Traveling wave tube and method of manufacture

Information

  • Patent Grant
  • 6747412
  • Patent Number
    6,747,412
  • Date Filed
    Wednesday, April 17, 2002
    22 years ago
  • Date Issued
    Tuesday, June 8, 2004
    20 years ago
  • Inventors
  • Examiners
    • Wong; Don
    • Dinh; Trinh Vo
    Agents
    • Dellett & Walters
Abstract
A traveling wave tube includes a glass or other insulating envelope having a plurality of substantially parallel glass rods supported therewithin which in turn support an electron gun, a collector and an intermediate slow wave structure. The slow wave structure itself provides electrostatic focussing of a central electron beam thereby eliminating the need for focussing magnetics and materially decreasing the cost of construction as well as enabling miniaturization. The slow wave structure advantageously includes cavities along the electron beam through which the r.f. energy is propagated, or a double, interleaved ring loop structure supported by dielectric fins within a ground plane cylinder disposed coaxially within the glass envelope.
Description




BACKGROUND OF THE INVENTION




The present invention relates to traveling wave tubes and particularly to traveling wave tubes that can be economically manufactured to provide amplification at low to medium power levels.




Conventional traveling wave tubes utilize a slow wave structure through which an electron beam passes. In the tube, the electrons in the beam travel with velocities slightly greater than that of an r.f. wave, and on the average are slowed down by the field of the wave. A loss of kinetic energy of the electrons appears as increased energy conveyed to the field of the wave. The traveling wave tube may be employed as an amplifier or an oscillator.




Conventional traveling wave tubes employ periodic permanent magnets all along the electron beam to focus the electron beam. They also employ a ceramic-metal brazed construction with sometimes hundreds of ceramic and metal parts fitted and brazed together by skilled artisans. Consequently expense is very high. While this expense appears to be justified at high output power levels, at low output power the cost per watt renders the device economically unfeasible for many purposes. Thus, despite many advantages of the traveling wave tube (high bandwidth, high power, high frequency), it is sometimes replaced by solid state amplifiers at low power levels, say 5 to 100 watts.




In summary much of the expense is attributable to the ceramic-metal-brazed assembly technique and the use of dozens of periodic permanent magnets for focusing. If these were eliminated, tube cost would be dramatically reduced. It would appear that another form of focussing such as electrostatic focussing could be an alternative. However, attempts at providing electrostatic focussing in traveling wave tubes have not heretofore resulted in a practical device.




SUMMARY OF THE INVENTION




In accordance with the present invention, a substantially unitary structure comprising an electron gun, a collector and an intermediate slow wave structure is supported on a plurality of substantially parallel glass rods which are themselves disposed within an elongated cylindrical glass envelope. The electron gun and the collector may comprise a series of conductive wafers having pins embedded in the glass rods and apertures to pass the electron beam. Differing voltages are applied to alternate conducting members in the slow wave structure to provide focussing, while r.f. input and output means are located proximate the beginning and end of the slow wave structure for supplying the input r.f. energy and withdrawing the amplified output. The glass rodded structure is economically constructed and maintains excellent alignment for the passage of the electron beam.




In one embodiment, the slow wave structure comprises a ladder circuit within which r.f. energy is propagated back and forth across the electron beam.




In another embodiment, a plurality of r.f. cavities are disposed along the path of the electron beam.




In yet another embodiment, the slow wave circuit comprises a double helix supported by dielectric fins in turn provided with means for attaching the same to the glass rods.




In another embodiment, the slow wave structure comprises a double, interleaved ring loop structure supported by dielectric fins having means for attaching the same to envelope enclosed glass rods.




It is accordingly an object of the present invention to provide an improved traveling wave tube operable at relatively low power levels and providing substantial amplification.




It is another object of the present invention to provide an improved traveling wave tube of economical construction.




It is a further object of the present invention to provide an improved traveling wave tube utilizing electrostatic focussing but characterized by low beam losses in operation.




The subject matter of the present invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. However, both the organization and method of operation, together with further advantages and objects thereof, may best be understood by reference to the following description taken in connection with accompanying drawings wherein like reference characters refer to like elements.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a longitudinal cross-sectional view of a first traveling wave tube according to the present invention employing a ladder circuit slow wave structure;





FIG. 2

is a cross section taken at


2





2


in

FIG. 1

;





FIG. 2A

is a view of a miniaturized cathode advantageously employed as part of the traveling wave tube of the present invention;





FIG. 3

is a cross-sectional view of another traveling wave tube according to the present invention including a slow wave structure comprising a plurality of coupled cavities;





FIG. 4

is a cross section taken at A—A in

FIG. 3

;





FIG. 5

is a view of a first wafer employed with the

FIG. 4

structure;





FIG. 6

is a vertical cross section of the

FIG. 5

wafer;





FIG. 7

is a view of a further wafer employed with the

FIG. 3

structure;





FIG. 8

is a vertical cross section of the

FIG. 7

wafer;





FIG. 9

is a cross-sectional view of a further embodiment according to the present invention employing a double helix in a slow wave circuit;





FIG. 9A

is a cross-sectional view taken at A-A in

FIG. 9

;





FIG. 10

is a more detailed view of a portion of the double helix slow wave circuit of

FIG. 9

;





FIG. 11

is a partial cross-sectional view taken at


11





11


in

FIG. 10

;





FIG. 12

is a longitudinal cross-sectional view of another traveling wave tube according to the present invention including a double ring loop slow wave structure;





FIG. 13

is a cross section taken at A—A in

FIG. 12

;





FIG. 14

is a partial longitudinal cross-sectional view of the

FIG. 12

tube;





FIG. 15

is a cross section taken at A—A in

FIG. 14

;





FIG. 16

is a partially broken-away perspective view of part of the

FIG. 12

tube, particularly illustrating the slow wave structure; and





FIG. 17

is a longitudinal cross section of an input or output coaxial coupling transformer employed with the

FIG. 12

embodiment.











DETAILED DESCRIPTION




Referring to

FIG. 1

illustrating a first embodiment of the present invention, a traveling wave tube comprises an elongated tubular glass envelope


10


, cylindrical in shape and supporting therewithin a plurality of longitudinal glass rods


12


. In this particular embodiment, there are four such rods running substantially the length of the glass envelope, parallel to the cylindrical axis of the envelope, in spaced relation within the walls of the envelope. The rods in turn support an electron gun


14


, a slow wave structure


16


and a collector structure


18


. The electron gun includes an axially central cathode


20


centered within the central aperture of a Pierce type focus electrode


22


and preferably just behind the lip of the aperture. Spaced forwardly along the tube from the electron source is an electron gun anode


24


which is tubular and hollow for passage of an axial electron beam as produced from the cathode.




A traveling wave tube according to the present embodiment further comprises pre-focus electrodes


26


which are anchored into the rods


12


when the latter are semi-molten during the manufacturing stage. Voltages are provided to the wafers


26


(by means not shown) for focussing the electron beam provided by the cathode.




Slow wave structure


16


comprises two intermeshing combs


28


and


30


wherein comb


28


comprises a metal base


32


having teeth


34


extending perpendicularly away from the base toward the opposite comb. The comb


30


comprises a base


36


and teeth


38


extending perpendicularly away from the base in the direction of comb


28


. Each of the teeth comprises a flat metal wafer joined to its metal base, and provided with an aperture to form a passage for the electron beam, to which each of the teeth are perpendicularly disposed. Each of the teeth is maintained in spaced relation from the teeth of the opposite comb, and from the base of the opposite comb, to provide a circuitous transmission line path back and forth (and through slots


40


) such that r.f. energy successively intersects the beam.




The r.f. input is provided by r.f. coupling


42


connected to a wave guide


44


having a transformer structure


46


extending through the side of envelope


10


whereby energy flows axially inward through microwave window


45


toward the electron beam and then circuitously back and forth through the slots between each tooth and the opposite base to exit at wave guide structure


48


at the opposite end of the tube via glass window


50


. Windows


45


and


50


maintain the vacuum within envelope


10


. After the slow wave structure, the electron beam passes through a succession of metal collector wafers


52


which are apertured to receive the beam, a successively lower voltage being supplied to each wafer


52


for slowing down the beam. The sides of the slow wave structure are provided with a metal wall


54


. The ladder structure comprising the combs


28


and


30


are positioned by means of a plurality of metal pins


56


extending inwardly from rods


12


as can be seen in FIG.


2


.




In operation of this embodiment, differing voltages are applied to the combs so that the electron beam is alternately slowed down and accelerated as it passes through apertures in the combs' teeth, whereby to produce focussing of the beam. Amplification of the r.f. energy is produced at the output as energy is withdrawn from the electron beam.




The cathode


20


in the electron gun comprised a miniature flat cathode as further disclosed and claimed in my U.S. patent application Ser. No. 09/448,665, filed Nov. 24, 1999, entitled RESERVOIR DISPENSER CATHODE AND METHOD OF MANUFACTURE, and was approximately 0.05 inches in diameter. The miniature cathode is depicted in FIG.


2


A and comprises a reservoir dispenser cathode having a reservoir cup


310


received within and supported by the upper portion of a cylindrical heater body


312


. Cup


310


is provided with a radially outwardly extending flange


314


at its upper end which, during the manufacturing stage, initially extends substantially radially outwardly beyond the circumference of heater body


312


. The reservoir cup


310


is formed of a refractory material, for example a tungsten-rhenium alloy, or platinum. The heater body


312


is suitably formed of molybdenum with a larger radius towards its upper end forming a hub


321


where it receives cup


310


. Within the heater body


312


is provided heater


317


.




Within the cup


310


is pressed an emission pellet


316


suitably comprising barium oxide mixed with tungsten powder. Just above cup


310


and supported by flange


314


is a diffuser plug


318


comprising a pelletized refractory material that is very porous and provided with a low work function overlay. The upper end of heater body


312


and particularly upper hub portion


321


thereof is received within and spot welded to support sleeve


320


. A heat shield


324


surrounds sleeve


320


.




Flange


314


is adapted to rest upon heater body


312


, while in turn supporting the peripheral region of diffuser plug


18


. The flange


314


, where it extends radially outwardly, is employed as fusible welding material by laser welding to form a continuous circumferential weld bead


314


′ securing parts


318


,


314


, and


321


together in hermetically sealed relation. The weld bead provides a hermetic seal between cup and plug and is accomplished without impairment of the emissive material or the plug while retaining essential vapor pressure. This miniaturized cathode construction is an important feature in achieving the small, effective and economical traveling wave tube according to the present invention. This configuration avoids heavy constructions that are a detriment to miniaturization.




Although a Pierce type traveling wave tube gun structure is disclosed and preferred, a CRT type gun is also suitable. The voltage for anode


24


in the specific embodiment was 10 KV. The two combs were maintained, by means not shown, at voltages of 12 and 8 KV, respectively. The central aperture diameter of gun anode


24


and all succeeding wafers was 0.03 inches. The traveling wave tube of

FIGS. 1 and 2

is suitable for operation at frequencies between 10 GHz and 32 GHz.




The apparatus of

FIGS. 1 and 2

is manufactured by pressing four semi-molten glass rods


12


into tabs or pins located at the corners of the respective wafers. After rodding, the rodded assembly was placed in a stemming fixture and feed through stems were attached to either end of the assembly. Getters were mounted. Next the glass envelope was sealed on. The envelope is made of glass tubing that is flame sealed to the stems at each end. An annealing process followed. Then the tube was pumped and baked. The cathode was activated and then the tube was sealed off and removed from the pumps and getters were activated. Finally hipotting, cathode reactivation and aging took place for 24 hours.




The advantageous construction employing the glass envelope and rods produces high accuracy of alignment as well as economy of construction while incorporating electrostatic focussing. It would not be practical to integrate a glass envelope with a stack of iron magnetic pole pieces that could carry a magnetic field through the envelope to a point close to the beam, nor would it be feasible to mount and adjust magnets within the vacuum envelope. The glass rods hold the three sections in precise alignment and this method of attachment can be highly automated. The tube is able to develop 20 dB to 40 dB gain.




Although glass rods and a glass envelope are described, quartz or Pyrex may be substituted, especially for powers above 100 watts. The collector wafers illustrated at


52


are suitably formed of molybdenum or graphite while the remaining wafers in the structure can be formed of copper or copper plated stainless steel.




A further embodiment is illustrated in

FIGS. 3 through 8

wherein corresponding elements are referred to employing primed reference numerals, including in this embodiment, a cathode


20


′, as depicted in FIG.


2


A. The embodiment of

FIGS. 3-8

differs principally in respect to an advantageous slow wave structure


16


′ comprising a plurality of conductive metal wafers supported by four insulating (e.g. glass) longitudinal rods


12


′ disposed longitudinally within insulating (e.g. glass) envelope


10


′. As in the previous embodiment, the apparatus of

FIGS. 3-8

utilizes electrostatic focussing and is disposed entirely within the glass envelope


10


′, i.e., it requires no focussing magnets either externally or internally of the structure. The glass rodded and enclosed construction renders the device easily manufactured whereby it can be economically produced in quantity.




Adjoining apertured metal wafers,


58


and


60


, are separated and insulated from one another by insulating spacers


62


suitably formed of Kapton, and are provided with differing voltages as in the previous embodiment whereby to focus the electron beam through successive acceleration and deceleration of the beam. The identical structure is repeated along the tube with successive wafers of the 58 type, illustrated more fully in

FIGS. 5 and 6

, separated by wafers of the 60 type illustrated more fully in

FIGS. 7 and 8

. Wafers


58


are provided with curved coupling slots


64


disposed on opposite sides of central beam aperture


70


, while wafers


60


are provided with similar curved coupling slots


66


on either side of central beam aperture


72


whereby to couple electromagnetic energy between successive cavities formed between successive wafers along the tube. As can be seen in

FIGS. 5 and 6

, the coupling slots


64


are here disposed at right angles to the coupling slots


66


in wafers


60


, that is, they are offset circumferentially by 90 degrees from one another.




The wafers


58


and


60


are thicker in their radially outward region whereby to abut one another along the stack, except for the Kapton insulation layer therebetween. The wafer


60


also has a central boss


74


through which the beam aperture


72


is provided, and this boss is axially thinner than the peripheral portion of the wafer.




R.F. input at


42


′ is coupled to the slow wave structure and therealong through cavities formed between successive wafers, and via the slots


64


and


66


. The r.f. is propagated along the cavity stack, taking energy from the beam, with an amplified output being provided at


48


′.




A still further embodiment of the present invention is illustrated in

FIGS. 9 through 11

wherein double primed reference numerals are employed to indicate elements similar to those discussed in the prior embodiments.




The traveling wave tube again comprises an elongated glass envelope, here numbered


10


″, cylindrical in shape and supporting therewithin a plurality of longitudinal glass rods


12


″. There are four such rods running substantially the length of the glass envelope, parallel to the axis of the envelope, in spaced relation within the wall of the envelope. The rods in turn support electron gun


14


″, slow wave structure


16


″ and collector structure


18


″. The electron gun has an electrically central cathode


20


″ centered within the central aperture of a Pierce type focus electrode


22


″. The traveling wave tube according to the present embodiment further comprises prefocus electrodes


26


″ which are anchored into rods


12


″ when the latter are semi-molten during the manufacturing stage. Voltages are provided to the wafers


26


″, (by means not shown) for focussing the electron beam provided by the cathode.




In this embodiment, slow wave structure


16


″ comprises a double helix including a first helix


80


and a second helix


82


wound together in interleaved fashion such that the central electron beam successively passes a turn of one helix and then a turn of the other as the beam is focussed axially by the helices. The helices are maintained within the envelope at different voltages, to maintain beam focussing, via central r.f. conductors


84


and


86


which form a coaxial central lead of r.f. input means


42


″ and


43


″, respectively. Each of the coaxial r.f. input means further comprises an outer conductor


402


and a larger diameter window


404


where the central conductor, e.g. conductor


84


, is discontinuous to provide voltage isolation while being capacitively coupled through the window. The helices


80


and


82


are located within metal ground plane cylinder


88


extending longitudinally within the envelope


10


″ and supported from insulating rods


12


″ on metal pins


90


extending from each of the rods


12


″, to cylinder


88


. The cylinder


88


is joined to the outer conductors of the input and output means while the inner conductors pass through to the helices. Six longitudinal dielectric fins


92


,


94


, suitably formed of alumina or other dielectric material, extend inwardly from the inside of cylinder


88


in supporting relation to the helices. Three first fins


92


support helix


80


, while three other fins


94


, separated from fins


92


by 60 degrees and interleaved therewith, support the remaining helix


82


. As can be seen in

FIG. 10

, fins


82


touch helix


80


but not helix


82


. Similarly, fins


94


touch helix


82


but not helix


80


. Supports


96


within cylinder


88


are disposed crossways of the tube at spaced locations whereby to position the alumina fins


92


and


94


. The beam is focussed within the slow wave structure inasmuch as the helices


80


and


82


have appropriately different focussing voltages applied thereto on conductors


84


and


86


within the tube. Meanwhile, amplification of the r.f. energy input at input means


42


″,


43


″ is provided for output at output means


48


″,


49


″ which are constructed in the same manner as the input means. Properly phased r.f. input signals are provided at input means


42


″ and


43


″ to account for movement of the electron beam between turns of the two helices.




After the slow wave structure, the electron beam passes through a succession of metal collector wafers


52


″ which are apertured to receive the beam, successively lower voltage being supplied to each wafer


52


″ for slowing down the beam.




In operation, as differing voltages are applied to the two helices, the electron beam is alternately slowed down and accelerated as it passes along the axis of the tube, whereby to produce focussing of the beam. Amplification of the r.f. energy is produced at the output as energy is withdrawn from the electron beam. The advantageous construction employing the envelope and rods produces high accuracy of alignment as well as economy of construction while incorporating electrostatic focussing. Although glass rods and a glass envelope are described, quartz or Pyrex may be substituted.




A still further and preferred embodiment of the present invention is illustrated in

FIGS. 12 through 17

. Reference numerals having the same last two digits as elements discussed in respect to the previous embodiments, are employed to refer to similar elements. The construction of this embodiment, as it pertains to similar elements, is substantially as hereinbefore described. The traveling wave tube comprises an elongated tubular glass envelope


110


, cylindrical in shape, and supporting therewithin a plurality of longitudinal glass rods


112


. There are four such rods running substantially the length of the glass envelope, parallel to the axis of the envelope, in spaced relation within the wall of the envelope. The rods in turn support electron gun


114


, a slow wave structure


116


and a collector structure


118


. The electron gun has an electrically central cathode


120


centered within the central aperture of a Pierce type focus electrode


122


. Spaced forwardly along the tube from the electron source is a first anode


124


and a second, cup shaped anode


125


, both apertured to pass the electron beam provided from the cathode. In a specific embodiment, focus electrode and cathode


120


and


122


were maintained at −7.3 KV, anode


124


at +3.5 KV and anode


125


at +5.5 KV with respect to grounded cylinder


188


of the slow wave structure.




Slow wave structure


116


comprises a double ring loop configuration including first and second sets of aligned, coaxial metal rings wherein, for example, rings


202


,


203


,


204


for a first set are interleaved with rings


206


,


207


,


208


of a second set. The rings of a set, e.g. rings


202


,


203


,


204


, are serially interconnected along the slow wave structure and similarly, the rings


206


,


207


,


208


are also serially interconnected along the slow wave structure. In the illustrated embodiment, and referring particularly to

FIG. 16

, rings


202


and


203


are interconnected by a radially outwardly extending loop


212


. Rings of the second set, for example rings


207


and


208


, are serially interconnected by a radially outwardly extending loop


214


which is circumferentially displaced from loop


212


by 90 degrees about the axis of the stack of rings.




The rings of a set as well as the interconnecting loops are formed from a flat metal material from which the whole structure is suitably stamped or laser cut and bent in a jig to the shape shown, after which the same is heat-treated to enable it to maintain the configuration. The circumferential width of each loop is comparable to the radial width of a ring, i.e. the difference between the inside radius and the outside radius of a ring. It will be seen that the interconnecting loops for a given set of rings, e.g. loop


212


and loop


216


, are disposed on alternate sides of the stack of rings and proceed along the stack in the same manner for completing a serial circuit of rings from one end of the slow wave structure to the other. Similarly, loops


213


and


214


connect rings of the other set. Each of the two sets of rings and their interconnecting loops provide a transmission line structure together with the ground plane metal cylinder


188


within which the rings are coaxially received. As hereinafter indicated, the two interleaved ring loop structures are provided with different d.c. voltages in order to maintain focussing of the electron beam as it passes coaxially within the rings.




Referring more particularly to

FIGS. 12 and 13

, the r.f. input to the tube is supplied via input coaxial coupling devices


142


in proper phase relation to one another to feed the two sets of rings, while output is provided via coaxial output coupling devices


148


. The two input devices


142


are disposed at 90 degrees to one another about the axis of the tube, each feeding a different set of rings, and the output devices


148


are similarly disposed and provide outputs for the two respective sets of rings.




The double ring loop structure is positioned within metal ground plane cylinder


188


extending longitudinally of envelope


110


and supported from insulating rods


112


via metal pins


190


extending from each of the rods


112


to the cylinder


188


. The cylinder


188


is joined to the outer conductors of input and output devices while the inner conductors (within the envelope) pass through apertures in the cylinder and connect to end loops of the ring loop structure. Six longitudinal dielectric fins


192


,


194


, suitably formed of alumina, extend inwardly from the inside of cylinder


188


in supporting relation to the rings. For example, first fins


192


support rings


202


,


203


,


204


, while fins


194


, separated from fins


192


by 60 degrees and interleaved therewith, support rings


206


,


207


,


208


. As can be seen in

FIG. 15

, fins


194


touch ring


207


but not the rings on either side. Similarly, fins


192


touch only the rings of the remaining set. Supports


196


within cylinder


188


are disposed crossways of the tube at spaced locations whereby to position the alumina fins


192


and


194


.





FIG. 17

illustrates a coaxial coupling device


142


used for accomplishing r.f. input to the slow wave structure. Both input devices as well as output devices


148


are suitably identical. Each such coupling device comprises a cylindrical exterior metal conductor


250


for extending in sealed relation through the wall of envelope


110


and being stepped down in diameter as indicated at


252


and


254


, exteriorly of the envelope, to provide impedance matching to an input (or output) coaxial cable or the like. On the interior side of the envelope wall, exterior conductor


250


is joined to the cylinder


188


while the central conductor


256


of the coupling device is suitably integral with, for example, tab


258


providing connection to a first ring


202


of the first ring loop set.




The outer and inner conductors of the coupling device in

FIG. 17

are separated by annular insulating member


260


that positions the central conductor


256


within the outer conductor


250


. Toward the exterior end of the coupling device, annular member


260


receives therewithin a ceramic standoff cylinder


262


which separates central conductor


256


from a central coaxial conductor


264


providing connection at the exterior of the tube envelope. Central conductor


264


is enlarged within a stepped down portion


252


of the exterior conductor, in part to enhance the impedance matching function, and is centrally bored to receive central standoff member


262


. The thickness of the ceramic standoff member is such as to provide capacitive coupling between central coaxial conductors


256


and


264


, while at the same time supplying insulation at the d.c. level whereby focussing voltages can be provided (by means not shown) to the central conductor


256


within the envelope and accordingly to the rings of the corresponding set. Turning to

FIG. 12

, subsequent to the slow wave structure


116


along the electron beam, said beam passes through a succession of metal collector wafers


118


which are apertured to receive the beam, a successively lower voltage being applied to each wafer


118


for slowing down the beam.




In operation of this embodiment, differing d.c. voltages are applied to the respective sets of rings so that the electron beam is alternately slowed down and accelerated as it passes through the rings, whereby to produce focussing of the beam. In a specific embodiment these voltages were +4 KV and −4 KV with respect to the ground plane cylinder. Amplification of the r.f. energy supplied at the input r.f. coupling devices


142


is provided at the output coaxial coupling devices


148


, as energy is withdrawn from the electron beam.




The overall manufacture of the tube of

FIGS. 12-17

is substantially the same as hereinbefore described. The advantageous construction employing the glass envelope and rods produces high accuracy of alignment as well as economy of construction while incorporating electrostatic focussing. As hereinbefore mentioned, despite the advantages of glass envelope construction, it would not be practical to integrate a glass envelope with a stack of iron magnetic pole pieces that could carry a magnetic field through the envelope to a point close to the beam, nor would it be feasible to mount and adjust magnets within the vacuum envelope. Also, in the case of the ring loop structure, the loops extending outwardly would render placement of the magnets even more difficult, even if the magnets could be placed within the vacuum envelope.




The glass rods hold the sections of the electrostatic structure in precise alignment and the method of manufacture can be highly automated. Although glass rods and a glass envelope are described, quartz or Pyrex or other materials may be substituted. The collector wafers illustrated at


152


are suitably formed of molybdenum while the rings and loops are also suitably formed of molybdenum. The embodiment of

FIGS. 12 through 17

is preferred because of economy of construction as well as enhanced immunity from backward wave oscillation.




While preferred embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that many changes and modifications may be made without departing from the invention in its broader aspects. The appended claims are therefore intended to cover all such changes and modifications as fall within the true spirit and scope of the invention.



Claims
  • 1. A traveling wave tube comprising:an electron gun structure, a slow wave structure through which an electron beam provided by said electron gun structure passes, and a collector structure, an elongated envelope enclosing said structures, said envelope being formed of insulating material and provided with a plurality of rods also formed of insulating material and supported longitudinally inside said envelope, said rods in turn rigidly supporting and aligning said electron gun structure, said slow wave structure, and said collector structure, and means for coupling an r.f. signal input to and receiving an r.f. signal output from said slow wave structure, wherein said slow wave structure has voltage applied thereto for providing electrostatic focussing of said electron beam, said slow wave structure providing amplification of the r.f. signal by interaction with said electron beam.
  • 2. The traveling wave tube according to claim 1 wherein said rods are formed of glass.
  • 3. The traveling wave tube according to claim 1 wherein said envelope is formed of glass.
  • 4. A traveling wave tube comprising:an electron gun structure and a slow wave structure through which an electron beam provided by said electron gun structure passes, an elongated envelope enclosing said structures, said envelope being formed of insulating material and provided with a plurality of rods also formed of insulating material and supported longitudinally in said envelope, said rods in turn rigidly supporting said electron gun structure and said slow wave structure, and means for coupling an r.f. signal input to and receiving an r.f. signal output from said slow wave structure, wherein said slow wave structure provides electrostatic focussing of said electron beam as well as amplification of the r.f. signal by interaction with said electron beam, wherein at least one of said structures comprises a plurality of spaced conducting wafers along the path of said beam which are apertured to receive said electron beam and wherein differing voltages are applied to alternate wafers.
  • 5. A traveling wave tube comprising:an electron gun structure and a slow wave structure through which an electron beam provided by said electron gun structure passes, an elongated envelope enclosing said structures, said envelope being formed of insulating material and provided with a plurality of rods also formed of insulating material and supported longitudinally in said envelope, said rods in turn rigidly supporting said electron gun structure and said slow wave structure, and means for coupling an r.f. signal input to and receiving an r.f. signal output from said slow wave structure, wherein said slow wave structure provides electrostatic focussing of said electron beam as well as amplification of the r.f. signal by interaction with said electron beam, and wherein said slow wave structure comprises a ladder circuit having voltage applied thereto for producing said focussing of said beam, said slow wave structure providing amplification of r.f. energy.
  • 6. A traveling wave tube comprising:an electron gun structure and a slow wave structure through which an electron beam provided by said electron gun structure passes, an elongated envelope enclosing said structures, said envelope being formed of insulating material and provided with a plurality of rods also formed of insulating material and supported longitudinally in said envelope, said rods in turn rigidly supporting said electron gun structure and said slow wave structure, and means for coupling an r.f. signal input to and receiving an r.f. signal output from said slow wave structure, wherein said slow wave structure provides electrostatic focussing of said electron beam as well as amplification of the r.f. signal by interaction with said electron beam, wherein said slow wave structure comprises a ladder circuit for said, focussing of said beam as well as amplifying r.f. energy, and wherein said electron gun structure includes a reservoir dispenser cathode having a reservoir cup with a radially outwardly extending flange and receiving therewithin an emissive material, and further including a diffuser plug comprising porous refractory material supported on said flange, said flange further comprising a circumferential weld bead securing said diffuser plug to said flange in sealing relation.
  • 7. A traveling wave tube comprising:an electron gun structure and a slow wave structure through which an electron beam provided by said electron gun structure passes, an elongated envelope enclosing said structures, said envelope being formed of insulating material and provided with a plurality of rods also formed of insulating material and supported longitudinally in said envelope, said rods in turn rigidly supporting said electron gun structure and said slow wave structure, and means for coupling an r.f. signal input to and receiving an r.f. signal output from said slow wave structure, wherein said slow wave structure provides electrostatic focussing of said electron beam as well as amplification of the r.f. signal by interaction with said electron beam, and wherein said slow wave structure comprises a coupled cavity stack having voltage applied thereto for producing said focussing of said beam, said slow wave structure providing amplification of r.f. energy.
  • 8. A traveling wave tube comprising:an electron gun structure and a slow wave structure through which an electron beam provided by said electron gun structure passes, an elongated envelope enclosing said structures, said envelope being formed of insulating material and provided with a plurality of rods also formed of insulating material and supported longitudinally in said envelope, said rods in turn rigidly supporting said electron gun structure and said slow wave structure, and means for coupling an r.f. signal input to and receiving an r.f. signal output from said slow wave structure, wherein said slow wave structure provides electrostatic focussing of said electron beam as well as amplification of the r.f. signal by interaction with said electron beam, wherein said slow wave structure comprises a coupled cavity stack for said focussing of said beam as well as amplifying r.f. energy, and wherein said electron gun structure includes a reservoir dispenser cathode having a reservoir cup with a radially outwardly extending flange and receiving therewithin an emissive material and further including a diffuser plug comprising porous refractory material supported on said flange, said flange further comprising a circumferential weld bead securing said diffuser plug to said flange in sealing relation.
  • 9. A traveling wave tube comprising:an electron gun structure and a slow wave structure through which an electron beam provided by said electron gun structure passes, an elongated envelope enclosing said structures, said envelope being formed of insulating material and provided with a plurality of rods also formed of insulating material and supported longitudinally in said envelope, said rods in turn rigidly supporting said electron gun structure and said slow wave structure, and means for coupling an r.f. signal input to and receiving an r.f. signal output from said slow wave structure, wherein said slow wave structure provides electrostatic focussing of said electron beam as well as amplification of the r.f. signal by interaction with said electron beam, and wherein said slow wave structure comprises a double ring loop structure including interleaved loops in separate circuits for focussing said beam as well as amplifying r.f. energy.
  • 10. A traveling wave tube comprising:an electron gun structure and a slow wave structure through which an electron beam provided by said electron gun structure passes, an elongated envelope enclosing said structures, said envelope being formed of insulating material and provided with a plurality of rods also formed of insulating material and supported longitudinally in said envelope, said rods in turn rigidly supporting said electron gun structure and said slow wave structure, and means for coupling an r.f. signal input to and receiving an r.f. signal output from said slow wave structure, wherein said slow wave structure provides electrostatic focussing of said electron beam as well as amplification of the r.f. signal by interaction with said electron beam, and wherein said slow wave structure comprises a double helix structure for focussing said beam as well as amplifying r.f. energy and wherein said double helix structure comprises first and second helices, the turns of the first helix being substantially coaxial with and interleaved with the turns of the second helix, the two helices being maintained at different voltage levels for focussing, wherein adjacent turns are at different voltage levels.
  • 11. A traveling wave tube comprising:an electron gun structure and a slow wave structure through which an electron beam provided by said electron gun structure passes, an elongated envelope enclosing said structures, said envelope being formed of insulating material and provided with a plurality of rods also formed of insulating material and supported longitudinally in said envelope, said rods in turn rigidly supporting said electron gun structure and said slow wave structure, and means for coupling an r.f. signal input to and receiving an r.f. signal output from said slow wave structure, wherein said slow wave structure provides electrostatic focussing of said electron beam as well as amplification of the r.f. signal by interaction with said electron beam, and wherein said slow wave structure comprises a ladder circuit including a pair of interleaved conductive combs insulated from one another and maintained at different voltage level for focussing said beam, said slow wave structure providing amplification of r.f. energy, each comb having a body and outwardly extending teeth, wherein the teeth of each comb comprise apertured wafers for passing said electron beam, the ends of the teeth of one comb being spaced from the body of the remaining comb to provide a folded transmission line passage through which r.f. energy is propagated.
  • 12. A traveling wave tube comprising:an electron gun structure and a slow wave structure through which an electron beam provided by said electron gun structure passes, an elongated envelope enclosing said structures, said envelope being formed of insulating material and provided with a plurality of rods also formed, of insulating material and supported longitudinally in said envelope, said rods in turn rigidly supporting said electron gun structure and said slow wave structure, and means for coupling an r.f. signal input to and receiving an r.f. signal output from said slow wave structure, wherein said slow wave structure provides electrostatic focussing of said electron beam as well as amplification of the r.f. signal by interaction with said electron beam, and wherein said slow wave structure comprises a coupled cavity stack including a plurality of conducting wafers apertured to receive said electron beam and supported by said insulating rods, wherein said wafers are centrally spaced along said electron beam to form cavities therebetween which are coupled to provide a path through which r.f. energy is propagated, adjacent wafers being insulated from one another and maintained at different voltage levels for said focussing.
  • 13. A traveling wave tube comprising:an electron gun structure and a slow wave structure through which an electron beam provided by said electron gun structure passes, an elongated envelope enclosing said structures, said envelope being formed of insulating material and provided with a plurality of rods also formed of insulating material and supported longitudinally in said envelope, said rods in turn rigidly supporting said electron gun structure and said slow wave structure, and means for coupling an r.f. signal input to and receiving an r.f. signal output from said slow wave structure, wherein said slow wave structure provides electrostatic focussing of said electron beam as well as amplification of the r.f. signal by interaction with said electron beam, and wherein said slow wave structure comprises a stack of spaced coaxially aligned conducting rings having central apertures aligned to receive said electron beam, including a first set of spaced rings and means serially connecting the rings of said first set along said slow wave structure, said stack further including a second set of spaced rings coaxial with, interleaved with and spaced between the rings of the first set and means serially connecting the rings of the second set along said slow wave structure, and means for providing different voltages to the rings of the first and second sets to maintain beam focussing.
  • 14. A traveling wave tube comprising:an electron gun structure and a slow wave structure through which an electron beam provided by said electron gun structure passes, an elongated envelope enclosing said structure, said envelope being formed of insulating material and provided with a plurality of rods also formed of insulating material and supported longitudinally in said envelope, said rods in turn rigidly supporting said electron gun structure and said slow wave structure, and means for coupling an r.f. signal input to and receiving an r.f. signal output from said slow wave structure, wherein said slow wave structure provides electrostatic focussing of said electron beam as well as amplification of the r.f. signal by interaction with said electron beam, and wherein said slow wave structure comprises a stack of conducting rings having central apertures aligned to receive said electron beam, including a first set of spaced rings serially interconnected by first loops peripheral to said rings on alternate sides of said stack, and a second set of spaced rings interleaved with and spaced between the rings of the first set, said rings of said second set being serially interconnected by second loops peripheral to said rings of said second set on alternate sides of said stack, said second loops being circumferentially spaced around said stack from the first loops, and means for providing different voltages to the rings of the first and second set respectively to maintain beam focussing.
  • 15. A traveling wave tube comprising:an electron gun structure and a slow wave structure through which an electron beam provided by said electron gun structure passes, and a collector structure, an elongated envelope enclosing said structures, said envelope being formed of insulating material and provided with a plurality of rods also formed of insulating material and supported longitudinally in said envelope, said rods in turn rigidly supporting said electron gun structure and said slow wave structure, and means for coupling an r.f. signal input to and receiving an r.f. signal output from said slow wave structure, wherein said slow wave structure provides electrostatic focussing of said electron beam as well as amplification of the r.f. signal by interaction with said electron beam, and wherein said collector structure comprises a plurality of spaced conducting wafers apertured to receive said electron beam and supported by said insulating rods, said wafers being maintained at successively lower voltage levels along said beam.
  • 16. The traveling wave tube according to claim 15 wherein said wafers are formed of molybdenum or graphite.
  • 17. A traveling wave tube comprising:an electron gun structure and a slow wave structure through which an electron beam provided by said electron gun structure passes, said slow wave structure comprising at least several metal wafers disposed along the path of said electron beam, said wafers being centrally apertured to pass said electron beam, and insulating rods supporting said wafers, successive wafers along the path of said electron beam being insulated from one another and receiving different voltages for focussing said electron beam, wherein successive wafers are spaced from one another adjacent the path of said electron beam to form electromagnetic cavities coupled from one to the next along said beam to provide a path through which electromagnetic energy is propagated.
  • 18. A traveling wave tube comprising:an electron gun structure and a slow wave structure through which an electron beam provided by said electron gun structure passes, said slow wave structure comprising a stack of conductive metal rings including a first set of serially interconnected rings, and a second set of serially interconnected rings wherein the rings of the second set are interleaved between the rings of the first set, and means for providing different electron beam focussing voltages to the first and second sets of rings respectively.
  • 19. A traveling wave tube comprising:an electron gun structure, a collector structure, and a slow wave structure intermediate said electron gun structure and said collector structure and through which an electron beam provided by said electron gun structure passes, an elongated envelope enclosing said structures, said envelope being formed of insulating material and provided with a plurality of insulating rods disposed longitudinally therewithin for in turn supporting said electron gun structure, said collector structure, and said slow wave structure, means for coupling an r.f. signal input to and receiving an r.f. signal output from said slow wave structure, wherein said slow wave structure provides electrostatic focussing of said electron beam as well as amplification of the r.f. signal by interaction with said electron beam, wherein said slow wave structure comprises a stack of conducting rings having central apertures aligned to receive said electron beam, including a first set of spaced rings serially interconnected by first loops peripheral to said rings on alternate sides of said stack, and a second set of spaced rings interleaved with and spaced between the rings of the first set, said rings of said second set being serially interconnected by the second loops peripheral to said rings of said second set on alternate sides of said stack, said second loops being circumferentially spaced around said stack from the first loops, and means for providing different voltages to the rings of the first and second set respectively to maintain beam focussing.
  • 20. A traveling wave tube comprising:an electron gun structure, a collector structure, and a slow wave structure intermediate said electron gun structure and said collector structure and through which an electron beam provided by said electron gun structure passes, an elongated envelope enclosing said structures, said envelope being formed of insulating material and provided with a plurality of insulating rods disposed longitudinally therewithin for in turn supporting said electron gun structure, said collector structure, and said slow wave structure, means for coupling an r.f. signal input to and receiving an r.f. signal output from said slow wave structure, wherein said slow wave structure provides electrostatic focussing of said electron beam as well as amplification of the r.f. signal by interaction with said electron beam, wherein said slow wave structure comprises a stack of conducting rings having central apertures aligned to receive said electron beam, including a first set of spaced rings and first loops peripheral to said rings for interconnecting said rings on alternate sides of said stack, and a second set of spaced rings interleaved with and spaced between the rings of the first set, and second loops peripheral to said rings of said second set on alternate sides of said stack for interconnecting rings of said second set, said second loops being circumferentially spaced around said stack from the first loops, a metal ground plane cylinder receiving said sets of rings in spaced relation therewithin, a first set of dielectric fins extending longitudinally within said ground plane cylinder and radially inwardly in supporting relation to rings of the first set, and a second set of dielectric fins extending longitudinally of said ground plane cylinder and radially therewithin in supporting relation to the second set of rings, wherein the fins supporting the first set of rings are circumferentially spaced about the axis of said cylinder from the fins supporting the other set of rings, means supporting said cylinder from said insulating rods, and means for providing different voltages to the rings of the first and second set respectively to maintain beam focussing.
  • 21. A traveling wave tube comprising:an electron gun structure, a collector structure, and a slow wave structure intermediate said electron gun structure and said collector structure and through which an electron beam provided by said electron gun structure passes, an elongated envelope enclosing said structures, said envelope being formed of insulating material and provided with a plurality of insulating rods disposed longitudinally therewithin for in turn supporting said electron gun structure, said collector structure, and said slow wave structure, means for coupling an r.f. signal input to and receiving an r.f. signal output from said slow wave structure, wherein said slow wave structure provides electrostatic focussing of said electron beam as well as amplification of the r.f. signal by interaction with said electron beam, wherein said slow wave structure comprises first and second helices, the turns of the first helix being substantially coaxial with and interleaved with the turns of the second helix, a ground plane cylinder supported within said elongated envelope and in turn receiving said helices in spaced relation hereto, a first set of dielectric fins extending longitudinally within said ground plane cylinder and radially therewithin in supporting relation to one of said helices, and a second set of dielectric fins extending longitudinally within said ground plane cylinder and radially therewithin in supporting relation to the second of said helices, the fins of the second set being circumferentially spaced within said ground plane cylinder from the fins of the first set, and means supporting said metal ground plane cylinder from said insulating rods, and means for providing different voltages to the respective helices.
  • 22. The method of manufacturing a traveling wave tube comprising:supporting an electron gun structure, a collector structure, and a slow wave structure in alignment in between said electron gun structure and said collector structure by joining said structures to a common set of insulating rods disposed in surrounding relation to said structures, and positioning said rods and said structures within a common insulating envelope extending longitudinally of said rods in enclosing relation thereto.
  • 23. The method according to claim 22 wherein joining said structures to said common set of insulating rods is accomplished by bringing said rods to a semi-molten state and embedding portions of at least ones of said structures into said rods while said rods are semi-molten to provide a common rigid structure.
  • 24. The method according to claim 23 including forming said insulating rods of glass.
  • 25. The method according to claim 23 including providing ones of said structures as metal wafers, portions of said wafers being embedded in said rods.
  • 26. The method according to claim 23 including rigidly supporting said common structure within a glass envelope.
  • 27. A traveling wave tube comprising:an electron gun structure, a slow wave structure through which an electron beam provided by said electron gun structure passes, and a collector structure; an envelope enclosing said structures, said envelope being formed of insulating material and provided with a plurality of rods also formed of insulating material and supported inside said envelope, said rods in turn rigidly supporting said electron gun structure, said slow wave structure, and said collector structure, and means for coupling an r.f. signal input to and receiving an r.f. signal output from said slow wave structure.
  • 28. A traveling wave tube comprising:an electron gun structure and a slow wave structure through which an electron beam provided by said electron gun structure passes, and a collector structure, an envelope enclosing said structures, said envelope being formed of insulating material and provided with a plurality of rods also formed of insulating material and supported in said envelope, said rods in turn rigidly supporting said electron gun structure and said slow wave structure, and means for coupling an r.f. signal input to and receiving an r.f. signal output from said slow wave structure, wherein said collector structure comprises a plurality of spaced conducting wafers apertured to receive said electron beam and supported by said rods, said wafers being maintained at successively lower voltage levels along said beam.
  • 29. A traveling wave tube comprising:an electron gun structure and a slow wave structure through which an electron beam provided by said electron gun structure passes, said slow wave structure comprising a plurality of metal wafers disposed along the path of said electron beam, said wafers being centrally apertured to pass said electron beam, and insulating rods supporting said wafers, successive wafers along the path of said electron beam being insulated from one another and receiving different voltages for focussing said electron beam, wherein successive wafers are spaced from one another along said path of said electron beam to form electromagnetic cavities, at least ones of said wafers also having apertures spaced radially from the path of said electron beam to provide coupling between cavities to supply a path through which electromagnetic energy is propagated.
  • 30. A traveling wave tube comprising:an electron gun structure, a slow wave structure through which an electron beam provided by said electron gun structure passes, and a collector structure, an envelope enclosing said structures, said envelope being formed of insulating material and provided with a plurality of rods also formed of insulating material and supported in said envelope, said rods in turn rigidly supporting said electron gun structure and said slow wave structure, and means for coupling an r.f. signal input to and receiving an r.f. signal output from said slow wave structure, wherein said slow wave structure provides electrostatic focussing of said electron beam as well as amplification of the r.f. signal by interaction with said electron beams, and wherein said slow wave structure comprises a coupled cavity stack having voltage applied thereto for producing said focussing of said beam, said slow wave structure providing amplification of r.f. energy, said cavity stack comprising at least several apertured wafers having apertures thereof lined to receive said electron beam while also being insulated from one another, the cavities of said cavity stack being formed between successive wafers, said wafers being provided with additional apertures for r.f. coupling between cavities.
Government Interests

This invention was made with Government support under contract NAS3-01003 awarded by NASA. The Government has certain rights in this invention.

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Provisional Applications (1)
Number Date Country
60/290505 May 2001 US