US2845571A - Electrostatically focused traveling wave tube - Google Patents

Description

129. .1 58 Btmzm 2,845,571

. ELEGTROSTATICALLY FOCUSED TRAVELING WAVE "TUBE Filed April 17. 1953 b 5?:I:22111211112117.1222:1112211222211 G@EEBFBBQBBB -mmmu-armmb- FIG. I

FIG. 3

INVENTOR.

BENJAMIN KAZAN 4H0 ray different potential. are formed acting toconcentrate the electron beam;

the invention Will be described in p V I Patented July 29, 19 58 1 A i i a invention may, however, have application in'a wide vari- 2.s4s,57.1 ety of fields. I

' HELECTROSTATICALLY FOCUSED TRAVELING WAVE TUBE Benjamin K'aian, Princeton, N. J., assignor to the United States of America as represented by the Secretary of the Army (Granted underTitle 35, U. S..Cde 1952 sec. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment, of any royalty thereon.

This invention relates to that type of'radio frequency amplifier known as a traveling wave tube in which the amplifying ability of the tube results from the transfer of'power to the traveling wave from an electron beam and the invention is particularly directed to a manner of forming the electron beam. 7 V

In tubes of the type suggested a special problem arises in providing an electron'be'am which will remain under control for the purpose intended throughout the relatively long path of travel of the electrons. It has been common practice to provide an electromagnetic field to control the beam. Such a field is created by an elongated hollow cylindrical coil of a length to embrace 'thelengtli of the beam and Within'which the tube itself is received. This construction is of necessity relatively large an'd'heavy and is very wasteful of power which must be supplied to the coil.

metallic electrodes arranged in' alignment and having aligned apertures through which the'ielect-ron beam is axially directedand dielectric rings between the metal rings. 1 a

In operation direct current potentials are; applied to the metallic electrodes in a pattern to suit the particular requirements of a'given application. A desirable arrangement would be to divide the metallic members into groups in su'cha way-that successive electrodes have'a Thus a series ofelectrostatic lenses Preferred forms of detail hereinafter. I

Itis a primary object ofthe invention to provide'a simplified and more efiicient traveling wave tube.

A further objectof the invention is toprovide a traveling wave tube having an electron beam focusing means characterized by great versatility-of control and particularly by its ability to control subdivided portions, thereof.

A further object of the invention is to provideina traveling wave tube an electron beamv focusing device which requires only a minimum of'power-forits operation. a I Other objects and features of the invention will more fully appear fromthe following description taken in connection with the. accompanying drawings in which Fig. 1 is a diagrammatic illustration of a -preferred embodiment of'the invention.

Fig. 2 illustrates a modified formof the invention. Fig. 3 is a cross-sectional view taken on line 3-3 F g.1. v The invention will be described in connectionwith a traveling wave amplifier tube. The ,principlesjoffthe The elements (of the invention are inclosed within an evacuated envelope 4. The beam of electronsmay be supplied in any suitable manner such as by a conventional electron gun having a cathode 5, an accelerator anode 6 and a collector 7.. The gun issupplied with suitable power from sources not shown.

To provide efiicient operation of the device the electron beam must be kept under the influence of a concentrating or focusing element. The present invention provides such. an element which possesses qualities which are novel and which contribute to the overall operating efliciency and versatility. of the device.

In place of the usual electromagnetic coil, the focusing device is constructed to function upon theelectrostatic principle and is composed of a plurality of electrodes 8 spaced apart and arranged symmetrically with respect to'the axis of the electron beam. The discs are held in place by spacing rings 9 of dielectric material situated between the adjacent electrodes 8. I The succession of metallic electrodes8 arranged as they are provides an ideal means for controlling the dispersion of the beam since it is possible not only'to apply any desired potential to each one but it is also possible to provide diiferent potentials to successive individual electrodes or groups of electrodes.

In the drawings a suggested arrangement is tov interconnect every other electrode to a common .lead wire 10' and, the remaining groups of electrodes to a separate common lead Wire 11. The voltage applied to each group may be so chosen that in elfect' the successive groups of electrodes constitute a series of electroniclenses of the required strength to confine the electrons to..a path along the tube axis.

Along with the above arrangement of electrostatic lenses other matters must'be considered. It Will he understood that provision must be madefor synchronizing the phase velocity of the radio frequency wave with the velocity of the electron beam which must. be correct. to sustain the amplifyingability of the .tube as in a conventional traveling wave tube.

In all traveling wave tubes there must be some means for slowing the traveling wave such as a heliX of conductive material which is widely used in conventional tubes for this purpose. In the present invention, however, the wave slowing means is not determined solely by the electrodes 8 butthe degree of retardation is determined by the dielectric constant of the dielectric used for the spacing rings 9 and the dimensions of the electrodes 8 and insulator rings 9. The combination of insulator rings and electrodes together comprise a wave loading or wave slowing structure.

In orderto prevent the successive electrodes 8 from being held at a common R.-F. potential' by the leads from the battery, resistors are shown inserted between each electrode and the battery so that the electrodes will have high R.-F. impedances to each other through the battery supply. Instead of resistors, other, high impedance R.-F. elements may be substituted. I p

A tube embodying the invention may therefore be designed, by choosing the proper: dielectric for-the spacer rings 9 and determining the dimensions of the-structure which will cause the-tube to function within the specifications desired. Then by choosing the correct potential to be applied to the cathode with respect to thegroups of,

electrodes 8 connected respectively to wires 10,-and 11, the

electron beam will have the correct average velocity to be synchronized with the: travelingwaveon the wave slowing structure. As above stated, the potentialson the groups of electrodes 8 may also be so chosen that their dilference.

will be a value which satisfies the condition wherein successive pairs of electrodes 8 act as electrostatic lenses to concentrate the electron beam to the required degree.

It will thus be apparent that all conditions for amplification of the Wave are provided and the tube may be efficiently operated without an external cumbersome electromagnetic coil to concentrate the electron beam.

The power to be amplified may be introduced in any suitable manner. A method for accomplishing this is shown in Fig. 1 wherein the input end of the tube is provided with an opening within which is sealed a section of waveguide 12 of standard dimensions which is provided with a flange for connection to a waveguide system conducting power to be amplified. A similar section of waveguide 13 may be provided at the output end of the tube to feed amplified power to a subsequent utilization circuit or device.

The invention may embody other structural forms such as that shown in Fig. 2 wherein the peripheral edge of the aperture in each of the electrodes 8 is made relatively wide to form a short section of tube 14 through which the electron beam passes. By thus modifying the structure a stronger focusing effect on the beam may be realized.

What is claimed is:

1. A traveling Wave amplifier tube circuit comprising an exhausted envelope to enclose the elements thereof, combined electrostatic focusing and wave retarding means including a plurality of spaced metallic electrodes arranged in alignment within said envelope, a plurality of di electric elements alternately arranged with said electrodes, acting to insulate successive electrodes and to act as a radio frequency wave slowing means, means to supply and direct a beam of electrons along said electrodes, a source of direct-current potential separately connected to each of said electrodes to electrostatically converge said electron beam, and means having a high impedance to radio-frequency currents connected between said electrodes and said source of potential, and means to feed power to be amplified to the input of the tube and to conduct the amplified power therefrom.

2. A traveling wave amplifier tube circuit comprising an exhausted envelope, a combined electrostatic focusing and wave retarding means including a plurality of spaced metallic electrodes arranged in alignment within the envelope, a plurality of dielectric elements alternately arranged with said electrodes, means to supply and direct an electron beam along said electrodes and dielectric elements, a source of potential of one polarity separately connected to each of one group of said electrodes and a potential source having an opposite polarity separately connected to each one of another group of said electrodes to provide a series of electrostatic lenses for converging said electron beam, high impedance means connected between said electrodes and said potential source, and means to feed power to the tube and to conduct amplified power therefrom.

3. A traveling wave amplifier tube circuit comprising an exhausted envelope, a combined electrostatic focusing and wave retarding means including a plurality of spaced metallic electrodes within the envelope having aligned apertures, means to supply and direct a beam of electrons along said electrodes, a plurality of annular shaped dielectric elements alternately arranged with said electrodes presenting a radio frequency wave slowing channel for the passage of power therethru, a stepped source of direct-current potential separately connected to each of said electrodes whereby adjacent electrodes may have different potential values to create a series of electrostatic lenses for concentrating the electron beam, radio-frequency isolating means connected betwen said electrodes and said source of electrical potential, and means to feed radio frequency power to and conduct it from the tube.

4. A traveling wave amplifier tube circuit comprising an exhausted envelope, a plurality of aligned metallic electrodes spaced apart within said envelope, means to supply and direct a beam of electrons along said electrodes, a stepped direct-current potential source separately connected to each of said electrodes to supply successive electrodes with different potentials whereby a series of electrostatic lenses are formed to concentrate said electron beam, high impedance means connected between electrodes and said potential source, and a channel structure of dielectric attenuating material extending along said electron beam acting as a radio frequency wave slowing and synchronizing means, said channel structure comprising a plurality of dielectric elements alternating with said electrodes.

5. A traveling wave amplifier tube circuit comprising an evacuated envelope, means to supply and direct a beam of electrons along a predetermined path, a plurality of spaced metallic electrodes extending in line along said path, a wave loading structure of dielectric material extending along said path, said structure comprising a plurality of dielectric elements alternating with said electrodes, a stepped direct-current potential source separately connected to each of said electrodes and having an average value calculated to synchronize the electron velocity with the phase velocity of the loaded wave at the operating frequency and wherein different values of potential are applied to successive electrodes to form a series of electrostatic lenses acting to concentrate said electron beam, and radio-frequency isolating means connected between said electrodes and said potential source.

6. A traveling wave amplifier tube circuit comprising an exhausted envelope, a plurality of aligned spaced electrodes in said envelope, means to supply and direct a beam of electrons along said electrodes, a plurality of spaced aligned metallic plate-like electrodes in said envelope, a wave loading dielectric structure having elements alternately arranged with said electrodes acting to support and insulate them in spaced relation, a stepped potential source including wave isolating means connected to each of said electrodes separately and having an average value to synchronize the phase velocity of the loaded wave with the electron velocity at the operating frequency and wherein diflerent values of potential are applied to successive electrodes to form a series of electrostatic lenses acting to concentrate the electron beam.

7. A traveling wave amplifier tube circuit comprising an exhausted envelope, a plurality of spaced electrodes in said envelope, each electrode having short tubular axially aligned portions forming an open channel, means for sup plying and directing a beam of electrons through said channel, a wave loading structure of dielectric material also extending along said electron beam, said structure comprising a plurality of dielectric elements alternating with said electrodes a stepped source of potential including wave isolating means connected to each of said electrodes separately and having an average value to synchronize the electron velocity to that of the traveling wave at the operating frequency and to supply successive electrodes with difierent potentials to form a series of electrostatic lenses, operable to concentrate the electron beam.

8. A traveling wave amplifier comprising means to generate an electron beam, means to propagate radio frequency wave energy along said beam, and a combined wave retarding and beam focusing structure comprising a plurality of substantially noninductive electrostatic wherein said elements have aligned apertures through which said beam is directed.

10. A traveling wave amplifier comprising means to generate an electron beam, means to propagate radio frequency wave energy along said beam, and a combined wave retarding and beam focusing structure compris- 1 ing a plurality of electrostatic focusing elements having I 11. A traveling wave amplifier as set forth in claim 8, wherein said focusing elements are insulated from each other.

References Cited in the file of this patent UNITED STATES PATENTS 2,313,018 Krause Mar. 2, 1943 2,533,790 Grivet Dec. 12, 1950 2,654,047 Clavier Sept. 29, 1953 2,660,689 Touraton et a1 Nov. 24, 1953 2,661,441 Mueller Dec. 1, 1953 2,672,572 Tiley Mar. 16, 1954 2,725,499

Field Nov. 29, 1955

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