EP1364425B1 - Fenetre hyperfrequence en ceramique - Google Patents
Fenetre hyperfrequence en ceramique Download PDFInfo
- Publication number
- EP1364425B1 EP1364425B1 EP02704882A EP02704882A EP1364425B1 EP 1364425 B1 EP1364425 B1 EP 1364425B1 EP 02704882 A EP02704882 A EP 02704882A EP 02704882 A EP02704882 A EP 02704882A EP 1364425 B1 EP1364425 B1 EP 1364425B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- skirt
- ring
- disc
- prestressing
- microwave window
- 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
Links
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P1/00—Auxiliary devices
- H01P1/08—Dielectric windows
Definitions
- the invention relates to microwave-tight windows vacuum, used in principle at the output of an electronic power tube to transmit microwave electromagnetic energy between the inside of the tube (under high vacuum) and the outside (in ambient atmospheric for example).
- the tube can in particular be an amplifier such as a tube with progressive waves (TOP in French, TWT in English for "traveling wave tube "), or a klystron for example. It can also be an oscillator (magnetron, etc ). Typically, we want to send the amplified energy to inside the tube to a waveguide that contains air.
- the window microwave ensures free passage, at least in a band of given frequencies, from electromagnetic energy to the waveguide all maintaining the vacuum seal inside the tube.
- the windows include a flat disc in insulating dielectric, through which electromagnetic energy passes.
- This disc is made of alumina or another ceramic having no only very good dielectric properties but also good thermal conductivity and good resistance to high temperatures and with strong temperature gradients. Indeed, for strong tubes power and operating with high electric fields, the passage energy generates losses in the dielectric, thus a heating important.
- the tubes concerned here can provide powers of several tens of kilowatts.
- the dielectric disc can typically have dimensions of ten centimeters in diameter for a thickness from 1 millimeter to a few millimeters.
- the dielectric disc is brazed on all its periphery against the interior surface of a metallic cylindrical skirt (usually copper) that surrounds it.
- the skirt cylindrical 10 is itself surrounded by a holding block 20, by example in stainless steel, which serves as a support for fixing the dielectric disc 30 and its skirt 10 between the power tube and a waveguide.
- the dielectric disc 30 is brazed inside the skirt.
- the holding block 20 can be used for radiator and transition times between the tube and the waveguide. It comprises a lower part 22 constituting the start of the waveguide, with a flange device 24 used to fix the waveguide to block 20.
- the part upper 26 of block 20 is cylindrical and it surrounds cylindrical skirt 10. It is intended to be welded or brazed around an outlet opening of the power tube (not shown). The bottom and top of the skirt are brazed inside the holding block 20.
- solder between the dielectric disc and the skirt, as well as the solder between the skirt and the holding block participate in the maintenance of vacuum tightness.
- the thermal constraints in operation can be very important considering the high power dissipation that occurs in the dielectric disc. Power dissipation is usually maximum towards the center and lower at the edges.
- the qualities of thermal conduction of the ceramic allow to dissipate the heat radially towards the edges; the copper skirt and the block stainless steel support serve as a radiator.
- thermal stresses are very important because of the temperature difference between different areas of the ceramic. They are compounded by the fact that the distribution of power dissipation in the window is not necessarily completely radial. Constraints can cause ruptures of ceramic, or copper, or various solders which ensure vacuum tightness. Faults that may result of these thermal constraints are unacceptable for the tube as soon as they result in loss of vacuum tightness. This is why we are limited in the power level likely to pass through the window during the use of the tube.
- An object of the invention is to produce a microwave window having higher power handling capacities than in art while retaining the advantages of existing windows.
- the prestressing ring is constituted by a annular portion of a holding block used to fix the window on the outlet of a microwave tube, this annular portion pressing locally on an outer surface of the skirt all around the periphery of the disc dielectric.
- the holding block is made of a much more rigid material than the metallic skirt.
- the holding block can be made of stainless steel, the skirt being made of copper and the alumina disc.
- the thickness of the compression preload ring can be about 2 or 3 millimeters. For example, if the holding block is in metal about 1 millimeter thick, the prestressing ring can be made up of an extra thickness (in total about 3 millimeters) of metal.
- the temperature rise of the dielectric disc does not change compared to the prior art, but the breaking strength is considerably improved.
- the prestressing is preferably of the order of several tens bars, or more. It is exercised at rest, when the tube is cold; in operation, the window becomes hotter the more the power transmitted through the window is high.
- the preload ring expands and relieves internal thermal stresses that appear in the window due to the strong temperature gradients in the window; but, because the cold ring exerts a radial compression stress, its expansion at hot does not exert an unacceptable constraint on the solder between the ring and the window.
- the invention also relates to a method for producing a window. microwave.
- the method involves placing a dielectric disc at the inside of a metallic skirt, with a brazing material, and with a small clearance between the periphery of the disc and the skirt, to place the entire disc and skirt inside a holding block comprising a ring prestress around the skirt around the entire periphery of the disc, a slight clearance being provided between the ring and the skirt, to place a brazing hoop around this ring with a slight clearance between the hoop and the ring, the hoop material having a lower coefficient of expansion than that of the ring, to bring the hoop, ring, skirt and disc assembly to a temperature sufficient to ensure the brazing of the disc in the skirt, and to leave cool, the cooling ensuring a compression preload radial of the ring on the skirt and on the disc.
- the brazing band is then removed.
- the top and the bottom of the skirt are brazed to the holding block.
- a solder bead is therefore placed in the appropriate places before passing the assembly through the brazing furnace.
- a lubricating substance preferably graphite, preventing sintering between the ring and the skirt in case of elevation of ring temperature, for example during steaming cycles of the tube microwave with window.
- These baking cycles are intended for degassing the different parts of the tube while making a high vacuum inside the tube. Sintering between the ring and the skirt, due to the pressure, friction and temperature, would lead to a stiffening of the ring / skirt connection and the risk of subsequent leakage.
- the invention will be described with reference to FIG. 2, in a example corresponding to an improvement of the window of FIG. 1, that is to say in a case where a metal skirt is interposed between a block holding and the dielectric disc, without this example being limiting.
- the holding block is made of more rigid metal than the skirt metallic and ensures the rigidity of the entire window.
- the prestressing ring according to the invention is in this case part integral with the retaining block 20 which surrounds the skirt 10.
- This ring is designated by the reference 40. It is constituted for simplicity by local reinforcement of the thickness of the retaining block. She could also be independent of the block.
- the holding block has a central part cylindrical generally surrounding the metal skirt 10, and the ring is constituted by a localized zone of this cylindrical part, this zone having a greater thickness and being located around the periphery of the dielectric disc 30.
- the ring prestress 40 can have a radial thickness of around 3 millimeters over a height of a few millimeters.
- the holding block is made of stainless steel with a thickness generally around 1 millimeter around the skirt 10, and it locally includes an extra thickness (2 millimeters thicker all around the disc 30)
- the inside diameter of the holding block, in its central part cylindrical, is greater than the outside diameter of the metal skirt, except at the location of the preload ring 40; at this point, the inside diameter of the ring is equal to that of the metallic skirt, the ring exerting permanently a compressive stress on the skirt 10 and, through the skirt, on the periphery of the dielectric disc 30.
- the internal diameter of the cylindrical central part of the holding block 20 is about 1 millimeter greater than the outside diameter skirt 10.
- the metal skirt is preferably welded or brazed to the block of maintained by its upper part on the one hand, by its lower part on the other part, the dielectric disc being located in a central part of the skirt 10.
- the upper part 26 of the holding block is shaped so that it can be welded tightly to the power tube, around an electromagnetic energy outlet opening.
- the tube and its outlet opening is not shown.
- the part bottom of block 20 is shaped so that it can be fixed (but in a manner not necessarily sealed) to an element of use of the output power of the tube, for example a waveguide not shown.
- a lower fixing flange 24 can be provided for this purpose.
- the part lower 22 of the holding block 20 can be machined internally to constitute a waveguide of dimensions corresponding to the waveguide on which it should be fixed.
- the preload ring 40 exerts strong compression on the periphery of the skirt and the dielectric disc and preferably interposed between the ring and the skirt a thin layer of a lubricating substance, preferably a thin layer of graphite, to avoid any joining by sintering in case of temperature rise.
- a lubricating substance preferably a thin layer of graphite
- the brazing band is a circular ring 50 whose cold internal diameter is equal to a small clearance, to the cold outside diameter of the holding block at the location of the prestressing ring 40.
- the hoop 50 is made of a rigid material of lower expansion coefficient than that of the holding block (and the skirt).
- the dielectric disc also has a higher coefficient of expansion weaker than that of the holding block and the skirt.
- the skirt is made of copper
- the holding block is made of stainless steel
- the hoop is made of molybdenum, or tungsten, or even of alumina.
- the coefficient of expansion of molybdenum is about 3 times lower than that stainless steel and copper.
- the coefficient of expansion of alumina is also much lower than that of the holding block (about 3 times).
- the dielectric disc is placed in the skirt with a peripheral brazing bead 60.
- a clearance exists between the disc and the skirt.
- the molten solder will penetrate by wetting into the gap between the disc and the skirt at the periphery of the disc.
- the cold play is such that by the afterwards, when hot, during the soldering operation, the clearance becomes very weak (from on the order of 0.1 millimeters, however allowing the solder material to penetrate the gap between disc and skirt.
- the skirt is placed in the block holding with little cold play between the block and the skirt at the place of the preload ring 40.
- the interior of the ring 40 has been previously coated with a lubricating substance mentioned above (graphite in principle).
- Solder cords 62 and 64 are placed at the top and bottom of skirt 10.
- the molybdenum hoop 50 is slid cold around the holding block containing the metal skirt.
- the fret could also be heated before being placed around the cold holding block. She is placed at the level of the prestressing ring 40.
- the clearance between the hoop and the holding block is weak during the introduction (normally cold) of the hoop around the block. This play becomes zero during the soldering operation.
- the whole is heated to the temperature necessary for the soldering operation.
- the solder cords melt.
- the disc, the skirt, the retaining block, and the hoop expand.
- hoop 50 expands much less than the holding block (and the skirt). It therefore prevents partially the expansion of the preload ring 40.
- the preload ring 40 contracts, the block support 20 contracts, as does skirt 10 at the disc dielectric (the stainless steel ring is made of a much stiffer material than the skirt).
- the ring 40 exerts compression on the dielectric disc 30 which contracts less. This compression is permanent: it is present at rest, but it remains in operation. It is radial. She depends clearances between parts, materials used, diameters of elements, and the thickness of the preload ring. She can reach 100 bars. It is therefore a strong compression preload. Fret 50 is removed after cooling.
- the structure overall will be much more resistant to breakage when the window will undergo thermal stresses, either in steaming or in operation.
- the exit window according to the invention can be used in particular out of TOP, or klystrons.
Landscapes
- Waveguide Connection Structure (AREA)
- Ceramic Products (AREA)
Description
- la figure 1, déjà décrite, représente une fenêtre de l'art antérieur ;
- la figure 2 représente une fenêtre selon l'invention ;
- la figure 3 représente l'opération de brasage nécessaire à la réalisation de la fenêtre selon l'invention.
Claims (11)
- Fenêtre hyperfréquence comportant un disque diélectrique (30), caractérisée par le fait qu'elle comporte une jupe métallique (10) brasée tout autour de la périphérie du disque et une bague de précontrainte (40) entourant la jupe métallique autour de la périphérie du disque et exerçant au repos, sur toute la périphérie du disque, une contrainte de compression radiale dirigée vers le centre du disque.
- Fenêtre hyperfréquence selon la revendication 1, caractérisée en ce que la bague de précontrainte (40) est constituée par une zone annulaire d'un bloc de maintien (20) servant à fixer la fenêtre sur la sortie d'un tube hyperfréquence, cette zone annulaire appuyant sur une surface extérieure de la jupe métallique (10) tout autour de la périphérie du disque diélectrique.
- Fenêtre hyperfréquence selon la revendication 2, caractérisé en ce que le bloc de maintien est en métal plus rigide que la jupe.
- Fenêtre hyperfréquence selon la revendication 3, caractérisé en ce que la jupe est en cuivre, le bloc de maintien en inox, et le disque diélectrique en alumine.
- Fenêtre hyperfréquence selon l'une des revendications 1 à 4, caractérisée en ce que la jupe métallique est brasée en haut et en bas sur le bloc de maintien.
- Fenêtre hyperfréquence selon l'une des revendications 1 à 5, caractérisée en ce que l'épaisseur de la bague de précontrainte de compression (40) est d'environ 3 millimètres.
- Fenêtre hyperfréquence selon l'une des revendications précédentes, caractérisée en ce qu'une substance de lubrification, de préférence du graphite, est interposée entre la bague de précontrainte (40) et la jupe métallique (10), pour empêcher un frittage entre la bague et la jupe en cas d'élévation de température de la bague.
- Fenêtre hyperfréquence selon la revendication 7, caractérisée en ce que la contrainte de compression est de plusieurs dizaines de bars ou plus.
- Procédé de fabrication d'une fenêtre hyperfréquence consistant à placer un disque diélectrique (30) à l'intérieur d'une jupe métallique (10), avec une matière de brasage (60), et avec un faible jeu entre la périphérie du disque et la jupe, à placer le disque et la jupe à l'intérieur d'un bloc de maintien (20) comportant une bague de précontrainte (40) entourant la jupe sur toute la périphérie du disque, un faible jeu étant ménagé entre la bague et la jupe, à placer une frette de brasage (50) autour de cette bague avec un faible jeu entre la frette et la bague, le matériau de la frette ayant un coefficient de dilatation plus faible que celui de la bague, à porter l'ensemble frette, bague, jupe et disque à une température suffisante pour assurer le brasage du disque dans la jupe, et à laisser refroidir, le refroidissement assurant une précontrainte en compression radiale de la bague sur la jupe et sur le disque.
- Procédé selon la revendication 9, caractérisé en ce que, au cours de la même opération de brasage, on brase les extrémités supérieure et inférieure de la jupe sur le bloc de maintien, des cordons de brasure (62, 64) ayant été mis en place préalablement à l'introduction de l'ensemble dans le four de brasage.
- Procédé selon l'une des revendications 9 et 10, caractérisé en ce qu'avant la mise en place de la bague de précontrainte (40) autour de la jupe, on interpose entre la bague de contrainte et la jupe métallique une substance de lubrification, de préférence du graphite, empêchant un frittage entre la bague et la jupe en cas d'élévation de température de la bague.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR0102512A FR2821487B1 (fr) | 2001-02-23 | 2001-02-23 | Fenetre hyperfrequence en ceramique |
FR0102512 | 2001-02-23 | ||
PCT/FR2002/000666 WO2002069434A1 (fr) | 2001-02-23 | 2002-02-22 | Fenetre hyperfrequence en ceramique |
Publications (2)
Publication Number | Publication Date |
---|---|
EP1364425A1 EP1364425A1 (fr) | 2003-11-26 |
EP1364425B1 true EP1364425B1 (fr) | 2004-08-11 |
Family
ID=8860387
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP02704882A Expired - Lifetime EP1364425B1 (fr) | 2001-02-23 | 2002-02-22 | Fenetre hyperfrequence en ceramique |
Country Status (5)
Country | Link |
---|---|
US (1) | US7049909B2 (fr) |
EP (1) | EP1364425B1 (fr) |
JP (1) | JP2004521543A (fr) |
FR (1) | FR2821487B1 (fr) |
WO (1) | WO2002069434A1 (fr) |
Families Citing this family (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE102005050528B4 (de) * | 2005-10-21 | 2007-07-26 | Deutsches Zentrum für Luft- und Raumfahrt e.V. | Mikrowellenautoklav |
US9455483B2 (en) | 2009-12-01 | 2016-09-27 | Schlumberger Technology Corporation | Pre-stressed gamma densitometer window and method of fabrication |
FR3043497B1 (fr) | 2015-11-06 | 2019-05-10 | Thales | Fenetre hyperfrequence |
CN113193312B (zh) * | 2021-04-25 | 2022-05-03 | 电子科技大学 | 圆波导TE0n模式超宽带输出窗结构 |
Family Cites Families (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3156881A (en) * | 1962-08-22 | 1964-11-10 | Gen Electric | Vacuum tight electromagnetic radiation permeable window seal |
US3436694A (en) * | 1966-07-28 | 1969-04-01 | Microwave Ass | Controlling ghost-mode resonant frequencies in sealed waveguide windows |
US3936779A (en) * | 1974-03-12 | 1976-02-03 | Siemens Aktiengesellschaft | Vacuum-tight window arrangement for a rectangular-hollow conductor |
FR2558306B1 (fr) * | 1984-01-17 | 1988-01-22 | Thomson Csf | Fenetre circulaire pour guide d'onde hyperfrequence |
JPH07131201A (ja) * | 1993-11-02 | 1995-05-19 | Tokyo Seimitsu Sokki Kk | 真空パイプ |
JPH0936602A (ja) * | 1995-07-24 | 1997-02-07 | Swan Seiki Kogyo:Kk | 気密保持弾性筒 |
-
2001
- 2001-02-23 FR FR0102512A patent/FR2821487B1/fr not_active Expired - Fee Related
-
2002
- 2002-02-22 WO PCT/FR2002/000666 patent/WO2002069434A1/fr active IP Right Grant
- 2002-02-22 EP EP02704882A patent/EP1364425B1/fr not_active Expired - Lifetime
- 2002-02-22 JP JP2002568451A patent/JP2004521543A/ja active Pending
- 2002-02-22 US US10/470,001 patent/US7049909B2/en not_active Expired - Lifetime
Also Published As
Publication number | Publication date |
---|---|
EP1364425A1 (fr) | 2003-11-26 |
FR2821487A1 (fr) | 2002-08-30 |
US20040080387A1 (en) | 2004-04-29 |
WO2002069434A1 (fr) | 2002-09-06 |
FR2821487B1 (fr) | 2004-09-17 |
JP2004521543A (ja) | 2004-07-15 |
US7049909B2 (en) | 2006-05-23 |
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