US3292101A - Plasma tube for microwave circuits - Google Patents

Plasma tube for microwave circuits Download PDF

Info

Publication number
US3292101A
US3292101A US379969A US37996964A US3292101A US 3292101 A US3292101 A US 3292101A US 379969 A US379969 A US 379969A US 37996964 A US37996964 A US 37996964A US 3292101 A US3292101 A US 3292101A
Authority
US
United States
Prior art keywords
grid
cavity
coaxial
tube
anode
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US379969A
Other languages
English (en)
Inventor
Jean L Favalier
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Societe Thomson Varian
Original Assignee
Societe Thomson Varian
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Societe Thomson Varian filed Critical Societe Thomson Varian
Application granted granted Critical
Publication of US3292101A publication Critical patent/US3292101A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J25/00—Transit-time tubes, e.g. klystrons, travelling-wave tubes, magnetrons
    • H01J25/005—Gas-filled transit-time tubes
    • 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

Definitions

  • This invention relates to a plasma tube adapted to be used as a component in microwave circuitry, particularly as a rea-ctance cavity resonator for frequency modulating microwave electron tubes.
  • a gas under low pressure when used as a transmission medium for microwave signals, behaves as a dielectric medium whose dielectric constant is a function of the electron density, and therefore, a function of the discharge current.
  • the resonant frequency of a plasma cavity resonator can be controlled by varying the discharge current.
  • the simplest technique for producing a plasma consists in establishing a direct current discharge through a noble gas between a hot cathode and an anode. It is well known that plasmas thus produced exhibit important instabilities that can be detected by observing the spontaneous fluctuations of the voltage at the terminals of the tube. These fluctuations are associated with instabilities of the electron density of the plasma, thus making it impossible to utilize plasma tubes for cavity resonator frequency modulation.
  • the grid potential in this case is the same as the cathode potential. Ionization take place solely in the region between the grid and anode, and the ions thus produced diffuse through the grid to form a cold plasma in the cathode region.
  • This operating mode is called the anode glow mode, and has the advantage of producing a noiseless plasma as is required to control the resonant frequency of cavity resonators.
  • the structure of the tube does not allow for this kind of utilization due to the difliculties which would be encountered in preventing microwave energy from escaping in the cathode region of the plasma tube.
  • the object of the invention is to provide a plasma tube which can be used in a microwave circuit as a variable reactance or frequency modifying component.
  • a further object of the invention is to provide plasma tube means adapted to modulate cavity resonator oscillator tubes.
  • the plasma tube according to the invention consists of an electron discharge tube having a cathode, a grid and an anode, filled with a noble gas under low pressure, operating in the anode glow mode, whose anode forms a reentrant cavity resonator extending up to the proximity of the grid, the outer wall of the cavity forming a waveguide section beyond cut-ofi for all the frequencies of the frequency range of the tube. Consequently when the gas is not ionized, the cavity resonator does not vibrate in the usual reentrant cavity mode but as a quarter wave coaxial cavity closed at one end and Patented Dec. 13, 1966 open in the transverse plane passing through the end of its ridged portion, microwave energy being prevented from escaping the coaxial cavity by means of the guide section beyond cut-off.
  • the diameter of a coaxial cavity resonator being, for a given frequency of the wave resonating within the cavity, smaller than the diameter of cylindrical cavity resonators, the outer wall of the coaxial cavity resonator can be given a diameter equal to that of the circular guide stub beyond cut-off.
  • the walls of the cylindrical portion and of the coaxial portion of the plasma tube can be made flush with each other. It results that the electron density of the plasma can be made larger and more uniform in the volume of the coaxial cavity than in prior art cavities and can allow a larger resonant frequency variation without lowering the Q of the cavity. Further the absorption of microwave energy due to the conductivity of the plasma is, for a given gas pressure and frequency variation, inversely related to the uniformity of the electron density of the plasma in the cavity.
  • the length of the coaxial cavity between its end wall and the plane passing through the end of the ridged portion is substantially a quarter of the resonant wavelength of the cavity when the discharge current in the same is Zero.
  • FIG. 1 is a schematic representation of a variable reactance plasma tube according to the invention.
  • FIG. 2 is a front, partially cross-sectional, view of a plasma tube according to the invention associated with a reflex-klystron tube.
  • FIG. 1 shows a vacuum sealed glass tube 1, filled with a noble gas under low pressure, for example xenon.
  • the pressure is between 0.02 and 0.2 millimeter of mercury.
  • an oxide-coated cathode structure 2 and its heater 3 Inside the tube are placed an oxide-coated cathode structure 2 and its heater 3, a grid 4 and an anode structure 5.
  • a fine mesh grid 4 is supported by a metallic cylinder 41 surrounding the cathode structure 2 and secured thereto by plate-like ring 42.
  • An anode structure 5, brought to a variable modulating voltage by means, not shown, consists of a reentrant cavity resonator 50 having a lateral wall 54 and a ridged end wall 51.
  • This cavity resonator is so dimensioned as not to vibrate in the usual reentrant cavity mode, but in the TEM mode as regards the coaxial portion, the remainder of the cavity resonator forming a wave guide section beyond cut-off, i.e.
  • the cut-off frequency of which is at least equal to the higher limit of the frequency range of the microwave oscillator tube associated with the plasma tube.
  • the coaxial portion of the cavity resonator has an axial length near one quarter of the wavelength corresponding to the lower frequency of the frequency range of the associated oscillator tube.
  • the coaxial cavity resonates when the xenon gas is not ionized as a coaxial cavity resonator closed at one end and open at the other end on a resonant wavelength substantially equal to four times its height.
  • the higher limit frequency being 9000 mHz. corresponding to a Wavelength of 333 cms.
  • the axial length of the cavity resonator 50 is 7 turns.
  • a pair of wave permeable gas tight window members 52 and 53 as of alumina ceramic are sealed across the outer wall of cavity resonator 50, near the closed end thereof.
  • Grid 4 is placed at a sufficient distance from the inner conductor 51 of the coaxial cavity in order to prevent the microwave energy from the evanescent mode in waveguide 54 from escaping into the cathode side of the discharge tube.
  • the microwave fields are therefore quite weak in the neighborhood of the grid, and thus the influence of the cathode-grid region and of the grid-anode region adjacent to the grid on the plasma tube operation is significantly reduced.
  • the ionization process is initiated by applying a direct voltage between anode 5 and heated cathode 2 by means of variable voltage supply 8.
  • the plasma formed by the collisions of the electrons at their exit fromthe grid 4 with the atoms of the noble gas, diffuse into the inside of the anodic part of the tube.
  • the electron density is maximal in the neighborhood of the end of the central conductor 51. This condition of operation is favorable for obtaining a large variation of the resonant frequency of the cavity since this cavity, operating in the TEM mode, has a maximal electric field in the open terminal plane passing through the end of the central conductor 51.
  • Maximal ionization potential between anode and FIG. 2 represents a plasma tube designated generally by the reference numeral 100, and associated with a refiex-klystron 200, the two tubes 100 and 200 constituting an over-all unit often called klysmatron, the name coined from the words ldystron and plasma.
  • the plasma tube 100 is different from the one in FIG. 1 only as regards its outer envelope. Its different parts already represented in FIG. 1 are denominated by the same reference numerals increased by 100
  • a hollow metallic relatively thick walled chamber 150 is defined by and bounded by cylindrical side wall 154 and end Wall 105 provided with a central, hemispherically ended, post 151.
  • the side wall 154 is vacuum sealed to a socket 110 which coaxially supports cathode assembly 102 and cylinder 141, this last cylinder carrying grid 104.
  • the chamber 150 is filled in use with xenon to a low pressure Within the range above indicated.
  • a pair of port terminals 6 and 7 form input and output waveguide terminal sections, respectively, of the cavity resonator 150 for applying wave energy to the cavity and for abstracting wave energy therefrom.
  • a pair of RF. window members 152 and 153 are vacuum sealed across the input and output terminals.
  • An input flange 155 as of copper connects to the output flange 256 of a reflex-klystron oscillator 200.
  • An output flange 156 connects to a load (not shown).
  • a pair of capacitive phase adjusting posts 155 and 157 are provided, respectively extending into the input and output waveguide sections 6 and 7 from the broad wall thereof. The post 155 adjusts the effective electric length of the guide between the cavity resonator of the refiux-klystron and the cavity resonator for impedance matching.
  • a variable reactance plasma tube adapted to oscillate in a given frequency range comprising a vacuum sealed envelope filled with a low pressure gas, a cathode assembly, a grid and an anode assembly, said anode assembly forming a metallic reentrant cavity resonator having a coaxial cavity portion and an adjacent cylindrical waveguide portion extending substantially up to to the grid, said cylindrical waveguide portion being beyond cut-off for all the frequencie comprised in said frequency range, means for coupling to said coaxial portion microwave energy having a frequency in said range, means for abstracting from said coaxial cavity portion microwave energy and means for applying a variable voltage between said cathode and anode assemblies.
  • a variable reactance plasma tube adapted to oscillate in a given frequency range comprising a vacuum sealed envelope filled with a low pressure gas, a cathode assembly, a grid and an anode assembly, said anode assembly forming a metallic reentrant cavity resonator having a coaxial cavity portion, the length of .which is substantially equal to the quarter of the wavelength corresponding to the lower frequency of said frequency range, and an adjacent cylindrical waveguide portion extending substantially up to the grid, said cylindrical waveguide portion being beyond cut-oif for all the frequencies comprised in said frequency range, means for coupling to said coaxial portion microwave energy having a frequency in said range, means for abstracting from said coaxial cavity portion microwave energy and means for applying a variable voltage between said cathode and anode assemblies.
  • a variable reactance plasma tube according to claim 1 in which the means for coupling and abstracting microwave energy to and from the coaxial cavity portion of the reentrant cavity resonator are two waveguide sections aligned with each other and radially directed with respect to said coaxial cavity portion and coupled thereto by means of radio frequency permeable window members.
  • a frequency modulated oscillator tube assembly comprising a klystron tube oscillating in a given frequency range, having an evacuated envelope and at least one cavity resonator, a. variable reactance plasma tube comprising a vacuum sealed envelope filled with a low pressure gas, a cathode assembly, a grid and an anode assembly, said anode assembly forming a metallic reentrant cavity resonator comprising a coaxial cavity portion having an inner conductor and an outer hollow cylindrical conductor longer than the inner conductor, the portion of said outer conductor which is longer than said inner conductor forming a waveguide beyond cut ofi for all the frequencies comprised in said frequency range and extending substantially up to the grid, means for vacuum tightly coupling said klystron cavity resonator to said coaxial cavity portion of said reentrant cavity resonator, means for abstracting from said coaxial cavity portion microwave energy and mean for applying a variable voltage between said cathode and anode assemblies.
  • a frequency modulated oscillator tube assembly comprising a klystron tube oscillating in a given frequency range, having an evacuated envelope and at least one cavity resonator, a variable reactance plasma tube comprising a vacuum sealed envelope filled with a low pressure gas, a cathode assembly, a grid and an anode assembly, said anode assembly forming a metallic reentrant cavity resonator comprising a coaxial cavity portion having an inner conductor and an outer hollow cylindrical conductor longer than the inner conductor, the portion of said outer conductor which is longer than said inner conductor forming a waveguide beyond cutoff for all the frequencies comprised in said frequency range and extending substantially up to the grid, a first Waveguide section vacuum tightly coupling said klystron cavity resonator to said coaxial cavity portion of said reentrant cavity resonator, radially directed with respect to said coaxial cavity portion, a second waveguide section aligned with said first section for abstracting from said coaxial cavity portion microwave energy, radio frequency perme

Landscapes

  • Plasma Technology (AREA)
  • Inductance-Capacitance Distribution Constants And Capacitance-Resistance Oscillators (AREA)
  • Control Of Motors That Do Not Use Commutators (AREA)
US379969A 1963-07-03 1964-07-02 Plasma tube for microwave circuits Expired - Lifetime US3292101A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR940252A FR1383767A (fr) 1963-07-03 1963-07-03 Tube à plasma pour circuit hyperfréquence

Publications (1)

Publication Number Publication Date
US3292101A true US3292101A (en) 1966-12-13

Family

ID=8807508

Family Applications (1)

Application Number Title Priority Date Filing Date
US379969A Expired - Lifetime US3292101A (en) 1963-07-03 1964-07-02 Plasma tube for microwave circuits

Country Status (6)

Country Link
US (1) US3292101A (enExample)
DE (1) DE1270627B (enExample)
FR (1) FR1383767A (enExample)
GB (1) GB1024080A (enExample)
NL (1) NL6407552A (enExample)
SE (1) SE312180B (enExample)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5142250A (en) * 1992-01-14 1992-08-25 The United States Of America As Represented By The Secretary Of The Navy High power microwave generator
CN110931332A (zh) * 2019-12-10 2020-03-27 安徽华东光电技术研究所有限公司 真空微波振荡源
US10773092B2 (en) * 2017-05-29 2020-09-15 Elegant Mathematics LLC Real-time methods for magnetic resonance spectra acquisition

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3031399A (en) * 1958-12-08 1962-04-24 Csf High-frequency utilization apparatus for ionized gas
US3076917A (en) * 1959-05-05 1963-02-05 Thomson Houston Comp Francaise Electronic tuning devices for klystron valves
US3209285A (en) * 1962-09-24 1965-09-28 Thomas E Manwarren Folded cylinder gaseous discharge device

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1168571B (de) * 1959-05-05 1964-04-23 Thomson Houston Comp Francaise Einrichtung zur elektrischen Abstimmung oder Frequenzvariation eines Hohlraumresonators einer Elektronenroehre nach Art eines Klystrons

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3031399A (en) * 1958-12-08 1962-04-24 Csf High-frequency utilization apparatus for ionized gas
US3076917A (en) * 1959-05-05 1963-02-05 Thomson Houston Comp Francaise Electronic tuning devices for klystron valves
US3209285A (en) * 1962-09-24 1965-09-28 Thomas E Manwarren Folded cylinder gaseous discharge device

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5142250A (en) * 1992-01-14 1992-08-25 The United States Of America As Represented By The Secretary Of The Navy High power microwave generator
US10773092B2 (en) * 2017-05-29 2020-09-15 Elegant Mathematics LLC Real-time methods for magnetic resonance spectra acquisition
CN110931332A (zh) * 2019-12-10 2020-03-27 安徽华东光电技术研究所有限公司 真空微波振荡源

Also Published As

Publication number Publication date
GB1024080A (en) 1966-03-30
FR1383767A (fr) 1965-01-04
SE312180B (enExample) 1969-07-07
NL6407552A (enExample) 1965-01-04
DE1270627B (de) 1968-06-20

Similar Documents

Publication Publication Date Title
US4527091A (en) Density modulated electron beam tube with enhanced gain
US3310704A (en) Output coupling circuit for microwave tube apparatus
US3346766A (en) Microwave cold cathode magnetron with internal magnet
US3292101A (en) Plasma tube for microwave circuits
US3448331A (en) Composite coaxial coupling device and coaxial window
US3775709A (en) Improved output window structure for microwave tubes
US2404226A (en) High-frequency discharge device
US3479556A (en) Reverse magnetron having an output circuit employing mode absorbers in the internal cavity
US3376463A (en) Crossed field microwave tube having toroidal helical slow wave structure formed by a plurality of spaced slots
US2808568A (en) Magnetron
US3538377A (en) Traveling wave amplifier having an upstream wave reflective gain control element
US2608670A (en) High-frequency tube structure
US2929955A (en) Cavity resonator for klystron tube
US3594605A (en) Mode suppression means for a clover-leaf slow wave circuit
US2745072A (en) Wave guide gas switching device
US3441793A (en) Reverse magnetron having a circular electric mode purifier in the output waveguide
US3720889A (en) Electron discharge devices
US3480828A (en) Thyratron waveguide switch with density enhancement for operation in 27 to 40 ghz. range
US3483420A (en) Klystron amplifier employing helical distributed field buncher resonators and a coupled cavity extended interaction output resonator
US2724072A (en) Reflex klystron
US3270240A (en) Extended interaction resonant electric discharge system
US2904719A (en) Electron discharge devices and electrical resonators therefor
US3418522A (en) Mode control for theta mode magnetrons
US2949559A (en) Klystron tube
US3475645A (en) Gap tuned reflex klystron having an enlarged movable diaphragm disposed in r.f. isolation with respect to the r.f. cavity