US2890371A - Travelling wave tubes - Google Patents

Travelling wave tubes Download PDF

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Publication number
US2890371A
US2890371A US448816A US44881654A US2890371A US 2890371 A US2890371 A US 2890371A US 448816 A US448816 A US 448816A US 44881654 A US44881654 A US 44881654A US 2890371 A US2890371 A US 2890371A
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Prior art keywords
tube
travelling wave
waveguide
electron gun
helix
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US448816A
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English (en)
Inventor
Rogers Douglas Cecil
Burke Peter Francis Conway
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International Standard Electric Corp
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International Standard Electric Corp
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Priority claimed from GB839453A external-priority patent/GB755834A/en
Priority claimed from GB28268/53A external-priority patent/GB762106A/en
Priority claimed from GB18181/54A external-priority patent/GB787181A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J3/00—Details of electron-optical or ion-optical arrangements or of ion traps common to two or more basic types of discharge tubes or lamps
    • H01J3/02—Electron guns
    • H01J3/029—Schematic arrangements for beam forming
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
    • G09F7/00—Signs, name or number plates, letters, numerals, or symbols; Panels or boards
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F7/00—Magnets
    • H01F7/02—Permanent magnets [PM]
    • H01F7/0273—Magnetic circuits with PM for magnetic field generation
    • H01F7/0278—Magnetic circuits with PM for magnetic field generation for generating uniform fields, focusing, deflecting electrically charged particles
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J23/00—Details of transit-time tubes of the types covered by group H01J25/00
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J23/00—Details of transit-time tubes of the types covered by group H01J25/00
    • H01J23/02—Electrodes; Magnetic control means; Screens
    • H01J23/06—Electron or ion guns
    • H01J23/065—Electron or ion guns producing a solid cylindrical beam
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J23/00—Details of transit-time tubes of the types covered by group H01J25/00
    • H01J23/02—Electrodes; Magnetic control means; Screens
    • H01J23/08—Focusing arrangements, e.g. for concentrating stream of electrons, for preventing spreading of stream
    • H01J23/087—Magnetic focusing arrangements
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J23/00—Details of transit-time tubes of the types covered by group H01J25/00
    • H01J23/02—Electrodes; Magnetic control means; Screens
    • H01J23/08—Focusing arrangements, e.g. for concentrating stream of electrons, for preventing spreading of stream
    • H01J23/087—Magnetic focusing arrangements
    • H01J23/0873—Magnetic focusing arrangements with at least one axial-field reversal along the interaction space, e.g. P.P.M. focusing
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J23/00—Details of transit-time tubes of the types covered by group H01J25/00
    • H01J23/36—Coupling devices having distributed capacitance and inductance, structurally associated with the tube, for introducing or removing wave energy
    • H01J23/40—Coupling devices having distributed capacitance and inductance, structurally associated with the tube, for introducing or removing wave energy to or from the interaction circuit
    • H01J23/42—Coupling devices having distributed capacitance and inductance, structurally associated with the tube, for introducing or removing wave energy to or from the interaction circuit the interaction circuit being a helix or a helix-derived slow-wave structure
    • 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
    • H01J25/36—Tubes in which an electron stream interacts with a wave travelling along a delay line or equivalent sequence of impedance elements, and without magnet system producing an H-field crossing the E-field
    • H01J25/38—Tubes in which an electron stream interacts with a wave travelling along a delay line or equivalent sequence of impedance elements, and without magnet system producing an H-field crossing the E-field the forward travelling wave being utilised
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
    • H01J29/10—Screens on or from which an image or pattern is formed, picked up, converted or stored
    • H01J29/36—Photoelectric screens; Charge-storage screens
    • H01J29/38—Photoelectric screens; Charge-storage screens not using charge storage, e.g. photo-emissive screen, extended cathode

Definitions

  • the present invention relates to travelling wave tubes of the kind comprising, within a glass envelope, an electron gun, a helix of conducting material for guiding electromagnetic Waves in a slow mode of propagation to interchange energy with electrons projected from the said electron gun and means affording coupling between the said helix and an external waveguide.
  • Travelling wave tubes are normally used as amplifiers but can also be constructed to function as oscillators or modulators, mixers and the like. There must, therefore, in use be at least one wave feeder associated with the helix :and generally there will be both input and output wave couplings.
  • This wave coupling is usually achieved by inserting the tube through a hollow waveguide, built-out :cavity or the like, and providing probe antenna means associated with the helix internally of the tube envelope for coupling between the waveguide or cavity and the helix. Means must therefore normally be provided for avoiding undesirable leakage of wave energy around the outside of the tube through the waveguide apertures receiving the travelling wave tube.
  • the electron gun in the conventional travelling wave tube heretofore used, is housed within an envelope bulb portion similar to the envelope of a conventional radio receiving tube; the helix and waveguide coupling components are then contained within a long tubular envelope portion of smaller diameter than the said bulb portion.
  • This long tubular envelope portion is normally closed at the end opposite the electron gun by an electron collector electrode. Alignment and positioning of the various electrodes has been dependent to a large extent, if not entirely, upon the accurate dimensioning of the glass envelope portions of the tube. Owing to the inherent difficulties of accurate glass-working, it is very desirable in the manufacture of all types of electric discharge tube to avoid, so far as is possible, the use of glass to determine the relative position of electrodes.
  • the collector electrode must be able to dissipate most of the power in the electron beam, which is some 10 to 20 times the output radio-frequency power. For tubes giving an output power of several watts this requires that the collector be in intimate contact with a cooler of considerable size. It is an object of the present invention to provide a travelling wave tube in which the cooler is integral with the tube and does not need to be attached after the tube has been inserted in its circuit.
  • a travelling wave tube comprising a glass envelope and within said envelope a unitary assembly of an electron gun, a helix for guiding electromagnetic waves to interchange energy with electrons projected from the said gun and means for coupling the said helix to an external wave guide, a first annular metal end cap member hermetically sealed to said envelope, a second metal end cap member secured to the said electron gun and hermetically sealed to said first metal end cap member.
  • the invention provides a travelling wave tube comprising a first unitary assembly which comprises an electron gun, a terminal plate having leads hermetically sealed therethrough for connection to the said electron gun, a helix for guiding electromagnetic waves to interchange energy with the electrons projected from the said electron gun, and means comprising an antenna probe and a Wave-guide choke sleeve member affording coupling between the helix and an external waveguide; a second unitary assembly which comprises an electron collector electrode and a metal end cap sealed to one end of the glass envelope; mechanical coupling means having metal members secured respectively to the said first assembly and to the other end of the glass envelope such that, with the first unitary assembly inserted in the said glass envelope, the two assemblies are hermetically united by the sealing together of the said metal coupling members.
  • the said first unitary assembly is :based upon an electron gun structure which combines, in a single element, the electron gun, a ferromagnetic pole piece and a waveguide sleeve member to which structure the remaining members of the electrode assembly are secured.
  • Fig. 1 shows, for purposes of comparison, a view in partial section of a known type of travelling wave tube mounted in its associated apparatus;
  • Fig. 2 shows a perspective view of a travelling wave tube according to the present invention
  • Fig. 3 shows the component electrodes of the tube of Fig. 1 laid out to approximate an exploded view of the assembly thereof;
  • Fig. 4 shows, in partial section, an enlarged view of the electron gun end of the tube of Fig. 2;
  • Fig. shows a longitudinal cross section through the tube of Fig. 2 and its associated apparatus
  • Fig. 6 shows a preferred modification to parts of the tube of Figs. 2 to 5.
  • the travelling wave tube 1 comprises an el ctron gun 2 housed within an envelope bulb portion 3, which is provided with a conventional valve base 4 carrying pins 5 and a locating spigot 6 for use with a conventional type of valve socket providing 11C. supply connection means for feeding the electron and suitably polarising the helix of the tube.
  • the helix '7 is housed within a long glass tube 8 sealed on to the bulb 3, the envelope portion 8 being closed at the far end by an electron collectorelectrode 9, to which is secured a cooler 10, having cooling fins 11.
  • the tube is inserted through opposed apertures arranged the wide sides of an-input hollow rectangular waveguide 12 and a similar output waveguide '13, both of which extend into shortcircuited matchingsections 14 and 15 respectively.
  • the assembly consists of a set of coils 17, each wound upon a brass former 18.
  • the formers 18, in the positions intermediate the ends of the assembly, are each supported between brass bushes 19, or between a bush 19 and a washer 20, pairs of the latter bounding the respective waveguides.
  • the assembly steel plates 21 and 22 receive the ends of the adjacent formers 18 and are clamped together by means of a squirrel ca e system of ferromagnetic tie-rods 23, of which two are shown in Fig. 1.
  • the waveguides 12 and 13, with their extensions, are held in position by means of annular brass bosses 24 let in the apertures in the waveguide walls about the travelling wave tube 1, forming a seating for the washers 20.
  • the end plate 21 carries an insulating washer 25 which forms a support for the travelling wave tube at the electron gun end.
  • a mounting plate 26, secured to the end plate 22 by means of distance pieces 27 and bolts 28, receives and locates a flange 29 mounted on the base 4 of the travelling wave tube.
  • the electron gun 2 is mounted inside a cylindrical ferromagnetic pole piece and anode member, which is the only part of the gun visible in the drawing, and carries at its forward end a mica washer 30.
  • the gun is located in position in the bulb portion 3 of the glass envelope by means of this. washer 30, together with other mica washers not shown.
  • a hollow metal tube 31, through which the electron beam is projected, is mounted on the mica washer 30, and carries at its further end an inner waveguide choke member 32, which is formed of a cylindrical skirt portion closed by a centrally apertured front portion flush with the wall of waveguide 12.
  • the helix 7 is mounted within the envelope portion 8 by means of glass rods 33, which rest against the inner wall of envelope portion 8 and whose respective ends fit into suitable recesses in the waveguide choke member 32, at the electron gun end, and in a similar waveguide choke member 34 at the electron collector end of the tube.
  • the helix is of uniform pitch throughout its length and approximately one turn at each end projects into the respective waveguides 12 or 13.
  • the ends of the Wire of the helix are bent to project parallel to the axis of the tube and are joined to short tubular members which surround the electron beam and are secured to the respective inner waveguide choke members 32 and 34.
  • T he end plate 22 of the assembly 16 carries a central hollow cylinder 36 of ferromagnetic material which surrounds the electron gun 2 and projects beyond it towards the base of the travelling wave tube.
  • This cylinder helps to provide a low impedance path for the magnetic flux from the coil 17 into the internalpole piece member of the electron gun and also greatly attenuates the penetration of magnetic field towards the rear of the gun, so that the cathode of the electron gun is very adequately shielded from the magnetic focussing field.
  • the end plate 21 provides the other pole piece of the magnet system.
  • Fig. 1 The arrangement of Fig. 1 has been rather fully described in order to make clear some of the constructional problems regarding location of elements to be solved in the manufacture of the travelling wave tube and, by contrast, to assist in the understanding of the present invention. It should be noted, first, that there is a complete electrode system housed within an envelope the elements of which system have to be properly aligned with corresponding elements of the assembly 16: thus the end face of the electron gun 2 must be accurately positioned with respect to the forward edge of the end plate 22; the front face of the waveguide choke member 32 must be aligned with the inner wall of the input wave guide 12, while the corresponding waveguide choke member 34 must have its face portion aligned with the inner wall of the output waveguide 13.
  • the axial alignment of the travelling wave tube in the assembly which is of vital importance (as an incorrectly focused electron beam may well burn out the helix), depends upon the accurate positioning of the flange 29 with respect to the internal axis of the electrode system.
  • the bore of the tube portion 8 must be of accurate dimensions and must be accurately coaxial with the bore of the bulb portion 3 of the envelope.
  • Figs. 2 and 3 which are reproduced from photographs of an experimental tube according to the present invention, the completely assembled travelling wave tube is shown in Fig. 2 and the principal component parts of the electrode assembly laid out in Fig. 3 for comparison with Fig. 2.
  • the travelling wave tube comprises a unitary electrode assembly 37 housed within a glass envelope 38, which is sealed at either end to ferromagnetic end caps 39 and 40 respectively.
  • the tube carries pins 41 and a locating spigot 42 for insertion into a conventional valve socket.
  • a cooler 43 is secured as an integral member of the tube and carries cooling fins 44 and an aligning and locating boss 45.
  • the end cap 40 comprises two main parts: a ring 46, which is sealed to one end of the envelope 38, and an inner member 47 which is a sliding fit within the ring 46 and carries a glass inset 48 in which are sealed the pins 41 and the locating spigot 42
  • An electron gun structure 49 which will be more fully described later, is housed, similarly to the electron gun 2 of Fig. 1, in a ferromagnetic pole piece member 50, which is in the form of a cylinder closed by a face portion 51 integral with the anode of the electron gun.
  • the electron gun structure 49 is mounted on a thin cylindrical skirt member 52 which is secured to the end cap member 47.
  • a further pair of waveguide choke inner sleeve members 57 and 58 which have no direct counterpart in the arrangement of Fig. 1, are secured respectively to the electron gun structure and to the waveguide choke member 54 by means of pairs of rods 59 and 60. (On later models of the travelling wave tube these rods, as will be described later, have been substituted by plated portions of the ceramic rods 53.)
  • the helix supporting tube 56 is slit near either end to allow the wire of the helix 55 to be brought out without fear of distorting the helix and to be welded to respective antenna probe members 61, of which one is indicated in Fig. 3, but which is shown more clearly in Figs. 4 and 5.
  • One probe member 61 is secured to the waveguide structure 49 and the other is secured to the waveguide choke member 54.
  • An electron collector electrode 62 carrying a tubular extension 63, which engages with an insulating washer mounted in choke member 54, is secured to the end cap 39 and carries a further tubular extension 64 communicating with a copper exhaust tubulation 65, which, in Fig. 3, is shown joined to a member 66 for connection to an exhaust system during processing of the valve. After processing the tubulation 65 is squeezed off and the cooler 43 is secured over the extension 64.
  • the end cap 39 with the collector electrode, is sealed to one end of the glass envelope 38, the cap portion 46 being sealed to the other end.
  • the remaining members, except for the cooler 43 are assembled together, inserted into the envelope until the tube 63 engages in the member 54, and the end cap members 46 and 47 are finally sealed together with a metal to metal seal.
  • Fig. 4 shows a longitudinal cross section through the electron gun and the surrounding tube envelope. Largely because of the various thicknesses of the materials involved, the various components are not shown strictly to scale. It should be pointed out that the electron gun construction employed is that forming the subject matter of the application of P. F. C. Burke Serial No. 448,850 filed August 10, 1954, now US. Patent 2,822,492, granted February 4, 1958.
  • the pole piece member 50 of the electron gun structure 49 is a hollow soft iron cylinder, closed at one end by the face portion 51, which includes an anode 67,
  • An indirectly heated cathode 68 is secured by means of a ceramic washer 69 whose diameter is less than the bore of the pole piece 50, and a further ceramic washer 70.
  • the base of the cathode projects through the washer 69 and is turned or spun over so as to be clamped between the two ceramic Washers.
  • the upper surface of washer 70 is ground flat and seats against an annular shoulder 71 in the base of the pole piece cylinder.
  • the diameter of the washer 7b is somewhat less than that of the surrounding pole piece, and its thickness is slightly greater than the recess of the pole piece in which it sits.
  • a focussing electrode '72 surrounding the cathode is seated upon the ceramic washer 69, is centred in the pole piece by means of a mica centring washer 73 and is held in position by means of a plurality of tie-rods 74, which pass through clearance holes in the ceramic washers 69 and 70.
  • a hollow metal cylinder 75 fits inside the assembly of rods 74 and is welded to them, so as to clamp together the assembly of cathode, focussing electrode, and ceramic washers 69 and 70.
  • the cathode being centred with respect to the focussing electrode prior to being clamped in position.
  • This cathode and focussing electrode assembly is secured to the pole piece 50 a further mica or resilient metal washer 76 which is held against the washer 7t?
  • the ceramic washer 70 is slightly thicker than the corresponding recess in the pole piece in which it seats, so that it is pressed against the shoulder 71 due to the resilience of the washer 76.
  • the face 51 of the pole piece 50 is provided with seatings for end caps 79, shown more clearly in Fig. 3, which are welded to the ceramic rods 53. During the assembly of the travelling wave tube these end caps 79 are welded to the face 51 of the electron gun structure. This portion of the gun structure also carries one end of the helix supporting tube 56, which in Pig.
  • FIG. 4 is shown seated over a thin resilient tube protruding from the anode member 67.
  • face member 51 of the gun structure is shown in Fig. 4 carrying an antenna probe member 61 which is joined to the end of the helix 55.
  • the probe member 61 is generally U-shaped so as to allow the helix to be brought up closer to the electron gun as discussed in the copending application of D. C. Rogers Serial No. 407,732 filed February 2, 1954.
  • the drawing of Fig. 4 also shows the way in which the tube 51 is slotted at 80 to permit the end of the helix wire being brought out without risk of distortion of the end turns of the helix.
  • the outer surface of the cylindrical pole piece 50 is reduced in diameter to receive the metal skirt 52.
  • the glass terminal plate 48 let into the end cap portion 47 is sealed to an additional cup-shaped member 81 to which is secured a metal spinning 82 fitting over part of the cylindrical portion of the member 81 and engaging internally with the end cap member 46.
  • the junction between the members 81 and 82 must provide a sound hermetic seal, the parts normally being hard soldered together before scaling in the glass insert 48.
  • the lower end of the skirt 52 sits over the end of member 81 and butts against the spinning 82, being Welded in position to secure the end cap member 47 to the electron gun structure 49.
  • the skirt member 52 is cut away as much as is consistent with its mechanical strength by means of a series of apertures 33, which are shown in proper proportion in Figs. 2 and 3. it is found that these apertures allow adequate access for Welding leads such as 84 to the pin 41.
  • the glass envelope 38 is sealed to the end cap member 46, in a manner to be described later, the seal being indicated at 85.
  • the outer diameter of the end cap portion 46 is slightly greater than that of the envelope 38, the travelling wave tube being supported at one end in its circuit by the end cap.
  • all the electrodes of the travelling wave tube except for the electron collector electrode are mounted from the gun structure 49 by means of the ceramic rods 53 so as to form a unitary assembly which may then be inserted into the glass envelope through the end cap member 46, which is finally sealed to the end cap portion by means of a flash braze.
  • a flash braze we mean a brazing or welding operation which is rapidly completed before excessive heat is allowed to reach the glass insert 48.
  • Fig. 1 For comparison with the assembly of Fig. 1 there is shown in Fig. an assembly of the travelling wave tube 37 of Figs. 2, 3 and 4 in a montage 86 which is generally similar to the assembly 16 of Fig. 1, but modified to accommodate the'tube of the present invention; similar reference numerals will therefore be used as far as pos sible to identify corresponding parts of the two assemblies.
  • One of the main dilferences between the arrange ment of Fig. 1 and that of Fig. 5 is that in embodiments of the present invention Lhe electron beam path from the exit of the electron gun to the entry into the helix has been very considerably reduced, and, in fact, the face of the electron gun is brought up flush with the inner surface of the input waveguide 12, instead of being some distance therefrom as in Fig.
  • the electron gun structure itself performs the function of the inner sleeve member 32 of Fig. l as well as forming a pole piece for the magnetic focussing system.
  • a comparatively small brass collar 87 is let into the waveguide.
  • a ferromagnetic cylinder88 which surrounds the electron gun structure and the base of the travelling wave tube, butts against the collar 87 and against the end plate 22 of the assembly. As the cylinder 88 forms part of a waveguide choke, its inner surface is copper-plated.
  • the waveguide choke formed between the structure 49 and the member 88 is no longer a quarter wave length as was the corresponding choke of Fig. 1; its dimensions are, however, such as to provide adequate attenuation for electromagnetic waves tending to escape from the waveguide system past the electron gun.
  • an additional cylinder 89 of ferromagnetic material is provided. This is re ceased internally to clear the collar 87 and butts against the wall of waveguide 12 and its extension 14. At its other end the cylinder 89 is in magnetic contact with the end plate 22.
  • suppor for the electron gun end of the tube is provided by ferromagnetic cylinder 88 in which the end cap i sliding fit.
  • the wave-guide choke member 54 is of ferromagnetic material and provides the internal pole piece of the magnet the normal helix mode.
  • the inner choke member 54 carries a probe antenna 61 and is secured to the ends of the ceramic rods 53, the arrangement being generally similar to that at the input end of the tube.
  • the member 54 car ies a mica locating washer it receives the end of the tube 63 projecting from the forward end of the electron collector electrode 62.
  • the tube 63 is formed with a seating on its outer end surface to mate with the washer 93, and also carries a series of holes 94 to assist in evacuating the portion of the travelling wave tube enclosed by the helix supportin tube 56.
  • the electron collector electrode On its other side, as previously mentioned, the electron collector electrode carries a tubular extension 64 in which is sealed the copper exhaust tubulation 65, here shown sealed off.
  • the cooler 43 At some convenient stage after the sealing-off operation, the cooler 43 is secured over the tube 64- and is made an integral part of the travelling tube, whereas in Fig. 1 the cooler is attached after the travelling wave tube is inserted into its associated apparatus.
  • the cooler carries a projection 95 which engages with a metal boss 96 let into a supporting platform 97, which is mounted by means of insulating supports 98 from the end plate 21.
  • the projection 95 carries a key-way 99, which is visible in Fig. 3, in which a peg 100, let into the boss 96, engages to ensure the correct angular location of the travelling wave tube.
  • the projection 95 is also threaded internally to engage a screw N1 having a knolled head 102 of insulating material. By tightening the screw 101 the projection 95 can be drawn up to the limit of the recess in the boss 96 and the tube firmly fastened in position.
  • the travelling wave tube of the present invention Due to the larger diameter of the travelling wave tube of the present invention compared with the tube 1 of Fig. 1, provision must be made to prevent leakage of electromagnetic energy along the outside of the helix from the waveguide apertures.
  • the intermediate bosses 24 immediately surrounding the helix are of sufficiently small internal diameter to prevent the propagation electromagnetic Waves in any mode other than
  • the waveguide apertures in 'Fig. 5 are much larger and some choke provision intermediate the ends of the tube in addition to those already mentioned must be provided.
  • brass bushes 103 are let into the waveguides immediately surrounding the travelling wave tube and the travelling wave tube assembly comprises the additional inner wave guide choke members 57 and 58, previously mentioned, which are generally similar to the choke members 32 and 34 of Fig.
  • a coating of resistive material 1 55 is preferably provided on the inside of the envelope 38 to further attenuate electromagnetic waves which may travel between output and input waveguides in modes such that there exist appreciable radio frequency fields at a distance from the helix.
  • Such coating is not included in the tube of Fig. 2 but has been found desirable on later models.
  • short circuit terminations are, in fact, shown at 104 but effectively the actual termination of the waveguide 12 and its extension 14 is provided by the pair of shorting bars 59 secured between the electron gun structure and the sleeve member 57.
  • the shorting bars 63 terminate the extension 15 of waveguide 13.
  • the shorting bars also provide mechanical mounting means for the choke members 57 and 58.
  • the ceramic rods 53 pass through clearance holes in these intermediate choke members.
  • the electron gun structure 49, the helix55 in its support tube 56, and the waveguide choke members 57, 58 which, however, are undersize and do not need to be very accurately aligned and the member 54 are assembled together with the ceramic rods 53 in a jig which ensures accurate alignment and positioning of the respective electrodes.
  • the end caps 79 of the ceramicrods 53 are a loose fit in the respective recesses of the electron gun structure and waveguide 'choke' member 54.
  • the flanges 108 are welded to the face of the pole piece. Similar sleeves 107 are provided in conjunction with the waveguide choke member 57, passing through clearance holes in the face portion, the flanges 107 being welded to sheets.
  • One or more of the rods 53 is plated over the whole distance between the pole piece and the member 57, as indicated at 109, thus replacing the shorting bars 59.
  • the same arrangement is provided for the members 54 and 58 at the other end of the travelling wave tube.
  • the electrode assembly mounted on the electron gun structure has been aligned and welded up and the envelope 38 has been sealed to the end cap 39 and to the member 46 and provided with its resistive coating 106, the electrode assembly is slid into the envelope through the end cap member 46 and pushed home so that the member 63 projecting from the electron collector electrode seats in the mica washer 93.
  • the end cap members 82 and 46 are then flash brazed together, as described earlier, and the travelling wave tube is processed. After processing the exhaust tubulation 65 is squeezed off and the cooler 43 is secured over the tube 64. As the cooler is a close fit over the tube 64 the projection 95 is accurately coaxial with the electrode system.
  • the bore of the cooler may be provided with a step, as indicated at to seat against the end of tube 64. It is also secured with the key way 99 in correct angular position with respect to the probe antennae 61.
  • the travelling wave tube For use the travelling wave tube, with cooler attached, is inserted through the cylinder 88 (Fig. 5) until the cooler engages with its seating in the boss 96 and is there held by means of the screw 101. The tube is then correctly positioned in all directions with respect to the assembly 86. If desired the assembly 86 may include a forced air cooling duct, indicated by the dotted line 111.
  • the glass envelope can be made from standard glass tubing having ordinary commercial glass tolerances.
  • the electrode assembly is rigidly supported whilst longitudinal expansion is permitted by the elasticity of the mica washer 93.
  • the travelling wave tube may be made more easily and more accurately than that of Fig. l and is considerably shorted due to the substantial reduction of the inoperative part of the length of the electron beam. The tube is therefore more eflicient in use, due to the integral cooler it can handle more power, the magnetic focusing is not quite so critical and there is a considerable saving in the consumption of power required to provide the magnetic focusing field.
  • a traveling wave tube comprising a first unitary assembly which comprises an electron gun, a terminal plate having leads hermetically sealed therethrough rigidly connected to said gun forming an electron gun structure, a waveguide choke inner sleeve member joined to said electron gun structure by a plurality of insulating rods, a helical coil for guiding electromagnetic waves to interchange energy with the electrons projected from said gun, a helix supporting tube of insulating material supported at its respective ends by the said electron gun structure and the said inner sleeve member, said helix being positioned within and supported by the said helix supporting tube, a first probe antenna joined to one end of the said helix and secured to the electron gun structure, a second probe antenna joined to the other end of the said helix and secured to the said inner sleeve member, two further waveguide choke inner sleeve members respectively secured from and opposing the electron gun structure and the first-mentioned said sleeve member, a metal member of predetermined diameter sealed to said terminal plate
  • each of the said sleeve members comprises a plane face portion transverse the longitudinal axis of the travelling wave tube and a skirt portion projecting axially therefrom a quarter wave length at the mean operating frequency of the travelling wave tube.
  • a travelling wave tube according to claim '1 in which the said gun structure comprises a cylindrical ferromagnetic pole piece member surrounding a cathode and a beam forming electrode and is closed at the end facing the helix by a face portion integral with the electron gun anode.
  • a travelling wave tube according to claim 1 in which the said further waveguide choke members are secured respectively to the electron gun structure and to the said first mentioned waveguide choke member each by short-circuiting conducting means.

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  • Theoretical Computer Science (AREA)
  • Electromagnetism (AREA)
  • Power Engineering (AREA)
  • Microwave Tubes (AREA)
US448816A 1953-03-26 1954-08-10 Travelling wave tubes Expired - Lifetime US2890371A (en)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
GB328589X 1953-03-26
GB839453A GB755834A (en) 1953-03-26 1953-03-26 Improvements in or relating to the coupling of a helix in a travelling wave tube or the like to a waveguide
GB28268/53A GB762106A (en) 1953-03-26 1953-10-14 Improvements in or relating to travelling wave tubes
GB2890371X 1953-10-14
GB18181/54A GB787181A (en) 1953-03-26 1954-06-21 Improvements in or relating to travelling wave tubes

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Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2435804A (en) * 1944-01-01 1948-02-10 Rca Corp Cavity resonator magnetron device
US2602148A (en) * 1946-10-22 1952-07-01 Bell Telephone Labor Inc High-frequency amplifier
GB674758A (en) * 1949-08-12 1952-07-02 Standard Telephones Cables Ltd Improvements in or relating to electron discharge devices
US2608668A (en) * 1950-06-17 1952-08-26 Bell Telephone Labor Inc Magnetically focused electron gun
US2661441A (en) * 1947-12-31 1953-12-01 Bell Telephone Labor Inc High-frequency amplifier
US2672571A (en) * 1950-08-30 1954-03-16 Univ Leland Stanford Junior High-frequency oscillator
US2692351A (en) * 1949-12-31 1954-10-19 Bell Telephone Labor Inc Electron beam amplifier
US2790105A (en) * 1951-11-01 1957-04-23 Bell Telephone Labor Inc Traveling wave tubes
US2797353A (en) * 1951-06-15 1957-06-25 Bell Telephone Labor Inc Traveling wave type electron discharge devices
US2806170A (en) * 1953-09-30 1957-09-10 Rca Corp Traveling wave tube
US2808533A (en) * 1952-02-08 1957-10-01 Bell Telephone Labor Inc Electron discharge devices

Patent Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2435804A (en) * 1944-01-01 1948-02-10 Rca Corp Cavity resonator magnetron device
US2602148A (en) * 1946-10-22 1952-07-01 Bell Telephone Labor Inc High-frequency amplifier
US2661441A (en) * 1947-12-31 1953-12-01 Bell Telephone Labor Inc High-frequency amplifier
GB674758A (en) * 1949-08-12 1952-07-02 Standard Telephones Cables Ltd Improvements in or relating to electron discharge devices
US2692351A (en) * 1949-12-31 1954-10-19 Bell Telephone Labor Inc Electron beam amplifier
US2608668A (en) * 1950-06-17 1952-08-26 Bell Telephone Labor Inc Magnetically focused electron gun
US2672571A (en) * 1950-08-30 1954-03-16 Univ Leland Stanford Junior High-frequency oscillator
US2797353A (en) * 1951-06-15 1957-06-25 Bell Telephone Labor Inc Traveling wave type electron discharge devices
US2790105A (en) * 1951-11-01 1957-04-23 Bell Telephone Labor Inc Traveling wave tubes
US2808533A (en) * 1952-02-08 1957-10-01 Bell Telephone Labor Inc Electron discharge devices
US2806170A (en) * 1953-09-30 1957-09-10 Rca Corp Traveling wave tube

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