JPH10134724A - Electron beam focusing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce thermal resistance from a tunnel wall to a heat sink or heighten a magnetic flux level in a beam tunnel region, in an electron beam focusing device. SOLUTION: This device comprises a plurality of magnetic pole pieces 32 interposition provided with a non-magnetic spacer 34, tube 30 having a beam tunnel 38 facing the axial direction for an electron beam to pass through, and a means guiding the magnetic pole piece 32, ascending a magnetic field having a line of magnetic flux passing along a magnetic axis, into the tube 30. Heat generated inside the pipe 30 passes through the spacer 34, so as to lead to a flat surface in the outside along an axis in non-conformity to the magnetic axis.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a periodic focusing device for guiding an electron beam, and more particularly to a novel structure for periodically focusing an electron beam in a microwave amplification tube.

[0002]

BACKGROUND OF THE INVENTION Microwave amplifier tubes, such as traveling wave tubes (TWT), are well known. The microwave tube is used to increase, or amplify, the gain of RF (radio frequency) signals in the microwave range. The microwave RF signal guided into the amplification tube interacts with the electron beam projected through the circuit. As a result of this interaction, the energy in the beam transfers to the RF signal, amplifying the signal.

[0003] Periodic focusing devices are well known in the microwave amplifier tube art as directing an electron beam through a beam tunnel in a microwave tube. Periodic focusing devices of this kind are usually composed of ferromagnetic materials, known as pole pieces, between which a permanent magnet is inserted.

[0004] Microwave amplifier tubes utilize either "integral pole pieces" or "mounted pole pieces."
The integral pole piece forms part of a vacuum envelope that extends inwardly in the direction of the beam area, and the mounted pole piece is mounted completely outside the vacuum envelope of the amplifier tube. These magnets are usually annular and either completely surround the amplification tube or are button-shaped, covering only part of the area between the pole pieces azimuthally. However, in each case, the shape of the tube governed by the focusing device is necessarily cylindrical.

A conventional cylindrical permanent magnet (PP)
M) The focusing device 10 is shown in FIGS. An amplification tube incorporating a conventional PPM focusing device 10 includes a plurality of substantially annular pole pieces 12 alternately arranged with non-magnetic spacers 14. Generally, the pole pieces 12 are made of iron and the non-magnetic spacers 14 are made of copper. The pole piece 12 extends radially outward of the amplification tube and has an annular permanent magnet 16.
And a hub 15 connected to the

[0006] The amplification tube is symmetrical about the center and has a cylindrical shape as shown in FIG.
It is provided at the center. The configuration of FIG. 1 is known as a single cycle focusing device. This is because each polarity of the permanent magnet 16 is reversed in each of the pair of adjacent pole pieces 12. An alternative configuration of the multi-cycle focusing device is shown in FIG.
Is shown in This comprises a hubless polepiece 18 between the polepieces 12, wherein the permanent magnet 16 joins a pair of adjacent polepieces 12 and comprises two adjacent magnetic spacers 14 and a hubless polepiece. It straddles the piece 18.

In this circular PPM focusing device, the magnetic flux entering the pole piece 12 at the boundary with the permanent magnet 16 is:
First it is guided inward in the radial direction. Magnetic pole piece 12
In the radial direction inside, the magnetic flux reaching the beam tunnel 17 jumps axially towards its adjacent pole piece, connecting the beam tunnel section and the magnetic field to focus the beam. The directions of the magnetic flux inside the pole piece 12 are essentially the radial direction (R) and the axial direction (Z). Therefore,
Such a cylindrical focusing device can be referred to as an RZ PPM focusing device.

This RZ PPM focusing device is a preferred feature because the magnetic flux concentrates inside the pole piece 12, which is often close to the area where the beam should be concentrated. However, this focusing device also has inherent limitations due to the radial length of the circle. R-Z
In traveling wave tubes using a PPM focusing device, an RF path for microwave signals is provided through the entire tube.
For example, a coupled cavity traveling wave tube contains a number of tuned cavities that determine the bandwidth of the amplified R signal. Therefore, the diameter of the annular magnet surrounding the tube is limited by the required cavity size in the tube. However, the diameter of the ring magnet device has increased. When the cavity becomes large, that is, when the azimuthal position of the building magnet extends radially outward, the strength of the magnetic field concentrated in the beam tunnel decreases.

[0009] In a microwave amplification tube using a high pervians electron gun, the magnetic field intensity may be too weak to sufficiently focus an electron beam.

A related problem with circular PPM focusing devices is the problem of heat removal. As the electron beam travels inside the beam tunnel 17, it removes thermal energy from the tube due to stray electrons shielding the tunnel wall, causing a change in magnetoresistance in the magnetic material, thermal deformation of the cavity surface, or tunneling. Wall melting must be prevented. Generally, this heat flows from the tunnel wall through the pole pieces 12 to the outside of the tube, from where it is absorbed by one or more heat sinks. Copper spacers 14 also conduct heat from beam tunnel 17.

Similar to the flux conduction problem described above, large diameter tubes have a greater difficulty in conducting heat because the heat has to travel farther to an external heat sink. Reducing the diameter of the tube makes it easier to remove heat, but is not applicable to tubes having large sized coupling cavities.

[0012]

Therefore, in the conventional focusing device, the internal radius is reduced at the expense of both the magnetic flux density and the heat resistance.
I have to secure the F road. It is therefore possible to reduce the thermal resistance of the heat path from the tunnel wall to the heat sink or to increase the flux level in the beam tunnel area, while providing a portion of the tube adjacent to the tunnel for RF paths or other uses. What is needed is a periodic focusing device for a microwave amplification tube that can be used.

A primary object of the present invention is to provide a portion of a tube adjacent to a tunnel for RF paths or other uses,
By introducing a periodic focusing device for a microwave amplifier tube that allows the choice of either reducing the thermal resistance of the heat path from the tunnel wall to the heat sink or increasing the magnetic flux level in the beam tunnel area is there.

[0014]

SUMMARY OF THE INVENTION According to the present invention, there is provided, in order to achieve the above and other objects, a microwave amplification tube comprising a tube formed by a plurality of magnet pole pieces having a non-magnetic spacer interposed therebetween. An electron beam focusing device is provided. The tube has an axial beam tunnel through which the electron beam can pass. Also, at least one side of the tube is provided with a flat surface for mounting a heat sink. A magnetic field is induced in the tube and flux lines flow through the pole pieces in a first Cartesian coordinate direction (X) and in a second Cartesian coordinate direction (Z).
Jump through the beam tunnel to focus the beam. The heat generated in the tube passes through the spacer and flows in a third Cartesian coordinate direction (Y) toward a flat surface. This direction is perpendicular to both the first and second directions. The magnetic field is formed by permanent magnets located outside the tube and mechanically coupled to the pole pieces.

In a first embodiment of the present invention, a tube having a single period PPM focusing device is disclosed. In this tube, adjacent pairs of pole pieces are each connected by permanent magnets. The direction of the polarity of the magnet is alternated in adjacent pole pieces in pairs. The permanent magnet is mounted on one side of the tube different from the side having the flat surface for mounting the heat sink.

In a second embodiment of the present invention, a tube having a multi-period PPM convergence device is disclosed. In this tube, a set of three adjacent pole pieces are each connected by a permanent magnet. The polarity of the permanent magnets alternates in each of a set of three adjacent pole pieces. The permanent magnet is mounted on one side of the tube different from the mounting flat surface.

In an embodiment to which the present invention is further applied, X-
A plurality of tubes having a 2 PPM focusing device are mechanically coupled into one common tube, with a common heat sink between a pair of adjacent tubes. Further, the plurality of tubes have a common magnet bar that crosses the tubes at right angles. Each of the plurality of tubes focuses on an associated electron beam.

By reading the description of the following examples, those skilled in the art will appreciate that the configuration of a microwave tube having an XZ-shaped PPM focusing device of the present invention and how You will have a complete understanding of what other benefits and objectives will be achieved. Hereinafter, embodiments will be described with reference to the accompanying drawings.

[0019]

FIG. 4 shows an XZ-shaped PPM according to the present invention.
A tube 30 with a focusing device is shown. The tube 30 is formed by a plurality of magnetic pole pieces 32 sandwiching a plurality of non-magnetic spacers 34, which are alternately assembled. This tube 30 has a pole piece 32 at either end, and
It has flat sides 41,42,43,44. In the figure, a beam tunnel 38 is shown approximately in the center of the end pole piece 32, which extends through the entire length of the tube 30 in the axial direction. As will be described in more detail below, the electron beam is projected through a beam tunnel 38 and
Focused by

Each pole piece 32 is substantially rectangular or elliptical and is preferably formed of a magnetically conductive metal material such as iron. The non-magnetic spacer 34 is also substantially rectangular and is made of a heat conductive material such as copper. The non-magnetic spacer 34 is sandwiched between the pole pieces 32.
The center is traversing. Permanent magnets 36 are sandwiched between adjacent pole pieces 32 and provided above and below the spacer 34.

Like the pole pieces 32 and spacers 34,
The permanent magnet 36 has a square surface such that the entire tube has a substantially smooth outer surface. Alternatively, the permanent magnet 36 may be larger than the pole piece 32 and protrude from the side edge of the pole piece 36.

FIG. 4 shows a tube with a single-period PPM focusing device in which each permanent magnet 36 connects a pair of adjacent pole pieces 32. Obviously, this general configuration of a multi-period PPM focusing device can also be formed having an intermediate pole piece 32 of approximately the same size as the non-magnetic spacer 34.

As in a conventional focusing device, the purpose of the permanent magnet 36 is to create a magnetic field throughout the beam tunnel 38,
To guide and pass the electron beam. The magnetic flux emanating from the permanent magnet 36 is directed in the X direction through the pole piece 32, as indicated by the arrow 46 in FIGS. When the magnetic flux reaches the beam tunnel 38, the magnetic flux lines pass through the tunnel, jump in the Z direction and jump to the adjacent pole piece 32.
, From which it passes through adjacent pole pieces in the X direction and returns to the magnet 36.

When the electron beam passes through the tunnel 38,
The stray electrons striking the surface of the beam tunnel wall generate heat inside the tube 30 of the focusing device. To remove this heat, a planar heat sink 54 is provided on opposite sides 41 and 42 of the tube 30. The planar heat sink 54 may be a rod made of a heat conductive material such as copper, or may be of a type having an internal manifold and flowing a cooling liquid. Ideally, heat sink 54 is maintained at a constant temperature and heat is efficiently removed from tube 30. Heat is transmitted through the spacer 34 in the Y direction as indicated by the arrow 52 and reaches the heat sink 54.

The fact that the direction Y of the heat passage is substantially perpendicular to the X and Z directions, which are the directions in which the magnetic flux passes,
I think it will be easily understood. The unique shape of this tube 30 is
There is a distinct advantage over conventional cylindrical shapes. With a reduced width, but a significantly higher height, the heat sink 54 is relatively close to the beam tunnel 38. Thereby, heat is efficiently removed from the inside of the tube 30.

By providing a cavity in the spacer 34,
An RF path can be formed so that the microwave RF signal passes through tube 30. Or, alternatively, side 4
From 3 and 44, by forming a tube with permanent magnets 36 facing the inside of the beam tunnel 38, the RF
A high magnetic flux density can be obtained with the path held inside the tube spacer. Permanent magnets are placed on opposite sides of tube 30 while heat sink 54 is attached to permanent magnets 36.
If the permanent magnet 36 is provided on a side different from the above, the permanent magnet 36 does not interfere with the position of the heat sink 54. Thus, with this unique focusing device, the tube designer has the option of either efficient heat removal or high magnetic flux density.

An example of further application of a microwave tube having an XZ PPM focusing device according to the present invention is shown in FIG.
Indicated by 0. In this configuration, the beam tunnel 38
Is provided off the center of the tube 50 and is close to one side of the tube 50. In the previous embodiment, the spacer 34 was
Although positioned at the center of zero, in this embodiment the spacer 34 is provided on one side of the tube. Permanent magnet 3
6 is provided on the other side of the tube 50. Therefore, the heat sink 54 is also provided on the side adjacent to the nonmagnetic spacer 34.

In this application example, the third heat sink 5
4 is provided at the bottom of the tube 50 so that heat can be removed from three sides. In this case, the directions of the heat paths are the X and Y directions. It is clear that this tube 50 has significantly better heat resistance than the microwave tube design described above.

In yet another application according to the invention, FIG.
As shown in FIG. 4, a plurality of tubes having the XZ PPM focusing device in FIG. Each adjacent tube 30 has a common heat sink 54
Sharing. The tubes 30 can further share a common magnet bar that traverses each tube at right angles. Each adjacent tube 3
0 has an independent beam tunnel 38,
The combined tube 60 can focus multiple electron beams simultaneously. Such a function is required in a microwave application having a plurality of independent RF signals, such as a phase array radar.

In order to use the tube 30, the electron gun 74 and the collector 76 are connected as shown in FIG. Electron gun 7
4 has a launch surface 78 from which the electron beam 80
Penetrates through the tube 30. Spent electron beam 80 that has passed through tube 30 is collected by collector 76.

Having described a preferred embodiment of a microwave tube having an XZ PPM focusing device according to the present invention, it will be appreciated by those skilled in the art that this description will achieve the objects and advantages set forth above. If so, I think you have fully understood.

It will be apparent to those skilled in the art that the present invention can be embodied in various modifications, applications, and other embodiments without departing from the scope and spirit of the invention. . For example, the shape of the pole pieces and spacers can be set from long and thin to short and thick to achieve a desired balance between heat resistance and magnetic flux density. It is envisioned that the above described microwave tube configuration can be employed in various applications such as coupled cavity traveling wave tubes, cristrons or extended interaction circuits.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a single-period microwave tube to which a conventional RZ cylindrical focusing device is applied.

FIG. 2 is an end view of the conventional microwave tube of FIG. 1;

FIG. 3 is a side sectional view of a conventional multi-period microwave tube using an RZ cylindrical focusing.

FIG. 4 is a perspective view of a microwave tube having an embodiment of an XZ focusing device according to the present invention.

FIG. 5 is a perspective view of a microwave tube having an example in which the XZ-shaped focusing device according to the present invention is applied, in which a permanent magnet is disposed at one end of a circuit.

FIG. 6 illustrates a further application of the invention, a side view of a multiple electron beam focusing device having a plurality of tubes, each of the adjacent pair of tubes sharing a common heat sink.

FIG. 7 is a schematic diagram of an electron beam focusing device coupled to an electron gun and a collector.

FIG. 8 is a cross-sectional view of a microwave tube having an X-2 shape focusing device, showing a magnetic flux.

[Explanation of symbols]

 (30) Tube (32) Magnetic pole piece (34) Spacer (36) Permanent magnet (38) Beam tunnel (41) to (44) Side surface (46) Arrow (50) Tube (52) Arrow (54) Heat sink (60) Tube (74) electron gun (76) collector (78) launch surface (80) electron beam

Continued on the front page (72) Inventor Alan J. Seys United States 94062 Redwood City Oak Parkway 540 (72) Inventor Douglas Bee Lion United States of America 94070 San Carlos Northam Avenue 48

Claims (2)

[Claims] 1. An XZ periodic magnet focusing apparatus for focusing an electron beam, comprising: a tube having a plurality of pole pieces sandwiched between plate-shaped non-magnetic spacers;
A beam tunnel protruding arranged and the electron beam pass through through the tube, and having a heat flat surface disposed on at least one surface of said tube; to the axis of the tube through the pole piece Flow in a first direction at right angles,
And means for inducing a magnetic field in said tube having magnetic flux lines jumping through said beam tunnel to focus said beam; through it, the pipe shaft to flow to the heat flat surface of the perpendicular second direction, said first direction, for focusing the electron beam, characterized in that does not match the second direction XZ periodic permanent magnet focusing device. 2. A tube comprising a plurality of pole pieces sandwiched between plate-shaped non-magnetic spacers, said tube being disposed therein and being a beam tunnel through which an electron beam can pass. And a device for inducing a magnetic field in the tube for focusing the electron beam, wherein the magnetic field is along a magnetic axis perpendicular to the axis of the tube. A device for inducing heat in the tube with a heat flux passing through the spacer along a heat axis perpendicular to the axis of the tube in the tube. An electron beam focusing device which is substantially perpendicular to the thermal axis.