic whereby the focus electrode 45 can be provided with a positive or negative bias with respect to the cathode button 41 by means of an additional lead (not shown).

For mass production of tubes utilizing the beam generating assembly illustrated here the stem-heater assembly 29 and the cathode-electrode assembly 31 for every tube could be connected together with a standard distance between the forwardmost end of the stem assembly support member 38 and the cathode button 41. Then a spacer ring of selected thickness could be provided between the forwardmost portion of the stem assembly support member 38 and the annular flange 47 on the hollow cylinder 27 to compensate for variations in the distance between the annular flanges 47 and the tip of the anode structure 17 on individual tubes.

A tab 49 is attached to the outside wall of the central body portion 11 for electrically grounding the tube body.

A collector assembly 50 including an annular adapter 51 of non-magnetic material such as steel connected to one end of a hollow cylindrical collector 52 such as copper provided with radially outwardly extending cool ing fins 53 is fixedly secured to the end of the central body portion 11 adjacent the header 19 such as by a braze between the adapter 51 and the central body portion 11. An annular protective fin 54 of a hard material such as steel is fixedly secured to the other end of the collector 52 to protect the other fins 53 from being bent out of shape due to rough handling of the tube. An exhaust tubulation 55 closes off the outward extending end of the collector 52 and is provided therewithin with a milled baffle 56 which provides gas access between the tube and the tip of the exhaust tubulation 55 but prevents direct bombardment of the tip of the tubulation 55 by electrons traveling axially down the tube. Since the annular adapter 51 is made of non-magnetic material the col lector assembly 50 is magnetically shielded from the remainder of the tube to prevent focusing of the electron beam within the collector assembly 50.

A waveguiding recess 57 is milled into the central body portion 11 surrounding the milled opening 24, and within this recess 57 a wave permeable window 58 such as alumina ceramic is supported in a cup-shaped window frame 59 vacuum-sealed to the external surface of the central body portion 11 within the recess 57. A waveguide output flange 60 surrounds the recess 57 for coupling the tube to other microwave components.

Each of the cavity resonators 21 and 22 is tuned by an identical tuning assembly 62 contained in a tuner mounting block 63 supported on the side of the central body portion 11 opposite from the wave permeable window 58. A milled opening 64 is provided in the central body portion 11 into each cavity resonator, and then both cavity resonators are sealed closed by a flexible tuner diaphragm 65 which is held between the central body portion 11 and the tuner mounting block 63. For each cavity resonator a cylindrical tuner rod 66 is slideably mounted within a cylindrical bore in the mounting block 63, one end of the tuner rod 66 being fixedly secured to the tuner diaphragm 65 for moving the tuner diaphragm in and out to tune the cavity resonator. Each tuner rod 66 is provided with a transverse slot 67 thereacross, and the mounting block 63 is provided with a large cylindrical aperture 68 communicating with the bore which houses the tuner rod 66, the axis of the aperture 68 being substantially perpendicular to the axis of the tuner rod 67 and providing access to the transverse slot 67 in the tuner rod 66. A tuner tool which lideably fits within the aperture 68 and is provided with an eccentric projection on the end thereof adapted to fit within the transverse slot 67 can be used to tune each cavity resonator whereby when the tuner tool is engaged in the aperture 68, rotation of the tool will move the tuner rods 66 in and out to tune the cavities. A set screw (not shown) is provided on the opposite side of the mounting block 63 from the aperture 68 for locking the tuner rod 66 when the cavity resonators have been properly tuned.

The construction of the central body portion with the cavity resonator partitions and the beam generating assembly and the methods of assembling these portions of the tube would be equally applicable to electron discharge devices other than klystron tubes and utilizing a plurality of cavity resonators such as, for example, traveling wave tubes and linear accellerators using disc loaded waveguide.

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

What is claimed is:

An electron discharge device comprising a stem-heater assembly which includes an insulator disc adapted to close one end of the device, a cup-shaped heat shield supported axially on the inner face of said insulator disc, heater means supported axially within said heat shield and an axially aligned stem assembly support member positioned on said insulator disc surrounding said heat shield and a cathode-electrode assembly including a hollow, cylindrical support sleeve, an annular disc-shaped sleeve adaptor having an aperture therein and fixedly positioned within said support sleeve, a hollow cylindrical heater housing positioned within the aperture through said sleeve adaptor, a cathode button positioned on the end of said heater housing and an open-ended, cup-shaped focus electrode positioned on the end of said support sleeve in front of said cathode button, said support sleeve of said cathode-electrode assembly being fixedly secured within said heat shield of said stem-heater assembly whereby the distance between cathode button and the end at which the stem-heater assembly support member is supported on the electron discharge device will leave the desired distance between the cathode button and the anode structure of the electron discharge device when the stemheater assembly is fixedly secured to the end of the electron discharge device.

References Cited by the Examiner UNITED STATES PATENTS 2,018,071 10/35 Kuhle et a1 315-39 2,456,861 12/48 Carter 315-5 2,644,907 7/53 Drieschrnan et al. 313-249 2,655,614 10/53 Doolittle et a1 3 13-249 2,965,794 12/60 Gardner et al. 315-5 JOHN W. HUCKERT, Primary Examiner.

DAVID J. GALVIN, Examiner.

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