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
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J23/00—Details of transit-time tubes of the types covered by group H01J25/00
  • H01J23/02—Electrodes; Magnetic control means; Screens
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J25/00—Transit-time tubes, e.g. klystrons, travelling-wave tubes, magnetrons
  • H01J25/74—Tubes specially designed to act as transit-time diode oscillators, e.g. monotrons

Definitions

• the present invention relates to an oscillating virtual cathode microwave generator device.
• FIGS. 1 to 3 An oscillating virtual cathode microwave wave generator device of the prior art, commonly called a vircator (vircator for "VIRtual Oscillator Method"), is represented in FIGS. 1 to 3.
• the vircator comprises a diode consisting of a cathode 2 and an anode 3, 4 and a cylindrical waveguide 5.
• the anode consists of a thick reinforcement 3 and a thin sheet or thin anode 4. This type of device is known to produce high power microwave pulses.
• a potential difference whose amplitude increases with time is applied across the two electrodes of the diode.
• an electron beam 1 of increasing intensity is emitted by the cathode 2.
• the electron beam 1 flows laminarly along the axis ZZ of the waveguide 5 (cf. . figure 1) .
• the voltage applied to the diode reaches a threshold value, the beam begins to pinch under the effect of its magnetic field (see Figure 2). This nip results from the cancellation, at the level of the anode 4, of the transverse components of the electric field with respect to the ZZ axis.
• the virtual cathode 6 oscillates around an average position which is at a distance from the thin anode 4 equal to the distance separating the thin anode 4 from the cathode 2.
• the electrons E which are returned by the virtual cathode 6 towards the anode 4 return to the diode, are modulated by the latter at the frequency of the microwave and slightly modulate in turn the accelerated electron beam 1 in the cathode-anode space.
• These backscattered electrons are braked between the anode 4 and the cathode 2 and are diverted towards the armature of the anode 3.
• the electrons which cross the virtual cathode take up on average energy at the wave which propagates in the guide 5, thus decreasing its intensity.
• GHz is estimated from the distance d (expressed in cm) between the cathode 2 of the thin anode 4 and the relativistic factor ⁇ of the electron beam 1 by the following formula:
• ⁇ c / f
• the device described above is simple in design and its operation is robust. On the other hand, its power efficiency (ratio of the maximum power of the wave emitted to the maximum electrical power injected into the diode) is very low, of the order of 1%. Moreover, the frequencies of the emitted wave directly follow the temporal variations of the applied voltage, which leads to obtaining an electromagnetic wave of poor spectral quality.
• the invention does not have these disadvantages.
• the invention relates to a microwave wave generating device comprising a diode consisting of an anode and a cathode and capable of creating a virtual cathode by accumulation of electrons in a waveguide.
• circular wave capable of propagating a microwave wave emitted by oscillation of the virtual cathode, characterized in that it comprises a first reflector transparent to the electrons and reflecting the microwave wave and located in the waveguide so that the virtual cathode is positioned between the anode and the first reflector.
• the first reflector is positioned within the waveguide at a distance from the anode equal to substantially twice the distance between the anode and the cathode.
• the first reflector completely closes a straight section of the guide.
• the first reflector closes a cross section of the guide on a central portion of said cross section so that a substantially annular opening is present between the reflector and the wall of the guide.
• the central portion of the first reflector which closes the cross section of the guide has a radius greater than or equal to substantially 0.75 times the radius of the circular guide.
• the first reflector is made of aluminized mylar.
• the central portion of the open reflector closes the cross section of the guide on a radius greater than or equal to substantially 0.75 times the radius of the circular guide.
• each additional reflector is made of aluminized mylar.
• the virtual cathode microwave generator device makes it possible to obtain very significantly improved performances compared with the performances of the devices of the known art.
• the emitted microwave is of better spectral quality and the conversion efficiency is very substantially improved.
• FIG. 4 represents a longitudinal view of an example of a virtual cathode microwave generator device according to the invention.
• FIG. 5 represents a first sectional view of the virtual cathode microwave generator device of FIG. 4;
• FIG. 6 represents a second sectional view of the virtual cathode microwave generator device of FIG. 4.
• FIGS. 1 to 3 have been previously described. It is therefore useless to return to it.
• FIG. 4 represents a longitudinal view of an example of a virtual cathode microwave generator device according to the invention.
• the device comprises two reflector elements 8 and 9 located in the waveguide 5.
• the reflectors 8 and 9 are transparent to the electrons and able to reflect the electromagnetic waves generated in the waveguide. They are made, for example, aluminized mylar.
• the first reflector 8, which is closest to the thin anode 4 closes a straight section of the waveguide 5 (FIG. 5) over its entire surface, whereas the second reflector 9 closes only a centered fraction of cross-section of the waveguide (see FIG.
• the expression “closed reflector” will be used for a reflector which closes over its entire surface a cross section of the waveguide and the expression “open reflector” for any reflector which closes only one centered fraction of cross section of the guide, leaving a substantially annular opening between its periphery and the inner wall of the guide.
• the first reflector 8 is positioned so that the virtual cathode 6 is substantially in the center of the cylindrical cavity formed by the thin anode 4, the waveguide 5 and the first reflector 8.
• the distance D1 which separates the first reflector 8 of the thin anode 4 is then substantially equal to twice the distance d between the thin anode 4 of the cathode 2.
• the distance D2 between the second reflector 9 of the first reflector 8 is substantially equal to the distance dl.
• the first reflector 8 has the function of reflecting the wave created by the virtual cathode 6. The reflected wave then comes into interaction again with the electrons and the virtual cathode 6, increasing the microwave wave.
• the cylindrical cavity formed by the first closed reflector 8, the thin anode 4 and the waveguide 5 thus makes it possible to reinforce the power of the wave created by the virtual cathode 6.
• the electromagnetic wave emitted by this second virtual cathode can then propagate in the waveguide 5, via the substantially annular opening 10.
• the device of the invention according to the example given in Figures 4 to 6 comprises a first reflector 8 closed and a second reflector 9 open. More generally, the device of the invention comprises at least one closed or open reflector.
• the device of the invention allows a very significant improvement in performance.
• a device with a single closed reflector leads to a yield improvement of the order of 4%.
• a device with two reflectors such as that shown in Figures 4 to 6 leads to an efficiency improvement of the order of 6%, the addition of reflectors can further increase the yield.
• the reflectors can be closed or open.
• the reflector farthest from the anode is preferably open, to allow more easily the wave to propagate in the guide.
• the distance between the reflectors and that between the thin anode and the first reflector is substantially equal to twice the distance d between anode and cathode.
• the inner radius of an open reflector is preferably greater than 0.75 R to reflect the maximum of the radial component of the electric field of the wave (see equation (3)).
• the device of the invention can advantageously be used in many configurations among which can be mentioned: several phase vircators coupled together; a master / slave structure (s) in which one or more phase relativistic magnetrons or klystrons coupled together (the slaves) are triggered by an external vircator (the master); a vircator powered by an external radiation source in the region of the diode that promotes the bundling of the electron beam.

Landscapes

• Microwave Tubes (AREA)
• Particle Accelerators (AREA)
• Lasers (AREA)
• Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)
• Oscillators With Electromechanical Resonators (AREA)
• Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)
• Burglar Alarm Systems (AREA)
• Inductance-Capacitance Distribution Constants And Capacitance-Resistance Oscillators (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (2)

Family

ID=34951832

Family Applications (1)

Country Status (5)

Cited By (15)

Families Citing this family (2)

Family Cites Families (2)

• 2004
  • 2004-10-05 FR FR0452264A patent/FR2876218B1/fr not_active Expired - Fee Related
• 2005
  • 2005-10-03 AT AT05810745T patent/ATE441936T1/de not_active IP Right Cessation
  • 2005-10-03 DE DE602005016452T patent/DE602005016452D1/de not_active Expired - Lifetime
  • 2005-10-03 WO PCT/FR2005/050802 patent/WO2006037918A2/fr not_active Ceased
  • 2005-10-03 EP EP05810745A patent/EP1815492B1/de not_active Expired - Lifetime

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