US2865004A - Traveling wave electron discharge devices - Google Patents

Traveling wave electron discharge devices Download PDF

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US2865004A
US2865004A US575113A US57511356A US2865004A US 2865004 A US2865004 A US 2865004A US 575113 A US575113 A US 575113A US 57511356 A US57511356 A US 57511356A US 2865004 A US2865004 A US 2865004A
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interaction space
network
electron
periodic
tube
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US575113A
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Edward C Dench
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Raytheon Co
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Raytheon Manufacturing Co
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J25/00—Transit-time tubes, e.g. klystrons, travelling-wave tubes, magnetrons
    • H01J25/34—Travelling-wave tubes; Tubes in which a travelling wave is simulated at spaced gaps
    • H01J25/42—Tubes in which an electron stream interacts with a wave travelling along a delay line or equivalent sequence of impedance elements, and with a magnet system producing an H-field crossing the E-field
    • H01J25/44—Tubes in which an electron stream interacts with a wave travelling along a delay line or equivalent sequence of impedance elements, and with a magnet system producing an H-field crossing the E-field the forward travelling wave being utilised

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  • This invention relates to traveling Wave electron discharge devices and more specifically to means for increasing the power rating of such devices by novel beam injection techniques.
  • Traveling wave electron discharge devices are widely used either as amplifiers capable of operation over a large band width or as oscillators capable of being tuned electronically over a considerable frequency range in the microwave region.
  • Such devices utilize the interaction between an electron beam moving along paths adjacent a periodic non-resonant slow wave propagating structure and the electromagnetic field of the radio frequency wave propagating along said periodic structure.
  • the electromagnetic field along such a periodic structure may be resolved into a number of superimposed traveling waves or space harmonics each having its own phase velocity.
  • Some of the space harmonics of a phase velocity travel in the same direction as the wave energy or group velocity and are referred to as forward waves.
  • Other space harmonics have a phase velocity of opposite sense, that is, the phase velocity is in a direction opposite to the energy or group velocity.
  • Such harmonics are referred to as backward waves. If the electron beam velocity is adjusted so that it is in substantial synchronism with the phase velocity of a given space harmonic, interaction between the electron beam and this component will occur, and energy will be transferred from the electron beam to the electromagnetic field.
  • a radio frequency input signal is coupled to the periodic structure adjacent one end thereof, and, owing to the interaction between electron beams moving along a path adjacent the periodic structure and the electromagnetic field of the radio frequency Wave propagating along said structure, amplification of the input signal may be obtained, under proper operating conditions. This amplified signal may then be extracted from the periodic structure adjacent the other (output) end thereof.
  • the interaction is between the electron beam and a forward wave; the electrons thus are projected toward the output amplifier, interaction occurs between the electron beam and a backward wave and the electrons then move to ward the input end of the periodic structure.
  • a travel- In the backward wave r ing wave oscillator when the electron beam current exceeds a critical current at which oscillations can begin, and when the electron beam velocity is substantially equal to the velocity of one of the backward waves, oscillations may be generated within the device and the generated energy will propagate along the periodic structure and may be extracted at the end thereof away from which the electrons are moving.
  • the electron gun In traveling wave tubes in which the electron beam moves through transversely directed direct current electric and magnetic fields perpendicular to the motion of the electrons, it is desirable to provide a relatively flat beam which may be injected along an equipotential in ice .
  • the electron gun Widely in use, the electron gun is located near one end of the periodic delay structure and injection of the beam occurs from this end of the device.
  • the cathodes of such localized electron guns have a relatively small surface and mass and the power handling capabilities are correspondingly restricted.
  • a continuous cathode substantially coextensive with the periodic delay structure is used in order to increase the power rating of the traveling wave tube.
  • the electrical field is produced by the potential between the cathode and the periodic delay structure and the frequency of operation, in the case of traveling wave oscillators, is dependent upon the aforesaid potential.
  • amplitude modulation of the tube may be accomplished by varying the tube current; however, this current is a function of the voltage between the periodic delay structure and the cathode, and changes in current not only produce amplitude modulation but also are accompanied by an undesirable change in operating frequency of the tube.
  • the space charge cloud surrounding this cathode occupies a considerable space 'and is characterized by a large range of electron velocities from zero at the cathode surface to a maximum at the outer edge of the cloud.
  • the number of electrons in the electron beam available for synchronous interaction with the electromagnetic field is reduced.
  • the electron gun is positioned utside the interaction space between the periodic anode structure and the negative electrode or sole.
  • the electrons from the cathode of this electron gun are accelerated by means of one or more beam forming electrodes of the electron gun in a direction parallel to the magnetic field into the interaction space, where, under the influence of the transverse electric and magnetic fields previously referred to, they will be diverted and caused to travel along the interaction space in a direction determined by the polarity of the magnetic field.
  • the elec trons may be formed into a ribbon-type beam which may be projected substantially along only one equipotential level. Traveling wave oscillators according to the invention may be amplitude modulated by means of a signal applied to one or more of these beam forming electrodes. For example, this amplitude modulating signal may be applied between one or more of the beam forming electrodes and either the cathode or the negative sole.
  • the traveling wave tube of the invention is capable of handling considerably more power than prior traveling wave tubes which contain a limited cathode positioned only at one end of the periodic anode structure.
  • amplitude modulation in the traveling wave tube according to this invention 7 may be effected independently of frequency modulation.
  • the electrons may be shaped into a narrow beam prior to entrance into the interaction space action space to insure their entrance substantially at only one desired equipotential level, the velocity range of the electron beam is much less than that of prior traveling wave tubes employing acontinuous cathode, and the efli- 'ciency of interaction is correspondingly increased. It should -be noted, in this regard, that if beam shaping electrodes were used in continuous cathode systems of the prior art, these electrodes would have to be introduced into the interaction space and this would seriously affect the operation of such tubes.
  • Fig. 1 is an isometric view, particularly in section, of an embodiment of a traveling wave tube according to the invention
  • Fig. 2 is a cross-sectional view of the tube shown in Fig. 1;
  • Fig. 3 is a cross-sectional view of a modification of the tube of Figs. 1 and 2 in which electron injection occurs from both sides of the tube;
  • Fig. 4 is a diagram of a traveling wave tube similar to that of Figs. 1 to 3 in which means are provided for amplitude modulation;
  • Fig. 5 is a simple cross-sectional view of a traveling wave tube of cylindrical configuration according to the invention.
  • Fig. 6 is a sectional view taken along lines 66 of Fig. 5;
  • Fig. 7 is a detail showing a portion of the electron gun assembly
  • Fig. 8 is a detail view of a portion of the anode assembly of th tube of Fig. 5;
  • Fig. 9 is a detail view of another portion of the electron gun assembly.
  • Figs. 10 and 11 are sectional views of a modification of the cylindrical tube of Figs. 5 and 6.
  • a traveling wave amplifier tube 15 which contains an anode assembly having a linear periodic slow wave propagating structure 22.
  • This structure also referred to hereinafter as an anode delay network, comprises a pair of electrically conductive interleaved members 23, each including several spaced fingers 24 which connect to a longitudinal portion 25 and extend transversely to the latter almost to the opposite longitudinal portion.
  • the anode delay network is carried by an electrically insulating base plate 27, which in turn, is securely attached by any appropriate means to a continuous electrically conductive backing member 28.
  • Backing member 28 forms one of the walls of an evacuated envelope further including an oppositely disposed wall 29, side walls 30 and 31, and a pair of end walls, 32 and 33. Electrical connection between the anode delay network 22 and the wall 28 may be made by means of electrically conductive screws 34 used for attaching the anode assembly, including base plate 27, to the tube envelope, as well as by electrically conductive straps 35.
  • the device of Fig. 1 has an output energy coupling device 36 and an input coupling device 38 indicated as coaxial coupling devices, although the invention is not limited to coaxial type transmission lines; for example, wave guide coupling means also may be used.
  • the inner conductor 39 of output coupling device 36 extends throughout an aperture 41 in wall 28 and base plate 27 and is attached, as by brazing, to an end finger 24 of the interdigital delay network, as clearly shown in Fig. l.
  • the inner conductor 42 of the input coupling device 38 likewise extends through Wall 28 and base plate 27 and is attached to a finger at the end of the network 22 opposite that to which the output coupling device is attached.
  • the forward wave amplifier tube of Figs. 1 to 3 may be converted into a backward wave oscillator by omitting the coupling device 36 and using coupling device 38 as an output coupling device.
  • Attenuation may be introduced into the interdigital anode delay network by means of a coating of lossy material, such as iron, which may be plated on the fingers of the network of the region thereof in which attenuation is desired.
  • lossy material such as iron
  • attenuation is normally placed about one-third of the distance from the input end of the delay network, while, for an oscillator, the attenuation should be positioned adjacent the end of the line remote from the output end.
  • An auxiliary electrode 44 hereinafter referred to as a sole, is disposed substantially parallel to the anode delay network 22 and is spaced therefrom.
  • Sole 44 is a substantially U-shaped member, disposed coextensive with the anode network and having a base portion 44 and two upturned portions 44".
  • the sole is supported with respect to the tube envelope by means of a pair of tubular supporting rods 47 rigidly attached to the sole and extending through an aperture in the wall of the tube envelope.
  • a central conductor 48 is located inside support rod 47 and passes externally of the tube envelope.
  • Each rod 47 is insulatedly supported with respect to wall 29 by means of a metallic member 49 sealed, in turn, to insulating seals 50; these insulating seals are connected to an electrically conductive cylinder 51 surrounding rod 47 and cylinder 51 is attached to a recess in the wall 29 surrounding the aperture throughout which rod 47 passes.
  • the sole 44 is maintained negative with respect to the anode delay network by means of a unidirectional source of potential 52, such as a battery, which is connected between the sole 44 and some portion of the tube envelope.
  • Traveling wave tube 15 further includes an electron gun assembly 55 which comprises an elongated cathode 56 having an electron-emissive surface 57.
  • This cathode is arranged substantially parallel to the longitudinal axis of the tube and extends axially about half the length of the sole and anode network, as shown in Fig. l.
  • Cathode 56 is supported from the end walls 32 and 33 of the tube envelope by support rods 58 which are sealed in an electrically insulating seal 59, such as a vitreous seal, mounted in the end walls.
  • One of the two cathode support rods 58 extends through a corresponding seal 59 externally of the tube envelope.
  • the cathode is heated to a temperature sufficicnt for thermionic electron emission from the emissive surface 57 by means of a heater 60 which, for example, may be in the form of an elongated coil insulatedly mounted with respect to the cathode by electrically insulating spacers 61 secured to the cathode and containing apertures for passage of the heater coils.
  • a heater coil 60 is attached to the cathode and the other end thereof is connected by means of a flexible end portion to a heater supporting rod 63 which, like one of the cathode supporting rods 58, passes through a vitreous seal 59 within the wall 32 and externally of the tube envelope.
  • the necessary heater potential is supplied by the unidirectional voltage source 65.
  • the sole may be negatively biased with respect to the cathode by means of battery 68; in some instances, the sole and cathode may be held at the same potential.
  • the electron gun assembly 55 also may include beam forming electrodes 66 and 67, respectively positioned slightly above and below the cathode. The lowermost of these beam forming electrodes is spaced slightly from.
  • the sole as shown more clearly in Fig. 2; however, in some instances, the lowermost electrode may be supported by the sole.
  • the upwardly extending portion or edge 44 of the sole adjacent the electron gun preferably is cut away over the length of the electron gun, as shown in Figs. 1 and 2, in order to permit the electron beam to enter the interaction space between the sole and the anode delay network under the combined action of the transverse electric and magnetic fields, to be described subsequently.
  • the beam forming electrodes 66, 67 may be interconnected and made somewhat positive relative to the cathode by a battery 69.
  • a suitable electric field is used between the anode delay network and the sole by means of the voltage from source 52 applied therebetween.
  • a uniform magnetic field perpendicular to both the electric field and to the general direction of propagation of the electron beam along the longitudinal interaction space 70 is provided by either a permanent magnet or an electromagnet having pole pieces 71 and 72 positioned in contact with the adjacent respective side walls 30 and 31 of the tube envelope. The electron beam will be directed along the interaction space in either one direction or the other dependent upon the polarity of the transverse magnetic field.
  • the electron gun assembly extends only approximately half the length of the tube. This electron gun assembly is of less value near the downstream end of the tube, either in an amplifier or an oscillator, since .the portion of the electron beam adjacent the downstream end has little effect so far as interaction with the electromagnetic field of the wave guided by the periodic anode delay network is concerned.
  • the electrons injected into the interaction space near the collector, if a collector is used, or near the end of the anode network which intercepts a substantial portion of the electrons, where the anode network itself serves as the collector of electrons expend themselves with little energy interchange.
  • the electron gun assembly may extend the entire length of the anode delay network, especially in cases in which maximum interaction is desired.
  • FIG. 3 an arrangement is shown for increasing the beam current by injecting electrons into the interaction space 70 between the sole and the anode network from both sides thereof.
  • the traveling wave tube of Fig. 3 thus includes two electron gun assemblies 55, one mounted on each side of the tube; these electron gun assemblies may be of identical construction and may be supported within the tube in the manner indicated previously in connection with Figs. 1 and 2. Since the electrons are injected from both sides, the upturned portions 44" of the sole in the region of the gun assemblies either are eliminated or are made sufiiciently short as not to interfere with the electron beam as it was injected to the interaction space.
  • FIG. 4 an arrangement is shown for either frequency modulating or amplitude modulating the output of an oscillator tube. Elements of Fig. 4 corresponding to Figs. 1 and 2 are represented by the same reference numerals.
  • the electron gun assembly of Fig. 4 includes a cathode 56, heater 6'0, and beam forming electrodes 66 and 67, just as in Figs. 1 to 3, together with an additional pair of beam forming electrodes 74 and 75.
  • the electrodes 74 and 75 may be electrically connected; likewise, the cathode 56 and the electrodes 66 and 67 may be interconnected so as to be at the same electrical potential.
  • Amplitude modulation may be accomplished by varying the potential of the beam forming plates 74 and 75 relative to the cathode, as by modulation source 78 connected in series with the unidirectional source 79'between these beam forming plates and the cathode, or by varying the potential of these beam forming plates relative to sole 44 by means of modulation source 81, connected in series with voltage source 82, or by varying both in combination. Since variation of either or both of the modulation sources 78 or 81 will influence the beam current injected into the interaction space 70, the power of the tube may be varied over a considerable range. I
  • a traveling wave tube is shown which is of cylindrical construction, as contrasted with the linear configuration previously described.
  • the elements of Figs. 5 to 8 corresponding with those of Figs. 1 to 4 will be designated by the same reference numerals.
  • the oscillator tube includes an anode assembly including a periodic slow wave energy propagating structure 22, a sole electrode 44 maintained negative relative to the anode delay network 22, a lead-in assembly 85, an output coupling means 38, an electron gun assembly 55 including at least a cathode 56 and a heater 60, and a transverse magnetic field producing means, the pole pieces 71 and 72 of which are illustrated in Fig. 5.
  • the anode assembly 22 comprises a circular interdigital delay line including a plurality of interdigital fingers 24 which extend from oppositely disposed annular members 25. Members are secured by screws 26 (see Fig. 8) to the shoulder portion of a cylindrical electrically conductive ring 37. The remainder of the anode assembly includes a pair of oppositely positioned cover plates 18 and 19 electrically sealed to ring 37, as shown in Fig. 5
  • the sole 44 consists essentially of a'substantially cylindrical block of electrically conductive material, such as copper.
  • a centrally located aperture is provided in the sole to permit connection of lead-in assembly 85 and to allow for passage of external connecting leads, in a .manner to be shown subsequently.
  • the sole may be a tubular member whose outer periphery coincides with that of the solid member illustrated in Figs. 5 and 6.
  • Lead-in assembly 85 includes an electrically conductive cylindrical sleeve 86 inserted in an aperture in cover plate 19 and securely attached thereto.
  • a section of glass tubing 87 serves to interconnect metal sleeve -86 and a second metal sleeve 88.
  • the other end of sleeve 88 is provided with a glass seal 89 for sealing tube 15 after evacuation.
  • Sleeves 86 and 88 preferably are constructed of a material having an expansion coefficient closely approximating that of tubing 87.
  • the assembly 85 further includes an elongated electrically conductive hollow supporting cylinder 90 which serves as the main support for sole 44. One end of cylinder is fastened to the periphery of aperture 45 in the sole.
  • the other end of cylinder 90 contains an outwardly flared portion 91 which is connected to the inner surface of sleeve 88.
  • the necessary leads for the electron gun are fed through supporting cylinder 90 and are insulatedly supported therefrom and from one another by one or more glass beads 92.
  • the coaxial output coupling means 38 is sealed in an opening in wall 37 of the anode assembly 20 and are impedance matched to the anode delay network 22.
  • the inner conductor 39 of the coaxial input coupling means 38 is connected to a finger at or adjacent one end of the periodic anode delay network.
  • an input coupling means 36 is provided which is coupled to the anode delay network 22 at or near the end thereof opposite the end to which the output coupling means 38 is attached.
  • the particular location of the input and 'to 8 includes a cathode 56, a heater 60, and a pair of annular beam forming plates or electrodes 66 and 67, shown in detail in Fig. 9, and supported from cover plate 19 by rigid posts 107.
  • the cathode 56 may be an annular fiat ring, one surface of which is connected with an electron-emissive material 57.
  • the cathode is arranged coextensive with the annular interaction space 70 between the anode delay network 22 and sole 44.
  • Cathode 56 is supported from the cover plate 18 by means of several blocks 94 of electrically insulating material which are secured to the cathode by screws 95. See Fig. 7.
  • the blocks 94 contain a threaded portion 96 adapted to be screwed into threaded apertures in the cover plate 19.
  • the blocks 94 contain apertures 97 for receiving an arcuate heater wire 60 which is disposed adjacent the cathode on the side opposite the emitting surface 57.
  • a cathode lead 101 is connected at some point on the cathode 56 and is brought out through the tubular supporting cylinder 90 externally of the tube.
  • One end of heater 60 is connected to the cathode and the other end is attached to a heater lead 102 passing through cylinder 90 externally of the tube.
  • the beam forming plates 66 and 67 which may be supported from the cover plate 19 by support post 107, may be interconnected by a jumper 104; a lead 103 is connected to one of these beam forming plates and is brought out from the tube through cylinder 90.
  • a suitable electric field between the anode and sole may be attained by means of a unidirectional voltage applied therebetween.
  • the sole is maintained at a negative potential relative to the anode by means of a source 52 of voltage connected between metal sleeve 86 (which is connected to anode delay network 22) and cathode lead 101.
  • the sole 44 may be biased negatively with respect to cathode 56 by means of a source 68 of voltage connected between sleeve 88 and cathode lead 101.
  • the cathode in some instances, may be at the same potential as the sole, however.
  • the beam forming electrode 66 and 67 are made positive relative to the cathode by means of a source 69 of voltage interconnecting leads 101 and 103.
  • the heater potential source 65 is connected between leads 101 and 102.
  • Amplitude modulation source 105 may be connected in series with voltage source 69 between the cathode and the beam forming electrodes by means of a switch 110 for amplitude modulating the output of tube 15, when operation as an oscillator is desired. In some instances, particularly when modulation is not required, it is possible to omit the beam forming electrodes 66 and 67 shown in Figs. and 6.
  • the electron gun assembly may extend over only a portion of the entire length of the anode delay network 22, as shown in Fig. 6. It is possible, of course, to arrange the electron gun assembly so that it extends along the entire length of the anode delay network, as shown in Fig. 10.
  • the device in Fig. also indicates a traveling wave tube adapted to operate as an amplifier, as contrasted with the traveling wave tube oscillator shown in Figs. 5 and 6.
  • a uniform magnetic field transverse to the direction of propagation of the electron beam and the electrical field between theanode delay network and sole is provided by a permanent magnet or an electromagnet having cylindrical pole pieces 71 and 72 positioned on or adjacent the tube. Pole piece 71 is apertured to receive the lead-in assembly and pole piece 72 is apertured to maintain symmetry of the magnetic field.
  • the flux line should be concentrated in the interaction space 70 between sole 44 and anode delay network 22.
  • the traveling wave tube may be arranged as shown in Fig. 11 in which the collector electrode 40, shown in Figs. 6, 8 and 10, has been omitted.
  • the collector electrode 40 shown in Figs. 6, 8 and 10
  • the electron gun assembly may be continuous.
  • an extension of the wall 37 of the anode assembly is used to maintain the spacing between the anode and the sole equal to that in the interaction portion of the tube.
  • the construction of Fig. 11 may be used in an amplifier, as well as in the oscillator shown.
  • the output coupling means 38 of Fig. 10 is positioned at the opposite end of the delay line 22 from that in Fig. 6. This difference in location of the output coupling means is due to the fact that the direction of the magnetic field in the device of Fig. ll is opposite that in Fig. 6, and, consequently, the direction of motion of the electrons in interaction space 70 is reversed.
  • the electron gun shown in Fig. 4 may be used in a circular traveling wave tube, such as shown in Figs. 5 to 10, as well as in a tube of linear configuration.
  • a traveling wave electron discharge device comprising a periodic nonreentrant slow wave energy propagating network for transmitting electromagnetic wave energy, an electrically-conductive element spaced from and substantially coextensive with said periodic network, said network and said element at least partially defining an interaction space therebetween, an electron source disposed outside said interaction space and arranged coextensive with at least a portion of said network, means for producing a magnetic field substantially transverse to said interaction space, and means for injecting a beam of electrons from said source into said interaction space along a path a portion of which is substantially parallel to the direction of said magnetic field in energy interacting relationship with said wave energy.
  • a traveling wave electron discharge device comprising a periodic nonreentrant slow wave energy propagating network for transmitting electromagnetic wave energy, an electrically-conductive element spaced from and substantially coextensive with said periodic network,
  • a traveling wave electron discharge device comprising a periodic nonreentrant slow wave energy propagating network for transmitting electromagnetic wave energy, an electrode spaced from and substantially coextensive with said periodic network, said network and said electrode at least partially defining an interaction space therebetween, an electron source disposed outside said interaction space and arranged coextensive with at least a portion of said network, means for producing a magnetic field substantially transverse to said interaction space, and means for directing a beam of electrons along said interaction space in energy interacting relationship with said wave energy, said beam transversing a given point on said network more than once, said means for directing including beam forming means lo cated outside said interaction space and adjacent said electron source for injecting electrons from said source into said interaction space along a path at least a portion of which is substantially parallel to the direction of said magnetic field and in a direction substantially perpendicular to the direction of said electron beam in said interaction space.
  • a traveling wave electron discharge device comprising a periodic nonreentrant slow wave energy propagating network for transmitting electromagnetic wave energy, an electrode spaced from and substantially coextensive with said periodic network, said network and said electrode at least partially defining an interaction space therebetween, an electron source disposed outside said interaction space and arranged coextensive with at least a portion of said network, means for producing a magnetic field substantially transverse to said interaction space, and means for directing a beam of electrons along said interaction space in energy interacting relationship with said wave energy, said electron beam being nonreentrant, said means for directing including beam forming means located outside said interaction space and adjacent said electron source for injecting electrons from said source into said interaction space along a path at least a portion of which is substantially parallel to the direction of said magnetic field and in a direction substantially perpendicular to the direction of said electron beam in said interaction space.
  • Atraveling wave electron discharge device comprising a periodic nonreentrant slow wave energy propagating network for transmitting electromagnetic wave energy, an electrode spaced from and substantially coextensive with said periodic network, said network and said electrode at least partially defining an interaction space therebetween, an electron source disposed outside said interaction space, means for producing a magnetic field substantially transverse to said interaction space, and means for directing a beam of electrons from said source along said interaction space in energy interacting relationship with said wave energy, said electron source being arranged in juxtaposition with a portion of said network nearer the end thereof away from which electrons are directed, said means for directing including beam forming means located outside said interaction space and adjacent said electron source for injecting electrons from said source into said interaction space along a path at least a portion of which is substantially parallel to.the direction of said magnetic field and in a direction substantially perpendicular to the direction of said electron beam in said interaction space.
  • a traveling wave electron discharge device com prising a periodic nonreentrant slow wave energy propagating network for transmitting electromagnetic wave energy, an electrode spaced from and substantially co extensive with said periodic network, said network and said electrode at least partially defining an interaction space therebetween, an electron source disposed outside said interaction space, means for producing a magnetic field substantially transverse to said interaction space, and means for directing a beam of electrons from said source along said interaction space in energy interacting relationship with said wave energy, said electron source being arranged in juxtaposition with said entire network, said means for directing including beam forming means located outside said interaction space and adjacent said electron source for injecting electrons from said source into said interaction space along a path at least a portion of which is substantially parallel to the direction of said magnetic field and in a direction substantially perpendicular to the direction of said electron beam in said interaction space.
  • a traveling wave electron discharge device comprising a periodic nonreentrant slow wave energy propagat ing network for transmitting electromagnetic wave energy, an electrode spaced from and substantially coextensive with said periodic network, said network and said electrode at least partially defining an interaction space therebetween, a pair of electron sources disposed outside said interaction space and arranged coextensive with at least a portion of said network, said electron sources being disposed on opposite sides of said interaction space, means for producing a magnetic field substantially transverse to said interaction space, and means for injecting a beam of electrons from said source into said interaction space along a path a portion of which is substantially parallel to the direction of said magnetic field in energy interacting relationship with said wave energy.
  • a traveling wave electron discharge device comprising a periodic nonreentrant slow wave energy propagating network for transmitting electromagnetic wave energy, an electrode spaced from and substantially coextensive with said periodic network, said network and said electrode at least partially defining an interaction space therebetween, a pair of electron sources disposed outside said interaction space and arranged coextensive with at least a portion of said network, said electron sources being disposed on opposite sides of said interaction space, means for producing a magnetic field substantially transverse to said interaction space and means including beam forming means located outside said interaction space and adjacent said sources for injecting a beam of electrons from each of said sources into said interaction space in energy interacting relationship with said wave energy along a path a portion of which is substantially parallel to the direction of said magnetic field in a direction substantially perpendicular to the direction of said electron beam in said interaction space.
  • a traveling wave electron discharge device comprising a periodic nonreentrant slow wave energy propagating network for transmitting electromagnetic wave energy, an electrode spaced from and substantially coextensive with said periodic network, said network and said electrode at least partially defining an interaction space therebetween, an electron source disposed outside said interaction space and arranged coextensive with at least a portion of said network, means for producing a magnetic field substantially transverse to said interaction space, and means for injecting a beam of electrons into said interaction space along a path a portion of which is substantially parallel to the direction of said magnetic field and substantially perpendicular to said electron beam in energy interacting relationship with said wave energy, and means for varying the beam current independently of beam velocity in response to a modulation input signal applied to said means for injecting.
  • a traveling wave electron discharge device comprising a periodic nonreentrant slow wave energy propagating network for transmitting electromagnetic wave energy, an electrode spaced from and substantially coextensive with said periodic network, said network and said electrode at least partially defining an interaction space therebetween, an electron source disposed outside said interaction space and arranged coextensive with at least a portion of said network, and means for directing a beam of electrons along said interaction space in energy interacting relationship with said wave energy, said means for directing including means for producing mutually transverse electric and magnetic fields in the region of said interaction space and substantially perpendicular to said beam of electrons in said interaction space, said means for directing further including beam forming means located outside said interaction space and adjacent said electron source for injecting electrons from said source into said interaction space in a direction substantially parallel to the direction of said magnetic field.
  • a traveling wave electron discharge device comprising a curved periodic nonreentrant slow wave energy propagating network for transmitting electromagnetic wave energy, an arcuate electrode spaced from and substantially coaxial and coextensive with said periodic network, said network and said electrode at least partially defining an interaction space therebetween, an electron source disposed outside said interaction space, and means for directing a beam of electrons along said interaction space in energy interacting relationship with said wave energy, said electron source being arranged in juxtaposition with a portion of saidnetwork nearer the end thereof away from which electrons are directed, said means for directing including means for producing mutually transverse electric and magnetic fields in the region of said interaction space, said magnetic field being generally transverse to said interaction space, said means for directing further including beam forming means located outside said interaction space and substantially parallel to said electrode for injecting electrons from said source into said interaction space along a path a portion of which is substantially parallel to the direction of said magnetic field.
  • a traveling wave electron discharge device comprising a periodic nonreentrant slow wave energy propagating network for transmitting electromagnetic wave energy, an electrode spaced from and substantially coextensive with said periodic network, said network and said electrode at least partially defining an interaction space therebetween, an electron source, and means for directing a beam of electrons along said interaction space in energy interacting relationship with said wave energy, said electron source being arranged in juxtaposition with said entire network, said means for directing including means for producing mutually transverse electric and magnetic fields in the region of said interaction space and substantially perpendicular to said beam of electrons in said interaction space, said means for directing further including beam forming means adjacent said electron source for injecting electrons from said source into said interaction space in a direction substantially parallel to the direction of said magnetic field.
  • a traveling wave electron discharge device comprising a periodic nonreentrant slow wave energy propagatirv network for transmitting electromagnetic wave energy, an electrode spaced from and substantially coextensive with said periodic network, said network and said electrode at least partially defining an interaction space therebetween, a pair of electron sources arranged coextensive with at least a portion of said network, said electron sources being disposed on opposite sides of said interaction space, and means for directing a beam of electrons along said interaction space in energy interacting relationship with said wave energy, said means for directing including means for producing mutually transverse electric and magnetic fields in the region of sa d interaction space and substantially perpendicular to said beam of electrons in said interaction space, said magnetic field being generally transverse to said inter 12 action space, said means for directing further including beam forming means located outside said interaction space and adjacent said electron source for injecting electrons from said source into said interaction space along a path a portion of which is substantially parallel to the direction of said magnetic field.
  • a traveling wave electron discharge device comprising a periodic nonreentrant slow wave energy propagating network for transmitting electromagnetic wave energy and an electrode spaced from and substantially coextensive with said periodic network, said network and said electrode at least partially defining an interaction space therebetween, an electron source arranged coextensive with at least a portion of said network, means for directing a beam of electrons along said interaction space in energy interacting relationship with said wave energy, said means for directing including means for producing mutually transverse electric and magnetic fields in the region of said interaction space and substantially perpendicular to said beam of electrons in said interaction space, said means for directing further including beam forming means located outside said interaction space and adjacent said electron source for injecting electrons from said source into said interaction space in a direction substantially parallel to the direction of said magnetic field, and means for varying the beam current independently of beam velocity in response to a modulation input signal applied to said beam forming means.
  • a traveling wave electron discharge device comprising a periodic nonreentrant slow wave energy propagating network for transmitting electromagnetic wave energy, an electrode spaced from and substantially coextensive with said periodic network, said network and said electrode at least partially defining an interaction space therebetween, an electron source disposed outside said interaction space and arranged coextensive with at least a portion of said network, means for producing a magnetic field substantially transverse to said interaction space, means for directing a beam of electrons along said interaction space in energy interacting relationship with said wave energy, said beam traversing a given point of said network more than once, said means for directing including beam forming means located outside said interaction space and adjacent said electron source for injecting electrons from said source into said interaction space in a direction substantially perpendicular to the direction of said electron beam in said interaction space and along a path at least a portion of which is substantially parallel to the direction of said magnetic field, and means for varying the beam current independently of beam velocity in response to a modulation input signal applied to said beam forming means.
  • a traveling wave electron discharge device comprising a periodic nonreentrant slow wave energy propagating network for transmitting electromagnetic wave energy and an electrode spaced from and substantially coextensive with said periodic network, said network and said electrode at least partially defining an interaction space therebetween, a pair of electron sources disposed outside said interaction space and arranged coextensive with at least a portion of said network, said electron sources being disposed on opposite sides of said interaction space, means for directing a beam of electrons along said interaction space in energy interacting relationship with said wave energy, said means for directing including means for producing mutually transverse electrio and magnetic fields in the region of said interaction space and substantially perpendicular to said beam of electrons in said interaction space, said magnetic field being generally transverse to said interaction space, said means for directing further including beam forming means located outside said interaction space and adjacent said electron source for injecting electrons from said source into said interaction space in a direction substant ially parallel to the direction of said magnetic field, and
  • a traveling wave electron discharge device comprising a periodic nonreentrant slow wave energy propagating network for transmitting electromagnetic wave energy and an electrode spaced ,from and substantially coextensive with said periodic network and maintained at a negative voltage with respect to said network, said network and said electrode at least partially defining an interaction space therebetween, an electron source disposed outside said interaction space and arranged coextensive with at least a portion of said network, means for directing a beam of electrons along said interaction space in energy interacting relationship with said wave energy, said means for directing including means for producing mutually transverse electric and magnetic fields in the region of said interaction space and substantially perpendicular to said beam of electrons in said interaction space, said means for directing further including beam forming means located outside said interaction space and adjacent said electron source for injecting electrons from said source into said interaction space in a direction substantially parallel to the direction of said magnetic field, means for varying the frequency of operation of said device in accordance with the magnitude of the voltage between said network and said electrode, and means for varying the beam current independently of beam velocity in
  • a traveling wave oscillator comprising a nonreentrant slow wave energy propagating network for transmitting electromagnetic wave energy, an electrode spaced from and substantially coextensive with at least a portion of said network, said network and said electrode at least partially defining an interaction space therebetween, an electron source disposed coextensive with at least a portion of said network, means for producing a magnetic field substantially transverse to said interaction space, means for directing a beam of electrons along said interaction space in energy-exchanging relationship with said wave energy, said means for directing including beam forming means located outside said interaction space and adjacent said electron source for injecting electrons from said source into said interaction space in a direction substantially perpendicular to the direction of said electron beam in said interaction space and along a path a portion of which is substantially parallel to the direction of said magnetic field, and means for varying the beam current independently of frequency in response to an amplitude modulation input signal applied to said beam forming means.

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Description

Dec. 16, 1958 DENCH TRAVELING WAVE ELECTRON DISCHARGE DEVICES 2 Sheets-Sheet 1 Filed March 30, 1956 /Nl/ENTO Q @WAPD DENCH A T TOPNEY Dec. 16, 1958 E. C. DENCH TRAVELING WAVE ELECTRON DISCHARGE DEVICES Filed March 30, 1956 I 2 Sheds-Sheet 2 ATTORNEY ,end of the periodic structure.
United States Patent TRAVELING WAVE ELECTRON DISCHARGE DEVICES Edward C. Dench, Needham, Mass., assignor to Raytheon Manufacturing Company, Waltham, Mass., a corporation of Delaware Application March 30, 1956, Serial No. 575,113
18 Claims. (Cl. 332--7) This invention relates to traveling Wave electron discharge devices and more specifically to means for increasing the power rating of such devices by novel beam injection techniques.
Traveling wave electron discharge devices are widely used either as amplifiers capable of operation over a large band width or as oscillators capable of being tuned electronically over a considerable frequency range in the microwave region. Such devices utilize the interaction between an electron beam moving along paths adjacent a periodic non-resonant slow wave propagating structure and the electromagnetic field of the radio frequency wave propagating along said periodic structure. The electromagnetic field along such a periodic structure may be resolved into a number of superimposed traveling waves or space harmonics each having its own phase velocity. Some of the space harmonics of a phase velocity travel in the same direction as the wave energy or group velocity and are referred to as forward waves. Other space harmonics, on the other hand, have a phase velocity of opposite sense, that is, the phase velocity is in a direction opposite to the energy or group velocity. Such harmonics are referred to as backward waves. If the electron beam velocity is adjusted so that it is in substantial synchronism with the phase velocity of a given space harmonic, interaction between the electron beam and this component will occur, and energy will be transferred from the electron beam to the electromagnetic field. In a traveling wave amplifier, a radio frequency input signal is coupled to the periodic structure adjacent one end thereof, and, owing to the interaction between electron beams moving along a path adjacent the periodic structure and the electromagnetic field of the radio frequency Wave propagating along said structure, amplification of the input signal may be obtained, under proper operating conditions. This amplified signal may then be extracted from the periodic structure adjacent the other (output) end thereof. In the forward wave amplifier the interaction is between the electron beam and a forward wave; the electrons thus are projected toward the output amplifier, interaction occurs between the electron beam and a backward wave and the electrons then move to ward the input end of the periodic structure. In a travel- In the backward wave r ing wave oscillator, when the electron beam current exceeds a critical current at which oscillations can begin, and when the electron beam velocity is substantially equal to the velocity of one of the backward waves, oscillations may be generated within the device and the generated energy will propagate along the periodic structure and may be extracted at the end thereof away from which the electrons are moving.
, In traveling wave tubes in which the electron beam moves through transversely directed direct current electric and magnetic fields perpendicular to the motion of the electrons, it is desirable to provide a relatively flat beam which may be injected along an equipotential in ice . Widely in use, the electron gun is located near one end of the periodic delay structure and injection of the beam occurs from this end of the device. The cathodes of such localized electron guns have a relatively small surface and mass and the power handling capabilities are correspondingly restricted.
In other systems, particularly employed in traveling wave tubes of cylindrical construction, a continuous cathode substantially coextensive with the periodic delay structure is used in order to increase the power rating of the traveling wave tube. In tubes of this type, the electrical field is produced by the potential between the cathode and the periodic delay structure and the frequency of operation, in the case of traveling wave oscillators, is dependent upon the aforesaid potential. In such an oscillator, amplitude modulation of the tube may be accomplished by varying the tube current; however, this current is a function of the voltage between the periodic delay structure and the cathode, and changes in current not only produce amplitude modulation but also are accompanied by an undesirable change in operating frequency of the tube. Furthermore, in tubes of this type, whether they be amplifiers or oscillators, the space charge cloud surrounding this cathode occupies a considerable space 'and is characterized by a large range of electron velocities from zero at the cathode surface to a maximum at the outer edge of the cloud. As a result of this wide dispersion of electron velocities, the number of electrons in the electron beam available for synchronous interaction with the electromagnetic field is reduced.
In accordance with this invention, the electron gun is positioned utside the interaction space between the periodic anode structure and the negative electrode or sole. The electrons from the cathode of this electron gun are accelerated by means of one or more beam forming electrodes of the electron gun in a direction parallel to the magnetic field into the interaction space, where, under the influence of the transverse electric and magnetic fields previously referred to, they will be diverted and caused to travel along the interaction space in a direction determined by the polarity of the magnetic field. The elec trons may be formed into a ribbon-type beam which may be projected substantially along only one equipotential level. Traveling wave oscillators according to the invention may be amplitude modulated by means of a signal applied to one or more of these beam forming electrodes. For example, this amplitude modulating signal may be applied between one or more of the beam forming electrodes and either the cathode or the negative sole.
Since the electron gun assembly is located outside the electrodes of the tube which bound the main interaction space, a cathode of relatively large area and mass may be used and may, if desired, extend the entire length of the tube. Consequently, the traveling wave tube of the invention is capable of handling considerably more power than prior traveling wave tubes which contain a limited cathode positioned only at one end of the periodic anode structure.
In contrast with prior traveling wave oscillators of the type in which a continuous cathode and a periodic anode structure bound the interaction space, amplitude modulation in the traveling wave tube according to this invention 7 may be effected independently of frequency modulation.
Since the electrons may be shaped into a narrow beam prior to entrance into the interaction space action space to insure their entrance substantially at only one desired equipotential level, the velocity range of the electron beam is much less than that of prior traveling wave tubes employing acontinuous cathode, and the efli- 'ciency of interaction is correspondingly increased. It should -be noted, in this regard, that if beam shaping electrodes were used in continuous cathode systems of the prior art, these electrodes would have to be introduced into the interaction space and this would seriously affect the operation of such tubes.
Other objects and features of this invention will be understood more clearly and fully from the following detailed description of the invention with reference to the accompanying drawing wherein:
Fig. 1 is an isometric view, particularly in section, of an embodiment of a traveling wave tube according to the invention;
Fig. 2 is a cross-sectional view of the tube shown in Fig. 1;
Fig. 3 is a cross-sectional view of a modification of the tube of Figs. 1 and 2 in which electron injection occurs from both sides of the tube;
Fig. 4 is a diagram of a traveling wave tube similar to that of Figs. 1 to 3 in which means are provided for amplitude modulation;
Fig. 5 is a simple cross-sectional view of a traveling wave tube of cylindrical configuration according to the invention;
Fig. 6 is a sectional view taken along lines 66 of Fig. 5;
Fig. 7 is a detail showing a portion of the electron gun assembly;
Fig. 8 is a detail view of a portion of the anode assembly of th tube of Fig. 5;
Fig. 9 is a detail view of another portion of the electron gun assembly; and
Figs. 10 and 11 are sectional views of a modification of the cylindrical tube of Figs. 5 and 6.
Referring to Figs. 1 and 2, a traveling wave amplifier tube 15 is shown which contains an anode assembly having a linear periodic slow wave propagating structure 22. This structure, also referred to hereinafter as an anode delay network, comprises a pair of electrically conductive interleaved members 23, each including several spaced fingers 24 which connect to a longitudinal portion 25 and extend transversely to the latter almost to the opposite longitudinal portion. The anode delay network is carried by an electrically insulating base plate 27, which in turn, is securely attached by any appropriate means to a continuous electrically conductive backing member 28. Backing member 28 forms one of the walls of an evacuated envelope further including an oppositely disposed wall 29, side walls 30 and 31, and a pair of end walls, 32 and 33. Electrical connection between the anode delay network 22 and the wall 28 may be made by means of electrically conductive screws 34 used for attaching the anode assembly, including base plate 27, to the tube envelope, as well as by electrically conductive straps 35.
The device of Fig. 1 has an output energy coupling device 36 and an input coupling device 38 indicated as coaxial coupling devices, although the invention is not limited to coaxial type transmission lines; for example, wave guide coupling means also may be used. The inner conductor 39 of output coupling device 36 extends throughout an aperture 41 in wall 28 and base plate 27 and is attached, as by brazing, to an end finger 24 of the interdigital delay network, as clearly shown in Fig. l. The inner conductor 42 of the input coupling device 38 likewise extends through Wall 28 and base plate 27 and is attached to a finger at the end of the network 22 opposite that to which the output coupling device is attached. Although the device of Fig. 1 has two energy coupling means and is adapted to operate as a forward wave traveling wave amplifier, it should be understood .4 that the invention is notso restricted, but may be applied as well to a backward wave amplifier if the position of the input and output coupling means is reversed; furthermore, operation may be had as a traveling wave oscillator provided, of course, that the electron beam is synchronized with proper space harmonic of the electromagnetic field. If the tube 15 is to be used as an oscillator, one of the energy coupling means can be omitted. The forward wave amplifier tube of Figs. 1 to 3 may be converted into a backward wave oscillator by omitting the coupling device 36 and using coupling device 38 as an output coupling device.
Attenuation may be introduced into the interdigital anode delay network by means of a coating of lossy material, such as iron, which may be plated on the fingers of the network of the region thereof in which attenuation is desired. In the case of an amplifier, attenuation is normally placed about one-third of the distance from the input end of the delay network, while, for an oscillator, the attenuation should be positioned adjacent the end of the line remote from the output end.
An auxiliary electrode 44, hereinafter referred to as a sole, is disposed substantially parallel to the anode delay network 22 and is spaced therefrom. Sole 44 is a substantially U-shaped member, disposed coextensive with the anode network and having a base portion 44 and two upturned portions 44". The sole is supported with respect to the tube envelope by means of a pair of tubular supporting rods 47 rigidly attached to the sole and extending through an aperture in the wall of the tube envelope. A central conductor 48 is located inside support rod 47 and passes externally of the tube envelope. Each rod 47 is insulatedly supported with respect to wall 29 by means of a metallic member 49 sealed, in turn, to insulating seals 50; these insulating seals are connected to an electrically conductive cylinder 51 surrounding rod 47 and cylinder 51 is attached to a recess in the wall 29 surrounding the aperture throughout which rod 47 passes. The sole 44 is maintained negative with respect to the anode delay network by means of a unidirectional source of potential 52, such as a battery, which is connected between the sole 44 and some portion of the tube envelope.
Traveling wave tube 15 further includes an electron gun assembly 55 which comprises an elongated cathode 56 having an electron-emissive surface 57. This cathode is arranged substantially parallel to the longitudinal axis of the tube and extends axially about half the length of the sole and anode network, as shown in Fig. l. Cathode 56 is supported from the end walls 32 and 33 of the tube envelope by support rods 58 which are sealed in an electrically insulating seal 59, such as a vitreous seal, mounted in the end walls. One of the two cathode support rods 58 extends through a corresponding seal 59 externally of the tube envelope. The cathode is heated to a temperature sufficicnt for thermionic electron emission from the emissive surface 57 by means of a heater 60 which, for example, may be in the form of an elongated coil insulatedly mounted with respect to the cathode by electrically insulating spacers 61 secured to the cathode and containing apertures for passage of the heater coils. One end of the heater coil 60 is attached to the cathode and the other end thereof is connected by means of a flexible end portion to a heater supporting rod 63 which, like one of the cathode supporting rods 58, passes through a vitreous seal 59 within the wall 32 and externally of the tube envelope. The necessary heater potential is supplied by the unidirectional voltage source 65.
The sole may be negatively biased with respect to the cathode by means of battery 68; in some instances, the sole and cathode may be held at the same potential.
The electron gun assembly 55 also may include beam forming electrodes 66 and 67, respectively positioned slightly above and below the cathode. The lowermost of these beam forming electrodes is spaced slightly from.
the sole as shown more clearly in Fig. 2; however, in some instances, the lowermost electrode may be supported by the sole. The upwardly extending portion or edge 44 of the sole adjacent the electron gun preferably is cut away over the length of the electron gun, as shown in Figs. 1 and 2, in order to permit the electron beam to enter the interaction space between the sole and the anode delay network under the combined action of the transverse electric and magnetic fields, to be described subsequently. The beam forming electrodes 66, 67 may be interconnected and made somewhat positive relative to the cathode by a battery 69. v
A suitable electric field is used between the anode delay network and the sole by means of the voltage from source 52 applied therebetween. A uniform magnetic field perpendicular to both the electric field and to the general direction of propagation of the electron beam along the longitudinal interaction space 70 is provided by either a permanent magnet or an electromagnet having pole pieces 71 and 72 positioned in contact with the adjacent respective side walls 30 and 31 of the tube envelope. The electron beam will be directed along the interaction space in either one direction or the other dependent upon the polarity of the transverse magnetic field.
The electron gun assembly, as shown in Fig. 1, extends only approximately half the length of the tube. This electron gun assembly is of less value near the downstream end of the tube, either in an amplifier or an oscillator, since .the portion of the electron beam adjacent the downstream end has little effect so far as interaction with the electromagnetic field of the wave guided by the periodic anode delay network is concerned. In other words, the electrons injected into the interaction space near the collector, if a collector is used, or near the end of the anode network which intercepts a substantial portion of the electrons, where the anode network itself serves as the collector of electrons, expend themselves with little energy interchange. However, as shown in Fig. 4 the electron gun assembly may extend the entire length of the anode delay network, especially in cases in which maximum interaction is desired.
In Fig. 3, an arrangement is shown for increasing the beam current by injecting electrons into the interaction space 70 between the sole and the anode network from both sides thereof. The traveling wave tube of Fig. 3 thus includes two electron gun assemblies 55, one mounted on each side of the tube; these electron gun assemblies may be of identical construction and may be supported within the tube in the manner indicated previously in connection with Figs. 1 and 2. Since the electrons are injected from both sides, the upturned portions 44" of the sole in the region of the gun assemblies either are eliminated or are made sufiiciently short as not to interfere with the electron beam as it was injected to the interaction space. t
In Fig. 4, an arrangement is shown for either frequency modulating or amplitude modulating the output of an oscillator tube. Elements of Fig. 4 corresponding to Figs. 1 and 2 are represented by the same reference numerals. The electron gun assembly of Fig. 4 includes a cathode 56, heater 6'0, and beam forming electrodes 66 and 67, just as in Figs. 1 to 3, together with an additional pair of beam forming electrodes 74 and 75. The electrodes 74 and 75 may be electrically connected; likewise, the cathode 56 and the electrodes 66 and 67 may be interconnected so as to be at the same electrical potential.
When the device of Fig. 4 is used as an oscillator, the
source 52.
Amplitude modulation may be accomplished by varying the potential of the beam forming plates 74 and 75 relative to the cathode, as by modulation source 78 connected in series with the unidirectional source 79'between these beam forming plates and the cathode, or by varying the potential of these beam forming plates relative to sole 44 by means of modulation source 81, connected in series with voltage source 82, or by varying both in combination. Since variation of either or both of the modulation sources 78 or 81 will influence the beam current injected into the interaction space 70, the power of the tube may be varied over a considerable range. I
In Figs. to 8, a traveling wave tube is shown which is of cylindrical construction, as contrasted with the linear configuration previously described. The elements of Figs. 5 to 8 corresponding with those of Figs. 1 to 4 will be designated by the same reference numerals. The oscillator tube includes an anode assembly including a periodic slow wave energy propagating structure 22, a sole electrode 44 maintained negative relative to the anode delay network 22, a lead-in assembly 85, an output coupling means 38, an electron gun assembly 55 including at least a cathode 56 and a heater 60, and a transverse magnetic field producing means, the pole pieces 71 and 72 of which are illustrated in Fig. 5.
The anode assembly 22 comprises a circular interdigital delay line including a plurality of interdigital fingers 24 which extend from oppositely disposed annular members 25. Members are secured by screws 26 (see Fig. 8) to the shoulder portion of a cylindrical electrically conductive ring 37. The remainder of the anode assembly includes a pair of oppositely positioned cover plates 18 and 19 electrically sealed to ring 37, as shown in Fig. 5
The sole 44 consists essentially of a'substantially cylindrical block of electrically conductive material, such as copper. A centrally located aperture is provided in the sole to permit connection of lead-in assembly 85 and to allow for passage of external connecting leads, in a .manner to be shown subsequently. Alternatively, the sole may be a tubular member whose outer periphery coincides with that of the solid member illustrated in Figs. 5 and 6.
Lead-in assembly 85 includes an electrically conductive cylindrical sleeve 86 inserted in an aperture in cover plate 19 and securely attached thereto. A section of glass tubing 87 serves to interconnect metal sleeve -86 and a second metal sleeve 88. The other end of sleeve 88 is provided with a glass seal 89 for sealing tube 15 after evacuation. Sleeves 86 and 88 preferably are constructed of a material having an expansion coefficient closely approximating that of tubing 87. The assembly 85 further includes an elongated electrically conductive hollow supporting cylinder 90 which serves as the main support for sole 44. One end of cylinder is fastened to the periphery of aperture 45 in the sole. The other end of cylinder 90 contains an outwardly flared portion 91 which is connected to the inner surface of sleeve 88. The necessary leads for the electron gun are fed through supporting cylinder 90 and are insulatedly supported therefrom and from one another by one or more glass beads 92. The coaxial output coupling means 38 is sealed in an opening in wall 37 of the anode assembly 20 and are impedance matched to the anode delay network 22. The inner conductor 39 of the coaxial input coupling means 38 is connected to a finger at or adjacent one end of the periodic anode delay network.
Although an oscillator is shown and described in Figs. 5 and 6, the tube therein shown may, under the proper operating conditions, be used as a traveling wave amplifier, as shown in Fig. 10. In this case, an input coupling means 36 is provided which is coupled to the anode delay network 22 at or near the end thereof opposite the end to which the output coupling means 38 is attached. The particular location of the input and 'to 8 includes a cathode 56, a heater 60, and a pair of annular beam forming plates or electrodes 66 and 67, shown in detail in Fig. 9, and supported from cover plate 19 by rigid posts 107. The cathode 56 may be an annular fiat ring, one surface of which is connected with an electron-emissive material 57. The cathode is arranged coextensive with the annular interaction space 70 between the anode delay network 22 and sole 44. Cathode 56 is supported from the cover plate 18 by means of several blocks 94 of electrically insulating material which are secured to the cathode by screws 95. See Fig. 7. The blocks 94 contain a threaded portion 96 adapted to be screwed into threaded apertures in the cover plate 19. The blocks 94 contain apertures 97 for receiving an arcuate heater wire 60 which is disposed adjacent the cathode on the side opposite the emitting surface 57.
A cathode lead 101 is connected at some point on the cathode 56 and is brought out through the tubular supporting cylinder 90 externally of the tube. One end of heater 60 is connected to the cathode and the other end is attached to a heater lead 102 passing through cylinder 90 externally of the tube. The beam forming plates 66 and 67, which may be supported from the cover plate 19 by support post 107, may be interconnected by a jumper 104; a lead 103 is connected to one of these beam forming plates and is brought out from the tube through cylinder 90.
A suitable electric field between the anode and sole may be attained by means of a unidirectional voltage applied therebetween. The sole is maintained at a negative potential relative to the anode by means of a source 52 of voltage connected between metal sleeve 86 (which is connected to anode delay network 22) and cathode lead 101. The sole 44 may be biased negatively with respect to cathode 56 by means of a source 68 of voltage connected between sleeve 88 and cathode lead 101. The cathode, in some instances, may be at the same potential as the sole, however. The beam forming electrode 66 and 67 are made positive relative to the cathode by means of a source 69 of voltage interconnecting leads 101 and 103.
The heater potential source 65 is connected between leads 101 and 102. Amplitude modulation source 105 may be connected in series with voltage source 69 between the cathode and the beam forming electrodes by means of a switch 110 for amplitude modulating the output of tube 15, when operation as an oscillator is desired. In some instances, particularly when modulation is not required, it is possible to omit the beam forming electrodes 66 and 67 shown in Figs. and 6.
For reasons already explained in connection with the linear tube of Figs. 1 to 4, the electron gun assembly may extend over only a portion of the entire length of the anode delay network 22, as shown in Fig. 6. It is possible, of course, to arrange the electron gun assembly so that it extends along the entire length of the anode delay network, as shown in Fig. 10. The device in Fig. also indicates a traveling wave tube adapted to operate as an amplifier, as contrasted with the traveling wave tube oscillator shown in Figs. 5 and 6.
A uniform magnetic field transverse to the direction of propagation of the electron beam and the electrical field between theanode delay network and sole is provided by a permanent magnet or an electromagnet having cylindrical pole pieces 71 and 72 positioned on or adjacent the tube. Pole piece 71 is apertured to receive the lead-in assembly and pole piece 72 is apertured to maintain symmetry of the magnetic field. The flux line should be concentrated in the interaction space 70 between sole 44 and anode delay network 22. By proper adjustment of the magnitude and polarity of the transverse magnetic and electric fields, the electron beam may be made to follow a circular path about interaction space 70 under the combined influence of these fields.
The traveling wave tube may be arranged as shown in Fig. 11 in which the collector electrode 40, shown in Figs. 6, 8 and 10, has been omitted. In this device, the
'' interaction space 70 and the electron beam may be made reentrant, that is, the electron beam is capable of making more than one traversal of the interaction space 70. In a device of this type, the electron gun assembly may be continuous. In order to maintain the electric field uniform in the region between the ends of the anode delay network 22, an extension of the wall 37 of the anode assembly is used to maintain the spacing between the anode and the sole equal to that in the interaction portion of the tube. The construction of Fig. 11 may be used in an amplifier, as well as in the oscillator shown. It will be noted that the output coupling means 38 of Fig. 10 is positioned at the opposite end of the delay line 22 from that in Fig. 6. This difference in location of the output coupling means is due to the fact that the direction of the magnetic field in the device of Fig. ll is opposite that in Fig. 6, and, consequently, the direction of motion of the electrons in interaction space 70 is reversed.
This invention is not limited to the particular details of construction, materials and processes described, as many equivalents will suggest themselves to those skilled in the art. For example, the electron gun shown in Fig. 4 may be used in a circular traveling wave tube, such as shown in Figs. 5 to 10, as well as in a tube of linear configuration.
It is, accordingly, desired that the appended claims be given a broad interpretation commensurate with the scope of the invention within the art.
What is claimed is:
1. A traveling wave electron discharge device comprising a periodic nonreentrant slow wave energy propagating network for transmitting electromagnetic wave energy, an electrically-conductive element spaced from and substantially coextensive with said periodic network, said network and said element at least partially defining an interaction space therebetween, an electron source disposed outside said interaction space and arranged coextensive with at least a portion of said network, means for producing a magnetic field substantially transverse to said interaction space, and means for injecting a beam of electrons from said source into said interaction space along a path a portion of which is substantially parallel to the direction of said magnetic field in energy interacting relationship with said wave energy.
2. A traveling wave electron discharge device comprising a periodic nonreentrant slow wave energy propagating network for transmitting electromagnetic wave energy, an electrically-conductive element spaced from and substantially coextensive with said periodic network,
"9 interaction space along a path at least a portion of which is substantially parallel to the direction of said magnetic field and in a direction substantially perpendicular to the direction of said electron beam in said interaction space.
3. A traveling wave electron discharge device comprising a periodic nonreentrant slow wave energy propagating network for transmitting electromagnetic wave energy, an electrode spaced from and substantially coextensive with said periodic network, said network and said electrode at least partially defining an interaction space therebetween, an electron source disposed outside said interaction space and arranged coextensive with at least a portion of said network, means for producing a magnetic field substantially transverse to said interaction space, and means for directing a beam of electrons along said interaction space in energy interacting relationship with said wave energy, said beam transversing a given point on said network more than once, said means for directing including beam forming means lo cated outside said interaction space and adjacent said electron source for injecting electrons from said source into said interaction space along a path at least a portion of which is substantially parallel to the direction of said magnetic field and in a direction substantially perpendicular to the direction of said electron beam in said interaction space.
4. A traveling wave electron discharge device comprising a periodic nonreentrant slow wave energy propagating network for transmitting electromagnetic wave energy, an electrode spaced from and substantially coextensive with said periodic network, said network and said electrode at least partially defining an interaction space therebetween, an electron source disposed outside said interaction space and arranged coextensive with at least a portion of said network, means for producing a magnetic field substantially transverse to said interaction space, and means for directing a beam of electrons along said interaction space in energy interacting relationship with said wave energy, said electron beam being nonreentrant, said means for directing including beam forming means located outside said interaction space and adjacent said electron source for injecting electrons from said source into said interaction space along a path at least a portion of which is substantially parallel to the direction of said magnetic field and in a direction substantially perpendicular to the direction of said electron beam in said interaction space.
5. Atraveling wave electron discharge device comprising a periodic nonreentrant slow wave energy propagating network for transmitting electromagnetic wave energy, an electrode spaced from and substantially coextensive with said periodic network, said network and said electrode at least partially defining an interaction space therebetween, an electron source disposed outside said interaction space, means for producing a magnetic field substantially transverse to said interaction space, and means for directing a beam of electrons from said source along said interaction space in energy interacting relationship with said wave energy, said electron source being arranged in juxtaposition with a portion of said network nearer the end thereof away from which electrons are directed, said means for directing including beam forming means located outside said interaction space and adjacent said electron source for injecting electrons from said source into said interaction space along a path at least a portion of which is substantially parallel to.the direction of said magnetic field and in a direction substantially perpendicular to the direction of said electron beam in said interaction space.
6. A traveling wave electron discharge device com prising a periodic nonreentrant slow wave energy propagating network for transmitting electromagnetic wave energy, an electrode spaced from and substantially co extensive with said periodic network, said network and said electrode at least partially defining an interaction space therebetween, an electron source disposed outside said interaction space, means for producing a magnetic field substantially transverse to said interaction space, and means for directing a beam of electrons from said source along said interaction space in energy interacting relationship with said wave energy, said electron source being arranged in juxtaposition with said entire network, said means for directing including beam forming means located outside said interaction space and adjacent said electron source for injecting electrons from said source into said interaction space along a path at least a portion of which is substantially parallel to the direction of said magnetic field and in a direction substantially perpendicular to the direction of said electron beam in said interaction space.
7. A traveling wave electron discharge device comprising a periodic nonreentrant slow wave energy propagat ing network for transmitting electromagnetic wave energy, an electrode spaced from and substantially coextensive with said periodic network, said network and said electrode at least partially defining an interaction space therebetween, a pair of electron sources disposed outside said interaction space and arranged coextensive with at least a portion of said network, said electron sources being disposed on opposite sides of said interaction space, means for producing a magnetic field substantially transverse to said interaction space, and means for injecting a beam of electrons from said source into said interaction space along a path a portion of which is substantially parallel to the direction of said magnetic field in energy interacting relationship with said wave energy.
8. A traveling wave electron discharge device comprising a periodic nonreentrant slow wave energy propagating network for transmitting electromagnetic wave energy, an electrode spaced from and substantially coextensive with said periodic network, said network and said electrode at least partially defining an interaction space therebetween, a pair of electron sources disposed outside said interaction space and arranged coextensive with at least a portion of said network, said electron sources being disposed on opposite sides of said interaction space, means for producing a magnetic field substantially transverse to said interaction space and means including beam forming means located outside said interaction space and adjacent said sources for injecting a beam of electrons from each of said sources into said interaction space in energy interacting relationship with said wave energy along a path a portion of which is substantially parallel to the direction of said magnetic field in a direction substantially perpendicular to the direction of said electron beam in said interaction space.
9. A traveling wave electron discharge device comprising a periodic nonreentrant slow wave energy propagating network for transmitting electromagnetic wave energy, an electrode spaced from and substantially coextensive with said periodic network, said network and said electrode at least partially defining an interaction space therebetween, an electron source disposed outside said interaction space and arranged coextensive with at least a portion of said network, means for producing a magnetic field substantially transverse to said interaction space, and means for injecting a beam of electrons into said interaction space along a path a portion of which is substantially parallel to the direction of said magnetic field and substantially perpendicular to said electron beam in energy interacting relationship with said wave energy, and means for varying the beam current independently of beam velocity in response to a modulation input signal applied to said means for injecting.
10. A traveling wave electron discharge device comprising a periodic nonreentrant slow wave energy propagating network for transmitting electromagnetic wave energy, an electrode spaced from and substantially coextensive with said periodic network, said network and said electrode at least partially defining an interaction space therebetween, an electron source disposed outside said interaction space and arranged coextensive with at least a portion of said network, and means for directing a beam of electrons along said interaction space in energy interacting relationship with said wave energy, said means for directing including means for producing mutually transverse electric and magnetic fields in the region of said interaction space and substantially perpendicular to said beam of electrons in said interaction space, said means for directing further including beam forming means located outside said interaction space and adjacent said electron source for injecting electrons from said source into said interaction space in a direction substantially parallel to the direction of said magnetic field.
11. A traveling wave electron discharge device comprising a curved periodic nonreentrant slow wave energy propagating network for transmitting electromagnetic wave energy, an arcuate electrode spaced from and substantially coaxial and coextensive with said periodic network, said network and said electrode at least partially defining an interaction space therebetween, an electron source disposed outside said interaction space, and means for directing a beam of electrons along said interaction space in energy interacting relationship with said wave energy, said electron source being arranged in juxtaposition with a portion of saidnetwork nearer the end thereof away from which electrons are directed, said means for directing including means for producing mutually transverse electric and magnetic fields in the region of said interaction space, said magnetic field being generally transverse to said interaction space, said means for directing further including beam forming means located outside said interaction space and substantially parallel to said electrode for injecting electrons from said source into said interaction space along a path a portion of which is substantially parallel to the direction of said magnetic field.
12. A traveling wave electron discharge device comprising a periodic nonreentrant slow wave energy propagating network for transmitting electromagnetic wave energy, an electrode spaced from and substantially coextensive with said periodic network, said network and said electrode at least partially defining an interaction space therebetween, an electron source, and means for directing a beam of electrons along said interaction space in energy interacting relationship with said wave energy, said electron source being arranged in juxtaposition with said entire network, said means for directing including means for producing mutually transverse electric and magnetic fields in the region of said interaction space and substantially perpendicular to said beam of electrons in said interaction space, said means for directing further including beam forming means adjacent said electron source for injecting electrons from said source into said interaction space in a direction substantially parallel to the direction of said magnetic field.
13. A traveling wave electron discharge device comprising a periodic nonreentrant slow wave energy propagatirv network for transmitting electromagnetic wave energy, an electrode spaced from and substantially coextensive with said periodic network, said network and said electrode at least partially defining an interaction space therebetween, a pair of electron sources arranged coextensive with at least a portion of said network, said electron sources being disposed on opposite sides of said interaction space, and means for directing a beam of electrons along said interaction space in energy interacting relationship with said wave energy, said means for directing including means for producing mutually transverse electric and magnetic fields in the region of sa d interaction space and substantially perpendicular to said beam of electrons in said interaction space, said magnetic field being generally transverse to said inter 12 action space, said means for directing further including beam forming means located outside said interaction space and adjacent said electron source for injecting electrons from said source into said interaction space along a path a portion of which is substantially parallel to the direction of said magnetic field.
14. A traveling wave electron discharge device comprising a periodic nonreentrant slow wave energy propagating network for transmitting electromagnetic wave energy and an electrode spaced from and substantially coextensive with said periodic network, said network and said electrode at least partially defining an interaction space therebetween, an electron source arranged coextensive with at least a portion of said network, means for directing a beam of electrons along said interaction space in energy interacting relationship with said wave energy, said means for directing including means for producing mutually transverse electric and magnetic fields in the region of said interaction space and substantially perpendicular to said beam of electrons in said interaction space, said means for directing further including beam forming means located outside said interaction space and adjacent said electron source for injecting electrons from said source into said interaction space in a direction substantially parallel to the direction of said magnetic field, and means for varying the beam current independently of beam velocity in response to a modulation input signal applied to said beam forming means.
15. A traveling wave electron discharge device comprising a periodic nonreentrant slow wave energy propagating network for transmitting electromagnetic wave energy, an electrode spaced from and substantially coextensive with said periodic network, said network and said electrode at least partially defining an interaction space therebetween, an electron source disposed outside said interaction space and arranged coextensive with at least a portion of said network, means for producing a magnetic field substantially transverse to said interaction space, means for directing a beam of electrons along said interaction space in energy interacting relationship with said wave energy, said beam traversing a given point of said network more than once, said means for directing including beam forming means located outside said interaction space and adjacent said electron source for injecting electrons from said source into said interaction space in a direction substantially perpendicular to the direction of said electron beam in said interaction space and along a path at least a portion of which is substantially parallel to the direction of said magnetic field, and means for varying the beam current independently of beam velocity in response to a modulation input signal applied to said beam forming means.
16. A traveling wave electron discharge device comprising a periodic nonreentrant slow wave energy propagating network for transmitting electromagnetic wave energy and an electrode spaced from and substantially coextensive with said periodic network, said network and said electrode at least partially defining an interaction space therebetween, a pair of electron sources disposed outside said interaction space and arranged coextensive with at least a portion of said network, said electron sources being disposed on opposite sides of said interaction space, means for directing a beam of electrons along said interaction space in energy interacting relationship with said wave energy, said means for directing including means for producing mutually transverse electrio and magnetic fields in the region of said interaction space and substantially perpendicular to said beam of electrons in said interaction space, said magnetic field being generally transverse to said interaction space, said means for directing further including beam forming means located outside said interaction space and adjacent said electron source for injecting electrons from said source into said interaction space in a direction substant ially parallel to the direction of said magnetic field, and
means for varying the beam current independently of beam velocity in response to a-modulation input signal applied to said beam forming means.
17. A traveling wave electron discharge device comprising a periodic nonreentrant slow wave energy propagating network for transmitting electromagnetic wave energy and an electrode spaced ,from and substantially coextensive with said periodic network and maintained at a negative voltage with respect to said network, said network and said electrode at least partially defining an interaction space therebetween, an electron source disposed outside said interaction space and arranged coextensive with at least a portion of said network, means for directing a beam of electrons along said interaction space in energy interacting relationship with said wave energy, said means for directing including means for producing mutually transverse electric and magnetic fields in the region of said interaction space and substantially perpendicular to said beam of electrons in said interaction space, said means for directing further including beam forming means located outside said interaction space and adjacent said electron source for injecting electrons from said source into said interaction space in a direction substantially parallel to the direction of said magnetic field, means for varying the frequency of operation of said device in accordance with the magnitude of the voltage between said network and said electrode, and means for varying the beam current independently of beam velocity in response to a modulation input signal applied to said beam forming means..
18. A traveling wave oscillator comprising a nonreentrant slow wave energy propagating network for transmitting electromagnetic wave energy, an electrode spaced from and substantially coextensive with at least a portion of said network, said network and said electrode at least partially defining an interaction space therebetween, an electron source disposed coextensive with at least a portion of said network, means for producing a magnetic field substantially transverse to said interaction space, means for directing a beam of electrons along said interaction space in energy-exchanging relationship with said wave energy, said means for directing including beam forming means located outside said interaction space and adjacent said electron source for injecting electrons from said source into said interaction space in a direction substantially perpendicular to the direction of said electron beam in said interaction space and along a path a portion of which is substantially parallel to the direction of said magnetic field, and means for varying the beam current independently of frequency in response to an amplitude modulation input signal applied to said beam forming means.
References Cited in the file of this patent UNITED STATES PATENTS
US575113A 1956-03-30 1956-03-30 Traveling wave electron discharge devices Expired - Lifetime US2865004A (en)

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Cited By (1)

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US2976455A (en) * 1958-03-19 1961-03-21 Gen Electric High frequency energy interchange device

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US2702370A (en) * 1953-03-18 1955-02-15 Csf Pulse-modulated traveling wave tube with crossed electric and magnetic fields
US2768328A (en) * 1946-11-05 1956-10-23 Bell Telephone Labor Inc High frequency electronic device

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Publication number Priority date Publication date Assignee Title
US2768328A (en) * 1946-11-05 1956-10-23 Bell Telephone Labor Inc High frequency electronic device
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2976455A (en) * 1958-03-19 1961-03-21 Gen Electric High frequency energy interchange device

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