US2323735A - Electric discharge apparatus - Google Patents

Description

July 6, 1943.. e. L. TAWNEY 2,323,735

ELECTRIC DI SCHARGE APPARATUS Filed March 14, 1940 Insulation INVENTOR WITNESSES Gerald L. Tawne l 1 BY A67 I ATTORN Patented July 6, 1943 ELECTRIC DISCHARGE APPARATUS Gereld L. lawney, Wilkinsburg, Pa, assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application March 14, 1940, Serial No. 323,935

Claims. (Cl. 250-Z7) My invention relates to electric discharge apparatus, and has particular relation to ultrahigh frequency generators.

In oscillation generators primarily used for supplying ultra-high frequency radiation at substantial power ratings, the radiated energy is derived from a high velocity stream of electrons passing through a vacuum or an attenuated atmosphere. Because the output energy of the generator is substantial, the input energy, and therefore, the potential impressed on the electron stream, is large, the latter beim usually of the order of several thousand volts. After the stream leaves the region in which the radiant energy is derived from the electrons, the charge must be dissipated so as to prevent the building up of a static field opposing the movement of the electrons. Customarily this object is accomplished by a plate disposed in the path of the electrons which deflects the stream to a grounded conductor, such as the wall of the container through which the stream passes. The deflecting plate is maintained at a substantial potential opposing the stream so that it does not itself absorb the electrons and become excessively heated.

In accordance with the teachings of the prior art, the opposing potential is impressed on the deflecting plate from an external source by a conductor which passes through an insulating seal in the wall of the container. Since sub tantial quantities of energy are to be dissipated, the seal must necessarily be large and difliculties are involved, not only in its construction, but also in its maintenance.

It is, accordingly, an object of my invention to provide an electric discharge device of the cathode ray type in which the seal used in connection with the plate for deflecting an electron stream to a charge dissipating conductor shall be eliminated.

Another object of my invention is to provide a generator of ultra-high frequency radiation of the cathode ray type, capable of delivering substantial power, in which the necessary insulatng seals shall be maintained at a minimum.

A further object of my invention is to provide a deflecting electrode of simple and inexpensive structure for the electron stream of a discharge device of the cathode ray type.

More generally stated, it is an object of my invention to provide an electric discharge device having an electrode for deflecting a stream of charges to a charge dissipating conductor in which the possibility of leakage by reason of defecti've insulating seals shall be reduced to a minimum.

In accordance with my invention, the deflecting electrode is suspended from the wall of the container through which the electron stream passes by suitable insulating suspensions. The electrode thus floats electrically. The electrons impart a negative potential to the electrode when the stream fist impinges on it and the electrode potential is soon decreased to a value such that it opposes the motion of the stream and deflects it to the dissipating conductor. So that the deflecting electrode shall attain the necessary opposing potential as soon as possible, it is desirable that it shall be composed of a material having a low secondary emission ratio. A graphite electrode is particularly suitable for this reason.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of a specific embodiment when read in connection with the accompanying drawing, in which the single figure is a diagrammatic view showing a preferred embodiment of my invention.

The apparatus shown in the drawing comprises a cylindrical metallic container l of a suitable vacuum-tight material such as copper or steel. Since substantial heat is developed in the container and must necessarily be dissipated, it is provided with external cooling coils 3 through which a cooling medium such as Water may be conducted.

An electron emissive cathode assembly 5 is supported from an insulating ring l secured to an end wall of the container. The cathode assembly 5 comprises a heater Q enclosed within an emissive cap ill, the outer surface of which is covered by a readily emissive material such as a combination of alkaline earth oxides. The cap it is flanged and the flanges iii are supported on a dish-shaped disc I?) having a perforation It at its center through which the heater 9 extends.

A potential of the order of several thousand volts is impressed between the emissive cap ll and ground from a suitable source ll which may be of the usual commercial cycle type. The container i is also grounded and the potential which is thus impressed between the container wall and the cathode cooperates with the dishshaped electrode [5 to converge the electrons emitted from the cap into a narrow high velocity stream.

A conducting partition |9 with an openwork 2| at its center is secured to the cylindrical wall of the container I a short distance from the cathode 5. The partition is at ground potential, and it accelerates the electrons in the stream. The stream passes through the openwork 2| and then, after moving across a narrow gap 23, passes through another openwork 25 which forms one end of a hollow conducting cylinder 21. The cylinder 2'! is supported from a second partition 29 which is centrally disposed in the container and to which it is secured coaxial with the container The supporting partition 29 is provided with a gap 3| adjacent one region of the wall of container and a vane 33 supported from a rod 35 extends into the gap. The rod 35 supporting the vane is secured to the end of a metallic Sylphon 31 which projects from a suitable opening in the side of the container and is sealed vacuum-tight to the container.

The cylinder 21 provides a field-free space through which the electron stream moves in an axial direction. The stream passes out of the cylinder through the remote end 39 which is also an openwork and then moves across another narrow gap ll. The openwork 43 of a third partition 45 is in the path of the stream at the end of the gap 4| and the stream passes through it and impinges on a deflecting electrode 41. The deflecting electrode 41 is suspended from a plurality of symmetrically disposed insulators 49 secured to the rear end of the container so that its axis is coincident with the axis of the container. It is composed of a material, such as graphite, that has a secondary-emission ratio substantially smaller than 1. When the stream first impinges on the electrode 41, the electrode collects a charge and becomes electrically negative. The potential of the electrode is soon such as to oppose the forward motion of the electrons in the stream and the latter are, therefore, defiected to the container wall where they are dissipated.

In passing through the gaps 23 and 4| and the cylinder 27 the energy imparted to the stream by the source I? is converted into high frequency radiant energy. The region bounded by the first partition IS, the openwork 25, the wall of the cylinder 21 between the central partition 29 and the openwork 25, the partition 29 and the wall of the container I between the partitions l9 and 29 and a portion of the vane 33, constitutes a hollow-body resonator, one of the resonant frequencies of which (preferably the fundamental) is equal to the frequency of the energy which is to be radiated. The resonator is excited to oscillate at the selected frequency and as the electron stream passes through the gap 23 within the resonator, the electrons are influenced by the electromagnetic field corresponding to the excitation of the resonator. The electromagnetic field superimposes on the electrons in the stream a periodic longitudinal velocity having the frequencies of the field. The electrons, therefore, move at diiferent speeds as they pass into the field-free space within the cylinder 21. As the electrons move through the cylinder, they collect in groups at a predetermined position because the fast electrons tend to catch up with the slow ones.

The cylinder 21 is of such length that the electrons are bunched in groups when they pass through the openwork 39 into the adjacent gap 4|. The gap 4| is a portion of a hollow body resonator bounded by the partition 45, the adjacent openwork 39 of the cylinder 21, the wall of the cylinder between the central partition 29 and the openwork 39, the central partition 29 and the wall of the container between the partition 29 and the partition 45, and including the portion of the vane 33.

The last mentioned resonator is preferably dimensioned the same as the resonator between the partition l9 and the central partition 29 so that one of its resonant frequencies is the same as the selected frequency of the latter. Slight differences in frequency may be compensated by pivoting the Sylphon 3'1 so that the vane 33 moves toward the one resonator or the other as indicated by the arrows.

The resonator including the gap 4| is thus excited to oscillate at the same frequency as the resonator including the other gap 23 and as the groups of electrons pass through the former gap 4|, they are opposed by the electric vector of the corresponding electromagnetic field of the second resonator. The dimensioning of the various elements of the device is such that the electrons are subjected to the field of the resonator including the gap 4| only when its electric field is such as to oppose their forward movement. When the field is such as to accelerate the electrons, one group of electrons is receding from the gap H and the succeeding group is approaching it. The electrons, therefore, give up a substantial fraction of their kinetic energy to the field and the energy is converted into radiant energy.

The energy is radiated by means of a suitable antenna 5| comprising a shielded elongated conductor 53 sealed through the container I having a loop 55 extending into the energy deriving resonator 3945. The loop is oriented so that it is threaded by the magnetic vector of the electromagnetic field Within the resonator, The resonator 2 |-25 whereby the velocity of the electron stream is modulated is excited to oscillate by a loop 51 which extends between the resonators through an opening 54 in the wall of the central partition 29. This is the usual feed back connection where the apparatus is used primarily to produce oscillations. Where the apparatus is used for amplifying purposes, the modulating resonator 2|25 may be excited to oscillate by a proper source of high frequency oscillations.

The electron stream does not give up its total energy to the energy deriving resonator 3945. After passing through the latter resonator, the stream is deflected by the insulated electrode 41 to the wall of the container where the charge is dissipated.

In addition to the elements included in the arrangement described herein the apparatus may incorporate any contrivances used generally in the cathode ray art in the same connection (such as improved processing devices) without departing from the scope of my invention.

Although I have shown and described a certain specific embodiment of my invention, I am fully aware that many modifications thereof are possible. My invention, therefore, is not to be restricted except insofar as is necessitated by the prior art and by the spirit or the appended claims.

I claim as my invention:

1. An electric discharge device comprising a container having a conducting portion of substantial area on its inner wall and containing an electron emitting electrode, means for deriving an attenuated stream of electrons from said electrode, a first hollow body resonator disposed in the path of said stream for impressing variations on the velocity of the electrons in said stream, a second hollow body resonator disposed in the path of said stream for deriving energy from the electrons in said stream, a circuit connecting said conducting portion with said emitting electrode for returning to the latter the electrons emerging from said second resonator and a deflecting electrode insulated from said resonators and said emitting electrode for deflecting the electrons emitting from said resonator to said conductor.

2. In combination, a conducting container, an electron emitting electrode within said container, means for deriving an attenuated stream of electrons from said electrode, said deriving means including means for impressing a potential of the order of several thousand volts between said container and said emitting electrode and an electrode for deflecting said stream to the container walls, said electrode being completely insulated from said container and from said emitting electrode.

3. In combination, a container having at least an inner conducting wall, an electron emitting electrode within said container, means for deriving an attenuated stream of electrons from said electrode, said deriving means including means for impressing a potential of the order of several thousand volts between said wall and said emitting electrode and an electrode for deflecting said stream to said wall, said electrode being completely insulated from said wall and from said emitting electrode.

4. In combination, a container having at least an inner conducting wall, an electron emitting electrode within said container, means for deriving an attenuated stream of electrons from said electrode, said deriving means including means for impressing a potential of the order of several thousand volts between said wall and said emitting electrode and an electrode for defiecting said stream to said wall, said electrode being composed of a material having a secondary emission ratio substantially less than 1 and being completely insulated from said wall and from said emitting electrode.

5. In combination, a container having at least an inner conducting wall, an electron emitting electrode within said container, means for deriving an attenuated stream of electrons from said electrode, said deriving means including means for impressing a potential of the order of several thousand volts between said wall and said emitting electrode and an electrode for defleeting said stream to said wall, said electrode being composed of graphite and being completely insulated from said wall and from said emitting electrode.

GERELD L. TAWNEY.

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