EP0224234B1 - Offener, quasi-optischer Resonator für elektromagnetische Millimeter- und Submilllimeterwellen - Google Patents

Offener, quasi-optischer Resonator für elektromagnetische Millimeter- und Submilllimeterwellen Download PDF

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Publication number
EP0224234B1
EP0224234B1 EP19860116277 EP86116277A EP0224234B1 EP 0224234 B1 EP0224234 B1 EP 0224234B1 EP 19860116277 EP19860116277 EP 19860116277 EP 86116277 A EP86116277 A EP 86116277A EP 0224234 B1 EP0224234 B1 EP 0224234B1
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EP
European Patent Office
Prior art keywords
quasi
open
optical resonator
radius
instance
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
EP19860116277
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German (de)
English (en)
French (fr)
Other versions
EP0224234A2 (de
EP0224234A3 (en
Inventor
Bernhard Isaak
André Perrenoud
Minh Quang Dr. Tran
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Schweizerische Eidgenossenschaft Vertreten Durch Den Generalsekretar Des Schweizerischen Schulrates
Original Assignee
Schweizerische Eidgenossenschaft Vertreten Durch Den Generalsekretar Des Schweizerischen Schulrates
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Publication of EP0224234A3 publication Critical patent/EP0224234A3/de
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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
    • H01J25/025—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 with an electron stream following a helical path
    • 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
    • H01J23/16—Circuit elements, having distributed capacitance and inductance, structurally associated with the tube and interacting with the discharge
    • H01J23/18—Resonators
    • H01J23/20—Cavity resonators; Adjustment or tuning thereof

Definitions

  • the invention relates to an open, quasi-optical resonator for electromagnetic millimeter and submillimeter waves according to the preamble of claim 1.
  • Such a resonator is preferably used in a microwave source, which is known under the term quasi-optical gyrotron and is described, for example, in an article by T.A. Hargreaves et al., Int. J. Electronics 57, 977 (1984), or also in an article by A. Perrenoud et al., Int. J. Electronics 57, 985 (1984).
  • a high-energy electron beam generated by an electron gun passes through the above-mentioned resonator in the middle between the two concave mirrors. Due to a strong magnetic field oriented parallel to the electron beam axis, the electrons move in a spiral Orbits with an orbital frequency corresponding to the cyclotron frequency. This is directly proportional to the strength of the magnetic field. With a suitable choice of the magnetic field strength, the spiraling electrons in the resonator excite the desired electromagnetic waves in the millimeter or submillimeter range. These are decoupled from the resonator and fed to the output of the gyrotron. An important area of application will be nuclear fusion, where the energy of the waves is used to heat the fusion plasma.
  • TEM mnp modes arise in the resonator.
  • the indices m and n denote transverse modes, while p stands for longitudinal modes (see also H. Kogelnik, 1966, Modes in Optical Resonators; Lasers, Vol. 1, edited by AK Levine, New York: Marcel Dekker, p. 295).
  • TEM oop modes are selected in a gyrotron because they have the lowest diffraction losses. For the sake of simplicity, only such modes will be considered below. Nevertheless, all of the following statements also apply to the more general TEM mnp modes.
  • Modes are standing waves in the resonator.
  • the surfaces of the concave mirrors are surfaces of the same phase.
  • the tangential component of the electric field vector disappears on them.
  • the surfaces of the concave mirrors are therefore node surfaces for the modes.
  • the concave mirrors have a plurality of mirror surfaces offset in a step-like manner.
  • Such modes are preferably formed in such a resonator structure, for which the step-like offset of the individual mirror surfaces relative to one another approximately corresponds to a whole multiple of their half wavelength and for which all mirror surfaces are therefore node surfaces.
  • the individual mirror surfaces are offset by one or more whole multiples of half the wavelength ⁇ p / 2 of the desired TEM oop mode, this condition applies precisely to the desired mode.
  • it does not apply to the TEM ooq modes adjacent to the desired mode.
  • These suffer higher diffraction losses in the resonator according to the invention than in a resonator without a step structure.
  • the desired mode TEM oop is preferably excited in the resonator according to the invention.
  • the excitation of the desired mode TEM oop in the resonator according to the invention is considerably more efficient than in a resonator without a step structure.
  • the total step-like offset of the individual mirror surfaces should be between 6 and 10 half wavelengths ⁇ p / 2 of the desired TEM oop mode.
  • the areas of the individual mirror areas are advantageously dimensioned relative to one another such that they have approximately the same energy flow. Slots can be provided for coupling out the electromagnetic waves.
  • the open, quasi-optical resonator shown in FIG. 1 consists of two identical, opposed, round concave mirrors 1 and 2. These each have two mirror surfaces 1.1 and 1.2 or 2.1 and 2.2, which are staggered with respect to one another.
  • the mirror surfaces 1.1, 1.2, 2.1 and 2.2 are spherically curved with approximately the same radii of curvature R and are adapted to the node surfaces of the standing waves that form in the resonator.
  • the mirror surfaces 1.1 and 1.2 on the one hand and the mirror surfaces 2.1 and 2.2 on the other hand are arranged concentrically to one another.
  • the inner mirror surfaces 1.1 and 2.1 are designed as continuous, central mirror surfaces. They are surrounded by the outer mirror surfaces 1.2 and 2.2 in a ring.
  • the inner mirror surfaces 1.1 and 2.1 limiting radius r 1.1 and r 2.1 corresponds to the inner radius of the outer mirror surfaces 1.2 and 2.2.
  • Annular slots 1.3 and 2.3 are provided in the outer mirror surfaces 1.2 and 2.2. These are used to decouple the electromagnetic waves from the resonator.
  • the slots 1.3 and 2.3 need not be closed. They can be interrupted by webs, as is evident from the view of one of the concave mirrors 1 or 2 shown in FIG. 2. A mechanical connection between the mirror region lying inside and outside the slots advantageously results via the webs.
  • the reference symbols in FIG. 2 correspond to the corresponding reference symbols in FIG. 1.
  • the step-like offset h of the mirror surfaces 1.1 and 1.2 on the one hand and the mirror surfaces 2.1 and 2.2 on the other hand, as already explained, amount to at least approximately one or more whole multiples of half the wavelength ⁇ p / 2 of the desired mode. It is preferably between 6 ⁇ p / 2 and 10 ⁇ p / 2.
  • the radius a of the concave mirrors 1 and 2 and their mutual distance d should give a Fresnel number N (defined as a2 / ( ⁇ p d)) between 0.5 and 10. Furthermore, the mutual distance d between the concave mirrors 1 and 2 should be greater than 50 ⁇ p . It is taken with respect to the base areas of the outer mirror surfaces 1.2 and 2.2.
  • the surfaces of the mirror surfaces 1.1 and 1.2 or 2.1 and 2.2 are dimensioned relative to one another in such a way that they each have approximately the same energy flow.
  • the energy distribution on the mirrors is given by a Gaussian distribution, so that the energy flow in the center of the concave mirror 1, 2 is greater than at the edge. Therefore, the outer mirror surfaces 1.2 and 2.2 are larger in area than the central mirror surfaces 1.1 and 2.1.
  • the resonator geometry can be selected for each desired resonance frequency in such a way that an optimum is achieved with regard to diffraction losses and the coupling of the energy through the slots.
  • the resonance frequency of 120 GHz with the corresponding wavelength of 2.5 mm.
  • this corresponds to a TEM oop with p 287.
  • the mutual offset h of the mirror surfaces 1.1 and 1.2 or 2.1 and 2.2 is approximately 8 ⁇ p / 2 and the mutual distance d of the concave mirrors 1 and 2 from each other is 144 ⁇ p .
  • the numbers for all radii are the polar angles ⁇ 1, ⁇ 2.1 , ⁇ 2.2 and ⁇ 3, below which the edges of the spherically curved mirror surfaces 1.1 and 2.1 or 2.1 and 2.2 and the edges of the slots 1.3 and 2.3 of their order h mutually offset centers of curvature appear.
  • the concave mirror 1 these polar angles and the centers of curvature are shown in FIG. 1.
  • the latter are designated M 1.1 and M 1.2 .
  • FIG. 3 shows in 6 diagrams a) to f) the results of a numerical simulation of the competition of modes 285 to 298 in their chronological order within a period of approximately 20 usec.
  • the modes TEM oo285 to TEM oo289 are plotted along the discrete abscissa in the individual diagrams. The ordinate corresponds to the efficiency E in% of the energy transfer from the electron beam to the individual modes.
  • Diagrams a) to f) show the situation in the resonator at successive times. After an initial competition of all modes (mainly in diagrams a) to c)), the desired mode TEM oo287 finally prevails and remains practically the only one with an electronic efficiency of 34%.
  • a simulation carried out for comparison purposes for a resonator without a step structure showed the dominance of two modes under otherwise identical conditions, namely the modes TEM oo285 and TEM oo286 and this only with an electronic efficiency of 25%.
  • Desired modes can thus be generated practically pure and with high efficiency by the invention.
  • the concave mirrors need not only have two mirror surfaces offset from one another. You can also be provided with three or even more staggered mirror surfaces.
  • the outer or the outer mirror surfaces need not be set back from the central mirror surface or from one another, as in the example in FIG. 1. Reverse dislocation is also possible since it is essentially physically equivalent.
  • slits in the concave mirrors for decoupling the electromagnetic waves are not the only possibility, but the electromagnetic power, since the resonator is open, could be collected in a suitable manner by diffraction at the mirror edges.
  • a concave mirror is shown in section with three mutually offset mirror surfaces without slots.
  • the mirror surfaces are offset from one another in the opposite manner to that of the concave mirrors 1 and 2 according to FIG. 1.

Landscapes

  • Lasers (AREA)
  • Microwave Tubes (AREA)
  • Control Of Motors That Do Not Use Commutators (AREA)
  • Plasma Technology (AREA)
EP19860116277 1985-11-29 1986-11-24 Offener, quasi-optischer Resonator für elektromagnetische Millimeter- und Submilllimeterwellen Expired - Lifetime EP0224234B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH5096/85 1985-11-29
CH509685A CH668865A5 (de) 1985-11-29 1985-11-29 Offener, quasi-optischer resonator fuer elektromagnetische millimeter- und submillimeterwellen.

Publications (3)

Publication Number Publication Date
EP0224234A2 EP0224234A2 (de) 1987-06-03
EP0224234A3 EP0224234A3 (en) 1989-04-05
EP0224234B1 true EP0224234B1 (de) 1992-06-03

Family

ID=4287864

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19860116277 Expired - Lifetime EP0224234B1 (de) 1985-11-29 1986-11-24 Offener, quasi-optischer Resonator für elektromagnetische Millimeter- und Submilllimeterwellen

Country Status (6)

Country Link
EP (1) EP0224234B1 (enrdf_load_stackoverflow)
JP (1) JPS62222546A (enrdf_load_stackoverflow)
CH (1) CH668865A5 (enrdf_load_stackoverflow)
DE (1) DE3685556D1 (enrdf_load_stackoverflow)
ES (1) ES2033232T3 (enrdf_load_stackoverflow)
GR (1) GR3005597T3 (enrdf_load_stackoverflow)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2639153B1 (fr) * 1988-11-15 1991-06-14 Thomson Tubes Electroniques Charge hyperfrequence en guide d'onde surdimensionne de faible longueur
EP0410217A1 (de) * 1989-07-28 1991-01-30 Asea Brown Boveri Ag Quasi-optisches Gyrotron
FR2688937B1 (fr) * 1992-03-17 1994-05-06 Thomson Tubes Electroniques Tube hyperfrequence a cavite a miroirs a rendement ameliore.
FR2690784B1 (fr) * 1992-04-30 1994-06-10 Thomson Tubes Electroniques Tube hyperfrequence a cavite quasi-optique muni d'un dispositif suppresseur d'oscillation parasite.

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE484122A (enrdf_load_stackoverflow) * 1947-07-29
US3559043A (en) * 1967-07-03 1971-01-26 Varian Associates Bimodal cavity resonator and microwave spectrometers using same

Also Published As

Publication number Publication date
DE3685556D1 (de) 1992-07-09
GR3005597T3 (enrdf_load_stackoverflow) 1993-06-07
JPS62222546A (ja) 1987-09-30
EP0224234A2 (de) 1987-06-03
ES2033232T3 (es) 1993-03-16
CH668865A5 (de) 1989-01-31
EP0224234A3 (en) 1989-04-05

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