JPS6129040A - Device for focusing electron beam - Google Patents

Abstract

PURPOSE:To simultaneously solve the problems of transmission and heat radiation of an electron beam by making the diameter of the outer periphery of pole pieces larger than that of the outer periphery of permanent magnets. CONSTITUTION:The diameter of the outer periphery surface of pole pieces 5 is made larger than that of the outer periphery surface of permanent magnets 6. And the pole pieces 5 are brought in close contact with a metal envelope 4, and heat can be effectively radiated by attaching a heat radiating body 9 to the outer periphery surface of the pole pieces 5. In addition, shunts 8 are inserted in gaps 7 which are formed by making the diameter of the outer periphery surface of the permanent magnets 6 smaller than that of theouter periphery surface of the pole pieces 5 to correct the deviation of magnetism of the permanent magnets 6 and to realize good transmission of an electron beam. Whereby, it is possible to simultaneously solve the problems of transmission and heat radiation of the electron beam.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an electron beam focusing device using a periodic permanent magnet (PPM) of an electron beam tube.

(Prior art) A traveling wave tube consists of an electron gun that emits an electron beam, a slow wave circuit that amplifies a circuit wave through interaction with the electron beam, and a magnetic field that provides a focus for the electron beam along the slow wave circuit. It consists of an electron beam focusing device, a collector that captures the electron beam after interaction, etc.

There are two types of traveling wave tube electron beam focusing devices: those using electromagnets or permanent magnets with a uniform magnetic field distribution, and those using periodic permanent magnets (PPM) in which the direction of the magnetic field changes alternately. Compared to a uniform magnetic field focusing device, a PPM focusing device has the feature that it can be configured to be smaller and lighter, and has recently come to be widely used not only for small power traveling wave tubes but also for high power traveling wave tubes. This PPM focusing device is made by stacking five-ring permanent magnets and ball pieces alternately, and the diameters of the outer peripheral surfaces of the permanent magnet and the ball piece are the same or the ball piece is smaller than the magnet.

(Problem to be Solved by the Invention) However, in order to obtain a strong magnetic field with a small magnet, the PPMPM focusing device is integrated with or in close contact with the slow wave circuit, so in the case of a high power traveling wave tube, the PPMPM focusing device If heat dissipation from the focusing device is not sufficient, the magnet will demagnetize due to temperature increase, resulting in insufficient focusing of the electron beam. Once demagnetized, the electron beam becomes more likely to collide with the slow-wave circuit, resulting in a vicious cycle in which the temperature of the magnet increases even further. That is,
It is necessary for a PPMPM focusing device of a high-power traveling wave tube to have good electron beam transmission, to reduce heat generation due to collision of the electron beam with a slow wave circuit, and to improve heat dissipation of the PPMPM focusing device. In the case of a PPMPM focusing device, the transmission of the electron beam can be improved by correcting the influence of biased magnetism of the magnets constituting the PPM. However, PPM according to the prior art
In the PM focusing device, since the outer circumferential surfaces of the magnet and the ball piece are the same or the outer circumferential surface of the magnet is larger than the outer circumferential surface of the ball piece, the outer circumferential surface of the magnet is coated with a magnetic material such as iron in order to correct the influence of biased magnetism. When a shunt is installed, the circumferential surface of the PPMPM focusing device becomes uneven, which causes a problem in that sufficient heat dissipation is not possible. 'Also. Prioritizing heat dissipation, P
If a heat sink is attached to the peripheral surface of the PMPM focusing device first, it is not possible to attach a shunt directly to the magnet, which causes another problem of insufficient correction of biased magnetism.

SUMMARY OF THE INVENTION An object of the present invention is to provide a high-power traveling wave tube PPMPM focusing device having a structure that simultaneously solves the problems of electron beam transmission and heat radiation.

(Means for Solving the Problems) The present invention provides a periodic magnetic field type electron beam focusing device used in an electron beam tube such as a traveling wave tube configured by alternately combining permanent magnets and ball pieces. It is characterized by having a diameter larger than the diameter of the outer periphery of the permanent magnet. Further, preferably, a heat radiator is provided on the outer periphery of the electron beam focusing device, and a magnetic material is partially inserted into the gap between the permanent magnet and the heat radiator. However, the insertion of a magnetic material for correcting biased magnetism is not necessarily necessary, and may be carried out for electron beam tubes whose meson beam transmission is degraded due to biased magnetism.

(Example) Figure '1 shows a PPMP of a high-power traveling wave tube implementing the present invention.
FIG. 3 is a partial axial cross-sectional view along the tube axis showing the configuration of the M focuser; A high-power traveling wave tube (electron gun, collector, and input/output parts are not shown) l has a slow wave circuit consisting of a helix 2 and a dielectric support 3. It consists of a metal envelope 4, a ball piece 5 and a permanent magnet d that are in close contact with the PPMPM focusing device envelope 4, and a shunt 8 made of a magnetic material such as iron that corrects the biased magnetism of the permanent magnet 6.
and a heat sink 9. The diameter of the outer peripheral surface of the ball piece 5 is larger than that of the outer peripheral surface of the permanent magnet 6. The heat source in the slow wave circuit is the helix 2, and this is thought to be due to two sources: high frequency loss and electron beam collision. helix 2
If the heat generated is not dissipated to the outside quickly, the helix 2 will melt, so a material with good thermal conductivity such as BeO is used for the dielectric support 3, and the helix 2 and the dielectric The contact thermal resistance between the supports 3 and between the dielectric support 5 integral 3 and the metal envelope 4 is reduced. Further, the ball piece 5 is brought into close contact with the metal envelope 4, and a heat sink 9 is attached to the outer peripheral surface of the ball piece 5, so that heat can be effectively dissipated. On top of that,
The shunt 8 is installed in the gap 7 formed by making the diameter of the outer peripheral surface of the permanent magnet 6 smaller than the diameter of the outer peripheral surface of the ball piece 5, without inhibiting heat conduction from the ball piece 5 to the heat sink 9. The biased magnetism of the permanent magnet 6 is corrected to achieve good transmission of the electron beam. Moreover, by matching the thickness of the shunt 8 to the width of the gap 7, the permanent magnet 6
It also has the effect of dissipating heat through it.

FIG. 2 is a sectional view taken along the line AA in FIG. 1, and clearly shows the structure of the shunt 8 and the heat sink 9. In this embodiment, four shunts 8 are installed on the circumference, but
It is not limited to four. Further, the heat radiating body 9 is of a heat radiating airfoil type.

In the embodiments of the present invention, the slow-wave circuit is of a helical type, but it is obvious that it can be easily applied to a cavity-coupled type of slow-wave circuit.

(Effects of the Invention) As detailed above, according to the present invention, in the PPM concentration device, the diameter of the outer circumferential surface of the ball piece is made υ larger than the diameter of the outer circumferential surface of the permanent magnet, so that good contact with the heat sink is achieved. In addition, sufficient heat dissipation can be achieved, and a magnetic material can be attached to the gap between the permanent magnet and the heat radiator to correct biased magnetism and increase the transmittance of the electron beam.

[Brief explanation of the drawing]

FIG. 1 is an axial sectional view of a portion along the tube axis showing the configuration of a PPM focusing device for a high power traveling wave tube embodying the present invention;
The figure is a sectional view taken along the line A-A in FIG. 1. 1... High power traveling wave tube, 2... Helix, 3... Dielectric support, 4... Golden envelope, 5... ...Ball piece, 6...
・Permanent magnet, 7...Gap, 8...JFI
Figure 2

Claims (2)

[Claims] (1) An electron beam focusing device configured by alternately combining permanent magnets and ball pieces, characterized in that the diameter of the outer periphery of the ball pieces is larger than the diameter of the outer periphery of the permanent magnet. (2) Claim (1) characterized in that a heat radiator is attached to the outer periphery of the ball piece, and a magnetic material such as iron is inserted into at least a portion of the gap between the heat radiator and the outer periphery of the permanent magnet. The described electron beam focusing device.