US2789248A - Electron discharge device - Google Patents

Description

April 16, 1957 2,789,248

J. A. BROWN ELECTRON DISCHARGE DEVICE Filed July 7, 1954 2 Sheets-Sheet 1 'Ilz-IIE.; l.

INVENTOR.

April 16, 1957 J. A. BROWN ELECTRON DISCHARGE DEVICE 2 Sheets-Sheet 2 Filed July 7, 1954 JUc/B/"awn I INVENTOR.

States ELECTRGN DISCHARGE DEVICE Application .uly 7, 1954, Serial No. 441,897

9 Cranes. (C1. 315-5) This invention relates in general to electron discharge devices and, more particularly, to such devices of the klystron class.

In order to meet the requirements for operation at increasingly higher radio frequencies, klystron tubes of decreasingly smaller structure are being constructed. As the frequencies increase, the size of the klystron cavity resonators decreases as do the other associated elements of the device. As these devices decrease in size, the problem of maintaining close tolerances of the critical elements becomes extremely acute. A minute variation in size or dimension of certain elements when working with such small devices will result in appreciable variation in operating characteristics from tube to tube and, therefore, tolerances must be maintained. For example, in K band klystrons in the frequency range of 30,000 megacycles, the tolerances of the critical elements such as the cavity resonator must be maintained to as close as .0002 inch or ner. Also, because of the extremely small dimensions of the cavity resonators, minute changes in critical dimensions during tuning, such as, for example, a minute change in the resonator gap spacing, results in an appreciable change in the operating frequency of the klystron. Therefore, if conventional heretofore known structures for mechanically tuning lthe klystron are utilized, one of which embodies the use of threaded struts and adjusting nuts, slight movement or slippage of the mechanical tuner wl result in an undesirably large change in operating characteristics.

lt is an object of the present invention to provide a klystron of improved construction wherein the elements are so fabricated and assembled that close tolerances are maintained and wherein the mechanical tuning arrangement is so constructed that relatively large movements of the tuning mechanism will result in small movements of the tube elements being tuned.

One feature of the present invention is the provision of a novel improved klystron construction wherein the ,cavity resonator is so constructed in the form of a stamped cup that very close tolerances may be maintained in the manufacture of the klystrons.

Another feature of the present invention is the provision of a novel klystron construction wherein one of the strong rigid tuning plates utilized in mechanically tuning the klystron has the output waveguide portion extending therethrough from an opening in the resonator cup.

Another feature of the present invention is the novel mechanical tuning structure wherein isosceles triangular shaped tuning plates having three angularly spaced tuning screws providing a three point tuning support are so adapted that relative movement of the plates by turning the screw at 'the smaller angle corner while pivoting on the screws at the other two equiangular corners results in a greatly reduced tuning movement at the resonator gap.

These and other features and advantages will become apparent from a perusal of the following specification taken in connection with the accompanying drawings wherein Fig. l is a longitudinal view partly in section of a klystron tube which embodies the present invention,

Fig. 2 is a part sectional view of the klystron of Fig. l taken along the section line 2-2, and l Fig. 3 is an exploded view of the resonator cavity construction of the klystron of Figs. 1 and 2.

Referring now to the drawings, there is shown a reex klystron which embodies the present invention. This klystron comprises a cylindrical metallic cathode shell 1 having an axially aligned bore therein. Secured over one open end of the shell 1 is a hollow cylindrical adapter sleeve 2 in which is securely mounted a cathode gun assembly 3 having a cathode button 4, filament heater 5 and focusing electrode 6. Mounted over the inner open end of the shell 1 is an annular shaped anode plate 8 having a centrally disposed, slightly raised bearing surface 9 and a protruding re-entrant tube portion 11. A resonator grid 10 is secured on the end of the re-entrant or drift tube portion 11 in axial alignment with the bore therethrough. Securely affixed as by brazing around the outer surface of the shell 1 is a tuning plate 12 which is in the shape of an isosceles triangle, the two equal sides being the longer sides. The large bore in the plate 12 into which the shell 1 is fitted is positioned off-center in the plate, the axis of the bore being equally spaced from the two longer sides of the plate and being spaced closer to the remaining short side. Three tuning-strut bores are located in the plate 12, the bores being positioned in the three corners of the plate providing a three point tuning support.

A hollow cylindrical body portion of steel 13 having a multi-stepped bore therein is provided with a rectangularshaped cavity or recess 14 extending through its side wall. A hollow cylindrical sleeve 15 is brazed within the smaller diameter bore section of the body portion 13. An annular header or plate 16 is mounted within this bore against the lower end of the sleeve. The central opening in the header has a resonator grid 17 mounted thereover axially aligned in the body. A cup-shaped resonator cavity portion 18 is brazed within the smaller diameter bore in body portion 13, the upper edge of the cup pressing against the underside of the header 16. The cup 18 has an output window cut in the side thereof which is aligned with the waveguide opening 14 in the body portion 13 and a small, centrally positioned hole in the bottom surface. The reentrant tube portion 11 extends through the hole in the cup into the resonator cavity, the bearing surface 9 of the anode plate 8 engaging the under-surface of the cup 18, surface and cup 18 being brazed together to form a vacuum tight seal. At this point of contact a small amount of exing of this klystron may be produced for tuning purposes.

A reector assembly including a reflector electrode 21, reector post 22, terminal 23, end cup 24 and glass seal 25 is brazed within the outer end of the body portion 13, the reflector electrode 21 extending within the sleeve 15 spaced apart from the resonator grid 17. A tuning plate 26 in the form of an isosceles triangle encircles and is brazed to the body portion 13, this plate 26 having a rectangular-shaped waveguide opening extending through one side in alignment with the opening 14 in the body portion 13. A waveguide flange 27 is brazed to this side of the plate, the mica sealed window opening of the flange coinciding with the waveguide opening in the plate 26 and body 13. The plate 26 has three threaded bores extending therethrough which are in alignment with the three bores in the lower tuning plate 12. Three threaded anguiarly spaced tuning struts, 28, 29 and 31 providing a three point tuning support are threaded through the three bores in the plate 26 and also extend down through the holes in the lower tuning plate 12. Lock nuts 32 are provided for locking the plates in position mer initially rough tuning theklystron b y rotation of the lower two nuts on each Vfrom the strut Si tothe plane.

Vof the three struts whereby the gap spacing between the nator in the klystron, very close tolerances are obtainable in the production of these klystron tubes.

The novel construction of this reflex klystron provides that minute changes in resonator gap spacing may be produced for ne tuning the klystron, these changes in gap Y Vspacing being produced by relatively larger distances of Ymovement atthe tuning strut. Fine tuning of this reex klystron is best accomplished by rotation of the lower two nuts on tuning strut 31, struts 23 and 29 remaining untouched.l rhe tuning plates 12 and 26 are pivoted in a plane which runs longitudinally through the struts 2S `and V2,9. Thus the plates 12 and 26 do not appreciably change their relative spacing in this region between the struts 23 and 29, the largest change in spacing occurring at strut 31 and decreasing in a tapering manner from the region of strut 3l to the region of struts 28 and 29. Since the axis of the lilystron is off-center in the tuning plates, the distance from the resonator gap to the plane through struts 28 and 29 is much less than the distance The ratio of these distances in this particular embodiment is about l to 4. Thus tuning movements at strut 3i will result in proportionally smaller movements at the resonator gap. The advantage of such a reduction in mechanical movement can be better realized when it is noted that in one preferred embodiment the normal gap spacing is only .010 inches and even an unnoticeable change in spacing would result in a change in the operating frequency of this klystron.

The triangular shape ot' tuning plate and three point Ytuning support also results in a more rigid balanced construction which resists distortion or bending of the klysvtron during use.

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 theY accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

l. In a reflex klystron comprising a vacuum envelope having therein a cathode means adapted to produce a beam of electrons and a reiiector electrode adapted to repel said beam, a cavity resonator structure positioned between the cathode means and the reflector for interaction with the beam, an anode having a protruding reentrant tube portion, -a resonator cup having Va bore in the bottom thereof, said cup having the re-entrant tube portion of said anode extending through the bore into the cup, a first resonator grid mounted on the end of the re-entrant tube portion, and an annular resonator grid header mounted over the end of the resonator cup, the resonator header having `a second resonator grid mounted over the central opening therein spaced from the iirst resonator grid.

2. In an evacuated retiex klystron comprising a vacuum envelope having a cathode means therein adapted to produce a beam of electrons therein yand a reiector electrode Yadapted to repel said beam, ananode plate forming a face and a protruding re-entrant tube portion both centrally disposed on the plate and having an axial bore extending therethrough, a resonator cup having a bore in the bottom thereof, said cup resting on and being vacuum sealed to the bearing surface with the re-entrant tube portion extending -through the bore into the cup, a first resonator grid mounted on the end of the re-entrant tube portion,V and an annular resonator grid header mounted over the end of the resonator cup, the resonator header having a second resonator grid mounted over the central opening therein spaced from the rst resonator grid.

3.Y ln a reex itlystron comprising a vacuum envelope having a cathode means therein adapted to produce a beam of electrons and a reector electrode adapted to repel said beam, a hollow cylindrical cathode shell having an Vanche plate over one end thereof, the plate having a centrai disposed raised bearing surface and a protruding ire-entrant tube portion extending from the surface of the plate, the plate and re-entrant tube having an axially aligned bore extending therethrough, a rst resonator grid secured over the end of the re-entrant tube portion, a cylindrical body portion having an axial'bore therein, a resonator cup having a bore in the bottom thereof, the cup resting on the bearing surface with the re-.entrant tube portion extending through the bore into the cup, an annular resonator grid header fitted over the resonator cup, the resonator header having a second resonator grid secured over the central opening therein, the two resonator grids having a gap therebetween, and a window opening extending through the resonator cup wall and the cylindrical body portion.

4. A reex klystron as claimed -in claim 3 including a tuning plate mounted on and encircling the body portion, the tuning plate having a waveguide opening therein aligned with the -window opening in the resonator cup wall and body portion.

5. A reiiex klystron `as claimed in claim 4 including a waveguide flange having an opening therein mounted on the tuning plate with the opening aligned with the waveguide opening in the plate.

6. A reflex klystron including a body portion, forming a part of the vacuum envelope having cathode means therein adapted to produce ya beam of electrons, a reflector electrode adapted to repel said beam, a resonator cup mounted within the portion between said cathode means and said reflector electrode for electromagnetic interaction with the electron beam, a tuning plate encircling the body portion and la waveguide flange mounted on the tuning plate, the wall of the resonator cup, body portion and tuning plate and the waveguide flange all having aligned openings extending therethrough for the extraction of wave energy from the cavity resonator, and a wave energy permeable material vacuum sealed over the waveguide ange opening.

7. ln a reiiex klystron including a vacuum envelope having a cathode means therein adapted to produce a beamof electrons and la reector electrode adapted to repel said beam, a cylindrical body portion having an axially aligned bore therein, a yhollow cylindrical sleeve secured in the bore of the body portion in axial alignment between said cathode means and said reflector electrode, a resonator cup mounted in said bore with'the cavity in the cup facing said sleeve, an annular resonator grid header in said bore between the sleeve and `the cup, the header having a Yiirst resonator grid mounted over the central opening therein, the cup having a bore in the bottom surface thereof, an anode plate having a raised bearing surface and a protruding re-entrant tube portion both centrally disposed on the plate and having an axial bore therethrough, the re-entrant tube portion extending through the borey in the cup with the bottom of the cup contacting the bearing surface on the anode plate.

8. In a klystron including a vacuum envelope having cathode means therein forrproducing a beam of electrons and a cavity resonator positioned in the beam path for electromagnetic interaction with the electron beam, first and second substantially cylindrical body Vportions adapted for rela-tive motion therebetween in an axial direction for tuning purpose, one of said body portions having the cavity resonator secured therein, rst and adjacent the apex of the isosceles triangles providing an extremey ne tuning adjustment of said klystron.

9. A klystron as claimed in claim 8 wherein said cavity resonator within said one body portion has a Window opening therein aligned with openings in said body portion and the associated encircling tuning plate.

No references cited.

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