JPS59114729A - Permanent magnet device - Google Patents

Abstract

PURPOSE:To reduce unwanted leakage magnetic field and realize reduction in size of magnet by cutting the upper and lower pole piece magnets like a through groove from the surface in the opposite side of the center gap to the magnetizing direction of said magnets. CONSTITUTION:A large groove is provided in the direction at a right angle to the center axis of magnetizing direction of magnet so that the surface not bonded to magnets in the upper pole piece 1 and lower pole piece 2 is almost removed. With such a structure, various kinds of leakage magnetic fields can be fantastically reduced and a magnet can be reduced in size.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the structure of a permanent magnet device used in a uniform magnetic field focusing type high power klystron.

As is well known, a high-power klystron consists of an electron gun section that generates an electron beam, and a high-frequency circuit section (cavity section) that applies velocity modulation and density modulation to the electron beam and performs high-frequency amplification.
, a collector section that collects the electron beam, and a beam focusing device that focuses the electron beam into a predetermined shape. Among these beam focusing devices, there are those that use electromagnets and those that use permanent magnets, but recently the latter has been mainly used in order to improve the overall efficiency of klystrons and simplify maintenance. There is a tendency.

An example of the conventional structure of a permanent magnet device used in a high-power Istron is shown in FIG. To briefly explain the first drawing, 1 and 2 are an upper pole piece and a lower pole piece. A hole is made in the upper pole piece 1 from the upper surface side, into which a part of the collector (not shown) is inserted. Similarly, a hole is made in the lower pole piece 2 from its lower surface, into which a part or all of the electron gun section (not shown) is inserted. The lower side of the upper pole piece 1 and the upper side of the lower pole piece 2 are usually provided with protrusions in the shape of a sungun, which serve to centralize and homogenize the magnetic field generated between the two. A high-frequency circuit section (not shown) of the klystron is placed in the gap between the two pole pieces, and applies the magnetic field (in the axial direction) to the electron beam passing through the center of the high-frequency circuit section to suppress divergence of the electron beam. . Both of the pole pieces 1 and 2 have a rectangular outermost diameter,
As shown in the figure, a pair of rectangular magnets are attached to both opposing parts. That is, the magnets 3 and 4 are attached to the upper pole piece 1.
Further, magnets 5 and 6 are attached to the lower pole piece 2. The polarity of each magnet is set to, for example, an N pole and an S pole as shown in the figure. A yoke 7.8 is installed on the opposite side of the magnet, and the above combination completes a klystron magnetic circuit.

In a permanent magnet structure like this, the biggest concern is how to downsize the magnet in order to generate a magnetic field of the necessary strength in the central gap. Assuming that the material of the magnet itself is constant, this results in the problem of how to prevent the generation of a magnetic field leaking to other parts when securing the magnet generated in the central gap. As a result of the inventor's detailed examination of the existence of the leakage A1a field Iff in the structure shown in FIG. 1, it was found that the following leakage magnetic field exists. In other words, the four sides of the upper pole piece 1 and the lower pole piece 2 where the magnet cannot be attached are the A side and the B side, respectively, and the sides near the magnets of the yokes on both sides are shown in the figure. D
I If it is the 1D2 plane, the leakage magnetic field that exists between the A plane and the B plane, the leakage magnetic field that exists between the A plane, 01 and D1 planes, the leakage magnetic field that exists between the B plane, 02 plane and D3 plane, etc. Existing. Due to the presence of such leakage magnetic fields,
This meant that the shapes of the magnets 3, 4, 5, and 6 had to be made larger than necessary.

In view of the above-mentioned drawbacks of the conventional structure, the present invention provides a new magnet structure in which unnecessary leakage magnetic fields can be relatively reduced and the size of the magnet can be reduced.

Fig. 2 shows a magnet structure employing the invention. In the present invention, in the upper pole piece and the lower pole piece, a large groove is provided in the direction perpendicular to the central axis of the magnetization direction, rather than eliminating most of the surface that is not joined to the magnet. It has been found that by adopting such a structure, the leakage magnetic fields of the various types mentioned above can be significantly reduced, and it is very effective in reducing the size of the magnet. It was found that the magnetic field was significantly reduced, making it very effective for miniaturizing magnets.

[Brief explanation of the drawing]

FIG. 1 shows a conventional permanent magnet structure. FIG. 2 shows a permanent magnet structure according to the invention. l... Upper pole piece, 2... Lower pole piece, 3-6... i stone, 7.8 old.
·yoke.

Claims (1)

[Claims] Two radially magnetized permanent magnets are arranged radially on the upper pole piece, the lower pole piece, and the opposing outer peripheral surfaces of each of these pole pieces, and the other end of each permanent magnet is connected to a yoke. In the permanent magnet structure, at least one of the upper pole piece and the lower pole piece is cut in the shape of a penetrating groove in the direction of magnetization of the magnet from a surface opposite to the central gap. A permanent magnet device characterized by: