US2856556A - Electron discharge device - Google Patents

Description

I Oct. 14, 1958 T. D. FENTRESS ELECTRON DISCHARGE DEVICE Filed Oct. 21, 1954 Ir JV! INVENTOR. THOMAS Q ILE/VTR ATTORNEY United States Patent ELECTRON DISCHARGE DEVICE Thomas D. Fentress, Shrewsbury, N. 1., assignor to Bendix Aviation Corporation, Eatontown, N. J., a corpo ration of Delaware Application October 21, 1954, Serial No. 463,655

2 Claims. (Cl. SIS-5.22)

The present invention relates to high frequency structure and more particularly to electron discharge devices embodying such structure.

In certain applications for electron discharge devices, such for example as a klystron, it is required that the device be capable of operating from a cold start with a minimum shift in frequency from the start to that of operation after a predetermined time.

One factor that aifects frequency in electron discharge devices that utilize resonant cavities is the spacing between the cavity grids. Heretofore, the structure supporting the grid has been of a material having relative high heat conductance in order to conduct heat away from the grid and supporting structure. Such material inherently has a high thermal coefiicient of expansion. Hence, during the warm up period, the heat, created by electron bombardment causes expansion of the supporting structure which changes the spacing between the grids, thereby changing the operating frequency of the device.

The present invention provides means for overcoming the aforenoted problem. A supporting member is provided that is made of a material having a low temperature coefiicient of expansion, such for example as Invar. In order to overcome the disadvantage of the low heat conductivity of the material, the support is provided with a heavy copper plating in order to provide a high thermal conductivity path from the grid to the wall of the device.

It is an object of the invention to provide an improved electron discharge device.

Another object of the invention is to provide a novel high frequency structure.

Another object of the invention is to provide novel means for preventing frequency shift with changes in temperature in an electron discharge device.

Another object of the invention is to provide a novel stabilized electron discharge device.

The above and other objects and features of the invention will appear more fully hereinafter from a con sideration of the following description taken in conjunction with the accompanying drawing wherein one embodiment of the invention is illustrated by way of example.

In the drawing:

The single figure is a cutaway view of an electron discharge device embodying the invention.

Reference is now made to the drawing wherein an electron discharge device is indicated generally by the numeral 1, which may, for purposes of illustration, be a klystron of the reflex type. Only that portion of the device embodying the invention will be described in 2 detail. The device 1 has an envelope 2 inclosing acavity 3. The cavity 3 has a side wall 4, top wall 5 and bottom wall 6. The top wall 5 has a grid 7 supported by a flexible diaphragm 8. The diaphragm 8 may be connected to suitable tuning apparatus (not shown) for tuning the device 1 over a range of frequencies. It is understood, however, that the grid 7 may be fixed and not tunable over a range of frequencies.

The bottom wall 6 is of a substantially inverted cup shaped configuration and carries a grid 9 arranged concentric with the grid 7. The wall 6 comprises a base 10 of a material having a low thermal coefiicient of expansion, such for example as Invar. The base 10 has a heavily plated skin 11 of a material having high thermal conductivity, such for example as copper.

The cavity 3 may be excited by an electron gun 12 of a suitable type. t

In operation the Wall 6 supporting the grid 9 is heated by electron beams. Heretofore, this heating would cause the structure to expand thereby changing the spacing between the grids '7 and 9. With the wall of a material having a low thermal coefficient of expansion, as long as the temperature is held within the thermal limits of the material, there will be a minimum change in spacing with changes in temperature. The heavy plated skin 11 provides a path of high thermal conductivity from the grid support to the envelope 1, thus reducing the internal temperature of the structure.

Although only one embodiment of the invention has been illustrated and described, various changes in the form and relative arrangement of the parts may be made to suit requirements.

What is claimed is:

1. An electron discharge device having a resonant cavity, a pair of grids forming a gap therein, one of said grids being movable for tuning said cavity, a fixed support for the other of said grids, an envelope for enclosing said cavity said fixed support being of a material having a low thermal coefficient of expansion and having a covering in good heat exchange relationship therewith of a material having high thermal conductivity and extending from said fixed grid to said envelope to provide a thermal path from said support to said envelope.

2. A reflex klystron comprising an envelope inclosing a resonant cavity, a movable grid, a fixed grid, means for mounting said movable grid in one wall of said cavity, means for mounting said fixed grid in an opposite wall of said cavity, said last means being constructed of a material having a low thermal coefiicient of expansion and having a heavy plating of copper thereon extending from said fixed grid to said envelope to provide a thermal path from said fixed grid to said envelope.

References Cited in the file of this patent UNITED STATES PATENTS 2,337,214 Tunick Dec. 21, 1943 2,374,810 Fremlin May 1, 1945 2,418,844 Le Van Apr. 15, 1947 2,468,141 True Apr. 26, 1949 2,503,266 Harrison et al. Apr. 11, 1950 2,508,141 Broadway et al. May 16, 1950 2,513,371 Shepherd July 4, 1950 2,523,031 Laflt'erty Sept. 19, 1950

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