Patent Grant
9666920
This application claims priority to foreign French patent application No. FR 1401301, filed on Jun. 6, 2014, the disclosure of which is incorporated by reference in its entirety.
The invention relates to a device allowing energy to be transmitted from one medium to another.
More precisely, the invention relates to a device, such as a microwave window, for example, allowing energy to pass. The device may notably be used at the exit of a power electron tube to transmit a microwave-frequency electromagnetic wave between the interior of a tube, for example, under vacuum, and the exterior of the tube at atmospheric pressure. The tube may be an amplifier, for example, a travelling wave tube.
The microwave window 1 furthermore comprises a core 3 passing through the wall 2, the core 3 extending in a longitudinal direction dLong.
A cladding 4 comprising a material ensuring thermomechanical and microwave matching is arranged coaxially around the wall 2.
A body 5 made of a metal, stainless steel for example, allows a coupled assembly to be created that can be assembled with an electron tube.
All of these parts are assembled by brazing, the core 3 being sufficiently small in size that expansion differences between these parts allow a satisfactory mechanical strength to be guaranteed. Typically, the diameter d1 of the core 3 is about 0.5 mm.
This first solution of
Another solution consists in using a core 3 comprising controlled expansion materials.
The low thermal expansion materials generally used are FENICO™ provided by Fenico Precision Castings of CA (or other types of expansion materials) having a low thermal elongation coefficient of about 0.0121 mm per mm at 1010° C., or molybdenum having an elongation coefficient of about 0.0057 mm per mm at 1010° C.
One drawback of microwave windows using controlled expansion materials is that these materials are highly resistive, thereby limiting power transmission capability.
Another possible solution consists in using a material such as moly-copper associating the low thermal expansion properties of molybdenum and the good energy conduction properties of copper.
One aim of the invention includes providing an alternative device for transferring energy from one medium to another, whether hermetically or otherwise.
According to one aspect of the invention, a device for transmitting energy is provided, comprising:
The invention allows highly energetically conductive materials such as copper, gold or silver to be assembled with thin dielectrics or thermal insulators such as alumina, for example.
This embodiment obtains a good compromise between the capacity of the conductive element to relieve mechanical stresses and a high level of power transfer.
Advantageously, the cross section of the conductive element in the thickness of the wall is circular and constant, thereby facilitating implementation. The cross section of the conductive element has a first diameter smaller than or equal to 3 mm.
When the invention is applied to microwave tube coaxial exit windows with such a dimension smaller than or equal to 3 mm (by way of example of such tubes, mention may be made of TWTs) output powers may be obtained in the 100-300 W range because power transmission through the window remains high (relative to this small cross section of 3 mm diameter) because the hollowed out portion of the window has a small cross section (10% of the cross section of a “solid” window).
Advantageously, the cross section of the hole is circular and constant.
Advantageously, the thickness of the wall in the longitudinal direction is smaller than or equal to 1 mm depending on the flexibility required to accommodate for the various thermomechanical stresses created during the various assembly phases and during stresses due to the transfer of electrical or microwave energy.
Advantageously, the device for transmitting energy such as described above is a microwave window.
According to another aspect of the invention, a device such as described above is provided comprising a plurality of conductive elements arranged substantially parallel to the longitudinal direction, the distance between two successive conductive elements being larger than or equal to 0.5 mm.
The invention will be better understood and other advantages will become apparent on reading the following nonlimiting description, and by virtue of the appended figures, in which:
One embodiment of the invention is shown in
In the case in point, the device comprises a wall 2 comprising an electrically and thermally insulating material such as a ceramic, alumina being very particularly suitable. The wall 2 is joined to connector parts 7, for example using brazed joints 6.
The transmitting device according to one aspect of the invention allows a conductive element 3 to be assembled with a thermally and/or electrically insulating wall 2.
The wall 2 may be of any thickness e. However, the device described is particularly applicable to devices notably having a small wall 2 of thickness e, typically smaller than about 1 mm.
This is because mechanical stresses due to temperature variations are, for this type of device, correspondingly more critical to the integrity of the energy transmitting device.
The conductive element 3 extends in a longitudinal direction dLong and passes through the wall 2.
The conductive element 3 comprises a material having good energy conduction properties, such as copper. The transmitted energy will possibly take the form of thermal energy, an electrical current or electromagnetic waves.
The cross section Sc of the conductive element 3, shown in
The conductive element 3 is joined to the wall 2, for example hermetically, depending on the applications for which the energy transmitting device is intended. The conductive element 3 may, for example, be joined to the wall 2 by means of an adhesive, brazed joints or welded joints. In the case in point, the joint of the conductive element 3 to the wall 2 is achieved using brazed joints 6.
The conductive element 3 furthermore comprises a hole 8 extending in a direction substantially parallel to the longitudinal direction dLong and protruding on either side of the surfaces of the wall 2 over lengths L that are greater than or equal to the largest dimension of the cross section Sc of the conductive element 3, the cross section Sc of the conductive element 3 being considered level or flush with the wall 2.
In other words, if the cross section Sc of the conductive element 3 is circular and constant within the thickness e of the wall 2, the hole 8 extends on either side of the surfaces of the wall 2 or, in other words, protrudes on either side of the surfaces of the wall 2, over respective lengths that are greater than or equal to the first diameter d1 thus limiting expansionary and compressive mechanical stresses generated by temperature variations during the passage of the energy.
The hole 8 may be located in any position, but advantageously the hole 8 is centered. The hole 8 may be closed or open onto one or other of the ends of the conductive element 3. Preferably, the hole 8 opens onto at least one of the ends of the conductive element 3. The hole 8 may have any cross section St (shown in
Advantageously, the ratio of the area of the cross section Sc of the conductive element 3 after the hole 8 has been drilled to the area of the cross section Sc of the conductive element 3 before the hole 8 has been drilled is comprised between 0.85 and 0.95, and is preferably higher than or equal to 0.9.
In other words, the cross section Sc of the conductive element 3 after drilling is larger than 90% of the cross section Sc of the conductive element 3 before drilling. Thus, the loss of effective area allowing energy to be transferred is very small.
Therefore, if the cross section Sc of the conductive element 3 and the cross section St of the hole 8 are circular in the thickness of the wall 2, the ratio of a diameter d2 of the hole 8 to a diameter d1 of the conductive element 3 is then 0.3 at least. The diameter d1 is referred to as the first diameter and the diameter d2 is referred to as the second diameter. The diameter of the drill hole may be the smallest producible, typically 0.2 mm.
Another aspect of the invention includes placing a plurality of high-power energy transmission enabling microwave devices substantially parallel to the longitudinal direction dLong. This aspect of the invention is shown in
Advantageously, the distance d, shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 14 01301 | Jun 2014 | FR | national |
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| Number | Date | Country | |
|---|---|---|---|
| 20150357694 A1 | Dec 2015 | US |
