US2782334A - Velocity modulated electron discharge devices - Google Patents

Velocity modulated electron discharge devices Download PDF

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US2782334A
US2782334A US275808A US27580852A US2782334A US 2782334 A US2782334 A US 2782334A US 275808 A US275808 A US 275808A US 27580852 A US27580852 A US 27580852A US 2782334 A US2782334 A US 2782334A
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cathode
electron
electrons
gap
electron discharge
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US275808A
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Bernard C Gardner
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Raytheon Co
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Raytheon Manufacturing Co
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Priority to US275808A priority Critical patent/US2782334A/en
Priority to GB24455/52A priority patent/GB737001A/en
Priority to FR1069704D priority patent/FR1069704A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J25/00—Transit-time tubes, e.g. klystrons, travelling-wave tubes, magnetrons
    • H01J25/02—Tubes with electron stream modulated in velocity or density in a modulator zone and thereafter giving up energy in an inducing zone, the zones being associated with one or more resonators
    • H01J25/22—Reflex klystrons, i.e. tubes having one or more resonators, with a single reflection of the electron stream, and in which the stream is modulated mainly by velocity in the modulator zone
    • H01J25/24—Reflex klystrons, i.e. tubes having one or more resonators, with a single reflection of the electron stream, and in which the stream is modulated mainly by velocity in the modulator zone in which the electron stream is in the axis of the resonator or resonators and is pencil-like before reflection

Definitions

  • This invention relates to electron discharge devices of the velocity modulated type, and more particularly relates to a means for reducing hysteresis in reflex klystron oscillators.
  • an electron beam from a cathode is projected through a gap to which a tuned circuit, such a cavity resonator, is connected.
  • An R. F. field exists across this gap so that the beam of electrons is velocity modulated on emerging from the gap.
  • the electron beam next passes through a region between the gap and a reflecting electrode or repeller. In this reflector region the 'electrons are stopped by a strong retarding field and the direction of electron travel is reversed.
  • the refiected electrons returning to the gap may be made ⁇ to deliver 'energy to the resonator owing to the interaction of the modulated beam current and the R; F. field across the gap.
  • a small elongated spike such as a tungsten wire or metal rod, may be mounted in the center of the repeller. This spike causes a force to be exerted on the electrons radially outward from the beam axis. The resulting divergence of the beam, although not sufiicient to prevent electrons from returning through the R. F. gap, is great enough to prevent a reflection from the klystron cathode.
  • v conductive material such as copper, which are ⁇ supported by thin discoidal portions 11 and 12 to which the glass
  • the spike repeller is useful only on short range tubes, that is, klystrons having relatively narrow frequency range of oscillation. rl ⁇ his limitation results vrom the fact that this structure has very poor depth field uniformity.
  • the equi-potential lines of the fieldk between the grids and the vrepeller are not uniformly spaced andthe equi-potential surfaces adjacent the resonator are substantially fiat while those near the repeller electrodes are irregular in contour.
  • the repeller voltage is varied to accommodate a variation in frequency, the entire field is shifted.
  • Fig. l is a longitudinal section view taken through the center of an electron discharge device according to the invention.
  • Fig. 2 is a plan view of a first type of cathode structure as used in the electron discharge device of Fig. l;
  • Fig. 3a is a fragmentary plan view of a second type of cathode structure as used in the electron discharge device of Fig. l;
  • Fig. 3b is a fragmentary view in elevation of the cath- Vode structure shown in Fig. 3a.
  • T represents an electron discharge device of the velocityy modulated type, known more particularly as a reflex 'klystron
  • An electron beam is produced by means of an electron gun which in the bottom portion of a Vsealed glass ⁇ envelope 7 mounted on tube base 8.
  • the electron beam passes through a gap 17 formed by a pair of spaced grid structures 9 and 1d made of highly envelope 7 is sealed; these discoidal portions are the means by which connection is made to an external tuned circuit, such as a toroidal cavity resonator. Since the latter forms no part of this inventiomit has not been Y illustrated.
  • the first grids structure 9 includes, in addition yto discoidal portion 11, cylindrical tubular portion 13 having a narrow inwardly fianged portion 14 at the 'end opposite said discoidal portion.
  • a mesh or screen 15 is supported between fianged portion 14 of grid structure 9 and retaining ring 16.
  • a second grid structurel() is substantially similar to grid structure 9 vand comprises a discoidal portion 12, aanged portion 18, a mesh 19 and f retaining ring 20.
  • a repeller or reflecting electrode 21 is supported', for example, by aV conductor 22 sealed in the end of tube 1 opopsite base 8, as shown in-liig. 1.
  • the repeller is spaced from grid structure 1t? and mounted coaxial with the cathode and grid structures.
  • a suitable voltage is applied to repeller electrode 21
  • the electrons in the electron beam which have passed through grids 9 land 10 are reflected baci ⁇ toward said grids. Some of these electrons will reach the cathode region and will be reflected therefrom. Because of the unevenly distributed field around the cathode, the second transit electrons'from the cathode direction arey phase scrambled so that the electrons enter the gap as a uniform distribution vrather than inbunches.
  • Electron emissive material 3 is supplied irregularly to the surface 2 of the cathode, as clearly shown in Fig. 2.
  • the irregular cathode coating may be produced in a large number of ways, 'such as scraping various areas from a uniformly coated cathode, spraying the cathode through a stencil, breaking the cathode down on exhaust in such manner as to cause coarse sintering, poisoning of various areas, or placing a metallic grid over the cathode. Any other means for providing avariable emission across the cathode is within the scope of the present invention.
  • a second type of irregular cathode is shown in plan and elevation in Figs. 3a and Fig. 3b, respectively.
  • the cathode 2 is non-uniformly shaped and has alternate projections 25 and depressions 26 similar to the surface of a wafile iron.
  • the disturbance of the equi-potential lines is controlled by the cathode emission space charge adjacent the coated areas.
  • the disturbance of the equi-potential lines by said space charge is not as effective as an irregular cathode geometry, as exemplied by the cathode of Fig. 3; an irregularly shaped cathode is therefore preferable to an irregularly coated cathode.
  • the principle according to the present invention is not to be limited to the type of klystron herein illustrated and described but may be used in any klystron in which ditliculties owing to hysteresis occur.
  • the cathode configuration and cathode surface are not to be limited to those shown in Figs. 2 and 3. It should also be understood that the cathode may be constructed so that both the cathode geometry and the coating on the cathode are irregular.
  • An electron discharge device of the reflex klystron type comprising an electron gun including a cathode for emitting a single composite beam of primary electrons, a substantially planar rellecting electrode positioned lin the path of said electrons, a pair of spaced electron-permeable members defining a unitary gap traversed by said beam, said cathode having an electron emissive surface of irregular configuration and including a series of projecting areas and depressed areas for providing an electron beam density in the vicinity of said cathode which varies in random manner from point to point throughout the crosssectional area of the beam as presented to said gap whereby hysteresis in said device is substantially reduced.
  • An electron discharge ⁇ device of the reflex klystron type comprising an electron gun including a cathode for emiting a single composite beam of primary electrons, a substantially planar reecting electrode positioned in the path of said electrons, a pair of spaced electron permeable members defining a unitary gap traversed by said beam, said cathode having an electron emissive surface of irregular configuration including a series of projecting areas and depressed areas which have an irregular layer of thermionic emissive material thereon for providing an electron beam density in the vicinity of said cathode which varies in random manner from point to point throughout the cross-sectional area of the beam as presented to said gap whereby hysteresis in said device is substantially reduced.
  • An electron discharge device of the reflex klystron type comprising an electron gun including a cathode for emitting a single composite beam of primary electrons, a substantially planar reflecting electrode positioned in the path of said electrons, a pair of sapced electron permeable members defining a unitary gap traversed by said beam, said cathode having an electron emissive surface of irregular configuration and including a series of projecting areas and depressed areas which have a substantially uniform layer of emissive material thereon for providing an electron beam density in the vicinity of said cathode which varies in random manner from point to point throughout the cross-sectional area of the beam as presented to said gap whereby hysteresis in said device is substantially reduced.

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Description

Feb. 19, 1957 B. c. GARDNER VELOCITY MODULATED ELECTRON DISCHARGE DEVICES Filed March 10, 1952 Dua Y z,7sz,3s4 f VELOCITY MODULATED ELacrnbN DISCHARGE DEVICES Bernard C. Gardner, Los Altos; Caliigf'assgnor to Raytheon Manufacturing Company, Newton, Mass., a corporation of Delaware Application Maren 1o, 1952, stan No. 275,808 3 claims. (ci. sis-si) This invention relates to electron discharge devices of the velocity modulated type, and more particularly relates to a means for reducing hysteresis in reflex klystron oscillators.
ln velocity modulated oscillators of the reflex klystron type, an electron beam from a cathode is projected through a gap to which a tuned circuit, such a cavity resonator, is connected. An R. F. field exists across this gap so that the beam of electrons is velocity modulated on emerging from the gap. The electron beam next passes through a region between the gap and a reflecting electrode or repeller. In this reflector region the 'electrons are stopped by a strong retarding field and the direction of electron travel is reversed. The refiected electrons returning to the gap may be made` to deliver 'energy to the resonator owing to the interaction of the modulated beam current and the R; F. field across the gap.
in the normal klystron there are always some electrons that make more than 'one return transit. These multipletransit electrons give rise to hysteresis, thatV is, the phenomenon iny which the amplitude and yfrequency of oscillation depend upon the direction from which thev operating value of the klystron reliector yvelu-ige is approached. For
example, it has been' found that' the characteristic curves of power output versus repell'erelectrode potential for a given reflex klystron differ dependingr on whether the repeller or reflecting electrode potential is made progressively less negative with respect to the cathode.
To reduce this undesirable non-uniform operating characteristic and also to prevent mode asymmetry which is associated with hysteresis, a small elongated spike, such as a tungsten wire or metal rod, may be mounted in the center of the repeller. This spike causes a force to be exerted on the electrons radially outward from the beam axis. The resulting divergence of the beam, although not sufiicient to prevent electrons from returning through the R. F. gap, is great enough to prevent a reflection from the klystron cathode.
v conductive material, such as copper, which are `supported by thin discoidal portions 11 and 12 to which the glass The spike repeller, however, is useful only on short range tubes, that is, klystrons having relatively narrow frequency range of oscillation. rl`his limitation results vrom the fact that this structure has very poor depth field uniformity. When a spike .is used, the equi-potential lines of the fieldk between the grids and the vrepeller are not uniformly spaced andthe equi-potential surfaces adjacent the resonator are substantially fiat while those near the repeller electrodes are irregular in contour. As the repeller voltage is varied to accommodate a variation in frequency, the entire field is shifted. Because of the v non-uniformity of the field, a variation of frequency will 2,782,334 new ,Fe er1-2u lCe electrons, which are productive of hysteresis, to have aneffect on the oscillatonvthey must arrive at the gapsome- 5 what hunched and in a particular phase tothe oscillation across the gap. The eectof` the unevenly distributed or lumpy fieldvwill be to vary the depth of 'penetration of the electron bunch near the cathode, which will cause a spread in transit time of the electrons within a particular bunch. This will phase scramble the second transit electrons so that they will enter the gap from the cathode direction the second time as a uniform distribution, rather than in bunches, thereby preventing them from adding to or subtracting from the cavity oscillation.
In the drawing:
Fig. l is a longitudinal section view taken through the center of an electron discharge device according to the invention;
Fig. 2 is a plan view of a first type of cathode structure as used in the electron discharge device of Fig. l;
Fig. 3a is a fragmentary plan view of a second type of cathode structure as used in the electron discharge device of Fig. l; and
Fig. 3b is a fragmentary view in elevation of the cath- Vode structure shown in Fig. 3a.
Referring now to Fig. l of the drawing, T represents an electron discharge device of the velocityy modulated type, known more particularly as a reflex 'klystron An electron beam is produced by means of an electron gun which in the bottom portion of a Vsealed glass `envelope 7 mounted on tube base 8. v v
The electron beam passes through a gap 17 formed by a pair of spaced grid structures 9 and 1d made of highly envelope 7 is sealed; these discoidal portions are the means by which connection is made to an external tuned circuit, such as a toroidal cavity resonator. Since the latter forms no part of this inventiomit has not been Y illustrated. The first grids structure 9 includes, in addition yto discoidal portion 11, cylindrical tubular portion 13 having a narrow inwardly fianged portion 14 at the 'end opposite said discoidal portion. A mesh or screen 15 is supported between fianged portion 14 of grid structure 9 and retaining ring 16. A second grid structurel() is substantially similar to grid structure 9 vand comprises a discoidal portion 12, aanged portion 18, a mesh 19 and f retaining ring 20. v y
A repeller or reflecting electrode 21 is supported', for example, by aV conductor 22 sealed in the end of tube 1 opopsite base 8, as shown in-liig. 1. The repeller is spaced from grid structure 1t? and mounted coaxial with the cathode and grid structures. When a suitable voltage is applied to repeller electrode 21, the electrons in the electron beam which have passed through grids 9 land 10 are reflected baci` toward said grids. Some of these electrons will reach the cathode region and will be reflected therefrom. Because of the unevenly distributed field around the cathode, the second transit electrons'from the cathode direction arey phase scrambled so that the electrons enter the gap as a uniform distribution vrather than inbunches. i A l Fig. 2, which is an enlarged plan view of the cathode,
i f' 2,782,334 ,Y Y t.
illustrates one manner of irregular cathode coating. Electron emissive material 3 is supplied irregularly to the surface 2 of the cathode, as clearly shown in Fig. 2.
The irregular cathode coating may be produced in a large number of ways, 'such as scraping various areas from a uniformly coated cathode, spraying the cathode through a stencil, breaking the cathode down on exhaust in such manner as to cause coarse sintering, poisoning of various areas, or placing a metallic grid over the cathode. Any other means for providing avariable emission across the cathode is within the scope of the present invention.
A second type of irregular cathode is shown in plan and elevation in Figs. 3a and Fig. 3b, respectively. The cathode 2 is non-uniformly shaped and has alternate projections 25 and depressions 26 similar to the surface of a wafile iron.
With a non-uniformly coated cathode, the disturbance of the equi-potential lines is controlled by the cathode emission space charge adjacent the coated areas. The disturbance of the equi-potential lines by said space charge is not as effective as an irregular cathode geometry, as exemplied by the cathode of Fig. 3; an irregularly shaped cathode is therefore preferable to an irregularly coated cathode.
The principle according to the present invention is not to be limited to the type of klystron herein illustrated and described but may be used in any klystron in which ditliculties owing to hysteresis occur. Furthermore, the cathode configuration and cathode surface are not to be limited to those shown in Figs. 2 and 3. It should also be understood that the cathode may be constructed so that both the cathode geometry and the coating on the cathode are irregular.
What is claimed is:
l. An electron discharge device of the reflex klystron type comprising an electron gun including a cathode for emitting a single composite beam of primary electrons, a substantially planar rellecting electrode positioned lin the path of said electrons, a pair of spaced electron-permeable members defining a unitary gap traversed by said beam, said cathode having an electron emissive surface of irregular configuration and including a series of projecting areas and depressed areas for providing an electron beam density in the vicinity of said cathode which varies in random manner from point to point throughout the crosssectional area of the beam as presented to said gap whereby hysteresis in said device is substantially reduced.
2. An electron discharge `device of the reflex klystron type comprising an electron gun including a cathode for emiting a single composite beam of primary electrons, a substantially planar reecting electrode positioned in the path of said electrons, a pair of spaced electron permeable members defining a unitary gap traversed by said beam, said cathode having an electron emissive surface of irregular configuration including a series of projecting areas and depressed areas which have an irregular layer of thermionic emissive material thereon for providing an electron beam density in the vicinity of said cathode which varies in random manner from point to point throughout the cross-sectional area of the beam as presented to said gap whereby hysteresis in said device is substantially reduced.
3. An electron discharge device of the reflex klystron type comprising an electron gun including a cathode for emitting a single composite beam of primary electrons, a substantially planar reflecting electrode positioned in the path of said electrons, a pair of sapced electron permeable members defining a unitary gap traversed by said beam, said cathode having an electron emissive surface of irregular configuration and including a series of projecting areas and depressed areas which have a substantially uniform layer of emissive material thereon for providing an electron beam density in the vicinity of said cathode which varies in random manner from point to point throughout the cross-sectional area of the beam as presented to said gap whereby hysteresis in said device is substantially reduced.
References Cited in the file of this patent UNTTED STATES PATENTS 1,797,990 Lucian Mar. 24, 1931 2,180,710 Knoll et al. Nov. 2l, 1939 2,207,846 Wolff July 16, 1940 2,254,128 Van Den Bosch Aug. 26, 1941 2,292,437 Farnsworth Aug. 11, 1942 2,322,807 Iams June 29, 1943 2,459,792 Chevigny lan. 25, 1949 2,506,627 Barford May 9, 1950 2,581,408 Hamilton Ian. 8, 1952
US275808A 1952-03-10 1952-03-10 Velocity modulated electron discharge devices Expired - Lifetime US2782334A (en)

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US275808A US2782334A (en) 1952-03-10 1952-03-10 Velocity modulated electron discharge devices
GB24455/52A GB737001A (en) 1952-03-10 1952-09-30 Improvements in or relating to reflex velocity modulated electron discharge devices
FR1069704D FR1069704A (en) 1952-03-10 1952-10-30 Electronic speed modulated discharge device

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Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2943234A (en) * 1956-02-24 1960-06-28 Varian Associates Charged particle flow control apparatus
US3175118A (en) * 1962-05-28 1965-03-23 Gen Electric Low power heater
US3205392A (en) * 1960-04-01 1965-09-07 Gen Electric Brillouin beam forming apparatus
US3278791A (en) * 1960-10-14 1966-10-11 Csf Electron discharge device having a plurality of emissive surfaces
US3377492A (en) * 1965-08-03 1968-04-09 Hughes Aircraft Co Flood gun for storage tubes having a dome-shaped cathode and dome-shaped grid electrodes
US3558967A (en) * 1969-06-16 1971-01-26 Varian Associates Linear beam tube with plural cathode beamlets providing a convergent electron stream
US3564317A (en) * 1967-05-13 1971-02-16 Philips Corp Cathode for an x-ray tube cooled by heat-conductive coaxial cylinders
US3783325A (en) * 1971-10-21 1974-01-01 Us Army Field effect electron gun having at least a million emitting fibers per square centimeter
US3967150A (en) * 1975-01-31 1976-06-29 Varian Associates Grid controlled electron source and method of making same
US4031425A (en) * 1974-10-19 1977-06-21 U.S. Philips Corporation Dispenser cathode for a grid-controlled electron tube and method of manufacturing same
US4380717A (en) * 1978-09-02 1983-04-19 English Electric Valve Company Limited Magnetrons
US4680500A (en) * 1986-03-06 1987-07-14 The United States Of America As Represented By The Secretary Of The Air Force Integral grid/cathode for vacuum tubes
US4686413A (en) * 1985-02-06 1987-08-11 New Japan Radio Co., Ltd. Cathode for magnetron

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1797990A (en) * 1926-02-06 1931-03-24 Arsene N Lucian Heater construction for cathodes
US2180710A (en) * 1936-03-19 1939-11-21 Telefunken Gmbh Cathode ray tube screen
US2207846A (en) * 1938-06-30 1940-07-16 Rca Corp Electronic discharge device
US2254128A (en) * 1938-06-02 1941-08-26 Vacuum Science Products Ltd Electron multiplier
US2292437A (en) * 1935-07-01 1942-08-11 Farnsworth Television & Radio Electron image amplifier
US2322807A (en) * 1940-12-28 1943-06-29 Rca Corp Electron discharge device and system
US2459792A (en) * 1944-07-08 1949-01-25 Standard Telephones Cables Ltd Beam type electron discharge device
US2506627A (en) * 1945-09-14 1950-05-09 Emi Ltd Electron discharge device
US2581408A (en) * 1947-04-16 1952-01-08 Sperry Corp High-frequency electron discharge device

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1797990A (en) * 1926-02-06 1931-03-24 Arsene N Lucian Heater construction for cathodes
US2292437A (en) * 1935-07-01 1942-08-11 Farnsworth Television & Radio Electron image amplifier
US2180710A (en) * 1936-03-19 1939-11-21 Telefunken Gmbh Cathode ray tube screen
US2254128A (en) * 1938-06-02 1941-08-26 Vacuum Science Products Ltd Electron multiplier
US2207846A (en) * 1938-06-30 1940-07-16 Rca Corp Electronic discharge device
US2322807A (en) * 1940-12-28 1943-06-29 Rca Corp Electron discharge device and system
US2459792A (en) * 1944-07-08 1949-01-25 Standard Telephones Cables Ltd Beam type electron discharge device
US2506627A (en) * 1945-09-14 1950-05-09 Emi Ltd Electron discharge device
US2581408A (en) * 1947-04-16 1952-01-08 Sperry Corp High-frequency electron discharge device

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2943234A (en) * 1956-02-24 1960-06-28 Varian Associates Charged particle flow control apparatus
US3205392A (en) * 1960-04-01 1965-09-07 Gen Electric Brillouin beam forming apparatus
US3278791A (en) * 1960-10-14 1966-10-11 Csf Electron discharge device having a plurality of emissive surfaces
US3175118A (en) * 1962-05-28 1965-03-23 Gen Electric Low power heater
US3377492A (en) * 1965-08-03 1968-04-09 Hughes Aircraft Co Flood gun for storage tubes having a dome-shaped cathode and dome-shaped grid electrodes
US3564317A (en) * 1967-05-13 1971-02-16 Philips Corp Cathode for an x-ray tube cooled by heat-conductive coaxial cylinders
US3558967A (en) * 1969-06-16 1971-01-26 Varian Associates Linear beam tube with plural cathode beamlets providing a convergent electron stream
US3783325A (en) * 1971-10-21 1974-01-01 Us Army Field effect electron gun having at least a million emitting fibers per square centimeter
US4031425A (en) * 1974-10-19 1977-06-21 U.S. Philips Corporation Dispenser cathode for a grid-controlled electron tube and method of manufacturing same
US3967150A (en) * 1975-01-31 1976-06-29 Varian Associates Grid controlled electron source and method of making same
US4380717A (en) * 1978-09-02 1983-04-19 English Electric Valve Company Limited Magnetrons
US4686413A (en) * 1985-02-06 1987-08-11 New Japan Radio Co., Ltd. Cathode for magnetron
US4680500A (en) * 1986-03-06 1987-07-14 The United States Of America As Represented By The Secretary Of The Air Force Integral grid/cathode for vacuum tubes

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GB737001A (en) 1955-09-21
FR1069704A (en) 1954-07-12

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