Tube comprising at least one end with an oblique cross-section

Abstract

The invention relates to a tube comprising at least one end with an oblique cross-section, in which said end, having an oblique plane cross-section not perpendicular to the central axis of the tube, has a constant thickness. Figure for the abstract: [Fig.1]

Description

Title of the invention: Tube comprising at least one end with an oblique cross-section

[0001] The invention relates to a tube comprising at least one end with an oblique section.

[0002] When a tube 1, of constant thickness, is cut obliquely, i.e. whose obliquely cut end has an oblique plane section not perpendicular to the central axis 2, its thickness is not constant, as shown in [Fig.1].

[0003] Indeed, since the cut is oblique, the thickness of the cut end 3 is not constant, as shown in [Fig.1], on which is shown the variation of the thickness, which takes for example several values, the extreme values ​​of which are shown ei and e2.

[0004] The assembly of such an end 3 of tube 1 on a flat surface of a different material, or on another tube with a corresponding oblique cut (cutting angles relative to the axis of the complementary tubes), leads to an asymmetry with the consequence that from a diameter greater than 30 mm the stresses linked to the difference in expansions and the large thicknesses of the collars or brazing in places create a catastrophic break of the assembly.

[0005] One aim of the invention is to overcome the problems mentioned above.

[0006] According to one aspect of the invention, a tube is proposed comprising at least one end with an oblique section in which said end has an oblique plane section not perpendicular to the central axis of the tube and is of constant thickness.

[0007] According to another aspect of the invention, a microwave power transmission window is also proposed, comprising an assembly including: - two tubes as previously described, each having two ends with parallel oblique plane sections; and - an optical blade assembled between two respective ends of the two tubes arranged opposite each other.

[0008] In one embodiment, the optical blade is made of diamond, or quartz, or sapphire, or glass.

[0009] According to one embodiment, the microwave power transmission window is a so-called Brewster window in which the oblique plane section is such that the angle between the central axis of the tube and a normal to an oblique plane section is 67.22°.

[0010] According to one embodiment, a microwave power transmission window assembly is also proposed, comprising: - a microwave power transmission window as previously described; - a tubular element extending the microwave power transmission window; - two centering rings for the microwave power transmission window in the tubular extension element; and - an external housing equipped with two transparent portions arranged at the ends of the tubular element extending the microwave power transmission window.

[0011] The invention will be better understood upon examination of some embodiments described by way of non-limiting examples and illustrated by the accompanying drawings, in which:

[0012] [Fig.1] schematically illustrates a tube, of constant thickness, cut obliquely, according to the prior art;

[0013] [Fig.2] schematically illustrates a tube having a flat-section end, and of constant thickness, according to one aspect of the invention;

[0014] [Fig.3] schematically illustrates a power transmission window microwave frequencies, according to one aspect of the invention;

[0015] [Fig.4] schematically illustrates a power transmission window microwaves of the [Fig. 3] in the case of a so-called Brewster window, according to another aspect of the invention; and

[0016] [Fig.5] schematically illustrates a power transmission window assembly microwaves, according to another aspect of the invention.

[0017] Across all figures, elements with identical references are similar.

[0018] Figure [Fig. 2] schematically illustrates a tube 4 having a flat-sectioned end 3, and of constant thickness e, according to one aspect of the invention.

[0019] The constant thickness e can be obtained by machining 5a.

[0020] Due to this angle, in the absence of such machining, the oblique ends do not have a constant dimension and in particular have an oblong shape and a non-constant wall thickness which goes thicker from the center towards the end of each side of the largest dimension.

[0021] Oblique means a plane cutting angle making a non-perpendicular angle with the axis 2 of the tube 4.

[0022] This asymmetry has the consequence that from a diameter greater than 30 mm the stresses linked to the difference in expansions and the large thicknesses of the oblique ends in places create a break in an assembly with a plate or tube of another material.

[0023] The object of the present invention is to mechanically achieve a machining process that creates a constant thickness e all along the circumference of the oblique cut, regardless of the angle of the oblique over a height large enough to minimize the forces due to thermo-mechanical stresses.

[0024] The assemblies can be made by brazing, welding, gluing.

[0025] Figure 3 schematically represents a power transmission window microwaves comprising an assembly including: - two tubes 4a, 4b, each having two ends of constant thickness and parallel oblique plane sections; and - an optical blade 5 assembled between two respective ends of the two tubes 4a, 4b, arranged opposite each other.

[0026] Indeed, the present invention is particularly well-suited to microwave power transmission windows for electron tubes. The power windows must be able to transmit the energy supplied by the microwave tube while minimizing losses due to the intrinsic properties of the material and microwave matching, while ensuring the maintenance of ultra-high vacuum sealing. Microwave matching is performed at a specific frequency or over a frequency band.

[0027] In some cases, it is necessary to have near-perfect matching not over a single frequency band but over two or more specific frequencies. This is particularly true for the use of dual-frequency gyrotron tubes that deliver very high power levels on the order of megawatts at very high frequencies exceeding 100 GHz. In this case, a window must be used whose design is such that it is adapted for all frequencies.

[0028] This is a window called a Brewster window, as illustrated in [Fig. 4], whose main property is the use of a blade, for example made of diamond, inclined at the so-called Brewster angle, which is exactly 67.22° when using a diamond blade. To create such a window, a tube must be made and placed on either side of the blade positioned at the appropriate angle to create a sealed assembly that fully meets the operating conditions of the power window on the electronic tube, thus guaranteeing its sealing.

[0029] Large windows of this type for mounting on a tube do not exist. There are numerous ways to assemble ceramics, for example on copper skirts, to guarantee microwave and sealing properties.

[0030] Due to the Brewster angle of 67.22°, in prior art designs, the ends of the oblique plane section not perpendicular to the central axis of the tube do not have a constant dimension and, in particular, have an oblong shape. The resulting wall thickness is not constant and increases from the center of the The collar is towards the end on each side of the largest dimension. This asymmetry results in the fact that, from a diameter greater than 30 mm, the stresses linked to the difference in expansion and the large thicknesses of the ends in some places create a catastrophic failure of the assembly.

[0031] The aim is to create a sealed assembly that is resistant to various thermal cycles. The basic concept is to assemble, for example by brazing, a wall made of a dielectric material such as diamond onto copper ends placed on either side of the microwave transmission wall, and to ensure that the assembly is sealed.

[0032] The present invention makes it possible to mechanically perform machining which creates a constant thickness throughout the brazed length regardless of the angle over a height which is sufficiently large in order to create flexibility and thus minimize the stresses due to thermo-mechanical stresses during assembly and curing operations.

[0033] In order to achieve this assembly under optimal conditions, given the Brewster angle as illustrated in [Fig. 4], the wall is brazed flat, as in the case of conventional cylindrical windows, and the necessary tooling is created to perform this operation without requiring complex tooling to ensure the positioning of the transmission blade relative to the oblique copper ends. A second brazing operation joins this first step with the rest of the assembly to create a window assembly that can be mounted onto the tube in question.

[0034] A window assembly is schematically represented in [Fig.5], comprising: - a microwave power transmission window 6 according to [Fig.2] - a tubular element 7 extending the microwave power transmission window; - two rings 8a, 8b for centering the microwave power transmission window 6 in the tubular extension element 7; and - an external housing 9 equipped with two transparent portions 10a, 10b arranged at the ends of the tubular element 7 extending the microwave power transmission window.

[0035] For example, given the ratio between the actual diameter dimensions and the apparent dimensions due to the Brewster angle in a ratio of 2.5, machining should be carried out to reduce the brazing area to a 1 mm wide ring while allowing flexibility in the tubes 4a, 4b without reducing the thickness of the tubes 4a, 4b to values ​​too small to avoid the phenomena of permeation, deformations and more generally of sealing defects.

[0036] The aim is to create flexibility at the end of the assembly 6 linked to the material allowing the transmission of microwave energy, in order to reduce the stresses due to differential expansion between the different materials and also linked to the Brewster angle which leads to having a ratio of 2.5 between the wall thickness at the diameter perpendicular to the cut which corresponds to the actual diameter of the tube and the wall thickness located at the cutting plane located on the diameter of the long side of the ellipse.

[0037] Furthermore, the wall thickness of assembly 6 is subjected to the same ratio, resulting in a thickness that does not allow assembly 6 to adapt to the stresses due to differential expansion. This machining depends on the actual diameter of the tube and its thickness.

[0038] To overcome this drawback, this width is reduced by machining around the tubes in places where the thickness becomes greater than the desired thickness.

Claims

Demands

1. Microwave power transmission window assembly comprising: - a microwave power transmission window comprising an assembly including: - two tubes each comprising two ends of parallel oblique plane sections, one end of oblique plane section being not perpendicular to the central axis of the tube and being of constant thickness; and - an optical blade assembled between two respective ends of the two tubes arranged opposite each other; - a tubular extension element of the microwave power transmission window; - two centering rings of the microwave power transmission window in the tubular extension element; and - an external housing provided with two transparent portions disposed at the ends of the tubular extension element of the microwave power transmission window.

2. Microwave power transmission window assembly according to claim 1, wherein the optical blade is made of diamond, or quartz, or sapphire, or glass.

3. Microwave power transmission window assembly according to any one of the preceding claims, wherein the microwave power transmission window is a so-called Brewster window in which the oblique plane section is such that the angle between the central axis of the tube and a normal to an oblique plane section is 67.22°.

Images