EP0848409B1 - Longitudinal interaction microwave tube with output cavity past the collector - Google Patents

Description

The present invention relates to microwave tubes with longitudinal interaction, also called "0" type, with cavity.

Longitudinal interaction microwave tube means a tube using a magnetic field focusing substantially parallel to the path of the beam electrons. These tubes call for the interaction of beam electrons in collective motion with a wave microwave.

These tubes can be klystrons or wave tubes progressive with coupled cavities and their derivatives.

A classic klystron has an electron gun that produces a long and thin electron beam through a succession of cavities interconnected by sliding tubes. At the end of the last cavity the electrons are collected in a coaxial collector with the beam. This collector heats up, it is cooled, for example, by making circulate at its periphery a coolant.

A focusing device surrounds the cavities, it prevents the electron beam to diverge. This focusing device is often formed of an electromagnet in the shape of a hollow cylinder.

A microwave wave to be amplified is introduced into the cavity closest to the cannon. The outlet cavity or cavity closest to the collector is intended to be connected to a member of use by via a transmission line, this transmission line conveying the amplified microwave wave towards the member of use. This transmission line is a rectangular, circular or coaxial.

This waveguide is generally arranged transversely to the electron beam. The coupling between the output cavity and the waveguide is made through at least one orifice in the side wall of the cavity.

A window can block the coupling hole. It is intended for let the extracted microwave wave pass while maintaining the vacuum thrust that reigns inside the cavity.

The transmission line being connected to a side wall of the output cavity, the focusing device must take account of this connection and have an indentation there. The magnetic field is reduced and asymmetrical at the exit cavity while this is where we need it the most. As a result the electron beam is defocused.

This transverse transmission line also causes a significant difficulty during the positioning of the tube. You have to slide the barrel-cavity-manifold assembly in the focusing device and adjust the relative position of the assembly and the device to fix the line of transmission. This operation is very delicate because of the masses put at stake and the fragility of the bond. The barrel-cavity-manifold assembly can weigh several hundred kilograms.

It has already been proposed to remedy these drawbacks at the level of the magnetic field and to simplify the assembly to use a line of transmission that surrounds the collector. But this provision has a major drawback. The collector is limited in size and not very accessible, its cooling is difficult and therefore costly. This configuration is reserved for weak tubes.

The present invention aims to produce a microwave tube with longitudinal interaction with cavity which has neither asymmetry of the field magnetic, nor collector of limited size and which is very simple to assemble and reduced cost.

To achieve these goals, the present invention proposes to make cohabit in the collector the microwave wave to extract and the electrons of the beam.

The present invention relates to a microwave tube with longitudinal interaction with at least one directed electron beam along an axis, crossing a so-called outlet cavity in which it interacts with a microwave wave, this cavity having a terminal wall which separates from a collector, the electron beam entering the collector by at least one opening in the end wall, characterized in that the end wall further comprises at least one coupling member for couple the output cavity to the collector, the microwave wave in front circulate in the collector before being extracted therefrom.

The coupling member can be an iris or a loop of coupling, for example.

To adapt the impedance of the collector to that of the cavity outlet, at least one obstacle can be provided in the collector microwave.

According to another characteristic of the invention, the collector has a end opposite to the outlet cavity fitted with a junction flange intended to be connected to a transmission line to convey the wave microwave out of the collector.

In order to maintain a high vacuum inside the collector, a microwave window is placed in the collector. She may be substantially transverse to the axis of the electron beam or else substantially parallel to the electron beam.

In order to protect the window from electronic bombardment, the collector may contain successive partitions mounted in a baffle, in upstream of the window.

Two successive partitions may have opposite portions. These portions can be edges or be larger.

The window can have one of its faces covered with a material slightly conductive such as titanium, so as to allow the flow of electrical charges due to electronic bombardment.

The collector can be externally equipped with means producing a magnetic field aimed at deflecting electrons before they don't reach the window.

The collector may include a bent portion so that that the microwave wave is extracted substantially transversely.

The window can be placed downstream of the angled portion of so as to be protected from electronic bombardment and to be accessible if cleaning is required.

The collector can have a transition so that the cross section of the elements placed downstream is different from that of the part of the collector upstream.

A section of waveguide attached to the collector can help form the bent portion, a bent waveguide can also be used.

The collector can have a non-circular section as very often, but rectangular.

The collector can be externally equipped with a cooling.

• la figure 1a une coupe longitudinale d'un tube selon l'invention ;
• la figure 1b une coupe transversale du collecteur du tube de la figure 1a ;
• la figure 1c le schéma électrique équivalent de la cavité de sortie couplée au collecteur du tube de la figure 1a ;
• les figures 2a, 2b deux coupes longitudinales partielles de deux variantes de collecteur d'un tube selon l'invention ;
• les figures 3a, 3b respectivement une coupe longitudinale et une coupe transversale d'une autre variante d'un collecteur d'un tube selon l'invention ;
• la figure 3c le détail d'une variante de l'organe de couplage ;
• la figure 4 une coupe longitudinale partielle d'un collecteur d'un tube selon l'invention ;
• les figures 5a à 5f diverses représentations de collecteurs coudés de tubes selon l'invention.

Other characteristics and advantages of the invention will appear on reading the description of examples of tubes according to the invention illustrated by the figures which represent:

• Figure 1a a longitudinal section of a tube according to the invention;
• Figure 1b a cross section of the manifold of the tube of Figure 1a;
• Figure 1c the equivalent electrical diagram of the outlet cavity coupled to the manifold of the tube of Figure 1a;
• Figures 2a, 2b two partial longitudinal sections of two variants of the collector of a tube according to the invention;
• Figures 3a, 3b respectively a longitudinal section and a cross section of another variant of a manifold of a tube according to the invention;
• Figure 3c the detail of a variant of the coupling member;
• Figure 4 a partial longitudinal section of a manifold of a tube according to the invention;
• Figures 5a to 5f various representations of bent collectors of tubes according to the invention.

Figure 1a shows a longitudinal section of a tube microwave according to the invention. Figure 1b is a section transverse along the axis AA.

The tube shown is a klystron. It behaves so classic, a gun 1 producing a long and thin axis 2 electron beam XX '. The electron beam 2 crosses a succession of cavities C1, C2, C3, C4, C5. They are aligned along the axis XX '. They are separated by sliding tubes 3. The cavities C1, C2, C3, C4, C5 are surrounded by a focusing device 4.

The cavity C1 closest to the barrel 1 is called the inlet cavity and the cavity C5 furthest from the barrel 1 is called the outlet cavity. A wave microwave to be amplified is introduced into the input cavity C1 using a coupling device 5. It will interact with the electrons who will give him part of their energy.

The electrons in beam 2 after passing through the cavity of output C5 are collected in a collector 6. The collector 6 generally in the form of a hollow cylinder is shown substantially coaxial with the axis XX '. The collector 6 is externally equipped with a device for cooling 7. In the example described, this device operates by fluid circulation.

The outlet cavity C5 has an end wall 8 which la separates from the collector 6. This end wall 8 has an orifice passage 11 for electrons.

The manifold 6 and the output cavity C5 are coupled electromagnetically using at least one coupling member 9 located in the end wall 8 but separate from the passage orifice 11 for the electrons. The microwave wave propagates in the collector 6 where it then coexists with the electrons of beam 2.

In the example shown in Figure 1a, the coupling member 9 is an orifice or iris in the end wall 8 of the outlet cavity C5.

The coupling is electrical between the output cavity C5 and the collector 6. The iris 9 cuts the current lines in the output cavity C5. An electric field is induced at the level of the iris and this field excites the electrical component of the propagation mode in the collector 6. This mode is preferably the TE11 circular fundamental mode because it propagates alone over a wide frequency range. It is possible to have use of other modes in collector 6, in particular using several orifices for coupling or at least one member for coupling a other type, for example a loop.

It is possible to adapt the impedance of the collector 6, usually a few hundred ohms, to that of the output cavity C5, usually a few thousand ohms, using one or more microwave obstacles 12. In FIGS. 1a, 1b, a corner 12 is visible in the manifold 6 downstream of the end wall 8, it is opposite to the coupling member 9 relative to the orifice 11 for the passage of the electrons. A pawn, a series of steps for example could be used to corner place.

The depth of the collector 6 is conventionally fixed by the expansion of the electron beam 2 when the magnetic field reduced.

It is conventional to produce the end wall 8 of the cavity of outlet in magnetic material, soft iron for example, the field magnetic then falls strongly in the collector 6 compared to what it was in the outlet cavity C5. Conventionally also the tubes of sliding are in non-magnetic material, copper for example.

Figure 1c shows the equivalent electrical diagram of the coupling between the outlet cavity C5 and the manifold 6. The outlet cavity is equivalent to an R, L, C circuit in parallel. The coupling member 9 is equivalent to a first transformer and the microwave obstacle 12 to one second transformer.

The collector 6 is designed to be connected to a line of transmission 10 at its end opposite the outlet cavity C5. This transmission line 10 is intended to convey the wave microwave extracted from the output cavity C5 and which has passed through the collector 6 to a user device (not shown).

In the example shown in Figure 1a, the line of transmission 10 is arranged in the extension of the manifold 6 substantially along the axis XX '. The manifold 6 ends with a flange of junction 14 to which the transmission line 10 is fixed. The transmission line transmission 10 can be a circular, rectangular or even waveguide coaxial. Exciting the circular fundamental mode in the collector has another advantage, it easily converts to TE10 mode rectangular which can be used in transmission line 10 if it is formed of a rectangular guide.

A microwave tube operates under vacuum. Generally the user device and the transmission line are not working at the same pressure as the tube, they can operate at pressure atmospheric or at a higher pressure. A microwave window 15 of dielectric material is then used to maintain the vacuum at inside the tube while letting the microwave pass through the transmission line 10.

In FIG. 1a, the window 15 is placed in the collector 6, at its end opposite to the outlet cavity C5, upstream of the flange of junction 14. It is substantially transverse to the axis XX '.

The microwave window 15 can be made of alumina and be soldered to the collector 6. Its shape depends on its environment. Here, it is adapted to the cross section of the manifold 6, it is a disc and the collector is a cylinder of revolution.

The shorter the tube, the more compact the manifold 6 and the more microwave window 15 risks being bombarded by electrons. This bombardment, damage or even risk breaking or piercing it. The electrons striking window 15 have several origins, there are those who entering the manifold 6 near the axis XX 'have not been deflected, those which are reflected by the collector wall as well as the electrons secondary emitted after an impact between a so-called primary electron and the wall of the collector. This bombardment causes an accumulation of charges on the window.

We can avoid, but only partially, this accumulation by covering the window with a thin layer of a slightly conductive material and preferably having a low secondary emission coefficient such as titanium. The charges can flow towards the walls of the collector 6.

It is also possible to reduce the bombardment of the window by subjecting the collector 6 to a transverse magnetic field in upstream of window 15 so that the electrons are deflected before reach it. This variant is illustrated in Figures 2a, 2b.

In this example, the collector 6 has at its end opposite the outlet cavity C5, a transition 20 then is extended by a waveguide portion 21 welcoming the window 15 and ends with the junction flange 14. The window 15 is always substantially transverse to axis XX 'and the transmission line (not shown) always directed along axis XX '. Depending on the type of transition 20, the waveguide portion 21 accommodating the window can have a different shape of cross section than that of manifold 6 and / or of different dimensions. The transition can transform, for example a circular guide into a rectangular guide, a rectangular guide into circular guide and / or carry out a reduction or a increase. In the example shown the transition 20 transforms a circular guide into a rectangular guide.

The collector 6 is externally equipped with means 22 producing a transverse magnetic field upstream of the window 15 of way to deflect the electrons passing through this area so that they do not reach window 15. Magnets 22 are located on the periphery of the waveguide portion 21.

This variant requires heavy magnets or even electromagnets and a power supply which increases the cost of equipment.

To avoid bombardment, it is also possible to place in the manifold 6, upstream of the window 15, baffled partitions.

Figures 3a, 3b show a manifold 6 of a tube along the invention equipped with two partitions 30. These partitions 30 are adapted to the shape of the collector 6. In the example shown, they have portions in vis-à-vis, these portions are edges 31 in the central part of the collector 6. It is also conceivable that two successive partitions 30 have larger portions opposite.

These partitions 30 are arranged towards the end of the manifold 6 opposite the outlet cavity C5, upstream of the window 15, in an area where the current of the electron beam is already well attenuated. These partitions 30 intercept electrons not yet collected regardless of their origin.

It is possible to use more than two successive partitions. The space between two successive partitions 30 will preferably be less than λg / 4, λg representing the length of the guided microwave wave in the manifold.

These partitions 30 can also serve as adaptation to the assembly collector 6 - window 15 - transmission line if necessary.

In FIG. 3a, it can be seen that the collector 6 contains, as microwave obstacle 12 a pawn instead of a corner. The coupling device 9 instead of being an iris is a conductive loop.

In Figure 3b which is a cross section of the manifold 6 along the axis BB ', we see that the pin 12 and the edges 31 of the partitions have substantially the same direction and this direction is substantially normal to the electric field existing in the collector 6. If the coupling member 9 was an iris as in Figures 1, its largest dimension would have been headed in that direction.

Figure 3c shows an alternative positioning of the loop one end of which is connected to the wall of the manifold 6, the other to the wall of the outlet cavity C5 and which crosses without touching the wall terminal 8.

In Figure 4, the manifold 6 has at its opposite end at the outlet cavity C5, as in FIGS. 2, a transition 20 followed by a portion 21 of waveguide on which the junction flange 14 is fixed. The manifold 6 is equipped with two partitions 30 in baffle. The partitions have facing portions 32. Window 15 is placed upstream of the transition 20 but downstream of the partitions 30.

Instead of being directed along the axis XX 'of the electron beam, the transmission line 10 can be placed substantially transversely to this axis. The fragility of the bond is no longer a problem in this configuration.

Figures 5a to 5f show various variants of collectors 6 ending with a junction flange 14 substantially transverse to the axis XX '. The transmission line will be mounted substantially transversely but the window 15 may be substantially transverse to the axis XX 'or substantially parallel.

In all these figures the manifold 6 is fitted with partitions 30 in chicane. It is understood that it could be fitted with magnets and / or that the window could be covered with a slightly conductive material. These three characteristics could be used alone or two by two or all together.

In FIG. 5a, the collector 6 extends at its end opposite the outlet cavity by a bent portion 50 and ends in the junction flange 14 to which is intended to be fixed the line of transmission (not shown).

Window 15 is now located beyond the bent portion 50, upstream of the junction flange 14 and is substantially parallel to the axis XX '. The bent portion 50 is here a bent waveguide. We assume that the manifold 6, the angled guide 50, the window 15 and the junction flange 14 have the same cross-section, for example, cylindrical or rectangular.

Similarly, in FIG. 5b, the manifold 6 is extended with a bend 50 and ends with a junction flange 14, a transition 51 is inserted between the angled guide 50 and the junction flange 14. The transition 51 modifies the cross section of the manifold 6 downstream of the bent guide 50.

The collector 6 is for example circular or rectangular, the angled guide 50 keeps the same shape, the transition 51 ensures a passage circular / rectangular or rectangular / circular or even retaining the same shape, reduce or increase the cross section.

Figures 5c and 5d show yet another variant of a collector 6. It has a bent guide 50 followed by a transition 51 and is ends with a junction flange 14. The window 15 is located between the transition 51 and flange 14. We assume that in this example, the manifold 6 has a rectangular cross section, that the bent guide 50 is rectangular, that the transition 51 reduces the cross section of the bent guide 50 while remaining rectangular and that the flange 14 is also rectangular.

In Figure 5d which is a cross section along the axis CC 'on can see iris 9, pin 12 and edges of partitions 30, all of these are arranged in the same direction.

In this variant, the window 15 placed downstream of a transition reducing has a reduced dimension which has the advantage of lowering the costs.

The advantage of placing window 15 as close as possible to the flange 14 is easily accessible if cleaning is required.

Instead of using a 50 bent guide as a bent portion, it is possible as illustrated in figures 5e and 5f, to fix directly on the collector 6 a section of waveguide 500 substantially transverse to the axis XX '.

This section 500 of waveguide ends, in FIG. 5e, by a junction flange 14 intended to be connected to a transmission line (not shown).

The window 15 is placed in this section 500 of waveguide.

In FIG. 5e, the waveguide section 500 has one of its walls which is an extension of the end of the manifold 6 to the opposite of the output cavity C5. This end is closed by a wall 501 substantially transverse to the axis XX '.

At the connection there is a corner 502 for adaptation. Regarding the dimensions of the two straight sections they can be equal or different. The main difference between Figure 5e and the FIG. 5f is located at the level of the waveguide section 500 which comprises a transition 503 upstream of the junction flange 14. As previously the transition 503 can modify the shape and / or the dimensions of the waveguide section 500. In FIG. 5f this transition 503 ensures a reduction in section without modification of shape. In Figure 5f the wall terminal 8 is visible and the coupling member 9 between the outlet cavity C5 and the collector 6 is a probe.

The window 15 is placed upstream of the transition 503. In order to reduce costs it could be downstream.

The invention is not limited as regards the portions cubits, transitions, window position, to the examples shown.

Claims (20)

1. Microwave tube with longitudinal interaction, comprising at least one electron beam (2) directed along an axis (XX'), passing through a cavity called the output cavity (C5) in which it interacts with a microwave, this cavity (C5) having an end wall (8) separating it from a collector (6), the electron beam (2) penetrating the collector (6) via at least one opening (11) in the end wall (8), characterized in that the end wall (8) additionally includes at least one coupling member (9) for coupling the output cavity (C5) to the collector (6), the microwave having to circulate in the collector before being extracted therefrom.
2. Microwave tube according to Claim 1, characterized in that the coupling member (9) is of the iris type.
3. Microwave tube according to Claim 1, characterized in that the coupling member (9) is a conducting loop.
4. Microwave tube according to one of Claims 1 to 3, characterized in that the collector (6) includes at least one microwave obstacle (12) for matching the impedance of the collector (6) to that of the output cavity (C5).
5. Microwave tube according to one of Claims 1 to 4, characterized in that the collector (6) has, on the opposite side to the output cavity (C5), an end equipped with a junction flange (14) intended to be connected to a transmission line (10) that has to convey the microwave out of the collector (6).
6. Microwave tube according to one of Claims 1 to 5, characterized in that a microwave window (16) is placed in the collector (6) so as to maintain a high vacuum inside the collector (6).
7. Microwave tube according to Claim 6, characterized in that the window (15) is directed approximately transversely to the axis (XX') of the electron beam (2).
8. Microwave tube according to Claim 6, characterized in that the window (15) is directed approximately parallel to the axis (XX') of the electron beam (2).
9. Microwave tube according to one of Claims 6 to 8, characterized in that the collector (6) contains successive partitions (30) mounted as baffles upstream of the window (15), with the purpose of protecting the window (15) from electron bombardment.
10. Microwave tube according to Claim 9, characterized in that two successive partitions (30) have facing portions.
11. Microwave tube according to Claim 10, characterized in that the facing portions are sharp edges.
12. Microwave tube according to one of Claims 6 to 11, characterized in that the window (15) has one of its faces covered with a slightly conducting material, such as titanium, so as to allow the electrical charges due to electron bombardment to flow away.
13. Microwave tube according to one of Claims 1 to 12, characterized in that the collector (6) is equipped on the outside with means producing a magnetic field for the purpose of deflecting the electrons before they reach the window (15).
14. Microwave tube according to one of Claims 1 to 13, characterized in that the collector (6) includes a right-angle portion (50).
15. Microwave tube according to one of Claims 1 to 14, characterized in that the collector includes a transition (51).
16. Microwave tube according to Claim 15, characterized in that the transition (51) is placed downstream of the right-angle portion (50).
17. Microwave tube according to one of Claims 14 to 16, characterized in that a waveguide section (500) fastened to the collector contributes to forming the right-angle portion.
18. Microwave tube according to one of Claims 14 to 16, characterized in that the right-angle portion (51) is a right-angle waveguide.
19. Microwave tube according to one of Claims 14 to 18, characterized in that the window is placed downstream of the right-angle portion.
20. Microwave tube according to one of Claims 1 to 19, characterized in that the collector is equipped on the outside with a cooling device (7).

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