US3441782A

US3441782A - Crossed-field microwave devices with gun shielding means

Info

Publication number: US3441782A
Application number: US478576A
Authority: US
Inventors: Jacques Arnaud
Original assignee: CSF Compagnie Generale de Telegraphie sans Fil SA
Current assignee: Thales SA
Priority date: 1964-08-26
Filing date: 1965-08-10
Publication date: 1969-04-29
Anticipated expiration: 1986-04-29
Also published as: FR1413183A; DE1491317A1; GB1056626A

Description

CROSSED-FIELD MICROWAVE DEVICES WITH GUN SHIELDING MEANS J.- AR-NAUD April 29, 1969 Filed Aug. 10. 1965 INVENTORI J-AR/VAl/D mm ATTORNE United States Patent 3,441,782 CROSSED-FIELD MICROWAVE DEVICES WITH GUN SHIELDING MEANS Jacques Arnaud, Paris, France, assignor to CSF-Compagnie Generale de Telegraphic Sans F il, a corporation of France Filed Aug. 10, 1965, Ser. No. 478,576 Claims priority, applicgationogrance, Aug. 26, 1964,

Int. Cl. H01 25/34 U.S. Cl. SIS-3.5 7 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to microwave devices and more particularly to crossed-field tubes.

It is known that in the functioning of various types of crossed-field devices very often the following perturbations are noticed:

Spurious oscillations in travelling wave tubes,

Discontinuities in the frequency bands in backward wave oscillators (Carcinotrons),

Sudden variations of the noise spectrum in noise generators.

A crossed-field tube generally comprises, within an evacuated envelope, a wave delay line for propagating a microwave, an electrode called sole, defining with the delay line a wave and electron interaction space, an electron gun producing and injecting into the interaction space a beam of electrons, and a collector electrode that collects the electron-s of the electron beam.

Now it has been found that the above-mentioned perturbations are due to the detrimental action exerted upon the cathode by the unit composed of the delay line and the sole electrode, which unit propagates the microwave energy.

The present invention has as its object to suppress or at least considerably reduce the above-mentioned detrimental action, and to this effect a crossed-field tube in accordance with the invention is provided with an electrostatic shield. located between the electron gun and the sole electrode and carried preferably at the potential of the metallic envelope of the tube.

Accordingly, it is an object of the present invention to prevent spurious oscillations in travelling wave amplifier tubes.

Another object of the present invention is to suppress frequency band discontinuities in backward wave oscillators.

Still another object of the present invention is to avoid sudden variations of the noise spectrum in crossed-field type noise generators.

These and further features, objects and advantages of the present invention will be more clearly understood from the following description when taken in connection with the accompanying drawing, which shows, for purposes of illustration only, one embodiment of a crossedfield tube in accordance with the present invention, FIG- URE 1 being a cross-section taken along line I--I of FIGURE 2 and FIGURE 2 a cross-section taken along line IIII of FIGURE 1.

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The tube, represented in the two figures, comprises within an evacuated envelope 1, a wave delay line 2, an electrode 3, referred to as sole electrode, parallel to the line 2, a collector 4, and an electron gun including a cylindrical cathode 5, a positive electrode 6 and a negative electrode 7.

A source of potential E makes it possible to set the various electrodes at suitable potentials, while a magnet NS produces within the tube a magnetic field parallel to the axis of cathode cylinder 5.

The enumerated elements form the well known structure of a crossed-field device. In operation, the electrons emitted by cathode cylinder 5, which is heated by suitable means (not shown), form a beam 8, indicated in dash lines. The beam penetrates into and propagates through the interaction space comprised between line 2 and sole 3 and impinges upon collector 4. The functioning is based, as known, on the interaction between the electron beam and an electromagnetic wave that propagates along the delay line 2 with a speed substantially equal to that of the electrons.

In accordance with the present invention, the tube structure is improved by the addition of a metallic shield or screen, located between the electron gun and the sole.

In the illustrated embodiment, the shield comprises a partition 9, made up by the major portion of a cylinder, covered at the top (FIGURE 2) by a plate 10 and extending at the bottom into an annular element or ring 11. Plate 10 and ring 11 are in contact with the upper and lower walls of envelope 1, respectively, thereby setting the shield at the potential of the metallic envelope 1.

This disposition results in a considerable reduction of the coupling between the electron gun and the assembly or unit comprising the delay line and the sole. Under these conditions it has been found that the various perturbations indicated above are eliminated or considerably attenuated.

While I have shown and described one embodiment in accordance with the present invention, it is understood that the same is not limited thereto but is susceptible of numerous changes and modifications as known to a person skilled in the art, and I therefore do not wish to be limited to these details but intend to cover all such changes and modifications as are encompassed by the scope of the appended claims.

I claim:

1. A crossed-field tube comprising within an evacuated, metallic envelope, a wave delay line and a sole electrode extending substantially parallel to each other and defining therebetween an electron and wave interaction space, an electron gun adapted to produce and inject into said interaction space an electron beam, and an electrostatic shield located between said electron gun and the assembly composed of said sole electrode and said delay line.

2. A crossed-field tube as claimed in claim 1, wherein said electrostatic shield is set substantially at the same potential as said metallic envelope.

3. A crossed-field electron-discharge device, comprising within an envelope:

first means including wave retarding and sole electrode means defining an interaction space,

second memans including electron emissive means for producing an electron stream moving through said interaction space,

collector means for the electrons in said electron stream,

and shield means effectively shielding said electron emissive means with respect to said first means.

4. A crossed-field electron-discharge device, comprising within an envelope:

second means including electron emissive means for 5 substantially parallel to each other defining therebetween producing an electron stream moving through said interaction space,

collector means for the electrons in said electron stream,

and shield means effectively shielding said electron emissive means witth respect to the sole electrode means of said first means.

5. In a crossed-field device having, within an evacuated envelope, a wave retarding structure and a sole electrode defining therebetween an interaction space, means for producing within said interaction space substantially crossed electrostatic and electromagnetic fields, and means including electron-emissive means for producing an electron beam moving through said interaction space,

the improvement essentially consisting of electrostatic shield means efiectively shielding said electron emissive means with respect to at least one of the two parts consisting of said wave retarding structure and said sole electrode.

6. In a crossed-field device having, within an evacuated envelope,, a wave retarding structure and a sole electrode defining therebetween an interaction space, means for producing within said interaction space substantially crossed electrostatic and'electromagnetic fields, and means including electron-emissive means for producing an electron beam moving through said interaction space,

the improvement essentially consisting of electrostatic an elongaated electron and wave interaction space, an electron gun positioned at one end of said interaction space for directing an electron beam therein, a collector electrode positioned adjacent said interaction space for collecting said electron beam, an electrostatic shield located between said electron gun and the assembly composed of said sole electrode and said delay line, and means for generating crossed electric and magnetic fields in said interaction space transverse to the path of propogation of said electron beam.

A Gun and Focusing System for Crossed-Field Traveling-Wave Tubes by Watkins et a1. IRE Transactions on Electron Devices Jan. 1959, volume ED-6, No. 1, pps. 18-27, relied upon TK 7870 I-2.

HERMAN K. SAALBACH, Primary Examiner.

SAXFIELD CHATMON, ]R., Assistant Examiner.

US. Cl. X.R.