DE1256748B - Window permeable to electromagnetic waves - Google Patents

Description

GERMAN JfflWWl PATENT OFFICE

EDITORIAL H03h

German class: 21 a4 - 74

Number: 1 256 748

File number: E 29245IX d / 21 a4

J 256 T48 filing date: May 5, 1965

Opened on: December 21, 1967

The invention relates to a window permeable to electromagnetic waves, and more particularly on a window with a single, gas-tight, between waveguides with connecting flanges arranged and permeable to electromagnetic waves body, the a path for the electromagnetic Forms energy and extends with a window part transversely to the axis of the waveguide.

In known arrangements, windows permeable to electromagnetic waves were inside of hollow electromagnetic wave transmitting devices, e.g. B. waveguides, used so that gas-tight partition walls were built there. Such windows are made of an appropriate dielectric Material, e.g. B. mica, ceramic, quartz and the like. Manufactured, and their peripheral end parts are vacuum-tight connected to the inner walls of the waveguide. Such windows can be used within of the waveguide and a vertical transverse wall, an inclined wall, a Conical wall and the like. The particular use of some of these windows requires that they are used within the waveguide in an area of strong electric fields. These Electric fields cause arcing when they are of sufficient strength on the sealing surface, d. H. where the peripheral edges of the window are hermetically sealed with the inner peripheral surface of the waveguide are sealed, thereby limiting the amount of electromagnetic energy that can be passed through the window. The arcing also causes breaking through of the electric window, causing a loss of vacuum and destruction of the Tube occur. The peripheral edges of known windows and the inner peripheral surfaces of the waveguides, with which they are sealingly connected must also be manufactured very precisely so that they are satisfactory Seals are obtained, which causes known window arrangements to be relatively are complicated and expensive to manufacture.

It is the object of the invention to overcome these disadvantages of the known arrangements, so that According to the invention, an improved, wave-permeable window arrangement results.

The window that is permeable to waves should be easily sealable against a waveguide. It will be a proposed gas-tight window permeable to waves that allows large amounts of energy to be transmitted up to the order of several megawatts of peak power without arcing.

Permeable to electromagnetic waves
window

Applicant:

Varian Associates, Palo Alto, Calif. (V. St. A.)
Representative:

Dipl.-Ing. H. Marsch, patent attorney,
Düsseldorf, Lindemannstr. 31

Named as inventor:

Harry Max Weiss, San Jose, Calif. (V. St. A.)

Claimed priority:

V. St. v. America May 6, 1964 (365 253)

Based on the above known arrangement, this object of the invention is achieved by

as that the body consists of a peripheral flange part with an electrically conductive coating on the outer surface as a current path for the electromagnetic energy and the window part which is enclosed within the flange part. The body permeable to waves thus has an electromagnetic wave limiting part with an electrically conductive coating on the outer surface so that a current path for the electromagnetic energy is created, and a window part is provided within the wave limiting part so that a gas-tight part is attached to the the wave limiting part is created. The window part can be arranged transversely to the part delimiting the wave and, as is known per se, have a thickness which is substantially less than half an electrical wavelength of the mean frequency of the pass band of the part delimiting the wave, while the part delimiting the wave can have a length of n / 2 electrical wavelengths, where η can be any odd integer.

The invention is explained in more detail below in conjunction with the drawing. It shows

F i g. 1 in partial cross-section an embodiment according to the invention in connection with a microwave tube, z. B. a klystron,

FIG. 2A shows a section along the line 2A-2A of FIG. 1,

709 709/167

FIG. 2B shows a modified embodiment of the device according to FIG. 2 A and

F i g. 3, 4, 5, 6 and 7 different embodiments according to the invention.

In the drawings, F i g. 1 a microwave tube, e.g. B. a klystron, which has a beam generator section 11 for generating an electron beam, an RF interaction section 12 and a collector section 13 . The electron gun section, the intermediate action section and the collector section are axially aligned with one another in a known manner so that a projection of the electron beam generated by the beam generator section 11 through a series of drift tube sections 14 is possible. Each drift tube section ends in a cavity 15, 16 or 17 and has a conically tapered end part 18 which is arranged offset from the end of an associated drift tube section so that an intermediate action gap 19 is created therebetween. The drift tube sections are supported in axially offset alignment by relatively heavy, transverse, annular metal plates 20 which form end parts of the cavities 15 , 16 and 17.

The cavity 17 in the vicinity of the collector 13, which is shown in FIG. 1 shown in cross section is an outcoupling cavity. High-frequency electromagnetic energy that is present within the decoupling cavity is decoupled from there via a first tubular waveguide 25 , which can be rectangular. The end of the first waveguide that is remote from the outcoupling cavity is approximately in the manner shown in FIG. 1 is formed in the manner of a flange at 26.

A second tubular waveguide 31, which can also be a rectangular waveguide, has an end part flanged at 32. The flange-like portions 26 and 32 of the first and second waveguides 25 and 31 , respectively, are offset from one another, but are close to one another, and the first and second waveguides are aligned with their longitudinal axes.

Provided between the flanged parts is a body 27 which is permeable to electromagnetic waves and which is constructed in one piece and gas-tight. The electromagnetic wave transmitting body has a wave limiting part, e.g. B. a flange-like, tubular or hollow cylindrical part 28. An electrically conductive coating 29 is connected to the outer surface and to the edges of the part 28 limiting the electromagnetic waves. Opposite ends of the part 28 delimiting the waves are connected in a vacuum-tight manner to the flanged parts 26 and 32 , as a result of which a galvanic connection of the coating 29 with the first and second waveguides 25 and 31 is created. The one-piece, wave-permeable body 27 furthermore has a window part 30 which runs transversely to the wave-delimiting part 28 and is enclosed therein so that a gas-tight, wave-permeable partition is created on the wave-delimiting part.

The one-piece, wave-permeable body 27 and the flange parts 26 and 32 of the first and second waveguide 25 and 31 form a circular broadband waveguide in which reflections from various associated discontinuities and irregularities over a very wide frequency

area to be wiped out. According to a preferred embodiment of the invention, the tubular part 28 of the one-piece, wave-permeable body has a length parallel to the longitudinal axis of the first and second waveguides 25 and 31 of about n / 2 electrical wavelengths at the mean frequency of the passband of the tubular part 28 , where η can be any odd integer value. Although η can be any odd integer value, a value η − 1 gives a wider pass band than if n> 1. The window part 30 of the wave-permeable component also has a thickness which is substantially less than half an electrical wavelength at the mean frequency of the pass band of the tubular waveguide part 28 , and is approximately the same distance from opposite ends of the waveguide part 28 . The broadband device including the wave permeable body 27 and the flange portions 26 and 32 of the first and second waveguides have a bandwidth that is about 30%, that is, 30% between standing wave ratios of 1.2. The above ratings are all known per se.

The operation of the in F i g. 1 is such that the electromagnetic energy present within the coupling-out cavity 17 passes through the first waveguide 25, the one-piece, wave-permeable body 27 and the second waveguide 31 . Current paths associated with this electromagnetic energy run along the inner walls of the first waveguide 25, on the flange portion 26 of the first waveguide 25, on the electrically conductive coating 29 on the one-piece body 27, on the flange portion 32 of the second waveguide 31 and on the inner circumferential walls of the second waveguide 31. The broadband device, which includes the integral body 27 and the flanged waveguide members 26 and 32 , operates in such a way that a standing wave is generated which has a maximum electric field intensity in an area approximately equidistant between the ends of the Waveguide part 28 having, this field at the opposite ends of the waveguide part 28 in the vicinity of the flange parts 26 and 32 decreases to zero intensity. Thus, no arcing occurs at the points at which the flange parts 26 and 32 are sealed with opposite ends of the waveguide part 28 of the wave-permeable body 27 , since no or almost no electric field is present at the sealing surface. Due to the one-piece design of the wave-permeable body 27, which is preferably made of ceramic material, there is no metallic sealing material between the ends of the waveguide part (e.g. where the window part 30 receives the waveguide part 28 ) at which an arcing is present can occur, as is the case with known arrangements. There were over 100 megawatts of peak power in the S-band with a device according to FIG. 1 without arcing occurring, while in known windows arcing is already occurring in the vicinity of 20 megawatts peak power in S-band. Arcing in known broadband devices occurs due to the fact that heretofore

Claims (3)

a sealing material was required at the areas of high electric field intensity in order to maintain the properties for the broadband. For example, the bandwidth of the tubular waveguide part 28 is greatest when the window part 30 is arranged approximately at an equal distance between the ends of the waveguide part 28, where the electric field strength is a maximum. The flange parts 26 and 32 act as a transition device which electrically couples the current-conducting coating 29 on the one-piece permeable body to the first waveguide 25 and the second waveguide 31. The body 27 which is permeable to waves and which is airtight and is sealed in a vacuum-tight manner against at least the flange part 26 of the first waveguide is used to isolate the evacuated part of the klystron. A corresponding dielectric material that is vacuum-tight, e.g. B. mica, quartz, ceramic and the like. Can be used to produce the one-piece body 27 permeable to waves. The flange parts 26 and 32 of the first and second waveguides 25, 31 are simply vacuum-sealed with opposite ends of the waveguide part 28 of the one-piece body 27 by an ordinary abutment seal in the manner shown in FIG. 1 attached manner. This type of seal does not require the circumferential edges to be precisely dimensioned, as in the case of known windows and the inner circumferential surfaces of the waveguides with which they are necessarily connected in order to produce known coupling-out window arrangements. The arrangement according to the invention according to FIG. 1 simple and economical to build. The electrically conductive coating 29 on the outer surface of the waveguide part 28 of the wave-permeable body can be vapor-deposited, applied by flame spraying, metallized or otherwise connected to the wave-permeable body. For example, Fig. 2A, which is a section along the line 2A-2A of Fig. 1, shows a metallized layer 35 over the outer surface of the tubular waveguide portion 28 which is then coated with a layer of a material 36 of low electrical resistance, e.g. B. copper, is plated. The waveguide portion 28 of the wave-permeable body is not limited to the circular shape as shown in Fig. 2A, but may take any desired geometric shape. For example, Figure 2B shows a one-piece, wave permeable body having a rectangular waveguide portion 37 having an electrically conductive surface 38 on the outer surface. FIGS. 3 to 8 show various modifications of the device of FIG. 1. For example, FIG. 3 shows a one-piece, wave-permeable component 39 which is similar to component 27 according to FIG. 1 and which has a hollow channel 40 through the window part, wherein a gas or a liquid can simply be passed through the window part to prevent the Window becomes overheated due to the absorption of electromagnetic energy that is passed through. The gas or liquid enters the window area via an appropriate device, e.g. B. an inlet pipe 41 and an outlet pipe 42, in and out again. A modification of this device is shown in FIG. 4, in which the hollow channel within the window part is substantially enlarged by using two parallel window parts 45 and 46. The window parts are thus led away from the area of maximum electric field strength, as a result of which the bandwidth of the device is reduced. However, this disadvantage is offset by the advantage that high electromagnetic energies by means of the device according to FIG. 4 can be transferred without the window parts 45 and 46 being heated too much. Another embodiment of the present invention is shown in FIG. 5, in which a one-piece body 50 permeable to waves is shown with a window part 51 which has a section in the shape of a hollow spherical sector. This type of construction mechanically strengthens the window portion 51 and enables it to withstand large pressure differentials that exist on opposite sides. Also generates the electromagnetic energy flowing from left to right through the device of FIG. 5 migrates from an evacuated supply source, a significantly smaller multipactor phenomenon at the window 51 than with a flat transverse window. A modification of this embodiment is shown in FIG. 6, in which a hollow window part 52 is provided, which can be cooled by passing liquids or gases therethrough, and in which each side of the window part 52 is a hollow spherical sector-shaped section. This embodiment enables the multipactor phenomenon to be reduced regardless of which side is connected to the source of electromagnetic energy, and also provides a tough window arrangement that can withstand pressure differentials. F i g. 7 shows another embodiment of the present invention in which a one-piece, wave-permeable body has a window portion 55 which is beveled against a waveguide or boundary portion 56. Patent claims: 1. For electromagnetic waves permeable window with a single, gas-tight, arranged between waveguides with connecting flanges and permeable to electromagnetic waves body, which forms a path for the electromagnetic energy and extends with a window part transversely to the axis of the waveguide, characterized in that the Body (27) consists of a peripheral flange part (28) with an electrically conductive coating (29) on the outer surface as a current path for the electromagnetic energy and the window part (30) which is enclosed within the flange part (28). 2. Window according to claim 1, characterized in that the window part has a plurality of spaced apart window part sections (45, 46; 52) . 3. Window arrangement according to claim 1, characterized in that the one-piece body has a tubular peripheral flange part (28, 37) and that at least one end of the tubular peripheral flange part is connected in a vacuum-tight manner to the associated waveguide (25, 31), which is galvanically connected to the current-conducting Plating is connected.