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
  • 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 has for object a device generating microwave waves using the phe omene of virtual cathode. " I
• vircators which take advantage of the space charge effects existing in electron beams produced by the barrel of an electron tube. Indeed, as is known, it is these effects which fix, for given voltages, a maximum '-value to the current which can be produced by an electron gun, or which can be transported in a given space for a set of electrodes of given geometry '.
• a current of electrons is injected into a defined space, most often several times the maximum current that could actually cross this space, n
• n is then accumulation of electrons which form a potential well, called a virtual cathode, and which causes the reflection of a more or less large fraction of the electrons in the beam.
• This virtual cathode is unstable, that is to say that the amplitude of its potential trough and its position oscillate, causing a periodic variation in the number of electrons reflected or transmitted.
• Such a device makes it possible to create electromagnetic fields with high microwave powers and under a reduced volume.
• the signal transmitted is of poor quality, that is to say that the power is transmitted on "" many * mbaldes in a series of simultaneous or successive frequencies; the applications of this type of signal are thus quite reduced.
• the conversion efficiency is poor (of the order of 2 to 3% at best) compared to the efficiency which it is possible to obtain with other generators, such as conventional speed modulation electronic tubes. .
• the present invention relates to a microwave generator which uses the phenomenon of an oscillating virtual cathode but which makes it possible to obtain microwave energy of better spectral quality and with a better conversion efficiency than conventional vircators.
• the subject of the invention is a
• - microwave generator device comprising:
• an electronic gun capable of producing an electron beam in an injection region, the transported current being sufficient to cause the formation of a virtual cathode
• 25 d electrons are reflected by the virtual cathode, or even that it uses both the energy of the electrons transmitted and reflected that of the electrons, but suitably phase-shifted.
• FIG. 3 another embodiment of the device according to the invention, in which the output hyper ⁇ frequency circuit uses on the one hand the electrons transmitted by the virtual cathode and, on the other hand, the electrons reflected by this virtual cathode but suitably out of phase;
• FIG. 1 therefore represents a first embodiment of the device according to the invention, seen in longitudinal schematic section.
• the generator according to the invention is a structure of revolution around a longitudinal axis ZZ.
• the cathode 11 is in the form of a conductive cylinder of axis ZZ the circumference of which protrudes 10 so that the electrons emitted by this cathode form an annular beam, represented by a dotted feone 8 in the figure.
• the frame 20 of the anode is constituted by a
• the generator according to the invention also comprises an output microwave circuit 4 which is, in this embodiment, of the coaxial type; it is formed by an inner conductive cylinder 5 and an outer conductor formed by the extension of the armature 20, between which an annular space 44 is defined.
• the output circuit is substantially symmetrical of the electron gun 1 with respect to a normal plane in the plane of the figure, that is to say that the external conductor has an annular shoulder 43 and a screen 41 bearing for example by legs on the shoulder 43 and defining with this shoulder a circular slot 42 for passage electrons from the beam 8. The latter is received by an annular projection 50 of the inner conductor 5. More generally, the drawings of the output circuit 4 and of the barrel 1 are such that the two impedances are close.
• This zone is laterally limited by the wall 20.
• the application to the cathode 11 of a negative voltage with respect to that of the anode causes the emission of the annular electron beam 8.
• the armature 20, the screen 21 and the elements of the output circuit 4 are at ground potential and a voltage is applied to the cathode 11
• a virtual cathode 80 is formed in the injection region 3.
• the electrons transmitted by the virtual cathode 80 are represented by an arrow 82 and the electrons reflected by this cathode by arrows 81 Virtual.
• a longitudinal magnetic field (along the ZZ axis) is preferably applied to the structure, using means not shown, to focus the beam 8 thus produced.
• the mechanism for forming a virtual cathode is recalled below. Inside an electron beam there is a charge of space: on the axis of the beam, the potential and the speed of the electrons are lower than at the periphery of this beam. If the electron density * and, "per surf, the transported current increase, the potential and the speed of the electrons decrease until reaching zero: the electrons then form a negatively charged cluster, forming a well of •
• injection current it is commonly measured in Gégajjertz.
• the maximum current intensity beyond which the electrons form a virtual cathode is a function of the potential of the electron beam *, as well as of the dimensions of the beam and of the injection region 3; the maximum current for a given electron beam is' _ç ⁇ ⁇ low when the injection zone is of larger diameter.
• the dimensions of the device are chosen (electron gun and injection zone) and the cost of the electron beam so that it is greater than the maximum current likely to flow through region 3, thus causing formation. of a virtual cathode.
• the electrons transmitted represent a current modulated at the frequency of oscillation of the virtual cathode.
• the energy is transmitted paro ⁇ the coaxial output circuit 4 to the outside.
• the dimensions of the barrel and of the injection region are preferably chosen so that the beam current is greater than, but close to the maximum current, so that the transmitted current is on average a fraction. significant of the total current injected into the injection region.
• FIG. 2 shows another embodiment of the device according to the invention, which includes means for post-acceleration of the electrons used, also seen in longitudinal schematic section.
• the generator represented in FIG. 2 takes up the structure of that of FIG. 1, except that the output circuit 4 is electrically isolated from the electron gun 1. More precisely, the armature 20 forming the anode of the electron gun is without electrical contact with the external conductor, now marked 40, of the output circuit 4.
• the conductor 40 extends around the armature 20 in the form of a hollow cylinder with the same axis ZZ as this frame.
• This embodiment further comprises means 7 for applying between the cathode 11 and the output circuit 4 a voltage V., greater than the cathode / anode voltage V effet.
• the means 7 are constituted by a transformer whose primary 71 receives the supply voltage and the secondary 72 is connected:
• FIG. 3 represents another embodiment of the generator according to the invention, in which both the transmitted electrons and the electrons reflected by the virtual cathode are used.
• the electron gun 1 formed by the cathode 11 and the anode 20, 21.
• the gun 1 produces, here too, an electron beam 8 under conditions such that there is formation of a virtual cathode 80 with reflection (arrows 81) of a part of the electrons and transmission (arrow 82) of another part of the electrons towards, for example, a metal wall 50 delimiting the injection region 3.
• the output microwave circuit 4 has two channels: one leads into a region marked 4A, between the anode 20 and the virtual cathode 80 and intended to recover the energy of the reflected electrons 81; the other leads into a region marked 4B, between the virtual cathode 80 and the wall 50 and it is intended to recover the energy of transmitted electrons 82.
• phase shifter 45 which can be produced by any known means and connected on one of the channels, 4A or 4B, before the energies existing in the two channels combine to form the output energy.
• the wall 46 between the channels 4A and 4B, must be of sufficient thickness to prevent the fields present in the two channels from coupling before the virtual cathode 80, this thickness being of the order of magnitude of the distance from wall 46 to the virtual cathode.
• FIG. 3 shows a particular embodiment of the circuit 4.
• Other variants are of course possible, which consist, for example, of producing, for each of the channels 4A and 4B, a structure of coaxial type as described Figure 1 for circuit 4.
• FIG. 4 represents another embodiment of the device according to the invention, in which the beam produced by the electron gun is a solid cylinder, always seen in schematic longitudinal section.
• the diameter of the cat-Hjfide 12 must be substantially less than the wavelength of the microwave energy obtained at the output, for example of
• FIG. 5 shows another embodiment of the generator according to the invention, in which the beam
• the electronics used are a full cylindrical beam and where the generator further comprises post-acceleration means ".
• Figure 6 shows an embodiment similar to that of Figure 3, but in which the

Landscapes

• Microwave Tubes (AREA)
• Particle Accelerators (AREA)
• Electron Sources, Ion Sources (AREA)

Applications Claiming Priority (3)

Publications (2)

Family

ID=9378877

Family Applications (1)

Country Status (7)

Families Citing this family (4)

Family Cites Families (5)

• 1989
  • 1989-02-17 FR FR8902081A patent/FR2643506B1/fr not_active Expired - Fee Related
• 1990
  • 1990-02-16 US US07/582,913 patent/US5113154A/en not_active Expired - Fee Related
  • 1990-02-16 CA CA002027558A patent/CA2027558C/fr not_active Expired - Fee Related
  • 1990-02-16 JP JP2504231A patent/JP2863310B2/ja not_active Expired - Lifetime
  • 1990-02-16 WO PCT/FR1990/000112 patent/WO1990009674A1/fr active IP Right Grant
  • 1990-02-16 EP EP90903856A patent/EP0413018B1/de not_active Expired - Lifetime
  • 1990-02-16 DE DE69016712T patent/DE69016712T2/de not_active Expired - Fee Related

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events